EnblendCombining Multiple Images

with Enblend version 4.1.4, 7 August 2015

Andrew Mihal

This manual is for Enblend (version 4.1.4, 7 August 2015), a tool for compositing imagesin such a way that the seam between the images is invisible, or at least very difficult to see.

Copyright c© 2004–2015 Andrew Mihal.

Permission is granted to copy, distribute and/or modify this document underthe terms of the GNU Free Documentation License, Version 1.2 or any laterversion published by the Free Software Foundation; with no Invariant Sections,no Front-Cover Texts and no Back-Cover Texts. A copy of the license is includedin the section entitled “GNU Free Documentation License”.

i

Table of Contents

List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv

List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2 Workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.1 Standard Workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.2 External Mask Manipulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3 Invocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53.1 Image Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53.2 Response Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.2.1 Response File Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63.2.2 Syntactic Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.2.3 Globbing Algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.2.4 Default Layer Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.3 Common Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.4 Extended Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143.5 Mask Generation Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

4 Primary Seam Generators . . . . . . . . . . . . . . . . . . . . 26

5 Color Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

6 Understanding Masks . . . . . . . . . . . . . . . . . . . . . . . . . 286.1 Masks in Input Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286.2 Weight Mask Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

7 Tuning Memory Usage . . . . . . . . . . . . . . . . . . . . . . . . 30

8 Helpful Additional Programs . . . . . . . . . . . . . . . . . 32

Appendix A Bug Reports . . . . . . . . . . . . . . . . . . . . . . 34A.1 Have You Really Found a Bug? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34A.2 How to Report Bugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34A.3 Sending Patches for Enblend or Enfuse . . . . . . . . . . . . . . . . . . . . . . . . 35

Appendix B Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

ii

Appendix C GNU Free Documentation License. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Program Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

Syntactic-Comment Index . . . . . . . . . . . . . . . . . . . . . . . . 44

Option Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

General Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

List of Tables iv

List of Tables

Table 3.1: Grammar of response files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Table 3.2: Grammar of syntactic comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Table 3.3: Globbing algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Table 3.4: Mask generation options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Table 3.5: Optimizer strategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Table 3.6: Visualization colors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Table 3.7: Mask template characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Table 7.1: Suggested cache-size settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

List of Figures v

List of Figures

Figure 2.1: Photographic workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Figure 2.2: External masks workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Figure 3.1: Seam-line visualization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Chapter 1: Overview 1

1 Overview

Enblend overlays multiple images using the Burt-Adelson multiresolution spline algo-rithm.1 This technique tries to make the seams between the input images invisible. Thebasic idea is that image features should be blended across a transition zone proportional insize to the spatial frequency of the features. For example, objects like trees and window-panes have rapid changes in color. By blending these features in a narrow zone, you will notbe able to see the seam because the eye already expects to see color changes at the edge ofthese features. Clouds and sky are the opposite. These features have to be blended acrossa wide transition zone because any sudden change in color will be immediately noticeable.

Enblend expects each input file to have an alpha channel. The alpha channel shouldindicate the region of the file that has valid image data. Enblend compares the alpharegions in the input files to find the areas where images overlap. Alpha channels can beused to indicate to Enblend that certain portions of an input image should not contributeto the final image.

Enblend does not align images. Use a tool such as hugin or PanoTools to do this. TheTIFF files produced by these programs are exactly what Enblend is designed to work with.Sometimes these GUIs allow you to select feathering for the edges of your images. Thistreatment is detrimental to Enblend. Turn off feathering by deselecting it or setting thefeather width to zero.

Enblend blends the images in the order they are specified on the command line. Youshould order your images according to the way that they overlap, for example from left-to-right across the panorama. If you are making a multi-row panorama, we recommendblending each horizontal row individually, and then running Enblend a last time to blendall of the rows together vertically.

Enblend reads all layers of multi-layer images, like, for example, multi-directory TIFF

images2. The input images are processed in the order they appear on the command line.Multi-layer images are processed from the first layer to the last before Enblend considersthe next image on the command line.

Find out more about Enblend on its SourceForge web page.

1 Peter J. Burt and Edward H. Adelson, “A Multiresolution Spline With Application to ImageMosaics”, ACM Transactions on Graphics, Vol. 2, No. 4, October 1983, pages 217–236.

2 Use utilities like, e.g., tiffcopy and tiffsplit of LibTIFF to manipulate multi-directory TIFF images.See Chapter 8 [Helpful Programs], page 32.

Chapter 2: Workflow 2

2 Workflow

Enblend is a part of a chain of tools to assemble images. It combines a series of picturestaken at the same location but in different directions.

2.1 Standard Workflow

Figure 2.1 shows where Enblend and Enfuse sit in the tool chain of the standard workflow.

Take Images

Postprocess

Combine Images

Align Images

Convert Images

[else] [raw]

The Gimp, et al.

Enblend, Enfuse

Hugin, PanoTools

DCRaw, UFRaw, etc.

Figure 2.1: Photographic workflow with Enblend and Enfuse.

Take ImagesTake multiple images to form a panorama, an exposure series, a focus stack,etc.

There is one exception with Enfuse when a single raw image is converted mul-tiple times to get several – typically differently “exposed” – images.

Exemplary Benefits

• Many pictures taken from the same vantage point but showing differentviewing directions. – Panorama

Chapter 2: Workflow 3

• Pictures of the same subject exposed with different shutter speeds. – Ex-posure series

• Images of the same subject focussed at differing distances. – Focus stack

Remaining Problem: The “overlayed” images may not fit together, that is theoverlay regions may not match exactly.

Convert ImagesConvert the raw data exploiting the full dynamic range of the camera andcapitalize on a high-quality conversion.

Align ImagesAlign the images so as to make them match as well as possible.

Again there is one exception and this is when images naturally align. For ex-ample, a series of images taken from a rock solid tripod with a cable releasewithout touching the camera, or images taken with a shift lens, can align with-out further user intervention.

This step submits the images to affine transformations. If necessary, it rectifiesthe lens’ distortions (e.g. barrel or pincushion), too. Sometimes even luminanceor color differences between pairs of overlaying images are corrected (“photo-metric alignment”).

Benefit: The overlay areas of images match as closely as possible given thequality if the input images and the lens model used in the transformation.

Remaining Problem: The images may still not align perfectly, for example,because of parallax errors, or blur produced by camera shake.

Combine ImagesEnblend and Enfuse combine the aligned images into one.

Benefit: The overlay areas become imperceptible for all but the most mal-aligned images.

Remaining Problem: Enblend and Enfuse write images with an alpha channel.(For more information on alpha channels see Chapter 6 [Understanding Masks],page 28.) Furthermore, the final image rarely is rectangular.

PostprocessPostprocess the combined image with your favorite tool. Often the user willwant to crop the image and simultaneously throw away the alpha channel.

View

Print

Enjoy

2.2 External Mask Manipulation

In the usual workflow Enblend and Enfuse generate the blending and fusing masks accordingto the command-line options and the input images and then they immediately use thesemasks for blending or fusing the output image.

Sometimes more control over the masks is needed or wanted. To this end, both applica-tions provide the option pair --load-masks and --save-masks. See Chapter 3 [Invocation],

Chapter 2: Workflow 4

page 5, for detailed explanations of both options. With the help of these options the pro-cessing can be broken up into two steps:

Save masks with --save-masks.Generate masks and save them into image files.

Avoid option --output unless the blended or fused image at this point is nec-essary.

Load masks with --load-masks.Load masks from files and then blend or fuse the final image with the help ofthe loaded masks.

In between these two steps the user may apply whatever transformation to the maskfiles, as long as their geometries and offsets remain the same. Thus the “Combine Images”box of Figure 2.1 becomes three activities as is depicted in Figure 2.2.

Any tool

Enblend, Enfuse −−save−masksGenerate Masks

Modify Masks

Blend or Fuse

Using MasksEnblend, Enfuse −−load−masks

Figure 2.2: Workflow for externally modified masks.

To further optimize this kind of workflow, both Enblend and Enfuse stop after maskgeneration if option --save-masks is given, but no output file is specified with the --

output option. This way the time for pyramid generation, blending, fusing, and writingthe final image to disk is saved, as well as no output image gets generated.

Note that options --save-masks and --load-masks cannot be used simultaneously.

Chapter 3: Invocation 5

3 Invocation

enblend [OPTIONS] [--output=IMAGE] INPUT . . .

Assemble the sequence of images INPUT . . . into a single IMAGE.

Input images are either specified literally or via so-called response files (see below). Thelatter are an alternative to specifying image filenames on the command line.

3.1 Image Requirements

All input images must comply with the following requirements.

• Parts of the images overlap.

• Each image has an alpha channel also called “mask”.

• The images agree on their number of channels:

– one plus alpha or

– three plus alpha.

This is, either all images are black-and-white (one channel and alpha channel) or allare RGB-color images (three channels and alpha channel).

• The images agree on their number of bits-per-channel, this is, their “depth”:

– UINT8,

– UINT16,

– FLOAT,

– etc.

See option --depth below for an explanation of different (output) depths.

• Enblend understands the images’ filename extensions as well as their file formats.

You can check the supported extensions and formats by calling Enblend with the optionpair --version --verbose and scan the output for ‘Supported image formats’ or‘Supported file extensions’.

Moreover, there are some “good practices”, which are not enforced by the application,but almost certainly deliver superior results.

• Either all files lack an ICC profile, or all images are supplied with the same ICC profile.

• If the images’ meta-data contains resolution information (“DPI”), it is the same for allpictures.

3.2 Response Files

A response file contains names of images or other response filenames. Introduce responsefile names with an at-character (‘@’).

Enblend and Enfuse process the list INPUT strictly from left to right, expanding re-sponse files in depth-first order. (Multi-layer files are processed from first layer to the last.)The following examples only show Enblend, but Enfuse works exactly the same.

Solely image filenames.Example:

Chapter 3: Invocation 6

enblend image-1.tif image-2.tif image-3.tif

The ultimate order in which the images are processed is: image-1.tif, image-2.tif, image-3.tif.

Single response file.Example:

enblend @list

where file list contains

img1.exr

img2.exr

img3.exr

img4.exr

Ultimate order: img1.exr, img2.exr, img3.exr, img4.exr.

Mixed literal names and response files.Example:

enblend @master.list image-09.png image-10.png

where file master.list comprises of

image-01.png

@first.list

image-04.png

@second.list

image-08.png

first.list is

image-02.png

image-03.png

and second.list contains

image-05.png

image-06.png

image-07.png

Ultimate order: image-01.png, image-02.png, image-03.png, image-04.png,image-05.png, image-06.png, image-07.png, image-08.png, image-09.png,image-10.png,

3.2.1 Response File Format

Response files contain one filename per line. Blank lines or lines beginning with a sharpsign (‘#’) are ignored; the latter can serve as comments. Filenames that begin with an at-character (‘@’) denote other response files. Table 3.1 states a formal grammar of responsefiles in EBNF.

Chapter 3: Invocation 7

response-file ::= line*line ::= (comment | file-spec) [‘\r’] ‘\n’comment ::= space* ‘#’ textfile-spec ::= space* ‘@’ filename space*space ::= ‘ ’ | ‘\t’

where text is an arbitrary string and filename is any filename.

Table 3.1: EBNF definition of the grammar of response files.

In a response file relative filenames are used relative the response file itself, not relativeto the current-working directory of the application.

The above grammar might unpleasantly surprise the user in the some ways.

Whitespace trimmed at both line endsFor convenience, whitespace at the beginning and at the end of each line isignored. However, this implies that response files cannot represent filenamesthat start or end with whitespace, as there is no quoting syntax. Filenameswith embedded whitespace cause no problems, though.

Only whole-line commentsComments in response files always occupy a complete line. There are no “line-ending comments”. Thus, in

# exposure series

img-0.33ev.tif # "middle" EV

img-1.33ev.tif

img+0.67ev.tif

only the first line contains a comment, whereas the second line includes none.Rather, it refers to a file called ‘img-0.33ev.tif # "middle" EV’.

Image filenames cannot start with ‘@’An at-sign invariably introduces a response file, even if the filename’s extensionhints towards an image.

If Enblend or Enfuse do not recognize a response file, they will skip the file and issue awarning. To force a file being recognized as a response file add one of the following syntacticcomments to the first line of the file.

response-file: true

enblend-response-file: true

enfuse-response-file: true

Finally, here is an example of a valid response file.

Chapter 3: Invocation 8

# 4\pi panorama!

# These pictures were taken with the panorama head.

@round-shots.list

# Freehand sky shot.

zenith.tif

# "Legs, will you go away?" images.

nadir-2.tif

nadir-5.tif

nadir.tif

3.2.2 Syntactic Comments

Comments that follow the format described in Table 3.2 are treated as instructions how tointerpret the rest of the response file. A syntactic comment is effective immediately and itseffect persists to the end of the response file, unless another syntactic comment undoes it.

syntactic-comment ::= space* ‘#’ space* key space* ‘:’ space* valuekey ::= (‘A’ .. ‘Z’ | ‘a’ .. ‘z’ | ‘-’)+

where value is an arbitrary string.

Table 3.2: EBNF definition of the grammar of syntactic comments in response files.

Unknown syntactic comments are silently ignored.

3.2.3 Globbing Algorithms

The three equivalent syntactic keys

• glob,

• globbing, or

• filename-globbing

control the algorithm that Enblend or Enfuse use to glob filenames in response files.

All versions of Enblend and Enfuse support at least two algorithms: literal, which isthe default, and wildcard. See Table 3.3 for a list of all possible globbing algorithms. Tofind out about the algorithms in your version of Enblend or Enfuse team up the options --version and --verbose.

Chapter 3: Invocation 9

literal Do not glob. Interpret all filenames in response files as literals. This is thedefault.

Please keep in mind that whitespace at both ends of a line in a response filealways gets discarded.

wildcard Glob using the wildcard characters ‘?’, ‘*’, ‘[’, and ‘]’.

The W*N32 implementation only globs the filename part of a path, whereasall other implementations perform wildcard expansion in all path components.Also see glob(7).

none Alias for literal.

shell The shell globbing algorithm works as literal does. In addition, it interpretsthe wildcard characters ‘{’, ‘}’, and ‘~’. This makes the expansion processbehave more like common UN*X shells.

sh Alias for shell.

Table 3.3: Globbing algorithms for the use in response files

Example:

# Horizontal panorama

# 15 images

# filename-globbing: wildcard

image_000[0-9].tif

image_001[0-4].tif

3.2.4 Default Layer Selection

The key layer-selector provides the same functionality as does the command-line option -

-layer-selector, but on a per response-file basis. See Section 3.3 [Common Options],page 9.

This syntactic comment affects the layer selection of all images listed after it includingthose in included response files until another layer-selector overrides it.

3.3 Common Options

Common options control some overall features of Enblend.

Enblend accepts arguments to any option in uppercase as well as in lowercase letters. Forexample, ‘deflate’, ‘Deflate’ and ‘DEFLATE’ as arguments to the --compression optiondescribed below, all instruct Enblend to use theDeflate compression scheme. This manualdenotes all arguments in lowercase for consistency.

-a Pre-assemble non-overlapping images before each blending iteration.

This overrides the default behavior which is to blend the images sequentially inthe order given on the command line. Enblend will use fewer blending iterations,but it will do more work in each iteration.

Chapter 3: Invocation 10

--compression=COMPRESSION

Write a compressed output file.

Depending on the output file format, Enblend accepts different values forCOMPRESSION.

JPEG format.The compression either is a literal integer or a keyword-option com-bination.

LEVEL Set JPEG quality LEVEL, where LEVEL is an integerthat ranges from 0–100.

jpeg[:LEVEL]

Same as above; without the optional argument justswitch on (standard) JPEG compression.

jpeg-arith[:LEVEL]

Switch on arithmetic JPEG compression. Withoptional argument set the arithmetic compres-sion LEVEL, where LEVEL is an integer that rangesfrom 0–100.

TIF format.Here, COMPRESSION is one of the keywords:

none Do not compress. This is the default.

deflate Use the Deflate compression scheme also called ZIP-in-TIFF. Deflate is a lossless data compression algo-rithm that uses a combination of the LZ77 algorithmand Huffman coding.

jpeg[:LEVEL]

Use JPEG compression. With optional argument setthe compression LEVEL, where LEVEL is an integerthat ranges from 0–100.

lzw Use Lempel-Ziv-Welch (LZW) adaptive compressionscheme. LZW compression is lossless.

packbits Use PackBits compression scheme. PackBits is aparticular variant of run-length compression; it is loss-less.

Any other format.Other formats do not accept a COMPRESSION setting.

However, VIGRA automatically compresses png-files with the De-flate method.

--layer-selector=ALGORITHM

Override the standard layer selector algorithm, which is ‘all-layers’.

This version of Enblend offers the following algorithms:

Chapter 3: Invocation 11

all-layers

Select all layers in all images.

first-layer

Select only first layer in each multi-layer image. For single-layerimages this is the same as ‘all-layers’.

largest-layer

Select largest layer in each multi-layer image, where the “largeness”,this is the size is defined by the product of the layer width and itsheight. The channel width of the layer is ignored. For single-layerimages this is the same as ‘all-layers’.

no-layer Do not select any layer in any image.

This algorithm is useful to temporarily exclude some images inresponse files.

-h

--help Print information on the available options and exit.

-l LEVELS

--levels=LEVELS

Use at most this many LEVELS for pyramid1 blending if LEVELS is positive,or reduce the maximum number of levels used by −LEVELS if LEVELS isnegative; ‘auto’ or ‘automatic’ restore the default, which is to use the maximumpossible number of levels for each overlapping region.

The number of levels used in a pyramid controls the balance between local andglobal image features (contrast, saturation, . . . ) in the blended region. Fewerlevels emphasize local features and suppress global ones. The more levels apyramid has, the more global features will be taken into account.

As a guideline, remember that each new level works on a linear scale twice aslarge as the previous one. So, the zeroth layer, the original image, obviouslydefines the image at single-pixel scale, the first level works at two-pixel scale,and generally, the n-th level contains image data at 2^n-pixel scale. This isthe reason why an image of widthxheightpixels cannot be deconstructed intoa pyramid of more than blog2(min(width, height))c levels.If too few levels are used, “halos” around regions of strong local feature variationcan show up. On the other hand, if too many levels are used, the image mightcontain too much global features. Usually, the latter is not a problem, but ishighly desired. This is the reason, why the default is to use as many levels asis possible given the size of the overlap regions. Enblend may still use a smallernumber of levels if the geometry of the overlap region demands.

Positive values of LEVELS limit the maximum number of pyramid levels. De-pending on the size and geometry of the overlap regions this may or may notinfluence any pyramid. Negative values of LEVELS reduce the number of pyra-mid levels below the maximum no matter what the actual maximum is and thus

1 As Dr. Daniel Jackson correctly noted, actually, it is not a pyramid: “Ziggaurat, it’s a Ziggaurat.”

Chapter 3: Invocation 12

always influence all pyramids. Use ‘auto’ or ‘automatic’ as LEVELS to restorethe automatic calculation of the maximum number of levels.

The valid range of the absolute value of LEVELS is 1 to 29.

-o

--output=FILE

Place output in FILE.

If --output is not specified, the default is to put the resulting image in a.tif.

--parameter=KEY[=VALUE]:...

Set a KEY-VALUE pair, where VALUE is optional. This option is cumulative.Separate multiple pairs with the usual numeric delimiters.

This option has the negated form --no-parameter, which takes one or moreKEY s and removes them from the list of defined parameters. The special key ‘*’deletes all parameters at once.

Parameters allow the developers to change the internal workings of Enblendwithout the need to recompile.

-v

--verbose[=LEVEL]

Without an argument, increase the verbosity of progress reporting. Giving more--verbose options will make Enblend more verbose. Directly set a verbositylevel with a non-negative integral LEVEL.

Each level includes all messages of the lower levels.

Level Messages

0 only warnings and errors

1 reading and writing of images

2 mask generation, pyramid, and blending

3 reading of response files, color conversions

4 image sizes, bounding boxes and intersection sizes

5 detailed information on the optimizer runs (Enblend only)

6 estimations of required memory in selected processing steps

The default verbosity level of Enblend is 1.

-V

--version

Output information on the Enblend version.

Team this option with --verbose to show configuration details, like the extrafeatures that have been compiled in.

-w

--wrap=MODE

Blend around the boundaries of the panorama.

As this option significantly increases memory usage and computation time onlyuse it, if the panorama will be

Chapter 3: Invocation 13

• consulted for any kind measurement, this is, all boundaries must match asaccurately as possible, or

• printed out and the boundaries glued together, or

• fed into a virtual reality (VR) generator, which creates a seamless environ-ment.

Otherwise, always avoid this option!

With this option Enblend treats the panorama of width w and height h as aninfinite data structure, where each pixel P (x, y) of the input images representsthe set of pixels SP (x, y)

2.

MODE takes the following values:

‘none’‘open’ This is a “no-op”; it has the same effect as not giving --wrap at

all. The set of input images is considered open at its boundaries.

‘horizontal’Wrap around horizontally:

SP (x, y) = {P (x+mw, y) : m ∈ Z}.

This is useful for 360◦ horizontal panoramas as it eliminates theleft and right borders.

‘vertical’Wrap around vertically:

SP (x, y) = {P (x, y + nh) : n ∈ Z}.

This is useful for 360◦ vertical panoramas as it eliminates the topand bottom borders.

‘both’‘horizontal+vertical’‘vertical+horizontal’

Wrap around both horizontally and vertically:

SP (x, y) = {P (x+mw, y + nh) : m,n ∈ Z}.

In this mode, both left and right borders, as well as top and bottomborders, are eliminated.

Specifying --wrap without MODE selects horizontal wrapping.

-x Checkpoint partial results to the output file after each blending step.

2 Solid-state physicists will be reminded of the Born-von Karman boundary condition.

Chapter 3: Invocation 14

3.4 Extended Options

Extended options control the image cache, the color model, and the cropping of the outputimage.

-b BLOCKSIZE

Set the BLOCKSIZE in kilobytes (KB) of Enblend’s image cache.

This is the amount of data that Enblend will move to and from the disk atone time. The default is 2048KB, which should be ok for most systems. SeeChapter 7 [Tuning Memory Usage], page 30 for details.

Note that Enblend must have been compiled with the image-cache feature forthis option to be effective. Find out about extra features with enblend --

version --verbose.

--blend-colorspace=COLORSPACE

Force blending in selected COLORSPACE. For well matched images this optionshould not change the output image much. However, if Enblend must blendvastly different colors (as e.g. anti-colors) the result image heavily depends onthe COLORSPACE.

Usually, Enblend chooses defaults depending on the input images:

• For input images with ICC profiles the default is to use CIECAM colorspace.

• Images without color profiles and floating-point images are blended in theRGB-color cube by default.

Enblend supports two blend colorspaces:

‘IDENTITY’, ‘ID’, ‘UNIT’Naively compute blended colors in the luminance interval (grayscaleimages) or RGB-cube (RGB images) spanned by the input ICC pro-file or sRGB if no profiles are present. Consider option --fallback-

profile to force a different profile than sRGB on all input images.

‘CIECAM’, ‘CIECAM02’, ‘JCH’Blend pixels in the CIECAM02 colorspace.

Please keep in mind that by using different blend colorspaces, blending may notonly change the colors in the output image, but Enblend may choose differentseam line routes as some seam-line optimizers are guided by image differences,which may be different when viewed in different colorspaces.

-c

--ciecam Use ‘--blend-colorspace=CIECAM’ instead. To mimic the negated option --

no-ciecam use ‘--blend-colorspace=IDENTITY’.

-d

--depth=DEPTH

Force the number of bits per channel and the numeric format of the outputimage.

Enblend always uses a smart way to change the channel depth to assure highestimage quality (at the expense of memory), whether requantization is implicitbecause of the output format or explicit with option --depth.

Chapter 3: Invocation 15

• If the output-channel width is larger than the input-channel width of theinput images, the input images’ channels are widened to the output channelwidth immediately after loading, that is, as soon as possible. Enblendthen performs all blending operations at the output-channel width, therebypreserving minute color details which can appear in the blending areas.

• If the output-channel width is smaller than the input-channel width of theinput images, the output image’s channels are narrowed only right beforeit is written to disk, that is, as late as possible. Thus the data benefitsfrom the wider input channels for the longest time.

All DEPTH specifications are valid in lowercase as well as uppercase letters.For integer format, use

8, uint8 Unsigned 8 bit; range: 0..255

int16 Signed 16 bit; range: −32768..32767

16, uint16Unsigned 16 bit; range: 0..65535

int32 Signed 32 bit; range: −2147483648..2147483647

32, uint32Unsigned 32 bit; range: 0..4294967295

For floating-point format, use

r32, real32, floatIEEE754 single precision floating-point, 32 bit wide, 24 bit signifi-cant

• Minimum normalized value: 1.2e-38

• Epsilon: 1.2e-7

• Maximum finite value: 3.4e38

r64, real64, doubleIEEE754 double precision floating-point, 64 bit wide, 53 bit signifi-cant

• Minimum normalized value: 2.2e-308

• Epsilon: 2.2e-16

• Maximum finite value: 1.8e308

If the requested DEPTH is not supported by the output file format, Enblendwarns and chooses the DEPTH that matches best.

The OpenEXR data format is treated as IEEE754 float internally. Externally, ondisk, OpenEXR data is represented by “half” precision floating-point numbers.

OpenEXR half precision floating-point, 16 bit wide, 10 bit significant

• Minimum normalized value: 9.3e-10

• Epsilon: 2.0e-3

• Maximum finite value: 4.3e9

Chapter 3: Invocation 16

-f WIDTHxHEIGHT

-f WIDTHxHEIGHT+xXOFFSET+yYOFFSET

Ensure that the minimum “canvas” size of the output image is at leastWIDTHxHEIGHT. Optionally specify the XOFFSET and YOFFSET, too.

This option only is useful when the input images are cropped TIFF files, suchas those produced by nona3.

Note that option -f neither rescales the output image, nor shrinks the canvassize below the minimum size occupied by the union of all input images.

--fallback-profile=PROFILE-FILENAME

Use the ICC profile in PROFILE-FILENAME instead of the default sRGB. Seeoption --blend-colorspace and Chapter 5 [Color Profiles], page 27.

This option only is effective if the input images come without color profiles andblending is performed in CIECAM02 color appearance model.

-g Save alpha channel as “associated”. See the TIFF documentation for an expla-nation.

Gimp (before version 2.0) and CinePaint (see Chapter 8 [Helpful Programs],page 32) exhibit unusual behavior when loading images with unassociated alphachannels. Use option -g to work around this problem. With this flag Enblendwill create the output image with the associated alpha tag set, even though theimage is really unassociated alpha.

--gpu Use the graphics card – in fact the graphics processing unit (GPU) – to acceleratesome computations.

This is an experimental feature that may not work on all systems. In this versionof Enblend, 4.1.4, only mask optimization by Simulated Annealing benefits fromthis option.

Note that GPU-support must have been compiled into Enblend for this option tobe available. Find out about this feature with enblend --version --verbose.

-m CACHESIZE

Set the CACHESIZE in megabytes (MB) of Enblend’s image cache.

This is the amount of memory Enblend will use for storing image data beforeswapping to disk. The default is 1024MB, which is good for systems with 3–4 gigabytes (GB) of RAM. See Chapter 7 [Tuning Memory Usage], page 30 fordetails.

Note that Enblend must have been compiled with the image-cache feature forthis option to be effective. Find out about extra features with enblend --

version --verbose.

--no-ciecam

Use ‘--blend-colorspace=IDENTITY’ instead.

See option --blend-colorspace for details. Also see Chapter 5 [Color Profiles],page 27.

3 The stitcher nona is part of Hugin. See Chapter 8 [Helpful Programs], page 32.

Chapter 3: Invocation 17

3.5 Mask Generation Options

These options control the generation and the usage of masks.

--anneal=TAU[:DELTA-E-MAX[:DELTA-E-MIN[:K-MAX]]]

Set the parameters of the Simulated Annealing optimizer (see Table 3.5).

TAU TAU is the temperature reduction factor in the Simulated Anneal-ing; it also can be thought of as “cooling factor”. The closer TAU isto one, the more accurate the annealing run will be, and the longerit will take.

Append a percent sign (‘%’) to specify TAU as a percentage.

Valid range: 0 < TAU < 1.

The default is 0.75; values around 0.95 are reasonable. Usually,slower cooling results in more converged points.

DELTA-E-MAXDELTA-E-MIN

DELTA-E-MAX and DELTA-E-MIN are the maximum and mini-mum cost change possible by any single annealing move.

Valid range: 0 < DELTA-E-MIN < DELTA-E-MAX.

In particular they determine the initial and final annealing temper-atures according to:

Tinitial =DELTA-E-MAX

log(K-MAX/(K-MAX− 2))

Tfinal =DELTA-E-MIN

log(K-MAX 2 −K-MAX− 1)

The defaults are: DELTA-E-MAX : 7000.0 and DELTA-E-MIN :5.0.

K-MAX K-MAX is the maximum number of “moves” the optimizer willmake for each line segment. Higher values more accurately samplethe state space, at the expense of a higher computation cost.

Valid range: K-MAX ≥ 3.

The default is 32. Values around 100 seem reasonable.

--coarse-mask[=FACTOR]

Use a scaled-down version of the input images to create the seam line. Thisoption reduces the number of computations necessary to compute the seam lineand the amount of memory necessary to do so. It is the default.

If omitted FACTOR defaults to 8, this means, option --coarse-mask shrinksthe overlapping areas by a factor of 8x8. With FACTOR = 8 the total mem-ory allocated during a run of Enblend shrinks approximately by 80% and themaximum amount of memory in use at a time is decreased to 60% (Enblendcompiled with image cache) or 40% (Enblend compiled without image cache).

Valid range: FACTOR = 1, 2, 3,. . . .

Chapter 3: Invocation 18

Also see Table 3.4.

--no-optimize --optimize

--fine-mask Use NFT mask. Vectorize NFT mask, opti-mize vertices with simulatedannealing and Dijkstra’sshortest path algorithm, fillvector contours.

--coarse-mask Scale down overlap region,compute NFT mask and vec-torize it, fill vector contours.

Scale down overlap region,vectorize NFT mask, opti-mize vertices with simulatedannealing and Dijkstra’sshortest path algorithm, fillvector contours.

Table 3.4: Various options that control the generation of masks. All maskcomputations are based on the Nearest-Feature Transformation (NFT) of theoverlap region.

--dijkstra=RADIUS

Set the search RADIUS of the Dijkstra Shortest Path algorithm used inDijkstra Optimization (see Table 3.5).

A small value prefers straight line segments and thus shorter seam lines. Largervalues instruct the optimizer to let the seam line take more detours when search-ing for the best seam line.

Valid range: RADIUS ≥ 1.

Default: 25 pixels.

--fine-mask

Instruct Enblend to employ the full-size images to create the seam line, whichcan be slow. Use this option, for example, if you have very narrow overlapregions.

Also see Table 3.4.

--image-difference=ALGORITHM[:LUMINANCE-WEIGHT[:CHROMINANCE-WEIGHT]]

Enblend calculates the difference of a pair of overlapping color images when itgenerates the primary seam with a Graph-Cut or before it optimizes a seam. Itemploys a user-selectable ALGORITHM that itself is controlled by the weightsfor luminance differences LUMINANCE-WEIGHT, wluminance and color differ-ences CHROMINANCE-WEIGHT, wchrominance.

For black-and-white images the difference is simple the absolute difference ofeach pair of pixels.

Chapter 3: Invocation 19

maximum-hue-luminance

maximum-hue-lum

max-hue-luminance

max-hue-lum

max Calculate the difference d as the maximum of the differences of theluminances l and hues h of each pair of pixels P1 and P2:

d = max(wluminance × |l(P1)− l(P2)|,wchrominance × |h(P1)− h(P2)|)

This algorithm was the default for Enblend up to version 4.0.

delta-e

de Calulate the difference d as the Euclidean distance of the pixelsin L*a*b* space:

d = (wluminance × (L(P1)− L(P2))2 +

wchrominance × (a(P1)− a(P2))2 +

wchrominance × (b(P1)− b(P2))2)1/2

This is the default in Enblend version 4.1 and later.

Note that the “delta-E” mentioned here has nothing to do withDELTA-E-MAX and DELTA-E-MIN of option --anneal.

Both LUMINANCE-WEIGHT and CHROMINANCE-WEIGHT mustbe non-negative, their sum must be positive. Enblend automaticallynormalizes the sum of LUMINANCE-WEIGHT and CHROMINANCE-WEIGHT to one. Thus ‘--image-difference=delta-e:2:1’ and‘--image-difference=delta-e:0.6667:0.3333’ define the same weightingfunction.

The default LUMINANCE-WEIGHT is 1.0 and the default CHROMINANCE-WEIGHT is 1.0.

At higher verbosity levels Enblend computes the true size of the overlap areain pixels and it calculates the average and standard deviation of the differenceper pixel in the normalized luminance interval [0. . . 1]. These statistical mea-sures are based on ALGORITHM, therefore they should only be compared foridentical ALGORITHMs. The average difference is a rough measure of qualitywith lower values meaning better matches.

--load-masks[=IMAGE-TEMPLATE]

Instead of generating masks, use those in IMAGE-TEMPLATE. The default ismask-%n.tif. The mask images have to be a 8-bit grayscale images.

See --save-masks below for details.

--mask-vectorize=DISTANCE

Set the mask vectorization DISTANCE Enblend uses to partition each seam.Thus, break down the seam to segments of length DISTANCE each.

Chapter 3: Invocation 20

If Enblend uses a coarse mask (--coarse-mask) or Enblend optimizes (--optimize) a mask it vectorizes the initial seam line before performing furtheroperations. See Table 3.4 for the precise conditions. DISTANCE tells Enblendhow long to make each of the line segments called vectors here.

The unit of DISTANCE is pixels unless it is a percentage as explained in thenext paragraph. In fine masks one mask pixel corresponds to one pixel in theinput image, whereas in coarse masks one pixel represents for example 8 pixelsin the input image.

Append a percentage sign (‘%’) to DISTANCE to specify the segment length asa fraction of the diagonal of the rectangle including the overlap region. Relativemeasures do not depend on coarse or fine masks, they are recomputed for eachmask. Values around 5%–10% are a good starting point.

This option massively influences the mask generation process! Large DIS-TANCE values lead to shorter, straighter, less wiggly, less baroque seams thatare on the other hand less optimal, because they run through regions of largerimage mismatch instead of avoiding them. Small DISTANCE values give theoptimizers more possibilities to run the seam around high mismatch areas.

What should never happen though, are loops in the seam line. Counterloops with higher weights of DISTANCE-WEIGHT (in option --optimizer-

weights), larger vectorization DISTANCEs, TAUs (in option --anneal)that are closer to one, and blurring of the difference image withoption --smooth-difference. Use option --visualize to check the results.

Valid range: DISTANCE ≥ 4.

Enblend limits DISTANCE so that it never gets below 4 even if it has beengiven as a percentage. The user will be warned in such cases.

Default: 4 pixels for coarse masks and 20 pixels for fine masks.

--no-optimize

Turn off seam line optimization. Combined with option --fine-mask this willproduce the same type of mask as Enblend version 2.5, namely the result of aNearest-Feature Transform (NFT).4

Also see Table 3.4.

--optimize

Use a multi-strategy approach to route the seam line around mismatches in theoverlap region. This is the default. Table 3.5 explains these strategies; also seeTable 3.4.

4 Muhammad H. Alsuwaiyel and Marina Gavrilova, “On the Distance Transform of Binary Images”,Proceedings of the International Conference on Imaging Science, Systems, and Technology, June 2000,Vols. I and II, pages 83–86.

Chapter 3: Invocation 21

Simulated AnnealingTune with option --anneal = TAU : DELTA-E-MAX : DELTA-E-MIN : K-MAX.

Simulated-Annealing

Dijkstra Shortest PathTune with option --dijkstra = RADIUS.

Dijkstra algorithm

Table 3.5: Enblend’s strategies to optimize the seam lines between images.

--optimizer-weights=DISTANCE-WEIGHT[:MISMATCH-WEIGHT]

Set the weights of the seam-line optimizer. If omitted, MISMATCH-WEIGHTdefaults to 1.

The seam-line optimizer considers two qualities of the seam line:

• The distance of the seam line from its initial position, which has beendetermined by NFT (see option --no-optimize).

• The total “mismatch” accumulated along it.

The optimizer weights DISTANCE-WEIGHT and MISMATCH-WEIGHT de-fine how to weight these two criteria. Enblend up to version 3.2 used 1:1. Thisversion of Enblend (4.1.4) uses 8.0:1.0.

A large DISTANCE-WEIGHT pulls the optimized seam line closer to the initialpostion. A large MISMATCH-WEIGHT makes the seam line go on detours tofind a path along which the mismatch between the images is small. If theoptimized seam line shows cusps or loops (see option --visualize), reduceMISMATCH-WEIGHT or increase DISTANCE-WEIGHT.

Both weights must be non-negative. They cannot be both zero at the same time.Otherwise, their absolute values are not important as Enblend normalizes theirsum.

--primary-seam-generator=ALGORITHM

Select the algorithm responsible for generating the general seam route.

This is the ALGORITHM that produces an initial seam line, which is the basisfor later, optional optimizations (see --optimize). Nearest Feature Transform(NFT) is the only algorithm up to and including Enblend version 4.0. Version 4.1adds a Graph-Cut (GC) algorithm. In this version of Enblend NFT is thedefault.

Valid ALGORITHM names are:

nearest-feature-transformnft Nearest Feature Transform

graph-cutgc Graph-Cut

See Chapter 4 [Primary Seam Generators], page 26 for details.

Chapter 3: Invocation 22

--save-masks

--save-masks=IMAGE-TEMPLATE

Save the generated masks to IMAGE-TEMPLATE. The default ismask-%n.tif. Enblend saves masks as 8 bit grayscale (single channel) images.For accuracy we recommend to choose a lossless format.

Use this option if you wish to edit the location of the seam line by hand. Thiswill give you images of the right sizes that you can edit to make your changes.Later, use option --load-masks to blend the project with your custom seamlines.

Enblend will stop after saving all masks unless option --output is given, too.With both options given, this is, --save-masks and --output, Enblend savesall masks and then proceeds to blend the output image.

IMAGE-TEMPLATE defines a template that is expanded for each input file. Ina template a percent sign (‘%’) introduces a variable part. All other charactersare copied literally. Lowercase letters refer to the name of the respective inputfile, whereas uppercase ones refer to the name of the output file (see Section 3.3[Common Options], page 9). Table 3.7 lists all variables.

A fancy mask filename template could look like this:

%D/mask-%02n-%f.tif

It puts the mask files into the same directory as the output file (‘%D’), generatesa two-digit index (‘%02n’) to keep the mask files nicely sorted, and decoratesthe mask filename with the name of the associated input file (‘%f’) for easyrecognition.

--smooth-difference=RADIUS

This option has been deprecated.

Smooth the difference image prior to seam-line optimization to get a shorterand – on the length scale of RADIUS – also a straighter seam-line. The defaultis not to smooth.

If RADIUS is larger than zero Enblend blurs the difference images of the overlapregions with a Gaussian filter having a radius of RADIUS pixels. Values of 0.5to 1.5 pixels for RADIUS are good starting points; use option --visualize todirectly judge the effect.

When using this option in conjunction with option --coarse-mask=FACTOR,keep in mind that the smoothing occurs after the overlap regions have beenshrunken. Thus, blurring affects a FACTORxFACTOR times larger area in theoriginal images.

Valid range: RADIUS ≥ 0.0.

--visualize[=VISUALIZE-TEMPLATE]

Create an image according to VISUALIZE-TEMPLATE that visualizes theunoptimized mask and the applied optimizations (if any). The default isvis-%n.tif.

The image shows Enblend’s view of the overlap region and how it decided toroute the seam line. If you are experiencing artifacts or unexpected output,

Chapter 3: Invocation 23

it may be useful to include this visualization image in your bug report. SeeAppendix A [Bug Reports], page 34.

VISUALIZE-TEMPLATE defines a template that is expanded for each inputfile. In a template, a percent sign (‘%’) introduces a variable part; all othercharacters are copied literally. Lowercase letters refer to the name of the re-spective input file, whereas uppercase ones refer to the name of the output file(see Section 3.3 [Common Options], page 9). Table 3.7 lists all variables.

Visualization Image.

The visualization image shows the symmetric difference of the pixels in therectangular region where two images overlap. The larger the difference thelighter shade of gray it appears in the visualization image. Enblend paintsthe non-overlapping parts of the image pair – these are the regions where noblending occurs – in dark red. Table 3.6 shows the meanings of all the colorsthat are used in seam-line visualization images.

dark red Non-overlapping parts of image pair.

various shades of grayDifference of the pixel values in the overlap region.

dark blue Location of an optimizer sample.

medium greenFirst sample of a line segment.

light greenAny other but first sample of a line segment.

bright cyanState space sample inside the Dijkstra radius.

bright magentaNon-converged point.

dark yellowInitial seam line as generated by the primary seam generator.

Enblend marks a non-movable (“frozen”) endpoint of a seam-linesegment with a bright white cross, whereas it uses a light orangediamond to denote an endpoint that the optimizer is allowed tomove around.

bright yellowFinal seam line.

Table 3.6: Colors used in seam-line visualization images.

Figure 3.1 shows an example of a seam-line visualization. It was produced withan Enblend run at all defaults, but --fine-mask and --visualize enabled.

The large dark red border is “off-limits” for Enblend, for the images do notoverlap there. The dark wedge inside the dark red frame is where the imagesshare a common region.

Chapter 3: Invocation 24

The initial seam-line (dark yellow) is almost straight with the exception of asingle bend on the left side of the image and the final seam-line (bright yellow)meanders around it.

Figure 3.1: Seam-line visualization of a simple overlap. The 853x238 pixel imagehas been rescaled to a width of approximately 15 cm.

Chapter 3: Invocation 25

%% Produces a literal ‘%’-sign.

%i Expands to the index of the mask file starting at zero.

‘%i’ supports setting a pad character or a width specification:

% PAD WIDTH i

PAD is either ‘0’ or any punctuation character; the default pad character is‘0’. WIDTH is an integer specifying the minimum width of the number. Thedefault is the smallest width given the number of input images, this is 1 for 2–9images, 2 for 10–99 images, 3 for 100–999 images, and so on.

Examples: ‘%i’, ‘%02i’, or ‘%_4i’.

%n Expands to the number of the mask file starting at one. Otherwise it behavesidentically to ‘%i’, including pad character and width specification.

%p This is the full name (path, filename, and extension) of the input file associatedwith the mask.

Example: If the input file is called /home/luser/snap/img.jpg, ‘%p’ expands to/home/luser/snap/img.jpg, or shorter: ‘%p’ ⇒ /home/luser/snap/img.jpg.

%P This is the full name of the output file.

%d Is replaced with the directory part of the associated input file. See Info filecoreutils.info, node ‘dirname invocation’.

Example (cont.): ‘%d’ ⇒ /home/luser/snap.

%D Is replaced with the directory part of the output file.

%b Is replaced with the non-directory part (often called “basename”) of the asso-ciated input file. See Info file coreutils.info, node ‘basename invocation’.

Example (cont.): ‘%b’ ⇒ img.jpg.

%B Is replaced with the non-directory part of the output file.

%f Is replaced with the filename without path and extension of the associated inputfile.

Example (cont.): ‘%f’ ⇒ img.

%F Is replaced with the filename without path and extension of the output file.

%e Is replaced with the extension (including the leading dot) of the associatedinput file.

Example (cont.): ‘%e’ ⇒ .jpg.

%E Is replaced with the extension of the output file.

Table 3.7: Special characters to control the generation of mask filenames.

Chapter 4: Primary Seam Generators 26

4 Primary Seam Generators

This version (4.1.4) of Enblend supports two main algorithms to generate seam lines. Useoption --primary-seam-generator to select one of the generators.

Nearest Feature Transform (NFT)The NFT, also known as Distance Transform, is a fast and efficient technique toproduce a seam line route given the geometries of multiple overlapping images.

NFT as implemented in this version of Enblend only takes into account theshape of the overlap area. It completely ignore the images’ contents.

Graph-Cut (GC)GC is a region-oriented way of segmenting images.

The generator is based on the idea of finding a minimum cost “cut” of a graphcreated from a given image pair. A “cut” is where the seam line appears. GC

determines the cost from the overlapping images’ contents.

The most significant difference between the two algorithms is the output mask grada-tion. NFT produces a coarse approximation of the seam, running as far away from theoverlap-region borders as possible. The resulting mask could then be blended as-is, how-ever, Enblend by default runs image-content dependent optimizers to increase the maskgradation and for example omits the regions where the images differ. The result is a finerseam line, which only loosely follows the shape of NFT’s primary seam.

Graph-Cut, on the other hand, is capable of producing the final mask in one pass withoutthe need of further optimizers. It looks for a seam line that is globally optimal, taking intoaccount

• feature frequency, as well as

• image dissimilarity.

This means, the seam is less likely to cross lines like for example fences, lampposts, or roadmarkings, where they would be visible.

The optimizers which run after NFT can also be run after GC. Nevertheless, GC worksbest just with a fine mask (option --fine-mask); optimizers are then automatically turnedoff to take full advantage of the detailed seam GC produces.

GC requires more memory and computation time to complete than NFT. Thus, it is bestto prefer NFT where the images used are large and execution time is crucial. If quality isthe priority, using GC and fine mask usually produces visually more pleasing results.

GC is currently limited to seams that begin and end on the images’ borders. Thismeans that the algorithm cannot run in cases where, for example, one image is containedin another, resulting in a loop-like seam. In such cases, though, Enblend automatically fallsback to a NFT-generated seam, making its application transparent to the user.

Chapter 5: Color Profiles 27

5 Color Profiles

Enblend and Enfuse expect that either

1. no input image has a color profile or

2. all come with the same ICC profile.

In case 1 the applications blend or fuse in the RGB-cube, whereas in case 2 the images firstare transformed to CIECAM02 color space – respecting the input color profile – then theyare blended or fused, and finally the data transformed back to RGB color space. Moreover,in case 2, Enblend and Enfuse assign the input color profile to the output image.

Mixing different ICC profiles or alternating between images with profiles and withoutthem generates warnings as it generally leads to unpredictable results.

The options --ciecam (see Section 3.4 [Extended Options], page 14) and its opposite--no-ciecam (see Section 3.4 [Extended Options], page 14) overrule the default profileselection procedure described above. Use option --ciecam on a set of input images withoutcolor profiles to assign a profile to them and perform the blending or fusing process inCIECAM02 color space.

The default profile is sRGB. Override this setting with option --fallback-profile (seeSection 3.4 [Extended Options], page 14).

On the other hand, suppress the utilization of CIECAM02 blending or fusing of a setof input images with color profiles with option --no-ciecam. The only reason for thelatter is to shorten the blending- or fusing-time, because transforming to and back from theCIECAM02 color space are computationally expensive operations.

Option --ciecam as well as --fallback-profile have no effect on images with attachedcolor profiles, just as option --no-ciecam has no effect on images without profiles.

The impact of blending in CIECAM02 color space as opposed to the RGB cube varywith the contents of the input images. Generally colors lying close together in RGB spaceexperience less change when switching the blending spaces. However, colors close the borderof any color space can see marked changes.

For color geeks: The transformations to CIECAM02 color space and back use

• perceptual rendering intent,

• the D50 white point,

• 500 lumen surrounding light (“average” in CIECAM02 parlance), and

• assume complete adaption.

Chapter 6: Understanding Masks 28

6 Understanding Masks

A binary mask indicates for every pixel of an image if this pixel must be considered infurther processing, or ignored. For a weight mask, the value of the mask determines howmuch the pixel contributes, zero again meaning “no contribution”.

Masks arise in two places: as part of the input files and as separate files, showing theactual pixel weights prior to image blendung or fusion. We shall explore both occurrencesin the next sections.

6.1 Masks in Input Files

Each of the input files for Enfuse and Enblend can contain its own mask. Both applicationsinterpret them as binary masks no matter how many bits per image pixel they contain.

Use ImageMagick’s identify or, for TIFF files, tiffinfo to inquire quickly whethera file contains a mask. Chapter 8 [Helpful Programs], page 32 shows where to find theseprograms on the web.

$ identify -format "%f %m %wx%h %r %q-bit" remapped-0000.tif

remapped-0000.tif TIFF 800x533 DirectClassRGBMatte 8-bit

^^^^^ mask

$ tiffinfo remapped-0000.tif

TIFF Directory at offset 0x1a398a (1718666)

Subfile Type: (0 = 0x0)

Image Width: 800 Image Length: 533

Resolution: 150, 150 pixels/inch

Position: 0, 0

Bits/Sample: 8

Sample Format: unsigned integer

Compression Scheme: PackBits

Photometric Interpretation: RGB color

Extra Samples: 1<unassoc-alpha> <<<<< mask

Orientation: row 0 top, col 0 lhs

Samples/Pixel: 4 <<<<< R, G, B, and mask

Rows/Strip: 327

Planar Configuration: single image plane

The “Matte” part of the image class and the “Extra Samples” line tell us that the filefeatures a mask. Also, many interactive image manipulation programs show the mask as aseparate channel, sometimes called “Alpha”. There, the white (high mask value) parts ofthe mask enable pixels and black (low mask value) parts suppress them.

The multitude of terms all describing the concept of a mask is confusing.

Mask A mask defines a selection of pixels. A value of zero represents an unselectedpixel. The maximum value (“white”) represents a selected pixel and the valuesbetween zero and the maximum are partially selected pixels. See Gimp-Savy.

Alpha ChannelThe alpha channel stores the transpacency value for each pixel, typically inthe range from zero to one. A value of zero means the pixel is completely

Chapter 6: Understanding Masks 29

transparent, thus does not contribute to the image. A value of one on the otherhand means the pixel is completely opaque.

Matte The notion “matte” as used by ImageMagick refers to an inverted alpha channel,more precisely: 1 - alpha. See ImageMagick for further explanations.

Enblend and Enfuse only consider pixels that have an associated mask value other thanzero. If an input image does not have an alpha channel, Enblend warns and assumes a maskof all non-zero values, that is, it will use every pixel of the input image for fusion.

Stitchers like nona add a mask to their output images.

Sometimes it is helpful to manually modify a mask before fusion. For example to suppressunwanted objects (insects and cars come into mind) that moved across the scene duringthe exposures. If the masks of all input images are black at a certain position, the outputimage will have a hole in that position.

6.2 Weight Mask Files

...

Chapter 7: Tuning Memory Usage 30

7 Tuning Memory Usage

The default configuration of Enblend and Enfuse assumes a system with 3–4GB of RAM.

If Enblend and Enfuse have been compiled with the “image-cache” feature, they do notrely on the operating system’s memory management, but use their own image cache in thefile system. To find out whether your version uses the image cache say

enblend --verbose --version

or

enfuse --verbose --version

Enblend and Enfuse put the file that holds the image cache either in the directory pointedto by the environment variable TMPDIR, or, if the variable is not set, in directory /tmp. It isprudent to ensure write permissions and enough of free space on the volume with the cachefile.

The size of the image cache is user configurable with the option ‘-m CACHE-SIZE’ (seeSection 3.4 [Extended Options], page 14). Furthermore, option ‘-b BUFFER-SIZE’ (seeSection 3.4 [Extended Options], page 14) allows for fine-tuning the size of a single bufferinside the image cache. Note that CACHE-SIZE is given in megabytes, whereas the unitof BUFFER-SIZE is kilobytes.

Usually the user lets the operating system take care of the memory management of allprocesses. However, users of Enblend or Enfuse might want to control the balance betweenthe operating systems’ Virtual Memory system and the image cache for several reasons.

• Paging in or out parts of a process’ image runs at kernel level and thus can make userprocesses appear unresponsive or “jumpy”. The caching mechanism of Enblend andEnfuse of course runs as a user process, which is why it has less detrimental effects onthe system’s overall responsiveness.

• The image cache has been optimized for accesses to image data. All algorithms inEnblend and Enfuse have been carefully arranged to play nice with the image cache. Anoperating system’s cache has no knowledge of these particular memory access patterns.

• The disk access of the operating system to the swap device has been highly optimized.Enblend and Enfuse on the other hand use the standard IO-layer, which is a muchslower interface.

• Limiting the amount of image cache prevents Enblend and Enfuse from eating up mostor all RAM, thereby forcing all user applications into the swap.

The CACHE-SIZE should be set in such a way as to reconcile all of the above aspects evenfor the biggest data sets, that is, projects with many large images.

Table 7.1 suggests some cache- and buffer-sizes for different amounts of available RAM.

RAM CACHE-SIZE BUFFER-SIZE CommentMB MB KB

4096 1024 2048 default2048 512–1024 10241024 256–512 256–512

Table 7.1: Suggested cache-size settings

Chapter 7: Tuning Memory Usage 31

On systems with considerably more than 4GB of RAM it is recommended to run Enblendor Enfuse versions without image cache.

Chapter 8: Helpful Additional Programs 32

8 Helpful Additional Programs

Several programs and libraries have proven helpful when working with Enfuse and Enblend.

Raw Image Conversion• DCRaw is a universal raw-converter written by David Coffin.

• UFRaw, a raw converter written by Udi Fuchs and based on DCRaw,adds a GUI (ufraw), versatile batch processing (ufraw-batch), and someadditional features such as cropping, noise reduction with wavelets, andautomatic lens error correction.

Image Alignment and Rendering• ALE, David Hilvert’s anti-lamenessing engine for the real die-hard

command-line users aligns, filters, and renders images.

• Hugin is a GUI that aligns and stitches images.

It comes with several command line tools, like nona to stitch panoramaimages, align_image_stack to align overlapping images for HDR or createfocus stacks, and fulla to correct lens errors.

• PanoTools the successor of Helmut Dersch’s original PanoTools offers aset of command-line driven applications to create panoramas. Most notableare PTOptimizer and PTmender.

Image Manipulation• CinePaint is a branch of an early Gimp forked off at version 1.0.4. It sports

much less features than the current Gimp, but offers 8 bit, 16 bit and 32 bitcolor channels, HDR (for example floating-point TIFF, and OpenEXR), anda tightly integrated color management system.

• The Gimp is a general purpose image manipulation program. At the timeof this writing it is still limited to images with only 8 bits per channel.

• ImageMagick and its clone GraphicsMagick are general purpose command-line driven image manipulation programs, for example, convert, display,identify, and montage.

High Dynamic Range• OpenEXR offers libraries and some programs to work with the EXR HDR

format.

• PFSTools create, modify, and tonemap high-dynamic range images.

Libraries

• LibJPEG is a library for handling the JPEG (JFIF) image format.

• LibPNG is a library that handles the Portable Network Graphics (PNG)image format.

• LibTIFF offers a library and utility programs to manipulate the ubiquitousTagged Image File Format, TIFF.

The nifty tiffinfo command quickly inquires the properties of TIFF files.

Meta-Data Handling• EXIFTool reads and writes EXIF meta data. In particular it copies meta

data from one image to another.

Chapter 8: Helpful Additional Programs 33

• LittleCMS is the color management library used by Hugin, DCRaw,UFRaw, Enblend, and Enfuse. It supplies some binaries, too. tifficc,an ICC color profile applier, is of particular interest.

Appendix A: Bug Reports 34

Appendix A Bug ReportsMost of this appendix was taken from theOctave documentation.

Bug reports play an important role in making Enblend and Enfuse reliable and enjoyable.

When you encounter a problem, the first thing to do is to see if it is already known. Tothis end visit the package’s LaunchPad bug database. Search it for your particular problem.If it is not known, please report it.

In order for a bug report to serve its purpose, you must include the information thatmakes it possible to fix the bug.

A.1 Have You Really Found a Bug?

If you are not sure whether you have found a bug, here are some guidelines:

• If Enblend or Enfuse get a fatal signal, for any options or input images, that is a bug.

• If Enblend or Enfuse produce incorrect results, for any input whatever, that is a bug.

• If Enblend or Enfuse produce an error message for valid input, that is a bug.

• If Enblend or Enfuse do not produce an error message for invalid input, that is a bug.

A.2 How to Report Bugs

The fundamental principle of reporting bugs usefully is this: report all the facts. If you arenot sure whether to state a fact or leave it out, state it. Often people omit facts becausethey think they know what causes the problem and they conclude that some details do notmatter. Play it safe and give a specific, complete example.

Keep in mind that the purpose of a bug report is to enable someone to fix the bug if itis not known. Always write your bug reports on the assumption that the bug is not known.

Try to make your bug report self-contained. If we have to ask you for more information, itis best if you include all the previous information in your response, as well as the informationthat was missing.

To enable someone to investigate the bug, you should include all these things:

• The exact version and configuration of Enblend or Enfuse. You can get this by runningit with the options --version and --verbose.

• A complete set of input images that will reproduce the bug. Strive for a minimal setof small1 images.

• The type of machine you are using, and the operating system name and its versionnumber.

• A complete list of any modifications you have made to the source. Be precise aboutthese changes. Show a diff for them.

• Details of any other deviations from the standard procedure for installing Enblend andEnfuse.

• The exact command line you use to call Enblend or Enfuse, which then triggers thebug.

Examples:

1 Images of a size less than 1500x1000 pixels qualify as small.

Appendix A: Bug Reports 35

~/local/bin/enblend -v \

--fine-mask \

--optimizer-weights=3:2 --mask-vectorize=12.5% \

image-1.png image-2.png

or:

/local/bin/enfuse \

--verbose \

--exposure-weight=0 --saturation-weight=0 --entropy-weight=1 \

--gray-projector=l-star \

--entropy-cutoff=1.667% \

layer-01.ppm layer-02.ppm layer-03.ppm

If you call Enblend or Enfuse from within a GUI like, for example, Hugin orKImageFuser by Harry van der Wolf, copy&paste or write down the commandline that launches Enblend or Enfuse.

• A description of what behavior you observe that you believe is incorrect. For example,“The application gets a fatal signal,” or, “The output image contains black holes.”

Of course, if the bug is that the application gets a fatal signal, then one cannot missit. But if the bug is incorrect output, we might not notice unless it is glaringly wrong.

A.3 Sending Patches for Enblend or Enfuse

If you would like to write bug fixes or improvements for Enblend or Enfuse, that is veryhelpful. When you send your changes, please follow these guidelines to avoid causing extrawork for us in studying the patches. If you do not follow these guidelines, your informationmight still be useful, but using it will take extra work.

• Send an explanation with your changes of what problem they fix or what improvementthey bring about. For a bug fix, just include a copy of the bug report, and explain whythe change fixes the bug.

• Always include a proper bug report for the problem you think you have fixed. We needto convince ourselves that the change is right before installing it. Even if it is right, wemight have trouble judging it if we do not have a way to reproduce the problem.

• Include all the comments that are appropriate to help people reading the source in thefuture understand why this change was needed.

• Do not mix together changes made for different reasons. Send them individually.

If you make two changes for separate reasons, then we might not want to install themboth. We might want to install just one.

• Use the version control system to make your diffs. Prefer the unified diff format: hg

diff --unified 4.

• You can increase the probability that your patch gets applied by basing it on a recentrevision of the sources.

Appendix B: Authors 36

Appendix B Authors

Andrew Mihal (acmihal@users.sourceforge.net) has written Enblend and Enfuse.

Contributors

• Pablo d’Angelo (dangelo@users.sourceforge.net) added the contrast criteria.

• Joe Beda: Win32 porting up to version 3.2.

• Kornel Benko, kornelbenko@users.sourceforge.net: CMake support for ver-sion 4.0.

• Roger Goodman: Proofreading of the manuals.

• Max Lyons.

• Mark aka mjz: Win32 porting up to version 3.2.

• Thomas Modes, tmodes@users.sourceforge.net: Win32 porting of version 4.0.

• Ryan Sleevi, ryansleevi@users.sourceforge.net: Win32 porting of version 4.0.

• Christoph Spiel (cspiel@users.sourceforge.net) added the gray projectors, theLoG-based edge detection, an O(n)-algorithm for the calculation of local contrast, en-tropy weighting, and various other features.

• Brent Townshend, btownshend@users.sourceforge.net: HDR support.

Thanks to Simon Andriot and Pablo Joubert for suggesting theMertens-Kautz-VanReeth technique and the name “Enfuse”.

Appendix C: GNU Free Documentation License 37

Appendix C GNU Free Documentation License

Version 1.2, November 2002

Copyright c© 2000, 2001, 2002 Free Software Foundation, Inc.51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA

Everyone is permitted to copy and distribute verbatim copiesof this license document, but changing it is not allowed.

0. PREAMBLE

The purpose of this License is to make a manual, textbook, or other functional anduseful document free in the sense of freedom: to assure everyone the effective freedomto copy and redistribute it, with or without modifying it, either commercially or non-commercially. Secondarily, this License preserves for the author and publisher a wayto get credit for their work, while not being considered responsible for modificationsmade by others.

This License is a kind of “copyleft”, which means that derivative works of the documentmust themselves be free in the same sense. It complements the GNU General PublicLicense, which is a copyleft license designed for free software.

We have designed this License in order to use it for manuals for free software, becausefree software needs free documentation: a free program should come with manualsproviding the same freedoms that the software does. But this License is not limited tosoftware manuals; it can be used for any textual work, regardless of subject matter orwhether it is published as a printed book. We recommend this License principally forworks whose purpose is instruction or reference.

1. APPLICABILITY AND DEFINITIONS

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Appendix C: GNU Free Documentation License 38

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2. VERBATIM COPYING

You may copy and distribute the Document in any medium, either commercially ornoncommercially, provided that this License, the copyright notices, and the licensenotice saying this License applies to the Document are reproduced in all copies, and

Appendix C: GNU Free Documentation License 39

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If you publish or distribute Opaque copies of the Document numbering more than 100,you must either include a machine-readable Transparent copy along with each Opaquecopy, or state in or with each Opaque copy a computer-network location from whichthe general network-using public has access to download using public-standard networkprotocols a complete Transparent copy of the Document, free of added material. Ifyou use the latter option, you must take reasonably prudent steps, when you begindistribution of Opaque copies in quantity, to ensure that this Transparent copy willremain thus accessible at the stated location until at least one year after the last timeyou distribute an Opaque copy (directly or through your agents or retailers) of thatedition to the public.

It is requested, but not required, that you contact the authors of the Document wellbefore redistributing any large number of copies, to give them a chance to provide youwith an updated version of the Document.

4. MODIFICATIONS

You may copy and distribute a Modified Version of the Document under the conditionsof sections 2 and 3 above, provided that you release the Modified Version under preciselythis License, with the Modified Version filling the role of the Document, thus licensingdistribution and modification of the Modified Version to whoever possesses a copy ofit. In addition, you must do these things in the Modified Version:

A. Use in the Title Page (and on the covers, if any) a title distinct from that of theDocument, and from those of previous versions (which should, if there were any,be listed in the History section of the Document). You may use the same title asa previous version if the original publisher of that version gives permission.

Appendix C: GNU Free Documentation License 40

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If the Modified Version includes new front-matter sections or appendices that qualifyas Secondary Sections and contain no material copied from the Document, you may atyour option designate some or all of these sections as invariant. To do this, add theirtitles to the list of Invariant Sections in the Modified Version’s license notice. Thesetitles must be distinct from any other section titles.

Appendix C: GNU Free Documentation License 41

You may add a section Entitled “Endorsements”, provided it contains nothing butendorsements of your Modified Version by various parties—for example, statements ofpeer review or that the text has been approved by an organization as the authoritativedefinition of a standard.

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6. COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other documents releasedunder this License, and replace the individual copies of this License in the variousdocuments with a single copy that is included in the collection, provided that youfollow the rules of this License for verbatim copying of each of the documents in allother respects.

You may extract a single document from such a collection, and distribute it individu-ally under this License, provided you insert a copy of this License into the extracteddocument, and follow this License in all other respects regarding verbatim copying ofthat document.

7. AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other separate and independentdocuments or works, in or on a volume of a storage or distribution medium, is called

Appendix C: GNU Free Documentation License 42

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You may not copy, modify, sublicense, or distribute the Document except as expresslyprovided for under this License. Any other attempt to copy, modify, sublicense ordistribute the Document is void, and will automatically terminate your rights underthis License. However, parties who have received copies, or rights, from you under thisLicense will not have their licenses terminated so long as such parties remain in fullcompliance.

10. FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions of the GNU FreeDocumentation License from time to time. Such new versions will be similar in spiritto the present version, but may differ in detail to address new problems or concerns.See http://www.gnu.org/copyleft/.

Each version of the License is given a distinguishing version number. If the Documentspecifies that a particular numbered version of this License “or any later version”applies to it, you have the option of following the terms and conditions either of thatspecified version or of any later version that has been published (not as a draft) bythe Free Software Foundation. If the Document does not specify a version number ofthis License, you may choose any version ever published (not as a draft) by the FreeSoftware Foundation.

Program Index 43

Program Index

Aale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32align_image_stack (Hugin) . . . . . . . . . . . . . . . . . . . 32

Ccinepaint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16, 32convert (ImageMagick) . . . . . . . . . . . . . . . . . . . . . . . . 32

Ddcraw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 32display (ImageMagick) . . . . . . . . . . . . . . . . . . . . . . . . 32

Eexiftool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32exrdisplay (OpenEXR) . . . . . . . . . . . . . . . . . . . . . . . 32

Ffulla (Hugin) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Ggimp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 16, 32gm (GraphicsMagick) . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Hhugin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 2, 16, 32

Iidentify (ImageMagick) . . . . . . . . . . . . . . . . . . . 28, 32

Mmontage (ImageMagick) . . . . . . . . . . . . . . . . . . . . . . . . 32

Nnona (Hugin) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16, 32

PPanoTools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 2pfshdrcalibrate (PFScalibration) . . . . . . . . . . . . . 32pfsin (PFSTools) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32pfsout (PFSTools) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32pfstmo_* (PFStmo) . . . . . . . . . . . . . . . . . . . . . . . . . . . 32pfsview (PFSTools) . . . . . . . . . . . . . . . . . . . . . . . . . . . 32PTmender (PanoTools) . . . . . . . . . . . . . . . . . . . . . . . . . 32PTOptimizer (PanoTools) . . . . . . . . . . . . . . . . . . . . . . 32

Ttifficc (LittleCMS) . . . . . . . . . . . . . . . . . . . . . . . . . . 33tiffinfo (libtiff) . . . . . . . . . . . . . . . . . . . . . . . . . . 28, 32

Uufraw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2, 32ufraw-batch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Syntactic-Comment Index 44

Syntactic-Comment Index

Eenblend-response-file . . . . . . . . . . . . . . . . . . . . . . . . 7enfuse-response-file . . . . . . . . . . . . . . . . . . . . . . . . . 7

Ffilename-globbing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Gglob . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

globbing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Llayer-selector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Rresponse-file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Option Index 45

Option Index

--anneal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17--blend-colorspace . . . . . . . . . . . . . . . . . . . . . . . . . . 14--ciecam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14--coarse-mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17--compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10--depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14--dijkstra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18--fallback-profile . . . . . . . . . . . . . . . . . . . . . . . . . . 16--fine-mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18--gpu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16--help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11--image-difference . . . . . . . . . . . . . . . . . . . . . . . . . . 18--layer-selector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10--levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11--load-masks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19--mask-vectorize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19--no-ciecam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16--no-optimize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20--no-parameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12--optimize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20--optimizer-weights . . . . . . . . . . . . . . . . . . . . . . . . . 21--output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

--parameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12--primary-seam-generator . . . . . . . . . . . . . . . . . . . 21--save-masks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22--smooth-difference . . . . . . . . . . . . . . . . . . . . . . . . . 22--verbose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12--version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12--visualize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22--wrap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14, 30-c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-f . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-h . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16, 30-o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-v . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-w . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-x . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

General Index 46

General Index

#‘#’ (response file comment) . . . . . . . . . . . . . . . . . . . . . . 6

@‘@’ (response file prefix) . . . . . . . . . . . . . . . . . . . . . . . . . 5

3360◦ panoramas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Aa.tif . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12affine transformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3algorithms, globbing . . . . . . . . . . . . . . . . . . . . . . . . . . 8, 9alpha channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1, 3alpha channel, associated . . . . . . . . . . . . . . . . . . . . . . 16anneal parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17arithmetic JPEG compression . . . . . . . . . . . . . . . . . . 10authors, list of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Bbinary mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28bits per channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14blend colorspace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14blur difference image . . . . . . . . . . . . . . . . . . . . . . . . . . 22bug database, LaunchPad . . . . . . . . . . . . . . . . . . . . . . 34bug reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Burt-Adelson multiresolution spline . . . . . . . . . . . . . 1

Ccanvas size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16channel width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14channel, alpha . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1checkpoint results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13chrominance weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18CIECAM02 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14, 16, 27CIECAM02 colorspace . . . . . . . . . . . . . . . . . . . . . . . . . . 14coarse mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17color appearance model . . . . . . . . . . . . . . . . . 14, 16, 27color cube, RGB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27color profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27color space, sRGB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27colors, visualization image . . . . . . . . . . . . . . . . . . . . . 23colorspace, blend . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10compression, arithmetic JPEG . . . . . . . . . . . . . . . . . 10compression, deflate . . . . . . . . . . . . . . . . . . . . . . . . . . . 10compression, JPEG . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10compression, LZW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

compression, packbits . . . . . . . . . . . . . . . . . . . . . . . . . . 10conversion, raw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

DD50 white point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27default layer selection . . . . . . . . . . . . . . . . . . . . . . . . . . . 9default output filename . . . . . . . . . . . . . . . . . . . . . . . . 12deflate compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10delta-E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19difference image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Dijkstra radius . . . . . . . . . . . . . . . . . . . . . . . . . . . 18, 23double precision float, IEEE754 . . . . . . . . . . . . . . . . . 15

Ffallback profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16feathering, detrimental effect of . . . . . . . . . . . . . . . . . 1filename, literal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5fine mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18format of response file . . . . . . . . . . . . . . . . . . . . . . . . . . 6free documentation license (FDL) . . . . . . . . . . . . . . 37frozen seam-line endpoint . . . . . . . . . . . . . . . . . . . . . . 23

Ggeneral index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46generator, seam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21glob(7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9globbing algorithm ‘literal’ . . . . . . . . . . . . . . . . . 8, 9globbing algorithm ‘none’ . . . . . . . . . . . . . . . . . . . . . . . 9globbing algorithm ‘sh’ . . . . . . . . . . . . . . . . . . . . . . . . . 9globbing algorithm ‘shell’ . . . . . . . . . . . . . . . . . . . . . . 9globbing algorithm ‘wildcard’ . . . . . . . . . . . . . . . . 8, 9globbing algorithms . . . . . . . . . . . . . . . . . . . . . . . . . . 8, 9GNU free documentation license . . . . . . . . . . . . . . . 37GPU (Graphics Processing Unit) . . . . . . . . . . . . . . . 16grammar, response file . . . . . . . . . . . . . . . . . . . . . . . . . . 7grammar, syntactic comment . . . . . . . . . . . . . . . . . . . 8graph-cut (GC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21graphcut (GC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26graphcut, details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26graphcut, limitations . . . . . . . . . . . . . . . . . . . . . . . . . . 26graphics processing unit . . . . . . . . . . . . . . . . . . . . . . . 16

Hhalf precision float, OpenEXR . . . . . . . . . . . . . . . . . . 15helpful programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32hue-luminance maximum . . . . . . . . . . . . . . . . . . . . . . 19Hugin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

General Index 47

IICC profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14, 27IEEE754 double precision float . . . . . . . . . . . . . . . . . 15IEEE754 single precision float . . . . . . . . . . . . . . . . . . 15image cache . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30image cache, block size . . . . . . . . . . . . . . . . . . . . . . . . 14image cache, cache size . . . . . . . . . . . . . . . . . . . . . . . . 16image cache, location . . . . . . . . . . . . . . . . . . . . . . . . . . 30image colors, visualization . . . . . . . . . . . . . . . . . . . . . 23image difference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18image, multi-layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1image, visualization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23index, general . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46index, option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45index, program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43index, syntactic-comment . . . . . . . . . . . . . . . . . . . . . . 44input image requirements . . . . . . . . . . . . . . . . . . . . . . . 5input mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28invocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

JJPEG compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

KKImageFuser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

LLaunchPad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34LaunchPad, bug database . . . . . . . . . . . . . . . . . . . . . . 34layer selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10layer selection, all layers . . . . . . . . . . . . . . . . . . . . . . . 11layer selection, default . . . . . . . . . . . . . . . . . . . . . . . . . . 9layer selection, first layer . . . . . . . . . . . . . . . . . . . . . . . 11layer selection, largest-layer . . . . . . . . . . . . . . . . . . . . 11layer selection, no layer . . . . . . . . . . . . . . . . . . . . . . . . 11lens distortion, correction of . . . . . . . . . . . . . . . . . . . . 3levels, pyramid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11LibJPEG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32LibPNG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32LibTiff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32literal filename . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5load mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19loops in seam line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20luminance weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18luminance-hue maximum . . . . . . . . . . . . . . . . . . . . . . 19LZW compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Mmask template character, ‘%’ . . . . . . . . . . . . . . . . . . . 25mask template character, ‘b’ . . . . . . . . . . . . . . . . . . . 25mask template character, ‘B’ . . . . . . . . . . . . . . . . . . . 25mask template character, ‘d’ . . . . . . . . . . . . . . . . . . . 25mask template character, ‘D’ . . . . . . . . . . . . . . . . . . . 25

mask template character, ‘e’ . . . . . . . . . . . . . . . . . . . 25mask template character, ‘E’ . . . . . . . . . . . . . . . . . . . 25mask template character, ‘f’ . . . . . . . . . . . . . . . . . . . 25mask template character, ‘F’ . . . . . . . . . . . . . . . . . . . 25mask template character, ‘i’ . . . . . . . . . . . . . . . . . . . 25mask template character, ‘n’ . . . . . . . . . . . . . . . . . . . 25mask template character, ‘p’ . . . . . . . . . . . . . . . . . . . 25mask template character, ‘P’ . . . . . . . . . . . . . . . . . . . 25mask template characters, table of . . . . . . . . . . . . . 25mask, binary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28mask, coarse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17mask, fine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18mask, generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18mask, input files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28mask, load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19mask, optimization visualization . . . . . . . . . . . . . . . 22mask, save . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22mask, vectorization distance . . . . . . . . . . . . . . . . . . . 19mask, weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28, 29masks, understanding . . . . . . . . . . . . . . . . . . . . . . . . . . 28match quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19maximum hue-luminance . . . . . . . . . . . . . . . . . . . . . . 19memory, tuning usage of . . . . . . . . . . . . . . . . . . . . . . . 30multi-directory TIFF . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1multi-layer image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Nnearest feature transform (NFT) . . . . . . . . . . . . 21, 26nearest-feature transform (NFT) . . . . . . . . . . . . 18, 20nearest-feature transform (NFT), Graph-Cut (GC)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

OOctave . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34only save mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22OpenEXR, data format . . . . . . . . . . . . . . . . . . . . . . . . . 15OpenEXR, half precision float . . . . . . . . . . . . . . . . . . 15optimize seam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20optimize strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21optimize, anneal parameters . . . . . . . . . . . . . . . . . . . 17optimizer weights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21optimizer, simulated annealing . . . . . . . . . . . . . 16, 17option index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45options, common . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9options, extended . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14options, mask generation . . . . . . . . . . . . . . . . . . . . . . 17order, of processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5output file compression . . . . . . . . . . . . . . . . . . . . . . . . 10output filename, default . . . . . . . . . . . . . . . . . . . . . . . 12output image, set size of . . . . . . . . . . . . . . . . . . . . . . . 16overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Ppackbits compression . . . . . . . . . . . . . . . . . . . . . . . . . . 10parallax error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

General Index 48

perceptual rendering intent . . . . . . . . . . . . . . . . . . . . 27photometric alignment . . . . . . . . . . . . . . . . . . . . . . . . . . 3primary seam generator . . . . . . . . . . . . . . . . . . . . 21, 26problem reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34processing order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5profile, fallback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16profile, ICC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14, 27program index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43programs, helpful additional . . . . . . . . . . . . . . . . . . . 32pyramid levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Qquality, match . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Rradius, Dijkstra . . . . . . . . . . . . . . . . . . . . . . . . . . 18, 23raw conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3rendering intent, perceptual . . . . . . . . . . . . . . . . . . . . 27response file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5response file, comment (‘#’) . . . . . . . . . . . . . . . . . . . . . 6response file, force recognition of . . . . . . . . . . . . . . . . 7response file, format . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6response file, grammar . . . . . . . . . . . . . . . . . . . . . . . . . . 7response file, syntactic comment . . . . . . . . . . . . . . . . 8results, checkpoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13RGB color cube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27RGB-cube . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Ssave mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22save mask, only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22seam generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26seam generation, details . . . . . . . . . . . . . . . . . . . . . . . 26seam line, loops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20seam optimization . . . . . . . . . . . . . . . . . . . . . . . . . 20, 21seam, primary generator . . . . . . . . . . . . . . . . . . . . . . . 21seam-line endpoint, frozen . . . . . . . . . . . . . . . . . . . . . 23seam-line visualization example . . . . . . . . . . . . . . . . 23simulated annealing optimizer . . . . . . . . . . . . . . 16, 17single precision float, IEEE754 . . . . . . . . . . . . . . . . . . 15

size, canvas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16smooth difference image . . . . . . . . . . . . . . . . . . . . . . . 22SourceForge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1sRGB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14sRGB color space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27syntactic comment, grammar . . . . . . . . . . . . . . . . . . . 8syntactic comment, response file . . . . . . . . . . . . . . . . 8syntactic-comment index . . . . . . . . . . . . . . . . . . . . . . . 44

TTIFF, multi-directory . . . . . . . . . . . . . . . . . . . . . . . . . . . 1tiffcopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1tiffsplit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1TMPDIR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30transformation, affine . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Uunderstanding masks . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Vvirtual reality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13visualization example . . . . . . . . . . . . . . . . . . . . . . . . . . 23visualization image . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23visualization image colors . . . . . . . . . . . . . . . . . . . . . . 23visualization of mask . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Wweight mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28, 29weight, chrominance . . . . . . . . . . . . . . . . . . . . . . . . . . . 18weight, luminance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18weights, optimizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21white point, D50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2workflow with Enblend . . . . . . . . . . . . . . . . . . . . . . . . . . 2workflow with Enfuse . . . . . . . . . . . . . . . . . . . . . . . . . . . 2workflow, external mask manipulation . . . . . . . . . . . 3workflow, external masks . . . . . . . . . . . . . . . . . . . . . . . 4workflow, standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2wrap around . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12