Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages....

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Image Warping

Transcript of Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages....

Page 1: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

ImageWarping

Page 2: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

ImageMapping

Page 3: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

ImageMapping- Examples

Page 4: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

ForwardMapping

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ForwardMapping- Disadvantages

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Example– ForwardMappingOriginal Rotated

ZoomIn

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BackwardMapping

𝑓"#

TheProblem:(u,v)arenotintegers!

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NearestNeighbor

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Example- NearestNeighborOriginal Rotated

ZoomIn

Page 13: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Bi-linearInterpolation• Bi-linearinterpolatesfourclosestpixels.• Theweightforeachpixelisproportionaltoitsdistancefromthesamplingpoint(x,y)

Page 14: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Bi-linearInterpolation

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Bi-linearInterpolation

Page 16: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Bi-linearInterpolation

Page 17: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Bi-linearInterpolation

Page 18: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

ExampleBi-linearOriginal Rotated

ZoomIn

Page 19: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Bi-cubic

(u,v)

• Bicubic interpolates16closestneighbors(4x4neighborhood)• Theresultismuchmoresmooth

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Bi-cubicInterpolation

Page 21: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Bi-cubicInterpolation

Page 22: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Bi-cubicInterpolation

Page 23: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

ExampleBi-cubicOriginal Rotated

ZoomIn

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NearestNeighbor

Page 25: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Bi-LinearInterpolation

Page 26: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Bi-CubicInterpolation

Page 27: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

ComparisonNearestNeighbor Bi-linear Bi-cubic

Page 28: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

DirectRotation

Page 29: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Shear

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Shear

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ShearandScaleOperatinglinebyline,fasterandsimplerfilters

Page 32: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Shear

÷÷ø

öççè

æ=÷÷

ø

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æyx

Avu

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æ=÷÷

ø

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æ=÷÷

ø

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æ=÷÷

ø

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æyx

Tyx

ABvu

Bsr

÷÷ø

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æ+

=÷÷ø

öççè

æ=÷÷

ø

öççè

æaaaa

cosysinx siny -cosx

yx

Tsr

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Shear

÷÷ø

öççè

æ=÷÷

ø

öççè

æ=÷÷

ø

öççè

æy)f(x,x

yx

Avu

Apreservecolumns

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æ=÷÷

ø

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æ=÷÷

ø

öççè

ævv)g(u,

vu

Bsr

Bpreserverows

Page 34: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Shear

÷÷ø

öççè

æ=÷÷

ø

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æ=÷÷

ø

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æ÷÷ø

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æ=÷÷

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æ=÷÷

ø

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æy)f(x,y))f(x,g(x,

y)f(x,x

Byx

ABvu

Bsr

Wegetaa cosy sinx sy)f(x, +==

÷÷ø

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æ+

=÷÷ø

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æ=÷÷

ø

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æaaaa

cosysinx siny -cosx

yx

Tsr

aa siny cosx v)g(u, -=

Page 35: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Shear

Weneedtoexpressitintermsofu,vWeknowthatx=u,and

aa cosy sinx y)f(x,v +==

aa siny cosx v)g(u, -=

Weget

aa

aa

cossinu -v

cossinx -vy ==

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Shear

aaaaaa tanvsecu sin

cossinu -v-cosu v)g(u, -==

Weputitalltogetherandget

Page 37: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Shear

Atlastweget

÷÷ø

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æ+

=÷÷ø

öççè

æaa cosy sinx

xyx

A

÷÷ø

öççè

æ -=÷÷

ø

öççè

æv

tanvsecu vu

Baa

Page 38: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Shear

Usingalargeangle(80degree)

Page 39: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Shear

Page 40: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Shear

Page 41: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Shear

SecondpasswithBackwardMapping

Page 42: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Shear

• Rotatein90degree,thenuseshearwithasmallangle

• Westillhaveascalefactorintheshearwhichcreateholes;onesolutionistousefilter

Page 43: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Shear

÷÷ø

öççè

æ -÷÷ø

öççè

æ÷÷ø

öççè

æ -=÷÷

ø

öççè

æ -10

2/tan11sin01

102/tan1

cossinsincos a

aa

aaaa

Theothersolutionisbyusingthreesheartransformations

WeneedThreepassesinsteadofTwo.Butnoscale!Justshiftlines!

Page 44: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Shear

Twofirstshears

Page 45: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Shear

Page 46: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Shear

Page 47: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Shear

Page 48: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Shear

Page 49: Image Warping - TAUdcor/Graphics/pdf.slides/... · 2017. 4. 24. · Forward Mapping -Disadvantages. Example –Forward Mapping Original Rotated Zoom In. Backward Mapping!"# The Problem:

Shear