Object Based Image Analysis Tools for Opticks
Mohit Kumar, KS Rajan, Dustan Adkins
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OSGEO-India: FOSS4G 2012- First National Conference "Open Source Geospatial Resources to Spearhead Development and Growth” 25-27th October 2012, @ IIIT Hyderabad
Why object-based?
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• Opticks is an open source, remote sensing application that supports imagery, video (motion imagery), Synthetic Aperture Radar (SAR), multi-spectral, hyper-spectral, and other types of remote sensing data.
• Opticks can also be used as a remote sensing software development framework. Developers can extend Opticks functionality using its plug-in architecture and public application programming interface
• http://opticks.org
• Object based approach is better than conventional per-pixel analysis as it deals with considerably reduced number of units. This approach is not that much sensitive to noise and hence is spatially consistent.
OPTICKS ?
Workflow
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Input image(RGB)
Input image (CIELAB colour
space)
5 Dimensional feature space
Modes(local maximas) Clustering
Objects formed (backtracking the
modes)
Points in feature space collapsing
to one mode form an object.
Pruning (spatial Bandwidth)
Pruning (Spectral Bandwidth)
Pruning ( Minimum region area)
Image Segmentation (Meanshift)
Object attribution• Calculating textural, geometric and spectral features for the objects
made in the Segmentation step in a feature vector. • Area, Perimeter, Roundness, Compactness, Centroid, Contrast,
Coarseness, Direction, Roughness, Mean red, Mean green, Mean blue, std. deviation Red, std. deviation Green, std. deviation Blue.
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Segmented Image For every object in the image
Initialize a vector having all 16 features
Calculate value for every feature and save in the vector.
Classification• Mahalanobis Distance• Di,j
2 = (x-µj)`S-1(x-µj)• The class which has the least Mahalanobis
distance to the object i is the class of that object.
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Vectorization• Creates vector polygons for all connected regions of pixels in the
object image sharing a common pixel value.• Polygon features are created on the output layer, with polygon
geometries representing the polygons.• The class which has the least Mahalanobis distance to the object i is
the class of that object.
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The Input Orbview3 (4m) data of a part of delhi (500X500) The output of the objects with area less than 100.
Output of object having area 100-200 and classified as building. The shapefile(.shp) displaying the objects
Image Size Number of objects
Running time (sec)
512 X 512 153 3.1
1024 X 1024 435 24.55
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Image Size Number of objects Running time (sec)
256 X 256 49 0.249
512 X 512 193 1.133
1024 X1024 752 5.359
2048 X 2048 2965 31.60
4096 X 4096 11922 286.59
Performance AnalysisPerformance Analysis
Table 1 : Image segmentation
Table 2 : Object Attribution
Source Code
• https://github.com/mohitkharb/Opticks_GSOC2012
• http://opticks.org/confluence/display/~mohitkharb/Workflow+of+the+pluggin
• http://code.google.com/soc/
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Any Questions?
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