a fast local descriptor for dense matching engin tola, vincent lepetit, pascal fua computer vision...
TRANSCRIPT
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1
A Fast Local Descriptor for Dense Matching
Engin Tola, Vincent Lepetit, Pascal FuaComputer Vision Laboratory, EPFL
Reporter: Jheng-You Lin
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• Introduction• DAISY Computation• Results• Conclusion
Outline
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• Wide-base line matching propose : SIFT、 GLOH、 SURF… (histogram based descriptor)– Good performance and robustness to image
transformations.– High computational cost and sensitivity to occlusions.
• Purpose– Design a descriptor that is as robust as SIFT or GLOH but
can be computed much more effectively and handle occlusions.
Introduction
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• Novelty– introduces DAISY local image descriptor
Introduction (cont.)
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• Novelty– introduces DAISY local image descriptor
Introduction (cont.)
* S. Winder and M. Brown. Learning Local Image Descriptors in CVPR’07
Improved performance : + Precise localization+ Rotational Robustness
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• Novelty– introduces DAISY local image descriptor
Introduction (cont.)
Replacing weighted sums by convolutions
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DAISY Computation
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DAISY Computation
First compute gradient magnitude layers in different orientations
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DAISY ComputationThen, apply convolution with a Gaussian kernel to pre-compute the histograms for every point
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DAISY Computation
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DAISY Computation
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DAISY Computation
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DAISY Computation
The computation mostly involves 1D convolutions, which is fast.
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DAISY Computation
Rotating the descriptor only involves reordering the histograms.
…
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DAISY Computation
Rotating the descriptor only involves reordering the histograms.
…
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DAISY Computation
Computation Time Comparison(in seconds)
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DAISY Computation
The full DAISY descriptor D(u, v) :
The descriptor of the same point that is close to an occlusion would be very different.
Normalize to unit norm
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Results
Laser scan DAISY SIFT
SURF Pixel DifferenceNCC
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Results
baseline increaseblock
Error threshold :
Top : 10%Middle : 5%Bottom : 1%
DAISY SIFT SURF
NCC
SURF Pixel Difference
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Results
Using low-resolution of the Brussels images[24]
768x510 (2048x1360 origin)
[24] Combined Depth and Outlier Estimation in Multi-View Stereo, CVPR’06
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Results
Using low-resolution of the Rathaus images[25]
768x512 (3072x2048 origin)
The holes are caused by the fact that a lot of the texture is not visible.
[25] Dense Matching of Multiple Wide-Baseline Views, ICCV’03
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ResultsInput images Virtual view Synthesized
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ResultsVirtual view Synthesized DAISY NCC
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• Efficient descriptor and produces good reconstructions.
• Can handle low quality imagery
Conclusion