ucf computer vision reu 2012 week 1 presentation
DESCRIPTION
UCF Computer Vision REU 2012 Week 1 Presentation. Paul Finkel 5/21/12. Accomplishments. Working version of the Lucas Kanade optical flow algorithm S emi-working version of the Lucas Kanade optical flow algorithm with pyramids - PowerPoint PPT PresentationTRANSCRIPT
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UCF Computer Vision REU 2012Week 1 Presentation
Paul Finkel5/21/12
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Accomplishments
• Working version of the Lucas Kanade optical flow algorithm
• Semi-working version of the Lucas Kanade optical flow algorithm with pyramids
• Algorithm to obtain 128-dimensional SIFT descriptor from 18x18 patch of image
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Lucas Kanade Optical Flow Difficulties
• Understanding that you didn’t have to loop through the images to calculate fx, fy, or ft, but you did have to loop through every 3x3 grid of pixels to calculate 1 u and 1 v value.
• Quiver flips the image over the horizontal axis• Making the A matrix correctly– Had to transpose before flattening
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Original Image 1
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Original Image 2
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Quiver Representation
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flowToColor Representation
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Optical Flow w/ Pyramids Difficulties
• Doesn’t quite work– Low resolution > medium resolution > high
resolution• Obtaining ft– Can’t make entire ft matrix in one go because each
value of ft is dependent on the position in the image and the lower level of resolution’s u and v values
• Expanding u and v matrices, as well as images
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Optical Flow w/ Pyramids Difficulties (cont’d)
• Dealing with non-integer indices– Decided to round indices– Could have also used bilinear interpolation
• Dealing with out of bounds indices due to larger u and v values, either positive or negative
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Low Resolution of Pyramids
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Medium Resolution of Pyramids
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High Resolution of Pyramids
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SIFT Difficulties
• Rotational invariance– Had to add modular arithmetic– Sift descriptor isn’t exactly the same with different
orientation angles, but most of them are the same, just shifted
– All of them should be the same– Slight differences in bin magnitudes
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SIFT, orientation angle = 0>> desc(1:8,:)
ans =
0.3743 2.0477 22.9537 0.1946 0 0 5.8930 0.7933
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SIFT, orientation angle = 2*pi>> desc(1:8,:)
ans =
0.3743 2.0477 22.9537 0.1946 0 0 5.8930 0.7933
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SIFT, orientation angle = pi/4>> desc(1:8,:)
ans =
2.0477 22.9537 0.1946 0 0 5.8930 0.7933 0.3077
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SIFT, orientation angle = pi/4+2*pi>> desc(1:8,:)
ans =
2.0477 22.9537 0.1946 0 0 5.8930 0.7933 0.3077
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SIFT, orientation angle = pi/4+4*pi>> desc(1:8,:)
ans =
2.0477 22.9537 0.1946 0 0 5.8930 0.7933 0.3077