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Multiview Imaging HW Overview

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Multiview Imaging HW Overview

  1. 1. Homework on multiview computer vision Victor Lempitsky (Skoltech) for the “Computational Camera” class “A taster of multiview computer vision”
  2. 2. Video example “A taster of multiview computer vision”
  3. 3. Pipeline 1. 2. 3. 4. 5. 6. Take photographs Detect/describe features Match features Estimate homography Generate a sequence of blended frames Write a video “A taster of multiview computer vision”
  4. 4. Take photographs 1. Take a sequence that will blend nicely 2. Remember that the algorithm will find the dominant matching plane 3. Downsample to 1-2Mpix “A taster of multiview computer vision”
  5. 5. Feature Detection/Description Detecting features: FeatureDetector::create (SIFT) FeatureDetector::detect Describing features: DescriptorDetector::create (SIFT) DescriptorExtractor::compute “A taster of multiview computer vision”
  6. 6. Reminder => Feature vector (128D) “A taster of multiview computer vision”
  7. 7. Matching features 1. DescriptorMatcher::knnMatch(k=2) 2. Take only matches, where the distance to the first neighbor is less then e.g. 0.7*distance to the second neighbor 3. (Do matching the opposite way and keep only reciprocal matches) 4. Use “drawMatches” to debug 5. Use FlannBasedMatcher if too slow “A taster of multiview computer vision”
  8. 8. Matching results “A taster of multiview computer vision”
  9. 9. Estimating homography • You need findHomography (calib3d module) • Use CV_RANSAC option • Play with ‘reprojThreshold’ • Apply the estimated homography to the candidate matches and store the verified matches for later • Use to Mat::inv() to find the reverse mapping “A taster of multiview computer vision”
  10. 10. Reminder how to apply homography “A taster of multiview computer vision”
  11. 11. Image blending 1. Use warpPerspective() to map images 2. Use image arithmetics (‘+’,’*’) to blend 3. Define intermediate frames (e.g. by moving the verified matches along the trajectories and refitting homographies without RANSAC) 4. Use VideoWriter (highgui) to do the video writing “A taster of multiview computer vision”

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