Fastest available algorithm for distance transform

This paper reviews the known exact distance transform algorithms: “2D Euclidean distance transform algorithms: A comparative survey” The fastest exact distance transform is from Meijster: “A General Algorithm for Computing Distance Transforms in Linear Time.” The design of the algorithm is particularly well suited for parallel calculation. This is implemented in my open … Read more

Rotate bitmap by real angle

tl;dr; Use GDI+ SetWorldTransform With WinAPI’s SetWorldTransform you can transform the space of device context: rotate, shear, offset, and scale. This is done by setting the members of a transform matrix of type XFORM. Fill its members according the documentation. procedure RotateBitmap(Bmp: TBitmap; Rads: Single; AdjustSize: Boolean; BkColor: TColor = clNone); var C: Single; S: … Read more

Using hierarchy in findContours () in OpenCV?

The hierarchy returned by findContours has the following form: hierarchy[idx][{0,1,2,3}]={next contour (same level), previous contour (same level), child contour, parent contour} CV_RETR_CCOMP, returns a hierarchy of outer contours and holes. This means elements 2 and 3 of hierarchy[idx] have at most one of these not equal to -1: that is, each element has either no … Read more

Video Stabilization with OpenCV

I can suggest one of the following solutions: Using local high level features: OpenCV includes SURF, so: for each frame, extract SURF features. Then build feature Kd-Tree (also in OpenCV), then match each two consecutive frames to find pairs of corresponding features. Feed those pairs into cvFindHomography to compute the homography between those frames. Warp … Read more

OpenCV / SURF How to generate a image hash / fingerprint / signature out of the descriptors?

The feature data you mention (position, laplacian, size, orientation, hessian) is insufficient for your purpose (these are actually the less relevant parts of the descriptor if you want to do matching). The data you want to look at are the “descriptors” (the 4th argument): void cvExtractSURF(const CvArr* image, const CvArr* mask, CvSeq** keypoints, CvSeq** descriptors, … Read more