display keypoints from opencv on iphone ios 4

Hey

I'm trying to implement feature detector algorithms in iphon开发者_如何学Pythone (surf and sift). I already manage to collect raw video stream which I proccess with OpenCV. The problem is that my function returns keypoint values (x,y) which I want to draw on screen. Now my question is how to draw them on top of AVCaptureVideoPreviewLayer?

I've done this for FAST Corner, and LK Optical Flow. You can find source code here: http://www.hatzlaha.co.il/150842/FAST%2DCorner%2DV2 http://www.hatzlaha.co.il/150842/Lucas%2DKanade%2DDetection%2Dfor%2Dthe%2DiPhone

Originally I was using UIView graphics to place the points. Like drawLine and stuff... But then I switched to OpenGL which is much more suiting, and proved much faster.

Notice that you have to do the math of converting coordinates in the frame, to the screen coordinates.

HTH, Oded.