OPenCV perspective transformation and Region of Interest

f41ardu

I start to play with OpenCV using Greg Borensteins Processing implementation. I've implemented a PVImage to MAT class to access OpenCV methods direct. Now I'm looking into perspective transformation and Region of Interest but have no success so far. Any hints are welcome.

f41ardu

Region of Interest seems to be very easy.

Rect ROI = new Rect(1280/2-300,300,500,300); Mat roiImg = new Mat(mask_yw_image, ROI);

But results like Hughlines have to be transferred back.

Core.line(img_BGR, new Point(val[0]+1280/2-300, val[1]+300), new Point(val[2]+1280/2-300, val[3]+300), new Scalar(255, 0, 0), 5);

f41ardu

And PerspectiveTransformation is slightly more difficult. It seems to be more difficult to define correct input and outputQuads.

f41ardu

Indeed , at least it is very simple.

// -------
 MatOfPoint2f srcMat = new MatOfPoint2f(new Point(0, 0), // Top-left corner 
    new Point(img.width-1, 0),                            // Top-right corner
    new Point(img.width-1, img.height-1),                 // Bottom-reight corner
    new Point(0,img.height-1));                           // Pottom-left corner

  MatOfPoint2f dstMat = new MatOfPoint2f(new Point(150, 300), 
    new Point(img.width-150, 300), 
    new Point(img.width-1, img.height-1),
    new Point(0, img.height-1));

  Mat affine = Imgproc.getPerspectiveTransform(srcMat, dstMat); 
  Mat in = cv.getBGR(); 
  Mat out = new Mat(in.size(), in.type()); 
  Mat outnew = new Mat(in.size(), in.type()); 
  Imgproc.warpPerspective(in, out, affine, out.size()); 
  Mat affineback = Imgproc.getPerspectiveTransform(dstMat, srcMat);
  Imgproc.warpPerspective(out, outnew, affineback, outnew.size());
 // --------