How to set ROI in OpenCV?

Question

I have two images, the first one smaller than the other. I need to copy the second image on the first image. To do so, I need to set the ROI on the first one, copy the secon

Answer 1

This is the code I used. I think the comments explain it.

/* ROI by creating mask for the parallelogram */
Mat mask = cvCreateMat(480, 640, CV_8UC1);
// Create black image with the same size as the original
for(int i=0; i(Point(i,j)) = 0;

// Create Polygon from vertices
vector approxedRectangle;
approxPolyDP(rectangleVertices, approxedRectangle, 1.0, true);

// Fill polygon white
fillConvexPoly(mask, &approxedRectangle[0], approxedRectangle.size(), 255, 8, 0);                 

// Create new image for result storage
Mat imageDest = cvCreateMat(480, 640, CV_8UC3);

// Cut out ROI and store it in imageDest
image->copyTo(imageDest, mask);

I also wrote about this and put some pictures here.