How to store all the pixels within a RotatedRect to another matrix?

Question

I am going to process a region of pixels defined by RotatedRect in OpenCV. Although I know the rectangle center, size, and angle, I am not sure how to store all the x and y of t

Answer 1

Implementation with OpenCV warpAffine.

Mat getAffineTransformForRotatedRect(RotatedRect rr) {
    float angle = rr.angle * M_PI / 180.0;
    // angle += M_PI; // you may want rotate it upsidedown
    float sinA = sin(angle), cosA = cos(angle);
    float data[6] = {
         cosA, sinA, rr.size.width/2.0f - cosA * rr.center.x - sinA * rr.center.y,
        -sinA, cosA, rr.size.height/2.0f - cosA * rr.center.y + sinA * rr.center.x};
    Mat rot_mat(2, 3, CV_32FC1, data);
    return rot_mat.clone();
}

Mat getRotatedRectImg(const cv::Mat &mat, RotatedRect rr) {
    Mat M, result;
    M = getAffineTransformForRotatedRect(rr);

    warpAffine(mat, result, M, rr.size, INTER_CUBIC);

    return result;
}