I’m having troubles with rotation. What I want to do is this:
- Rotate an image
- Detect features on the rotated image (points)
- Rotate back the points so I can have the points coordinates corresponding to the initial image
I’m a bit stuck on the third step.
I manage to rotated the image with the following code:
cv::Mat M(2, 3, CV_32FC1);
cv::Point2f center((float)dst_img.rows / 2.0f, (float)dst_img.cols / 2.0f);
M = cv::getRotationMatrix2D(center, rotateAngle, 1.0);
cv::warpAffine(dst_img, rotated, M, cv::Size(rotated.cols, rotated.rows));
I try to rotate back the points with this code:
float xp = r.x * std::cos( PI * (-rotateAngle) / 180 ) - r.y * sin(PI * (rotateAngle) / 180);
float yp = r.x * sin(PI * (-rotateAngle) / 180) + r.y * cos(PI * (rotateAngle) / 180);
It is not to fare to be working but the points don’t go back well on the image. There is an offset.
Thank you for your help