CvBOX2D Processing

I've already got my ROI(CvBOX2D type) by series of contour processing, now I just want to focus on the image part within the ROI, e.g.: feed this part into another processing function, how can I do that? I know there is CvSetImageROI, but the type is CvRect, so I should convert CvBox2D t开发者_运维百科o CvRect first? Or some way to apply a mask on it with the area outside the box set to 0?

Thanks in advance!

Only axis aligned ROIs are directly supported in OpenCV (CvRect or IplROI). This is because they allow direct access to the image memory buffer.

There are 2 ways to go about working on a non-axis aligned ROI in OpenCV. Neither of them is as efficient as using axis-aligned ROIs.

1. Rotate your image, or bounding box, so that your ROI is now axis aligned in the resulting rotated image.
   Note: the rotation will slightly blur your image.

2. Use a mask: Draw your ROI as a white rectangle on a black BG the same size as the image, and give your processing functions this mask as the additional parameter.
   Note: not all functions support masks.

I would recommend option 1 if you really must stay within the exact bounds of your ROI. Otherwise, just use the bounding rect.

Use c++ api of opencv. seriously. do it.

cv::Rect roi = cv::RotatedRect(box).boundingRect();
Mat_<type> working_area(original_mat, roi);
// now operate on working_area

Note: this will operate on the bounding rect. I didn't find information on how to create a mask out of rotatedrect. Probably you have to do it by hand in a scanline fashion.