Dealing with pixels in contours (OpenCV)?

Question

I have retrieved a contour from an image and want to specifically work on the pixels in the contour. I need to find the sum (not area) of the pixel values in the contour. Op

Answer 1

If I understand right you want to sum all the pixel intensities from a gray image that are inside a contour. If so, the method that i think of is to draw that contour on a blank image and fill it , in so making yourself a mask. After that to optimize the process you can also compute the bounding rect of the contour with :

CvRect cvBoundingRect(CvArr* points, int update=0 );

After this you can make an intermediate image with :

void cvAddS(const CvArr* src, CvScalar value, CvArr* dst, const CvArr* mask=NULL);

using the value 0, the mask obtained from the contour and setting before as ROI the bounding rect.

After this, a sum on the resulting image will be a little faster.