1 rectangle( rook_image,
2 Point( 0, 7*w/8.0 ),
3 Point( w, w),
4 Scalar( 0, 255, 255 ),
5 -1,
6 8 );
1 Rect in = boundingRect(InputArray points);
返回值in是点集最小外矩形左定点坐标和矩形的长宽；
int a = in.height;//矩形的宽
int b=in.width;//表示矩形的宽
原文：https://www.cnblogs.com/hsy1941/p/9003978.html