opencv数学运算,图像加减乘除https://blog.csdn.net/u011028345/article/details/77278467
findcontours
CV_RETR_EXTERNAL
retrieves only the extreme outer contours. It sets hierarchy[i][2]=hierarchy[i][3]=-1 for all the contours.CV_RETR_LIST
retrieves all of the contours without establishing any hierarchical relationships.CV_RETR_CCOMP
retrieves all of the contours and organizes them into a two-level hierarchy. At the top level, there are external boundaries of the components. At the second level, there are boundaries of the holes. If there is another contour inside a hole of a connected component, it is still put at the top level.CV_RETR_TREE
retrieves all of the contours and reconstructs a full hierarchy of nested contours. This full hierarchy is built and shown in the OpenCV contours.c demo.What is the retrieval method RETR_FLOODFILL?- connected components of a multi-level image