opencv使用 findContours

http://www.jb51.net/article/132217.htm

https://www.jianshu.com/p/4bc3349b4611

https://blog.csdn.net/sunny2038/article/details/12889059使用这个代码就可以直接使用

https://blog.csdn.net/sunny2038/article/details/12889059

https://docs.opencv.org/2.4/modules/imgproc/doc/structural_analysis_and_shape_descriptors.html?highlight=findcontours#findcontours

这两个是讲解的博客

输入给ｏｐｅｎｃｖ的是灰度图，并且是一个经过处理的二值化的灰度图，EXTERNAL这种ｍｏｄｅ更适合我想要的得到外部轮廓

ｏｐｅｎｃｖ的ｔｈｒｅｓｈｏｌｄ函数是阈值处理函数，返回的第二个参数就是处理后的图像，１２７就是阈值

https://blog.csdn.net/on2way/article/details/46812121

https://blog.csdn.net/guduruyu/article/details/68059450

代码：

import cv2  

img = cv2.imread('/home/sensetime/edgeBoxes-Cpp-version/output/img/000021_10.png')
gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
ret, binary = cv2.threshold(gray,127,255,cv2.THRESH_BINARY)
contours, hierarchy = cv2.findContours(binary,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE)
print len(contours)
cv2.drawContours(img,contours,-1,(0,0,255),3)
cv2.imwrite("EXTERNAL.png",img)
cv2.imshow("img", img)
cv2.waitKey(0)