图像凸性检测函数convexityDefects在Python2.7下使用opencv3.0的问题

红色石头

发布于 2017-12-28 16:11:57

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发布于 2017-12-28 16:11:57

最近在学习Python下的OpenCV，在图像的凸性检测中，发现opencv3.0下的convexityDefects函数对图像的凸性缺陷处理有错误。不知道是opencv3.0的版本问题还是我个人的错误代码。

例如使用的Python版本是2.7.6，使用的OpenCV版本是3.0，以下是图像凸性检测代码：

 import cv2
 import numpy as np
 
 img = cv2.imread('star2.png')
 img_gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
 ret,thresh = cv2.threshold(img_gray,127,255,0)
 img_c,contours,hierarchy = cv2.findContours(thresh,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)
 cnt = contours[0]
 
 hull = cv2.convexHull(cnt,returnPoints = False)
 defects = cv2.convexityDefects(cnt,hull)
 
 for i in range(defects.shape[0]):
 s,e,f,d = defects[i,0]
 start = tuple(cnt[s][0])
 end = tuple(cnt[e][0])
 far = tuple(cnt[f][0])
 print start,end,far,d
 cv2.line(img,start,end,[0,255,0],2)
 cv2.circle(img,far,5,[0,0,255],-1)
 
 
 cv2.imshow('img',img)
 cv2.waitKey(0)
 cv2.destroyAllWindows()

结果显示，某处缺陷最大值定位错误，如图：

而如果使用OpenCV2.4.13版本，以下是图像凸性检测代码：

 import cv2
 import numpy as np
 
 img = cv2.imread('star2.png')
 img_gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
 ret,thresh = cv2.threshold(img_gray,127,255,0)
 contours,hierarchy = cv2.findContours(thresh,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)
 cnt = contours[0]
 
 hull = cv2.convexHull(cnt,returnPoints = False)
 defects = cv2.convexityDefects(cnt,hull)
 
 for i in range(defects.shape[0]):
 s,e,f,d = defects[i,0]
 start = tuple(cnt[s][0])
 end = tuple(cnt[e][0])
 far = tuple(cnt[f][0])
 print start,end,far,d
 cv2.line(img,start,end,[0,255,0],2)
 cv2.circle(img,far,5,[0,0,255],-1)
 
 
 cv2.imshow('img',img)
 cv2.waitKey(0)
 cv2.destroyAllWindows()

结果显示，图像的凸性检测是正确的，如图所示：