我正在使用像这样的时刻获取轮廓的质心:
cnt = np.vstack([cnt[0]]).squeeze()
M = cv2.moments(cnt)
cx = int(M['m10']/M['m00'])
cy = int(M['m01']/M['m00'])
我想把轮廓分成4个象限,这样就需要画两条线,一纵一横,都穿过得到的质心。我该怎么做?
最佳答案
虽然这看起来像是 OpenCV 的任务,但您可能想看看 Shapely 包:
http://toblerity.org/shapely/manual.html
Shapely 允许您计算多边形之间的交点,因此解决方案变得非常简单:对于穿过等高线质心的水平线和垂直线,您只需计算与等高线的交点并在这些交点处画线.
由于缺少您的原始图形,我使用了一个椭圆来演示解决方案。既然你说你的轮廓只有一些样本点,我使用了一个“粗”椭圆,它只是近似于几个点。
输出看起来像这样,希望这是你要找的:
由于所有的可视化,源代码很长,但希望不言自明:
import shapely.geometry as shapgeo
import numpy as np
import cv2
def make_image():
img = np.zeros((500, 500), np.uint8)
white = 255
cv2.ellipse( img, (250, 300), (100,70), 30, 0, 360, white, -1 )
return img
if __name__ == '__main__':
img = make_image()
#Create a "coarse" ellipse
_, contours0, hierarchy = cv2.findContours( img.copy(), cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
contours = [cv2.approxPolyDP(cnt, 3, True) for cnt in contours0]
h, w = img.shape[:2]
vis = np.zeros((h, w, 3), np.uint8)
cv2.drawContours( vis, contours, -1, (128,255,255), 1)
#Extract contour of ellipse
cnt = np.vstack([contours[0]]).squeeze()
#Determine centroid
M = cv2.moments(cnt)
cx = int(M['m10']/M['m00'])
cy = int(M['m01']/M['m00'])
print cx, cy
#Draw full segment lines
cv2.line(vis,(cx,0),(cx,w),(150,0,0),1)
cv2.line(vis,(0,cy),(h,cy),(150,0,0),1)
# Calculate intersections using Shapely
# http://toblerity.org/shapely/manual.html
PolygonEllipse= shapgeo.asLineString(cnt)
PolygonVerticalLine=shapgeo.LineString([(cx,0),(cx,w)])
PolygonHorizontalLine=shapgeo.LineString([(0,cy),(h,cy)])
insecv= np.array(PolygonEllipse.intersection(PolygonVerticalLine)).astype(np.int)
insech= np.array(PolygonEllipse.intersection(PolygonHorizontalLine)).astype(np.int)
cv2.line(vis,(insecv[0,0], insecv[0,1]),(insecv[1,0], insecv[1,1]),(0,255,0),2)
cv2.line(vis,(insech[0,0], insech[0,1]),(insech[1,0], insech[1,1]),(0,255,0),2)
cv2.imshow('contours', vis)
0xFF & cv2.waitKey()
cv2.destroyAllWindows()
关于python - 如何从轮廓的质心到轮廓的周长画一条线?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/36314240/