如何找到线条和轮廓之间的交点

如何解决如何找到线条和轮廓之间的交点

考虑下图，其中轮廓以绿色显示，直线以红色显示

我们如何找到直线切割轮廓的交点

import cv2 
from matplotlib import pyplot as plt
import numpy as np

# Read image img

# Binarize
img_gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
_,thresh = cv2.threshold(img_gray,127,255,cv2.THRESH_BINARY)

# Find Contours
_,contours,_ = cv2.findContours(thresh,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)

# Draw Contours
blank_mask = np.zeros((thresh.shape[0],thresh.shape[1],3),np.uint8)
cv2.drawContours(blank_mask,-1,(0,0),1) 

# Define lines coordinates
line1 = [x1,y1,x2,y2]
line2 = [x1,y2]
line3 = [x1,y2]

# Draw Lines over Contours
cv2.line(blank_mask,(line1[0],line1[1]),(line1[2],line1[3]),(255,thickness=1)
cv2.line(blank_mask,(line2[0],line2[1]),(line2[2],line2[3]),(line3[0],line3[1]),(line3[2],line3[3]),thickness=1)

# Show Image
fig = plt.figure()
ax  = fig.add_subplot(111)
ax.imshow(blank_mask)

Sample Image

解决方法

您可以逐个像素地检查它们的重叠位置。在绘制线条之前，您必须保留轮廓所在像素的副本，因为这会用线条的颜色覆盖重叠的像素。在此处添加几行代码

# Draw Contours
blank_mask = np.zeros((thresh.shape[0],thresh.shape[1],3),np.uint8)
cv2.drawContours(blank_mask,contours,-1,(0,255,0),1)
contours_idx = blank_mask[...,1] == 255

# Define lines coordinates
line1 = [x1,y1,x2,y2]
line2 = [x1,y2]
line3 = [x1,y2]

# Draw Lines over Contours
cv2.line(blank_mask,(line1[0],line1[1]),(line1[2],line1[3]),(255,thickness=1)
cv2.line(blank_mask,(line2[0],line2[1]),(line2[2],line2[3]),(line3[0],line3[1]),(line3[2],line3[3]),thickness=1)
lines_idx = blank_mask[...,0] == 255

然后

overlap = np.where(contours_idx * lines_idx)

这会给你类似于下面的东西（我不得不猜测你的线坐标和图像大小调整形状，所以我可能有点偏离）

(array([ 90,110,140,140],dtype=int64),array([ 80,40,141,27,156],dtype=int64))

如果你想要它们在像素坐标元组中

list(zip(*overlap))

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编辑：对于轮廓/线条的颜色在多个平面中的更通用的解决方案，您可以在每次绘制后检查每个像素的全色。例如

# Change these
contours_idx = blank_mask[...,1] == 255
lines_idx = blank_mask[...,0] == 255

# To this
contours_idx = np.all(blank_mask == (0,axis=-1)
lines_idx = np.all(blank_mask == (255,axis=-1)