计算经过已知点A与已知线段L平行的线段

图像识别CV/pythoncv_learn/calc_parallel_lines.py

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+import cv2
+import numpy as np
+import math
+
+def calcX(p3x, p3y, A, B, y):
+    return int(p3x - ((p3y - y) * A / B))
+
+def calcY(p3y, A, B, L):
+    a = L * B
+    b = (A * A) + (B * B)
+    return int((a / math.sqrt(b)) + p3y)
+
+img = np.zeros((600, 600, 3), dtype = int)
+img = np.array(img,dtype='uint8')
+
+point1 = (100,230)
+point2 = (520,320)
+point3 = (500,200)
+
+cv2.line(img, point1, point2, (0,0,255), 1)
+cv2.circle(img, point3, 3, (0,255,0), -1)
+cv2.imshow('img1', img)
+
+p1x, p1y = point1
+p2x, p2y = point2
+p3x, p3y = point3
+
+A = p1x - p2x
+B = p1y - p2y
+
+y = calcY(p3y, A, B, 400)
+x = calcX(p3x, p3y, A, B, y)
+cv2.line(img, point3, (x, y), (255, 0, 0), 1)
+cv2.imshow('img2', img)
+
+cv2.waitKey(0)