opencv画直线，矩形
opencv 画直线要画一条线，你只需要告诉函数这条线的起点和终点。我们下面会画一条从左上方到右下角的蓝色线段。
import numpy as np
import cv2
# Create a black image
img = np.zeros((512,512,3), np.uint8)
# Draw a diagonal blue line with thickness of 5 px
cv2.line(img,(0,0),(511,511),(255,0,0),5)
cv2.imshow("img", img)
cv2.waitKey(0)
画矩形
要画一个矩形，你需要告诉函数的左上角顶点和右下角顶点的坐标。这次我们会在图像的右上角话一个绿色的矩形。
import numpy as np
import cv2
# Create a black image
img = np.zeros((512,512,3), np.uint8)
# Draw a diagonal blue line with thickness of 3 px
#cv2.line(img,(0,0),(511,511),(255,0,0),3)
cv2.rectangle(img,(384,0),(510,128),(0,255,0),3)
cv2.imshow("img", img)
cv2.waitKey(0)