opencv 综合案例 在画板上 画圆画矩形画线条

# 基本功能
# 可以用过鼠标进行基本图形的绘制
# 1. 可以画线，当用户l键，即选择画线，此时，滑动鼠标既可画线
# 2. 可以矩形，当用户r键，即选择画矩形，此时，滑动鼠标既可画矩形
# 3. 可以画圆，当用户c键，即选择画圆，此时，滑动鼠标既可画圆
# 4. 当用户q键 退出程序

# curshape 0-drawline，1-drawrect，2-circle
import cv2  as cv
import numpy as np

curshape = 0
startpos = (0, 0)
color = (0,0,255)
# 显示窗口和北京
img = np.zeros((480,640,3),np.uint8)
# 鼠标回调函数
def mouse_callback(event,x,y,flags,userdata):
    global startpos
    if event & cv.EVENT_LBUTTONDOWN == cv.EVENT_LBUTTONDOWN:
        startpos =(x,y)
    elif event & cv.EVENT_LBUTTONUP == cv.EVENT_LBUTTONUP:
        if curshape == 0:
            cv.line(img,startpos,(x,y),color)
        elif curshape == 1:
            cv.rectangle(img, startpos,(x,y), color)
        elif curshape == 2:
            a = x-startpos[0]
            b = y-startpos[1]
            r = int((a**2+b**2)**0.5)
            cv.circle(img,startpos, r, color)

    # print(event,x,y,flags,userdata)

# 创建窗口
cv.namedWindow("drawshape",cv.WINDOW_NORMAL)
# 设置鼠标回调
cv.setMouseCallback('drawshape',mouse_callback,'123')


while True:
    cv.imshow("drawshape",img)
    key = cv.waitKey(1) & 0xFF
    if key == ord('q'):
        break
    elif key == ord('l'):
        curshape = 0
    elif key == ord('r'):
        curshape = 1
    elif key == ord('c'):
        curshape = 2