1.3 OpenCV 中处理鼠标事件

把鼠标当画笔

根据我们选择的模式在拖动鼠标时绘制矩形或者是圆圈（就像画图程序中一样）

# -*- coding: utf-8 -*-
import numpy as np
import cv2

# 当鼠标按下时变为True
drawing = False
# 如果mode为true绘制矩形，按下'm'变成绘制曲线
mode = True
ix,iy = -1,-1

# 创建回调函数
def draw_circle(event, x, y, flags, param):
    global ix,iy,drawing,mode
    #当按下鼠标左键时返回起始位置坐标
    if event==cv2.EVENT_LBUTTONDOWN:
        drawing=True
        ix,iy=x,y
    # 当鼠标左键按下并移动是绘制图形，event可以查看移动，flag查看是否按下
    elif event==cv2.EVENT_MOUSEMOVE and flags==cv2.EVENT_LBUTTONDOWN:
        if drawing==True:
            if mode==True:
                cv2.rectangle(img, (ix,iy), (x,y), (0,255,0), -1)
            else:
                # 绘制圆圈，小圆点连在一起就成了线，3代表了线的粗细
                # cv2.circle(img, (x,y), 3, (0,0,255), -1)
                r = int(np.sqrt((x - ix) ** 2 + (y - iy) ** 2))
                cv2.circle(img, (x, y), r, (0, 0, 255), -1)
    elif event==cv2.EVENT_LBUTTONUP:
        drawing==False
img=np.zeros((512,512,3), np.uint8)
cv2.namedWindow('image', cv2.WINDOW_NORMAL)
cv2.setMouseCallback('image', draw_circle)
while(1):
    cv2.imshow('image', img)
    k=cv2.waitKey(1)&0xFF
    if k==ord('m'):
        mode = not mode
    elif k==27:
        break