Python-OpenCV按住鼠标左键绘制图形

 使用Python语言的OpenCV库，在按住鼠标左键的情况下，移动鼠标，绘制任意形状的图形

 event判断鼠标是否是移动状态（event == cv.EVENT_MOUSEMOVE），flags判断鼠标是否处于左键按下并拖动的状态（flags == cv.EVENT_FLAG_LBUTTON），当满足这两个条件之后，按住左键并移动鼠标可以实现绘制功能

双击鼠标左键可以清除画板上的所有图形（event == cv.EVENT_LBUTTONDBLCLK）

def drawing(event, x, y, flags, param):
    global img
    if event == cv.EVENT_MOUSEMOVE and flags == cv.EVENT_FLAG_LBUTTON:
        cv.circle(img, (x, y), 5, (0, 0, 255), -1)
    elif event == cv.EVENT_LBUTTONDBLCLK:
        img = np.zeros(img_size, np.uint8) + 255
    cv.imshow('image', img)

 完整代码如下：

import numpy as np
import cv2 as cv


def drawing(event, x, y, flags, param):
    global img
    if event == cv.EVENT_MOUSEMOVE and flags == cv.EVENT_FLAG_LBUTTON:
        cv.circle(img, (x, y), 5, (0, 0, 255), -1)
    elif event == cv.EVENT_LBUTTONDBLCLK:
        img = np.zeros(img_size, np.uint8) + 255
    cv.imshow('image', img)


img_size = [400, 500, 3]
img = np.zeros(img_size, np.uint8) + 255
cv.namedWindow('image')
cv.setMouseCallback('image', drawing)
cv.imshow('image', img)
cv.waitKey(0)
cv.destroyAllWindows()