opencv-python：鼠标操作

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１.鼠标事件

import cv2 as cv
events = [i for i in dir(cv) if 'EVENT' in i]
print( events )	# 将鼠标事件显示出来

'''
EVENT_FLAG_LBUTTON = 1		摁住左键
EVENT_FLAG_RBUTTON = 2		摁住右键
EVENT_FLAG_MBUTTON = 4		摁住中键
EVENT_FLAG_CTRLKEY = 8		摁住Ctrl
EVENT_FLAG_SHIFTKEY = 16	摁住Shift
EVENT_FLAG_ALTKEY = 32		摁住Alt

EVENT_MOUSEMOVE = 0			鼠标移动
EVENT_LBUTTONDOWN = 1		左键击下
EVENT_RBUTTONDOWN = 2		右键击下
EVENT_MBUTTONDOWN = 3		中键击下
EVENT_LBUTTONUP = 4			左键弹起
EVENT_RBUTTONUP = 5			右键弹起
EVENT_MBUTTONUP = 6			中键弹起
EVENT_LBUTTONDBLCLK = 7		左键双击
EVENT_RBUTTONDBLCLK = 8		右键双击
EVENT_MBUTTONDBLCLK = 9		中键双击
EVENT_MOUSEWHEEL = 10		滚动条向上，flags>0。向下，flags<0
EVENT_MOUSEHWHEEL = 11		滚动条向左，flags>0。向右，flags<0
'''

上半部分对应下面的函数参数中的flags，下半部分对应event。

注意：flags是叠加的，比如按住ATL和Shift，flags就是8+16=24。

2.特定函数参数

2.1.定义

函数名无所谓，但参数必须是这样

def XXX(event,x,y,flags,param):
	pass

2.2.调用

cv.namedWindow('image')
cv.setMouseCallback('image', draw_circle)

直接将函数名作为cv.setMouseCallback()的第二个参数，参数不需要你操心。

3.例

3.1.画圆

import cv2 as cv
import numpy as np

# 鼠标回调函数
def draw_circle(event,x,y,flags,param):
    if event == cv.EVENT_LBUTTONDBLCLK:	# 左键双击
        cv.circle(img,(x,y),100,(255,0,0),-1)
        
# 创建一个黑色的图像，一个窗口，并绑定到窗口的功能
img = np.zeros((512,512,3), np.uint8)
cv.namedWindow('image')
cv.setMouseCallback('image',draw_circle)
while(1):
    cv.imshow('image',img)
    if cv.waitKey(20) == 27:	# Esc
        break
cv.destroyAllWindows()

3.2.flags是叠加的

import cv2 as cv
import numpy as np

# 鼠标回调函数
def show_flags(event,x,y,flags,param):
    if event == cv.EVENT_LBUTTONDBLCLK:	# 左键双击
        print(flags)
        
# 创建一个黑色的图像，一个窗口，并绑定到窗口的功能
img = np.zeros((512,512,3), np.uint8)
cv.namedWindow('image')
cv.setMouseCallback('image',show_flags)
while(1):
    cv.imshow('image',img)
    if cv.waitKey() == 27:	# Esc
        break
cv.destroyAllWindows()

3.3.绘制矩形

import numpy as np
import cv2 as cv

drawing = False # 如果按下鼠标，则为真
ix,iy = -1,-1
# 鼠标回调函数
def draw(event,x,y,flags,param):
    global ix,iy,drawing
    if event == cv.EVENT_LBUTTONDOWN:	# 左键按下
        drawing = True
        ix,iy = x,y
    elif event == cv.EVENT_MOUSEMOVE:	# 鼠标移动
        if drawing == True:
            cv.rectangle(img,(ix,iy),(x,y),(0,255,0),-1)
    elif event == cv.EVENT_LBUTTONUP:	# 左键松开
        drawing = False
        cv.rectangle(img,(ix,iy),(x,y),(0,255,0),-1)
        
# 创建一个黑色的图像，一个窗口，并绑定到窗口的功能
img = np.zeros((512,512,3), np.uint8)
cv.namedWindow('image')
cv.setMouseCallback('image',draw)
while(1):
    cv.imshow('image',img)
    if cv.waitKey(20) == 27:	# Esc
        break
cv.destroyAllWindows()

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Reference

https://blog.csdn.net/lly1122334/article/details/88975503