OpenCV-Python——第4章：鼠标事件
1 鼠标回调函数
cv2.setMouseCallback(windowName, onMouse, param=None)
用于将鼠标事件与窗口联系起来
- windowName：窗口名称
- onMouse：鼠标响应函数
- param：响应函数传递的的参数
2 鼠标响应函数
onMouse(event, x, y, flags, param)
用于设置鼠标事件
- event：鼠标事件，可用参数对应值代替
- x：鼠标x坐标
- y：鼠标y坐标
- flags：鼠标状态，可用参数对应值代替
- param：param是用户定义的传递到setMouseCallback函数调用的参数
鼠标事件和状态可用以下程序获得
import cv2
events = [i for i in dir(cv2) if 'EVENT'in i]
print(events)可得到
['EVENT_FLAG_ALTKEY', 'EVENT_FLAG_CTRLKEY', 'EVENT_FLAG_LBUTTON', 'EVENT_FLAG_MBUTTON', 'EVENT_FLAG_RBUTTON', 'EVENT_FLAG_SHIFTKEY', 'EVENT_LBUTTONDBLCLK', 'EVENT_LBUTTONDOWN', 'EVENT_LBUTTONUP', 'EVENT_MBUTTONDBLCLK', 'EVENT_MBUTTONDOWN', 'EVENT_MBUTTONUP', 'EVENT_MOUSEHWHEEL', 'EVENT_MOUSEMOVE', 'EVENT_MOUSEWHEEL', 'EVENT_RBUTTONDBLCLK', 'EVENT_RBUTTONDOWN', 'EVENT_RBUTTONUP']
获得的结果按顺序其代表的含义为：
| 对应值 | 含义 | |
| flags |
|
|
| cv2.EVENT_FLAG_ALTKEY |
32 |
按Alt不放 |
| cv2.EVENT_FLAG_CTRLKEY |
8 |
按Ctrl不放 |
| cv2.EVENT_FLAG_LBUTTON |
1 |
左键拖拽 |
| cv2.EVENT_FLAG_MBUTTON |
4 |
中键拖拽 |
| cv2.EVENT_FLAG_RBUTTON |
2 |
右键拖拽 |
| cv2.EVENT_FLAG_SHIFTKEY |
16 |
按住Shift不放 |
| event |
|
|
| cv2.EVENT_LBUTTONDBLCLK |
7 |
左键双击 |
| cv2.EVENT_LBUTTONDOWN |
1 |
左键按下 |
| cv2.EVENT_LBUTTONUP |
4 |
左键释放 |
| cv2.EVENT_MBUTTONDBLCLK |
8 |
中键双击 |
| cv2.EVENT_MBUTTONDOWN |
2 |
中键按下 |
| cv2.EVENT_MBUTTONUP |
5 |
中键释放 |
| cv2.EVENT_MOUSEHWHEEL |
11 |
横向滚轮滚动 |
| cv2.EVENT_MOUSEMOVE |
0 |
鼠标移动 |
| cv2.EVENT_MOUSEWHEEL |
10 |
滚轮滚动 |
| cv2.EVENT_RBUTTONDBLCLK |
8 |
右键双击 |
| cv2.EVENT_RBUTTONDOWN |
2 |
右键按下 |
| cv2.EVENT_RBUTTONUP |
5 |
右键释放 |
下面举一个例子
import cv2
import numpy as np
drawing = False # 当鼠标按下变为True
mode = True # 按下‘m’变成False，true为绘制矩形，false为画笔
ix, iy = -1, -1 # 初始化鼠标位置
def onmouse(event, x, y, flags, param): # 创建回调函数
global ix, iy, drawing, mode
if event == cv2.EVENT_LBUTTONDOWN: # 按下左键
drawing = True # 开始绘制
ix, iy = x, y # 赋予按下时的鼠标坐标
elif event == cv2.EVENT_MOUSEMOVE and flags == cv2.EVENT_FLAG_LBUTTON: # 当按下左键拖拽鼠标时
if drawing is True:
if mode is True:
cv2.rectangle(img, (ix, iy), (x, y), (0, 255, 0), 1) # 当模式为True时画矩形
else:
cv2.circle(img, (x, y), 3, (0, 0, 255), -1) # 当模式为False时画线
elif event == cv2.EVENT_MOUSEWHEEL:
if drawing is True:
if mode is True:
cv2.circle(img, (x, y), 50, (255, 0, 0), -1) # 滚轮画实心圆
elif event == cv2.EVENT_LBUTTONDBLCLK:
if drawing is True:
if mode is True:
cv2.circle(img, (x, y), 50, (255, 255, 0), 3) # 双击左键画空心圆
elif event == cv2.EVENT_LBUTTONUP: # 当鼠标松开停止绘画
drawing is False
if mode is True:
cv2.rectangle(img, (ix, iy), (x, y), (255, 0, 0), 5) # 松开鼠标后画一个蓝色矩形
img = np.zeros((600, 800, 3), np.uint8) # 创建空图像
cv2.namedWindow('image') # 创建空窗口
cv2.setMouseCallback('image', onmouse) # 将回调函数与窗口绑定
while(1):
cv2.imshow('image', img)
k = cv2.waitKey(1) & 0xFF
if k == ord('m'): # 按m更换模式
mode = not mode
elif k == 27: # 按ESC退出
break
cv2.destroyAllWindows()
结果如下：
