P18 3-10

1 鼠標回調函數

import cv2
import numpy as npdef mouse_callback(event,x,y,flage,userdata):print(event,x,y,flage,userdata)cv2.namedWindow("mouse",cv2.WINDOW_NORMAL)
cv2.resizeWindow('mouse',640,360)#窗口尺寸，640行，360列cv2.setMouseCallback('mouse',mouse_callback,'123')#（高，寬，通道數）
img=np.zeros((360,640,3),np.uint8)#高=行數，寬=列數，3通道，每個通道是8位無符號整形數據
while True:cv2.imshow('mouse',img)key=cv2.waitKey(1)if key& 0xff == ord('q'):breakcv2.destroyAllWindows()

當鼠標在，窗口內移動、點擊，等操作時，
event,x,y,flag會輸出相應的值；

2 鼠標繪制基本圖形（直線、圓、矩形）

2.1 圖形繪制教程

圖形繪制教程：圖形繪制（line直線、ellipse橢圓、polylines多邊形、putText繪制文本）

2.2 鼠標繪制基本圖形（直線、圓、矩形）代碼實現

基本功能：

• 1 畫線：當按下l鍵，即選擇了畫線。此時，滑動鼠標即可畫線。
• 2 畫矩形：當按下r鍵，即選擇了畫矩形。此時，滑動鼠標即可畫矩形。
• 3 畫圓：當按下c鍵，即選擇了畫圓。此時，滑動鼠標即可畫圓。

#全局變量
curshape=0
startpos=(0,0)img=np.zeros((480,640,3),np.uint8)

def mouse_callback(event,x,y,flag,userdata):if event & cv2.EVENT_LBUTTONDOWN == cv2.EVENT_LBUTTONDOWN:startpos=(x,y)elif event & cv2.EVENT_LBUTTONUP == cv2.EVENT_LBUTTONUP:if curshape==0:cv2.line(img,startpos,(x,y),(255,0,0))#起點startpos,終點是當前x,yelif curshape==1:cv2.rectangle(img,startpos,(x,y),(255,0,0))elif curshape==2:cv2.circle(img,startpos,max(abs(startpos[0]-x),abs(startpos[1]-y)),(255,0,0))#選擇dx,dy中最大值，作為半徑else:print('error : no shape')

 File "e:\Program_Py\1.py", line 25, in mouse_callbackcv2.line(img,startpos,(x,y),(255,0,0))#起點startpos,終點是當前x,y
UnboundLocalError: local variable 'startpos' referenced before assignment

意思是：局部變量’startpos’在賦值前被引用

#全局變量
將全局變量前加上global

 global curshape,startpos

name ‘curshape’ is not defined

File "e:\Program_Py\1.py", line 23, in mouse_callbackif curshape==0:
NameError: name 'curshape' is not defined
Traceback (most recent call last):File "e:\Program_Py\1.py", line 24, in mouse_callbackcv2.line(img,startpos,(x,y),(255,0,0))#起點startpos,終點是當前x,y
UnboundLocalError: local variable 'startpos' referenced before assignment

正確做法，在函數外面定義一次，在函數里面使用的時候，需要再次全局申明

#全局變量
curshape=0
startpos=(0,0)img=np.zeros((480,640,3),np.uint8)

def mouse_callback(event,x,y,flag,userdata):global curshape,startpos#需要再次全局申明

startpos=(x,y)
當獲取點startpo中x值時，startpos.x，報錯

File "e:\Program_Py\1.py", line 29, in mouse_callbackcv2.circle(img,startpos,max(abs(startpos.x-x),abs(startpos.y-y)),(255,0,0))
AttributeError: 'tuple' object has no attribute 'x'

改成，startpos[0]，OK

#基本功能：
# 1 畫線：當按下l鍵，即選擇了畫線。此時，滑動鼠標即可畫線。
# 2 畫矩形：當按下r鍵，即選擇了畫矩形。此時，滑動鼠標即可畫矩形。
# 3 畫圓：當按下c鍵，即選擇了畫圓。此時，滑動鼠標即可畫圓。#curshape：0-drawline,1-drawrectangle,2-drawcircleimport cv2
import numpy as np#全局變量
curshape=0
startpos=(0,0)img=np.zeros((480,640,3),np.uint8)def mouse_callback(event,x,y,flag,userdata):global curshape,startpos#需要再次全局申明if event & cv2.EVENT_LBUTTONDOWN == cv2.EVENT_LBUTTONDOWN:startpos=(x,y)elif event & cv2.EVENT_LBUTTONUP == cv2.EVENT_LBUTTONUP:if curshape==0:cv2.line(img,startpos,(x,y),(255,0,0))#起點startpos,終點是當前x,yelif curshape==1:cv2.rectangle(img,startpos,(x,y),(255,0,0))elif curshape==2:cv2.circle(img,startpos,max(abs(startpos[0]-x),abs(startpos[1]-y)),(255,0,0))#選擇dx,dy中最大值，作為半徑else:print('error : no shape')cv2.namedWindow('drawshape',cv2.WINDOW_NORMAL)
cv2.setMouseCallback('drawshape',mouse_callback)while True:cv2.imshow("drawshape",img)key=cv2.waitKey(1) & 0xff if key == ord('q'):breakelif key==ord('l'):#linecurshape=0elif key==ord('r'):#rectcurshape=1elif key==ord('c'):#circlecurshape=2

當把，函數外面的定義注釋掉，也會報錯，但是可以使用畫圖功能；

# #全局變量
# curshape=0
# startpos=(0,0)img=np.zeros((480,640,3),np.uint8)def mouse_callback(event,x,y,flag,userdata):global curshape,startpos#需要再次全局申明

: name ‘curshape’ is not defined

Traceback (most recent call last):File "e:\Program_Py\1.py", line 23, in mouse_callbackif curshape==0:
NameError: name 'curshape' is not defined