In our last example, we drew filled rectangle. You modify the code to draw an unfilled rectangle.

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文章目录

前言
一、last example
二、modify the code to draw an unfilled rectangle.
- 1.修改方法
- - 第一步
  - 第二步

前言

题目地址为：https://docs.opencv.org/4.x/db/d5b/tutorial_py_mouse_handling.html
题目内容：In our last example, we drew filled rectangle. You modify the code to draw an unfilled rectangle.

一、last example

完整代码如下：

import numpy as np
import cv2 as cv
drawing = False # true if mouse is pressed
mode = True # if True, draw rectangle. Press 'm' to toggle to curve
ix,iy = -1,-1
# mouse callback function
def draw_circle(event,x,y,flags,param):global ix,iy,drawing,modeif event == cv.EVENT_LBUTTONDOWN:drawing = Trueix,iy = x,yelif event == cv.EVENT_MOUSEMOVE:if drawing == True:if mode == True:cv.rectangle(img,(ix,iy),(x,y),(0,255,0),-1)else:cv.circle(img,(x,y),5,(0,0,255),-1)elif event == cv.EVENT_LBUTTONUP:drawing = Falseif mode == True:cv.rectangle(img,(ix,iy),(x,y),(0,255,0),-1)else:cv.circle(img,(x,y),5,(0,0,255),-1)img = np.zeros((512,512,3), np.uint8)
cv.namedWindow('image')
cv.setMouseCallback('image',draw_circle)
while(1):cv.imshow('image',img)k = cv.waitKey(1) & 0xFFif k == ord('m'):mode = not modeelif k == 27:break
cv.destroyAllWindows()

效果图：

二、modify the code to draw an unfilled rectangle.

1.修改方法

第一步

首先将cv.rectangle(img,(ix,iy),(x,y),(0,255,0),-1)和cv.circle(img,(x,y),5,(0,0,255),-1)中最后一个参数修改，-1代表填充满，如果最后一个参数修改为正整数例如将最后一个参数修改为5,则代表的意思是绘制矩形时的线宽度为5。

第二步

注释掉绑定鼠标移动时绘制矩形的事件。就是注释掉这一部分:

# elif event == cv.EVENT_MOUSEMOVE:#     if drawing == True:#         if mode == True:#             cv.rectangle(img,(ix,iy),(x,y),(0,255,0),-1)#         else:#             cv.circle(img,(x,y),5,(0,0,255),-1)

修改后的完整代码如下：

import numpy as np
import cv2 as cv
drawing = False # true if mouse is pressed
mode = True # if True, draw rectangle. Press 'm' to toggle to curve
ix,iy = -1,-1
# mouse callback function
def draw_circle(event,x,y,flags,param):global ix,iy,drawing,modeif event == cv.EVENT_LBUTTONDOWN:drawing = Trueix,iy = x,y# elif event == cv.EVENT_MOUSEMOVE:#     if drawing == True:#         if mode == True:#             cv.rectangle(img,(ix,iy),(x,y),(0,255,0),-1)#         else:#             cv.circle(img,(x,y),5,(0,0,255),-1)elif event == cv.EVENT_LBUTTONUP:drawing = Falseif mode == True:cv.rectangle(img,(ix,iy),(x,y),(0,255,0),5) else:cv.circle(img,(x,y),5,(0,0,255),5)img = np.zeros((512,512,3), np.uint8)
cv.namedWindow('image')
cv.setMouseCallback('image',draw_circle)
while(1):cv.imshow('image',img)k = cv.waitKey(1) & 0xFFif k == ord('m'):mode = not modeelif k == 27:break
cv.destroyAllWindows()