python 3.x - Opencv在一个从未显示过的图片中画一个矩形

Question

大家好，我在使用opencv 3时遇到了一些麻烦。python 3.x。我想做的是在图片中画一个基本的矩形，但是这个矩形永远不会被画出来。我读过这个类似的帖子，但它对我的错误没有帮助。Python OpenCV:绘制矩形的鼠标回调

如果有人能给我点提示就好了。

#!/usr/bin/env python3
import cv2
import numpy as np
Path = 'picture.jpg'
image_float_size = 400.0
image_int_size = int(image_float_size)
color = [0,255,0]
rectangle = False
def on_event(event,x,y,flags,param):
    global startpointx,startpointy,rectangle
    if event == cv2.EVENT_LBUTTONDOWN:
        rectangle = True
        startpointx = x
        startpointy = y
        print('Down',x,y) #debugging
        cv2.rectangle(resized,(x,y),(x,y),(0,255,0),-1)
    elif event == cv2.EVENT_LBUTTONUP:
        rectangle = False
        print('Up',x,y)
        cv2.rectangle(resized,(startpointx,startpointy),(x,y),(0,255,0),-1)
    elif event == cv2.EVENT_MOUSEMOVE:
        if rectangle:
            print('Move',startpointx,startpointy,x,y)#debugging
            cv2.rectangle(resized,(startpointx,startpointy),(x,y),(0,255,0),-1)
# Read the image and convert it into gray
image = cv2.imread(Path)
gray_image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
# resize the image
ration = image_float_size / gray_image.shape[1]
dim = (image_int_size,int(gray_image.shape[0]*ration))
resized = cv2.resize(gray_image, dim, interpolation = cv2.INTER_AREA)
# set window for the image
cv2.namedWindow('window')
# mouse callback
cv2.setMouseCallback('window',on_event)
# wait forever for user to press any key, after key pressed close all windows
while True:
    cv2.imshow('window',resized)
    if cv2.waitKey(0):
        break
        cv2.destroyAllWindows()

Answer 1

您只执行一次绘图(通过使用cv2.imshow显示图像)，因为cv2.waitKey(0)无限期等待。如果你使用非零参数，它会等待那个毫秒数。但请注意，您正在不断地重写/修改图像。这可能不是你想要的。我认为你需要先创建一个图像的临时(绘图)副本，并在每次新绘图(矩形)之前从原始图像恢复它。

#!/usr/bin/env python3
import cv2
import numpy as np
Path = 'data/lena.jpg'
image_float_size = 400.0
image_int_size = int(image_float_size)
color = [0,255,0]
rectangle = False
def on_event(event,x,y,flags,param):
    global draw_image
    global startpointx,startpointy,rectangle
    if event == cv2.EVENT_LBUTTONDOWN:
        rectangle = True
        startpointx = x
        startpointy = y
        print('Down',x,y) #debugging
        draw_image = resized.copy()
        cv2.rectangle(draw_image,(x,y),(x,y),(0,255,0))
    elif event == cv2.EVENT_LBUTTONUP:
        rectangle = False
        print('Up',x,y)
        draw_image = resized.copy()
        cv2.rectangle(draw_image,(startpointx,startpointy),(x,y),(0,255,0))
    elif event == cv2.EVENT_MOUSEMOVE:
        if rectangle:
            print('Move',startpointx,startpointy,x,y)#debugging
            draw_image = resized.copy()
            cv2.rectangle(draw_image,(startpointx,startpointy),(x,y),(0,255,0))
# Read the image and convert it into gray
image = cv2.imread(Path)
gray_image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
# resize the image
ration = image_float_size / gray_image.shape[1]
dim = (image_int_size,int(gray_image.shape[0]*ration))
resized = cv2.resize(gray_image, dim, interpolation = cv2.INTER_AREA)
draw_image = resized.copy()
# set window for the image
cv2.namedWindow('window')
# mouse callback
cv2.setMouseCallback('window',on_event)
while True:
    cv2.imshow('window', draw_image)
    ch = 0xFF & cv2.waitKey(1)
    if ch == 27:
        break
cv2.destroyAllWindows()