如何在从网络摄像头源显示时更改 opencv 中圆圈的颜色？

Question

我正在尝试更改在按下某个键时在实时摄像机输入的输出帧上绘制的圆圈的颜色。当我按下 'c' 键时，我希望圆圈的颜色从蓝色到绿色。我正在尝试以下方法来实现这一点

# import the opencv library
import cv2
global circle_color
circle_color = (255,0,0)
# define a video capture object
vid = cv2.VideoCapture(0)
  
while(True):
      
    # Capture the video frame
    # by frame
    ret, frame = vid.read()
    cv2.circle(img=frame, center = (250,250), radius =100, color =circle_color, thickness=-1)

  
    # Display the resulting frame
    cv2.imshow('frame', frame)
      
    # the 'q' button is set as the
    # quitting button you may use any
    # desired button of your choice
    
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
    elif cv2.waitKey(1) & 0xFF == ord('c'): 
        # circle_color == (0,255,0)
        cv2.circle(img=frame, center = (250,250), radius =100, color =(0,255,0), thickness=-1)
        print("pressed c")
  
# After the loop release the cap object
vid.release()
# Destroy all the windows
cv2.destroyAllWindows()

当我尝试此代码并按下键时 'c' 我只看到控制台输出为按下 c 但我没有看到输出帧上的圆圈颜色有任何变化 window 它保持蓝色.

我什至尝试声明颜色的全局变量并在按下按键时更新它，但这也不起作用

如有任何帮助或建议，我们将不胜感激。

Answer 1

主要问题是在显示图像之前，您的绿色圆圈总是被蓝色圆圈覆盖。

将 cv2.imshow('frame', frame) 移动到 while 循环的末尾。

我会这样做：

# import the opencv library
import cv2

key_pressed = False

# define a video capture object
vid = cv2.VideoCapture(0)
  
while(True):
      
    # Capture the video frame
    # by frame
    ret, frame = vid.read()
    circle_color = (0, 255, 0) if key_pressed else (255, 0, 0)
    cv2.circle(img=frame, center = (250,250), radius =100, color = circle_color, thickness=-1)
      
    # the 'q' button is set as the
    # quitting button you may use any
    # desired button of your choice
    
    key = cv2.waitKey(1) 
    if key & 0xFF == ord('q'):
        break
    elif key & 0xFF == ord('c'): 
        # circle_color == (0,255,0)
        key_pressed = True
        print("pressed c")
    else:
        key_pressed = False
    
    # Display the resulting frame
    cv2.imshow('frame', frame)
  
# After the loop release the cap object
vid.release()
# Destroy all the windows
cv2.destroyAllWindows()

如果你想在释放按键后仍保持颜色，你应该直接覆盖circle_color:

# import the opencv library
import cv2

# define a video capture object
vid = cv2.VideoCapture(0)

circle_color = (255, 0, 0)

while(True):
      
    # Capture the video frame
    # by frame
    ret, frame = vid.read()
    
    cv2.circle(img=frame, center = (250,250), radius =100, color = circle_color, thickness=-1)
      
    # the 'q' button is set as the
    # quitting button you may use any
    # desired button of your choice
    
    key = cv2.waitKey(1) 
    if key & 0xFF == ord('q'):
        break
    elif key & 0xFF == ord('c'): 
        circle_color = (0, 255, 0) 
        print("pressed c")
    
    # Display the resulting frame
    cv2.imshow('frame', frame)
  
# After the loop release the cap object
vid.release()
# Destroy all the windows
cv2.destroyAllWindows()

如何在从网络摄像头源显示时更改 opencv 中圆圈的颜色？

How to change color of circle in opencv while displaying from webcam feed?

python

opencv

image-processing

python-3.x