Question

我有一个问题：我创建了一个小程序，打开网络摄像头并进行人脸识别。现在我想完成这个任务：当按下一个键（空格）时，程序必须进入第2阶段（人脸识别）。为此，我使用了cv2.waitkey（）。主要的问题是，当按下空格时我的功能，程序将进入阶段2，但只持续几秒钟（当按下空格时它进入阶段2，并且当它被释放时它停止）。

你有什么建议吗？

我将举例说明我的意思：

cam = cv2.VideoCapture(0)   ##Load Cam
cv2.namedWindow(name, cv2.WINDOW_AUTOSIZE)

while True:
   s, img = cam.read()
   gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

   cv2.imshow(name, img)    
   k = cv2.waitKey(1)

   if k == 13: ## if return is pressed, on the screen will appear the text 'instruction',but when it 
               ## released the text disappear, and i don't want this...
       s, img = cam.read()
       gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
       cv2.putText(img,'instructions',(10,25), font, 0.7,(255,255,255),1,cv2.LINE_AA)

       cv2.imshow(name, img)

溶液：

cv2.namedWindow(name, cv2.WINDOW_AUTOSIZE)

while True:
   s, img = cam.read()
   gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

   cv2.imshow(name, img)    
   k = cv2.waitKey(1)

   if k == 13: 
       break
while True:
   s, img = cam.read()
   gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
   cv2.putText(img,'instructions',(10,25), font, 0.7,(255,255,255),1,cv2.LINE_AA)

   cv2.imshow(name, img)

Answer 1

也许你需要某种“超时”＃39; ？

cam = cv2.VideoCapture(0)   ##Load Cam
cv2.namedWindow(name, cv2.WINDOW_AUTOSIZE)

timeout = 0
while True:
   s, img = cam.read()

   if timeout > 0:   # show message as long as timeout is valid
       cv2.putText(img,'instructions',(10,25), font, 0.7,(255,255,255),1,cv2.LINE_AA)
       timeout = timeout - 1

   cv2.imshow(name, img)

   k = cv2.waitKey(1)    
   if k == 13:                
       timeout = 100 # show message for 100 frames
   if k == 27:                
       break         # bail out on 'escape'

Answer 2

问题在于您的条件说明属于循环 - 只有在条件评估为 true 时才会运行它们。为避免这种情况，请考虑中断退出循环并遵循进一步说明。

 cam = cv2.VideoCapture(0)   ##Load Cam
 cv2.namedWindow(name, cv2.WINDOW_AUTOSIZE)

 while True:
     s, img = cam.read()
     gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

     cv2.imshow(name, img)    
     k = cv2.waitKey(1)

     if k == 13:
         break

 s, img = cam.read()
 gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
 cv2.putText(img,'instructions',(10,25), font, 0.7,(255,255,255),1,cv2.LINE_AA)
 cv2.imshow(name, img)
 cv2.waitKey(1)

强制waitkey（）执行操作{OpenCV} {PY}

2 个答案: