如何在我的代码中正确加入循环？

Question

我正在尝试做一个图像识别项目，我唯一的问题是当我运行程序时视频/实时摄像头冻结，这只给我一帧可以使用。循环很可能会帮助我解决这个问题，但我试图将它添加到我的代码中，但我惨遭失败。我怎样才能正确地做到这一点，以免出现错误？

def show_vid():      
    cap1 = cv2.VideoCapture(0)                                 
    if not cap1.isOpened():                             
        print("cant open the camera1")
    flag1, frame1 = cap1.read()
    frame1 = cv2.resize(frame1,(600,500))
    bounding_box = cv2.CascadeClassifier('C:/Users/Andreea/anaconda3/Lib/site-packages/cv2/data/haarcascade_frontalface_default.xml')
    gray_frame = cv2.cvtColor(frame1, cv2.COLOR_BGR2GRAY)
    num_faces = bounding_box.detectMultiScale(gray_frame,scaleFactor=1.3, minNeighbors=5)
    for (x, y, w, h) in num_faces:
        cv2.rectangle(frame1, (x, y-50), (x+w, y+h+10), (255, 0, 0), 2)
        roi_gray_frame = gray_frame[y:y + h, x:x + w]
        cropped_img = np.expand_dims(np.expand_dims(cv2.resize(roi_gray_frame, (48, 48)), -1), 0)
        prediction = emotion_model.predict(cropped_img)
        
        maxindex = int(np.argmax(prediction))
        cv2.putText(frame1, emotion_dict[maxindex], (x+20, y-60), cv2.FONT_HERSHEY_SIMPLEX, 1, (255, 255, 255), 2, cv2.LINE_AA)
        show_text[0]=maxindex
    if flag1 is None:
        print ("Major error!")
    elif flag1:
        global last_frame1
        last_frame1 = frame1.copy()
        pic = cv2.cvtColor(last_frame1, cv2.COLOR_BGR2RGB)     
        img = Image.fromarray(pic)
        imgtk = ImageTk.PhotoImage(image=img)
        lmain.imgtk = imgtk
        lmain.configure(image=imgtk)
        lmain.after(10, show_vid)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        exit()

我是新手，所以我不知道如何解决这个问题，我还在学习中。谢谢！

Answer 1

您遇到的问题是因为您没有连续读取相机的帧。您应该将帧读取和处理步骤移动到一个循环中。为此，我建议使用 while 循环。

这是带有 while 循环的修改后的代码：

def show_vid():      
    cap1 = cv2.VideoCapture(0)                                 
    if not cap1.isOpened():                             
        print("cant open the camera1")

    bounding_box = cv2.CascadeClassifier('C:/Users/Andreea/anaconda3/Lib/site-packages/cv2/data/haarcascade_frontalface_default.xml')
    
    while True:
        flag1, frame1 = cap1.read()
        frame1 = cv2.resize(frame1,(600,500))
        gray_frame = cv2.cvtColor(frame1, cv2.COLOR_BGR2GRAY)
        num_faces = bounding_box.detectMultiScale(gray_frame,scaleFactor=1.3, minNeighbors=5)
        for (x, y, w, h) in num_faces:
            cv2.rectangle(frame1, (x, y-50), (x+w, y+h+10), (255, 0, 0), 2)
            roi_gray_frame = gray_frame[y:y + h, x:x + w]
            cropped_img = np.expand_dims(np.expand_dims(cv2.resize(roi_gray_frame, (48, 48)), -1), 0)
            prediction = emotion_model.predict(cropped_img)
            
            maxindex = int(np.argmax(prediction))
            cv2.putText(frame1, emotion_dict[maxindex], (x+20, y-60), cv2.FONT_HERSHEY_SIMPLEX, 1, (255, 255, 255), 2, cv2.LINE_AA)
            show_text[0]=maxindex

        if flag1 is None:
            print ("Major error!")
        elif flag1:
            global last_frame1
            last_frame1 = frame1.copy()
            pic = cv2.cvtColor(last_frame1, cv2.COLOR_BGR2RGB)     
            img = Image.fromarray(pic)
            imgtk = ImageTk.PhotoImage(image=img)
            lmain.imgtk = imgtk
            lmain.configure(image=imgtk)
            lmain.update_idletasks()
            lmain.update()

        if cv2.waitKey(1) & 0xFF == ord('q'):
            break

    cap1.release()
    cv2.destroyAllWindows()