OpenCV 4.4.0 error: (-215:Assertion failed) !_src.empty() in function 'cv::cvtColor' , 14 other erros module cv2

Question

cap = cv2.VideoCapture(0)

while True:
    # Grab a single frame of video
    ret, frame = cap.read()
    gray = cv2.cvtColor(frame,cv2.COLOR_BGR2GRAY)
    faces = face_classifier.detectMultiScale(gray,1.3,5)
    for (x,y,w,h) in faces:
        cv2.rectangle(frame,(x,y),(x+w,y+h),(255,0,0),2)
        roi_gray = gray[y:y+h,x:x+w]
        roi_gray = cv2.resize(roi_gray,(48,48),interpolation=cv2.INTER_AREA)
    # rect,face,image = face_detector(frame)
        if np.sum([roi_gray])!=0:
            roi = roi_gray.astype('float')/255.0
            roi = img_to_array(roi)
            roi = np.expand_dims(roi,axis=0)
        # make a prediction on the ROI, then lookup the class
            preds = classifier.predict(roi)[0]
            label=class_labels[preds.argmax()]
            label_position = (x,y)
            cv2.putText(frame,label,label_position,cv2.FONT_HERSHEY_SIMPLEX,2,(0,255,0),3)
        else:
            cv2.putText(frame,'No Face Found',(20,60),cv2.FONT_HERSHEY_SIMPLEX,2,(0,255,0),3)
    cv2.imshow('Emotion Detector',frame)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

ERROR gray = cv2.cvtColor(frame,cv2.COLOR_BGR2GRAY) cv2.error: OpenCV(4.4.0) C:\Users\appveyor\AppData\Local\Temp\1\pip-req-build-6lylwdcz\opencv\modules\imgproc\src\color.cpp:182: error: (-215:Assertion failed) !_src.empty() in function 'cv::cvtColor' enter image description here enter image description here

Most probably, you can't get frame from the cap.read() check whether ret returns True. — Ahx
As @Ahx mentioned ret must be True, also for cap.isOpened(). If both of them are True, then try cap = cv2.VideoCapture(-1) — Elyas Karimi

sourab maity sourab maity · Accepted Answer · 2020-11-22T03:10:23

while True:
    # Grab a single frame of video
    ret, frame = cap.read()
    if ret==False:
        continue
    gray = cv2.cvtColor(frame,cv2.COLOR_BGR2GRAY)
    faces = face_classifier.detectMultiScale(gray,1.3,5)

Add this if condition in your code. If "ret" always return "False" then change "cap = cv2.VideoCapture(0)" as "cap = cv2.VideoCapture(1)" and try again

OpenCV 4.4.0 error: (-215:Assertion failed) !_src.empty() in function 'cv::cvtColor' , 14 other erros module cv2

3 Answers