我在使用Python命令“ cascPath = sys.argv [1]”时遇到问题，出现错误IndexError：列表索引超出范围

Question

I am using a Raspberry Pi 3 Model B, with Raspbian, opencv 2.x and Python 3 installed.

I want to access my USB Webcam and take a picture with it. I've found tons of code but none are of any use. I found one which is better but when I run the command

cascPath = sys.argv[1]

I get the error

Traceback (most recent call last):

File "/home/pi/test.py", line 4, in

cascPath = sys.argv[1]

IndexError: list index out of range

I simply need to access my webcam to take a picture.

I am using the following code :

import cv2

import sys

cascPath = sys.argv[1]

faceCascade = cv2.CascadeClassifier(cascPath)

video_capture = cv2.VideoCapture(0)

while True:

    # Capture frame-by-frame
    ret, frame = video_capture.read()

    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)

    faces = faceCascade.detectMultiScale(
        gray,
        scaleFactor=1.1,
        minNeighbors=5,
        minSize=(30, 30),
        flags=cv2.cv.CV_HAAR_SCALE_IMAGE
    )

    # Draw a rectangle around the faces
    for (x, y, w, h) in faces:
        cv2.rectangle(frame, (x, y), (x+w, y+h), (0, 255, 0), 2)

    # Display the resulting frame
    cv2.imshow('Video', frame)

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

#When everything is done, release the capture
video_capture.release()

Answer 1

This code try to recognize faces on image and sys.argv[1] expects you run script with path to XML file which help recognize faces.

If you don't want to recognize faces then you need only this code to display on monitor video from camera.

import cv2

import sys

video_capture = cv2.VideoCapture(0)

while True:

    # Capture frame-by-frame
    ret, frame = video_capture.read()

    # Display the resulting frame
    cv2.imshow('Video', frame)

    # exit if you press key `q`
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

#When everything is done, release the capture
video_capture.release()

Or this to save image

import cv2

video_capture = cv2.VideoCapture(0)

# Capture frame
ret, frame = video_capture.read()

# Write frame in file
cv2.imwrite('image.jpg', frame)

# When everything is done, release the capture
video_capture.release()