Stream OpenCV frame to HTML in Python

问题

I am trying to read a video from a URL in opencv(Python) and then process it frame by frame and then send it to an HTML page.

But I am only getting the first frame, after that the program gives the following error

This is my main file (main.py)

from flask import Flask, render_template, Response
from camera import VideoCamera
import pdb
app = Flask(__name__)

@app.route('/')
def index():
    return render_template('index.html')

def gen(camera):
    while True:
        frame = camera.get_frame()
        yield (b'--frame\r\n'
                b'Content-Type: image/jpeg\r\n\r\n' + frame + b'\r\n\r\n')

@app.route('/video_feed')
def video_feed():
    return Response(gen(VideoCamera()),
                    mimetype='multipart/x-mixed-replace; boundary=frame')

if __name__ == '__main__':
    app.run(host='127.0.0.1', debug=True)

And this is the camera.py file:

    import cv2
    import urllib
    import pdb
    import numpy as np

    face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')
    #https://github.com/Itseez/opencv/blob/master/data/haarcascades/haarcascade_eye.xml
    eye_cascade = cv2.CascadeClassifier('haarcascade_eye.xml')

    class VideoCamera(object):
        def __init__(self):
            # Using OpenCV to capture from device 0. If you have trouble capturing
            # from a webcam, comment the line below out and use a video file
            # instead.
            self.video = urllib.urlopen('http://192.168.10.12:8080/video')   #cv2.VideoCapture(0)
            # If you decide to use video.mp4, you must have this file in the folder
            # as the main.py.
            # self.video = cv2.VideoCapture('video.mp4')

        def __del__(self):
            self.video.release()

        def get_frame(self):

            bytes=''
            while True:
                # pdb.set_trace()
                bytes+=self.video.read(1024)
                a = bytes.find('\xff\xd8')
                b = bytes.find('\xff\xd9')
                if a!=-1 and b!=-1:
                    jpg = bytes[a:b+2]
                    bytes= bytes[b+2:]

                    img = cv2.imdecode(np.fromstring(jpg, dtype=np.uint8),cv2.IMREAD_COLOR) 
                    # pdb.set_trace()
                    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
                    faces = face_cascade.detectMultiScale(gray, 1.3, 5)
                    for (x,y,w,h) in faces:
                        cv2.rectangle(img,(x,y),(x+w,y+h),(255,0,0),2)
                        roi_gray = gray[y:y+h, x:x+w]
                        roi_color = img[y:y+h, x:x+w]

                    ret, jpeg = cv2.imencode('.jpg', img)
                    return jpeg.tobytes()

I only get the first frame( Shown below):

回答1:

I am sure you have solved your error by now but this is for other people who visit this question:

write this is your camera.py file

don't get confused by draw_box method, it's just custom square I am using. You can use normal cv2.rectangle for making rectangles on faces.

import cv2


WHITE = [255, 255, 255]
face_cascade = cv2.CascadeClassifier('Haar/haarcascade_frontalcatface.xml')
eye_cascade = cv2.CascadeClassifier('Haar/haarcascade_eye.xml')


def draw_box(Image, x, y, w, h):
    cv2.line(Image, (x, y), (x + int(w / 5), y), WHITE, 2)
    cv2.line(Image, (x + int((w / 5) * 4), y), (x + w, y), WHITE, 2)
    cv2.line(Image, (x, y), (x, y + int(h / 5)), WHITE, 2)
    cv2.line(Image, (x + w, y), (x + w, y + int(h / 5)), WHITE, 2)
    cv2.line(Image, (x, (y + int(h / 5 * 4))), (x, y + h), WHITE, 2)
    cv2.line(Image, (x, (y + h)), (x + int(w / 5), y + h), WHITE, 2)
    cv2.line(Image, (x + int((w / 5) * 4), y + h), (x + w, y + h), WHITE, 2)
    cv2.line(Image, (x + w, (y + int(h / 5 * 4))), (x + w, y + h), WHITE, 2)


class VideoCamera(object):
    def __init__(self):
        self.video = cv2.VideoCapture(0)

    def __del__(self):
        self.video.release()

    def get_frame(self):
        success, image = self.video.read()
        # We are using Motion JPEG, but OpenCV defaults to capture raw images,
        # so we must encode it into JPEG in order to correctly display the
        # video stream.

        gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
        faces = face_cascade.detectMultiScale(gray, 1.3, 5)
        for (x, y, w, h) in faces:
           gray_face = cv2.resize((gray[y:y + h, x:x + w]), (110, 110))
            eyes = eye_cascade.detectMultiScale(gray_face)
            for (ex, ey, ew, eh) in eyes:

                draw_box(gray, x, y, w, h)

        ret, jpeg = cv2.imencode('.jpg', gray)

        return jpeg.tobytes()

回答2:

Use small size for reading bytes in .read() function.

来源：https://stackoverflow.com/questions/44902550/stream-opencv-frame-to-html-in-python