Display a webcam stream in PyQt4 using OpenCV Camera Capture

Question

I am using this Python script to display my webcam:

from opencv.cv import *  
from opencv.highgui import *  

import sys

cvNamedWindow("w1", CV_WINDOW_AUTOSIZE)
camera_index = 0
capture = cvCreateCameraCapture(camera_index)

def repeat():
    global capture #declare as globals since we are assigning to them now
    global camera_index
    frame = cvQueryFrame(capture)
    cvShowImage("w1", frame)
    c = cvWaitKey(10)

    if c == "q":
        sys.exit(0)

if __name__ == "__main__":
    while True:
        repeat()

It is working quite well, but I would like to set this display inside my Qt application. How can I use the IplImage OpenCV image into a Qt VideoWidget?

Answer 1

I used the code bellow to covert a Iplimage objet to a QImage. It took me some time to get the right formats. Iplimage is a 3-channel format with BGR channel order while QImage uses RGB channel order.

camcapture = cv.CaptureFromCAM(0)       
cv.SetCaptureProperty(camcapture,cv.CV_CAP_PROP_FRAME_WIDTH, 1280)
cv.SetCaptureProperty(camcapture,cv.CV_CAP_PROP_FRAME_HEIGHT, 720);

frame = cv.QueryFrame(camcapture)
image = QImage(frame.tostring(), frame.width, frame.height, QImage.Format_RGB888).rgbSwapped()
pixmap = QPixmap.fromImage(image)

Answer 2

It looks like we need to bind this C++ code in Python :

QImage& cvxCopyIplImage(const IplImage *pIplImage, QImage &qImage)
{
        if(!CV_IS_IMAGE(pIplImage)) return qImage;

        int w = pIplImage->width;
        int h = pIplImage->height;


        if(qImage.width() != w || qImage.height() != h)
        {
                qImage = QImage(w, h, QImage::Format_RGB32);
        }

        int x, y;
        for(x = 0; x < pIplImage->width; ++x)
        {
                for(y = 0; y < pIplImage->height; ++y)
                {
                        CvScalar color = cvGet2D(pIplImage, y, x);

                        if(pIplImage->nChannels == 1)
                        {
                                int v = color.val[0];

                                qImage.setPixel(x, y, qRgb(v,v,v));
                        }
                        else
                        {
                                int r = color.val[2];
                                int g = color.val[1];
                                int b = color.val[0];

                                qImage.setPixel(x, y, qRgb(r,g,b));
                        }
                }
        }

        if(pIplImage->origin != IPL_ORIGIN_TL)
        {
                qImage = qImage.mirrored(false, true);
        }

        return qImage;
}

Answer 3

This one worked for me. I work on Linux with Python 2.6.5:

import base64
import Image
import time
import urllib2
import cv

# Basic HTTP Authentication...
url = 'http://192.168.0.11:82/Videostream.cgi'
ww = 'Username:Password'
encodedstring = base64.encodestring(ww)[:-1]
auth = "Basic %s" % encodedstring
req = urllib2.Request(url,None, {"Authorization": auth })
handle = urllib2.urlopen(req)

def read_stream():
    buf = ''
    b = handle.readlines(45)
    for a in b:
        if a.startswith('Content-Length'):
            readlen = str(a).split()[1]
    b1 = handle.read(int(readlen)+4)
    return b1

def test():
    pass

def write_stream():
    imgc = read_stream()
    cv_img = cv.CreateImageHeader((640,480), cv.IPL_DEPTH_8U, 3)
    buf = Image.fromstring('RGB',(640,480),imgc[2:], 'jpeg', 'RGB', None)
    cv.SetData(cv_img, buf.tostring(), (640*3))
    return cv_img


fps = 10.0

if __name__ == "__main__":
    while True:
        frame = write_stream()
        cv.ShowImage('Camera', frame)
        k = cv.WaitKey(10)
        time.sleep(int(1.0/fps))
        if k == 0x10001b: # ESC
            cv.DestroyWindow("Camera")
            print 'ESC pressed. Exiting ...'
            break