how to handle blob sent via javascript through websocket back at the python server?

Question

i have to process the image back at the python server with Opencv . the blob goes to the python server but i could not figure out how to convert this blob back into image with openCV

 //this is my javascript function to send image converted to blob, 
//back to my python server
         function () {

             ctx.drawImage(video, 0, 0, 320, 240);
            var data = canvas.get()[0].toDataURL('image/jpeg', 1.0);
             newblob = dataURItoBlob(data);
             ws.send(newblob);

            }

this is my python backend handling

class EchoServerProtocol(WebSocketServerProtocol):

       def onMessage(self, msg, binary):
         img = # here the code to convert blob into the image
         blur = cv2.blur(img, (5, 5))
         hsv = cv2.cvtColor(blur, cv2.COLOR_BGR2HSV)
         msg = hsv
         print "the image:", msg
         #conver the image back to blob and reply back to the websocket
         #havent written the code for this part yet
         self.sendMessage(msg, binary)

please help me figure this out

Try looking at the network tab in your developer tools to see how a blob is sent through a websocket. — Musa
– Musa, Commented Oct 9, 2013 at 15:03
it's probably b64 encoded, after that use imdecode to make a cv image from the jpeg — berak
– berak, Commented Oct 9, 2013 at 16:08

Jyotsna Dua · Accepted Answer · 2015-12-30 21:24:41Z

1

Check out how this blob is getting made and then reverse engineer it

answered Dec 30, 2015 at 21:24

Jyotsna Dua

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