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Need help in showing open cv output frame in browser

asked 2020-02-05 01:36:58 -0500

salmaUCP gravatar image

updated 2020-02-05 01:40:49 -0500

LBerger gravatar image

Hey I want to show the open cv frame output in window of browser. I am making flask app of human Activity Recognition.

# import the necessary packages
import time

import onnx
import numpy as np
import argparse
import imutils
import sys
import cv2
from import VideoStream
from flask import Flask, render_template, request

app = Flask(__name__)

app.secret_key = "my precious"
c = open('action_recognition_kinetics.txt')
def home():

    return render_template('harPro.html')  # render a template

@app.route('/recognize', methods= ['POST','GET'])
def Recognize():
    if request.method == 'POST':
        i = request.form['myFile']
        CLASSES ="\n")
        SAMPLE_DURATION = 16
        SAMPLE_SIZE = 112
# load the human activity recognition model
        print("[INFO] loading human activity recognition model...")
        net = cv2.dnn.readNet('resnet-34_kinetics.onnx')

        # grab a pointer to the input video stream
        print("[INFO] accessing video stream...")
        vs = cv2.VideoCapture(i if i else 0)

        # loop until we explicitly break from it
        while True:
            # initialize the batch of frames that will be passed through the
            # model
            frames = []

            # loop over the number of required sample frames
            for i in range(0, SAMPLE_DURATION):
                # read a frame from the video stream
                (grabbed, frame) =

                # if the frame was not grabbed then we've reached the end of
                # the video stream so exit the script
                if not grabbed:
                    print("[INFO] no frame read from stream - exiting")

                # otherwise, the frame was read so resize it and add it to
                # our frames list
                frame = imutils.resize(frame, width=400)

            # now that our frames array is filled we can construct our blob
            blob = cv2.dnn.blobFromImages(frames, 1.0,
                                          (SAMPLE_SIZE, SAMPLE_SIZE), (114.7748, 107.7354, 99.4750),
                                          swapRB=True, crop=True)
            blob = np.transpose(blob, (1, 0, 2, 3))
            blob = np.expand_dims(blob, axis=0)

            # pass the blob through the network to obtain our human activity
            # recognition predictions
            outputs = net.forward()
            label = CLASSES[np.argmax(outputs)]

            # loop over our frames
            for frame in frames:
                # draw the predicted activity on the frame
                cv2.rectangle(frame, (0, 0), (300, 40), (0, 0, 0), -1)
                cv2.putText(frame, label, (10, 25), cv2.FONT_HERSHEY_SIMPLEX,
                            0.8, (255, 255, 255), 2)

                # # display the frame to our screen
                cv2.imshow("Activity Recognition", frame)
            key = cv2.waitKey(1) & 0xFF
            # if the `q` key was pressed, break from the loop
            if key == ord("q"):


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  • we cant help with flask or how to write proper html, that's off-topic
  • no, you cannot use imshow() / waitKey() on a server. if you want to show an image, you have to save it to disk, and return html with an <img> or such.
  • the final output of it is a text string, why not send that back, not an image ?
  • don't sample the 1st 16 images only, but spread them uniformly over the whole duration of the video (see paper !)
berak gravatar imageberak ( 2020-02-05 02:01:03 -0500 )edit

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answered 2020-03-23 09:43:47 -0500

salmaUCP gravatar image

Okay Thank You!

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Asked: 2020-02-05 01:36:58 -0500

Seen: 990 times

Last updated: Feb 05 '20