How to convert image file object to numpy array in with openCv python?

Question

I am developing API to upload Image using Flask. After uploading i want to modify image using openCV, As openCV requires numpy array object to i have file object, how do i convert to numpy array? Here is my code

@app.route('/upload', methods=['POST'])
def enroll_user():
    file = request.files['fileName']
    # file.save(os.path.join(file.filename))
    return response

Edit: updated code

@app.route('/upload', methods=['POST'])
    def enroll_user():
        file = request.files['fileName']
        response = file.read()
        # file.save(os.path.join(file.filename))
        return response

I want to convert file to cv2 frame as i get with below code

ret, frame = cv2.imread(file)

One way is to write image to disk and read again with cv2.imread but i don't want to do that because it will be time consuming. So is there any way to convert to cv2 frame from file object?

Thanks

Answer 1

If you effectively have the contents of a JPEG/PNG file in your variable called response, I think you can do:

frame = cv2.imdecode(response)

Or, you may need to do:

frame = cv2.imdecode(np.fromstring(response, np.uint8), cv2.IMREAD_COLOR)

Failing that, another way is like this:

from io import BytesIO
from scipy import misc

frame = misc.imread(BytesIO(response))