Can an uploaded image be loaded directly by cv2?

Build a numpy array using the uploaded data. Decode this array using cv2.

img = cv2.imdecode(numpy.fromstring(request.files['file'].read(), numpy.uint8), cv2.IMREAD_UNCHANGED)

python opencv flask

If working with BaseHTTPRequestHandler, one should first create a FieldStorage form:

fm = cgi.FieldStorage(fp=self.rfile, headers=self.headers, environ={'REQUEST_METHOD':'POST'})

then:

if "file" in fm:                image = cv2.imdecode(np.frombuffer(fm['file'].file.read(), np.uint8), cv2.IMREAD_UNCHANGED)

Also, note that fromstring is deprecated, and that's why I'm updating davidism's answer with frombuffer.

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