Flask caching endpoint for images stored MongoDB

doc_view.py

@app.route('/doc/<docId>')
def getDoc(docId):
    userDoc = UserDocument.objects(id=docId).first()  # I use MongoEngine to query my mongodb instance
    if not userDoc:
        return abort(404)

    desiredWidthStr = request.args.get('width')
    desiredHeightStr = request.args.get('height')

    if desiredWidthStr or desiredHeightStr:
        try:
            desiredWidth = int(desiredWidthStr) if desiredWidthStr else None
            desiredHeight = int(desiredHeightStr) if desiredHeightStr else None
        except ValueError as e:
            print e
            return abort(400, "A width and a height can only be integers.")

        im = Image.open(userDoc.file_)
        originalWidth, originalHeight = im.size
        if desiredWidth and not desiredHeight:
            desiredHeight = originalHeight / (originalWidth / desiredWidth)  # Calculate height from width
        elif not desiredWidth and desiredHeight:
            desiredWidth = originalWidth / (originalHeight / desiredHeight)  # Calculate width from height
        else:
            return abort(400, "Please provide either a 'width' OR a 'height', but never both.")

        if desiredWidth < originalWidth and desiredHeight < originalHeight:  # if this is false there's no need to resize and we just serve the original image.
            thumbFilename = '/tmp/' + str(userDoc.id) + '_' + str(desiredWidth) + 'x' + str(desiredHeight) + '.' + im.format  # Create a filename with the id and the size of the image.
            if not os.path.isfile(thumbFilename):  # Check if the resized file already exists in the cache
                im.thumbnail((desiredWidth, desiredHeight))  # Resize the image
                im.save(thumbFilename, im.format)  # Save/cache the resized image in /tmp

            thumbFile = open(thumbFilename, 'r')  # Open the file from cache
            return Response(thumbFile, mimetype=mimetypes.guess_type(thumbFilename)[0])

    userDoc.file_.seek(0)  # ensure we are reading the image from the start
    return Response(userDoc.file_.read(), mimetype=userDoc.file_.content_type)