[PYTHON] Send and receive Flask images

Overview

There was not much Japanese processing for image transmission / reception processing, so I will summarize it.

Sample code

Here is a sample code for echoing back an image.

Send / receive

@app.route("/echo_back", methods=['POST'])
def test():
    img_bin = io.BytesIO(request.data).getvalue() #Receive
    response = make_response(img_bin) #Set the image in the response
    response.headers.set('Content-Type', request.content_type) #Header setting
    
    return response

The points are shown below. --Image information is stored in "request.data". If this is an io.ByteIO type, only image information can be acquired. Since it is echoed back this time, it is immediately converted to bytes type using getvalue (). --When storing image information in make_response (), it seems that it must be bytes type. Therefore, as mentioned above, getvalue () is used as bytes type. --Finally, "Content-type" is set in the header.

If you want to perform image processing on the way, convert the type as appropriate. If it is opencv, it will be a numpy array. In the case of PIL, should it be something like Image.open (io.BytesIO (request.data))?

Test method

I am using "POST MAN". This section describes the settings when "POST MAN" is used.

--Communication is "POST" (since only POST is allowed this time) --Add "Content-Type" to Header and set "Value" according to the file format of the image file --Set Body to "binary" and select an image file

Basically, use the above settings. This allows you to confirm that the file you sent will be returned as is.