Image sending / receiving memo in Python (Flask)

Introduction

This time, I will make a note of one of the ways to receive images in the python framework flask. Specifically, it receives the image in a base64-encoded format, decodes it on the flask side, and restores the image. Then, use open-cv to convert the restored image to grayscale, encode it to base64 again, and make a note of it.

Source

The library to be used is as follows.

`requirements.txt`


flask
flask-cors
opencv-python
opencv-contrib-python

I want to handle multiple data in the request, so I will use json format.

[
    {
        id : 0
        Image : id4zFjyrkAuSI2vUBKVLP...(Base64 encoded image)
    },
    {
        id : 1
        Image : k75GN/oll7KUCulSpSM/S...(Base64 encoded image)
    }
]

`main.py`


from flask import Flask, jsonify, request
from flask_cors import CORS
import cv2
import numpy as np
import base64

app = Flask('flask-tesseract-api')
CORS(app)

@app.route("/image/", methods=["POST"])
def post():
    """
Convert image to grayscale
    """

    response = []

    for json in request.json:

        #Decode Image
        img_stream = base64.b64decode(json['Image'])
        
        #Convert to an array
        img_array = np.asarray(bytearray(img_stream), dtype=np.uint8)
        
        # open-Grayscale with cv
        img_gray = cv2.imdecode(img_array, 0)
   
        #Save conversion result
        cv2.imwrite('result.png', img_before)

        #Encode for saved file
        with open('result.png', "rb") as f:
            img_base64 = base64.b64encode(f.read()).decode('utf-8')
        
        #Boxed in response json
        response.append({'id':json['id'], 'result' : img_base64})
       
    return jsonify(response)

if __name__ == '__main__':
    app.run(host='0.0.0.0',port=5000,debug=True)

Summary

I was able to send multiple images encoded to flask as json format. With this, you can implement the function to handle multiple images at the same time.