How to fetch from mysql table an img and encode it and send it as a jason to android

I want to fetch an imgs from mysql records . i've read how to send it to android i realized that it must to encode it to base64 then decode it in android so i just want to know how to fetch the img from the table and decode it ? i don't want to use url() and send it ! i just want to send decode string to android ??

heres my php code

**<?php

$response = array();

require_once __DIR__ . '/db_connect.php';

$obj = new DB_CONNECT();
 $con=$obj->connect();
     $result =mysqli_query($con,"SELECT * FROM doctors ");

    if (!empty($result)) {
        if (mysqli_num_rows($result) > 0) {

            $result = mysqli_fetch_array($result);

            $product = array();
            $product["d_id"] = $result["d_id"];
            $product["name"] = $result["name"];
            $product["major"] = $result["major"];
            $product["clinic"] = $result["clinic"];
            $product["img"] = $result["img"];
            $response["success"] = 1;

            $response["product"] = array();

            array_push($response["product"], $product);

            echo json_encode($response);
        } else {
            $response["success"] = 0;
            $response["message"] = "No data found";

            echo json_encode($response);
        }
    } else {
        $response["success"] = 0;
        $response["message"] = "No data found";

        echo json_encode($response);
    }
?>**