从Postgres DB获取PNG文本并将图像发送到前端React

Question

I have a postgreSQL server with table: "buildings" and it contains a column: "testimg" with a data type of "text". The text is a PNG file's text. I have an Express.js back-end app that is sucessfully connected to my database, and I have a created a Route that can read this column (row 1) to reveal the text contained. I don't know how to send this as an image file to my Front-End React app.

The React app is connected to the route and I know how to call the route and get a header and all. I also know I probably need to encode into base 64 but I'm really not sure. I have done some digging and this is what I have so far.

//in my express app:
router.get('/test_image', ( req, res, next ) => {
  client.query( "select testimg from buildings;" ).then( img_data => {
    let base_64_string = img_data.rows[1].testimg + "\n";
    let img = Buffer.from( base_64_string, 'base64' );
    res.writeHead(
      200, {
     'Content-Type': 'image/png',
     'Content-Length': img.length
    })
    res.end(img);
  } )
})


//in my react app:
let img_query = null;
fetch( '/api/sites/test_image' )
.then( res => { img_query = res;} )
.catch( ( err ) => console.log( 'error:',err ) )

This gives me a response with a body of "ReadableStream". Not sure if I'm going about this the right way but I need to eventually get "img_query" to contain my testimg.png.

Answer 1

This gives me a response with a body of "ReadableStream"

That's expected. From MDN body of response is A simple getter used to expose a ReadableStream of the body contents.

You can use one of the available methods to read the ReadableStream . In this case you could use text method. From MDN

Takes a Response stream and reads it to completion. It returns a promise that resolves with a USVString (text).

fetch( '/api/sites/test_image' )
  .then( res => res.text() )
  .then( base64img => {
    // base64img is the base64 string
  })
  .catch( ( err ) => console.log( 'error:',err ) )