nodeJS Convert Buffer to fs.ReadStream object

Question

I'm saving an image file locally so I can ready it using fs.createReadStream() and append it to my FormData to send it to a REST api. Like this: (I'm using the trello api https://developer.atlassian.com/cloud/trello/rest/#api-cards-id-attachments-post)

const fetch = require('node-fetch');
const Jimp = require('jimp');
const FormData = require('form-data');

// Save file locally
await Jimp.read(imagePNGURL).writeAsync(savedImagePath);

// Append it to the formdata using fs.createReadStream
const formData = new FormData();
formData.append('file', fs.createReadStream(savedImagePath));

// Send formData to api and image gets saved correctly
await fetch('TrelloUrl', { method: 'POST', body: formData })

Now I want to do the same thing but without saving the file locally but by using the image buffer. I've tried the following but I can't seem to make it work:

const fetch = require('node-fetch');
const Jimp = require('jimp');
const FormData = require('form-data');
const stream = require('stream');

// Save file to Buffer
const buffer = await Jimp.read(imagePNGURL).getBufferAsync('image/png');

// Convert buffer to stream
const bufferStream = new stream.PassThrough();
bufferStream.end(buffer);

// Try to append it to the formdata and send it to the api
const formData = new FormData();
formData.append('file', bufferStream); // Results in 400 Bad Request
formData.append('file', bufferStream.read()); // Results in empty image being uploaded

await fetch('TrelloUrl', { method: 'POST', body: formData })

---------
// Also tried to convert the buffer to stream like this:
const { Readable } = require('stream');

const bufferToStream = (buffer) => {
    const stream = new Readable();
    stream.push(buffer);
    stream.push(null);

    return stream;
};
formData.append('file', bufferToStream(buffer)); // Results in 400 Bad Request
formData.append('file', bufferToStream(buffer).read(); // Results in empty image being uploaded

How can I convert the buffer correctly to a fs.ReadStream() object so I can send it successfully to the api?

Or are there better ways to approach this?

All help is appreciated.

Answer 1

You can get the stream directly from the url using axios and append to form-data

const axios = require("axios")

const getImageStream =  async (url) => {
    const response = await axios.get(url, {responseType : "stream"});
    if (response.status === 200) {
        return response.data
    } 
}

const formData = new FormData();
 
formData.append('file', await getImageStream(imagePNGURL) );

Answer 2

set custom filename (set whatever name do you want) and content-type, worked for me

const formData = new FormData();
formData.append('file', bufferStream, {filename: 'photo.png', contentType: 'image/png');