How to get screenshots when using node-rdpjs. Write the partial bitmap and render it into the right section of the "buffer" image, then save that to disk whenever you need to.

rdp.js

const screen = require('./screen');
const SCREEN_SIZE = { width : 1364, height : 768 };

async function saveScreen(label) {
  await screen.write('screen-'+Date.now()+'-'+(label || '')+'.png');
}

async function createRemoteSession(userName, password, server, rdpScreenSaveInterval=0) {
    const clientConfig = {
        autoLogin: true,
        decompress: true,  // important for getting the screenshots properly
        screen: SCREEN_SIZE,
        userName: userName,
        password: password
    };

    let client = null;
    let sessionCreated = false;
    screen.create(SCREEN_SIZE).then(async function() {
      console.log(`connecting to ${server} using username=${userName}`);
      client = rdp.createClient(clientConfig).on('bitmap', function(bitmap) {
          // update the screen buffer
          screen.update(bitmap, true);
          // NOTE: this gets called sooooo much - don't just save to file here
      }).connect(server, 3389);

      // write screenshots ever rdpScreenSaveInterval ms
      if(rdpScreenSaveInterval) {
          setInterval(function() {
              await saveScreen();
          }, interval);
      }
      // NOTE: there's nothing special about using an interval.
      // You could screenshot based on whatever you want.

    }).catch(function(err) {
        console.error('error', err);
    });
}

screen.js

const Jimp = require('jimp');

let partialImage = null;
let image = null;

/**
 * create the canvas to right the screen updates to
 * @param size {object} - object with height and width of the screen
 */
function create(size) {
	return new Promise((resolve, reject) => {
		new Jimp(32,32, function(err, pImage) {
			partialImage = pImage;
			if(err) {
				console.error(err);
				reject(err);
			} else {
				new Jimp(size.width, size.height, function(err2, newImage) {
					image = newImage;
					if(err) {
						console.error(err2);
						reject(err2);
					} else {
						resolve();
					}
				});
			}
		});
	});
};
/**
 * update canvas with new bitmap
 * @param bitmap {object}
 */
function update (bitmap) {
	var output = {
		width: bitmap.width,
		height: bitmap.height,
		data: new Uint8ClampedArray(bitmap.data)
	};

	if(partialImage) {
		partialImage.bitmap.width = output.width;
		partialImage.bitmap.height = output.height;
		partialImage.bitmap.data = output.data;
		image.composite(partialImage, bitmap.destLeft, bitmap.destTop);
	}
}

/**
 * write the current image to disk
 * @param filename - file name to write to
 */
function write (filename) {
	image.write(filename);
}

module.exports = {
	create,
	update,
	write
};