Node

In this tutorial we will run the Digger game in Node.js and save a game screenshot to an image.

Let's start by creating an empty project:

npm init

To run DOS in Node.js, we need to install the emulators package. To create a screenshot, we will use the jimp library, so let's install both packages.

npm install --save emulators jimp

Next we need to download the Digger js-dos bundle:

curl https://v8.js-dos.com/bundles/digger.jsdos -o digger.jsdos

Let's create the source file digger.js. We can run it with node digger.js.

Use require to import all libraries

const fs = require("fs");
const jimp = require("jimp");

require("emulators");

const emulators = global.emulators;
emulators.pathPrefix = "./";

Now we need to read the contents of a js-dos bundle and start emulation

const bundle = fs.readFileSync("digger.jsdos");

emulators
    .dosboxDirect(bundle)
    .then((ci) => {
      // ...
    });

When DOS emulation starts, we will receive a Command Interface. We can use it to subscribe to frame updates and to send key/mouse events.

    ci.events().onFrame((rgb, rgba) => {
        // use rgb or rgba image data
    });

To save a screenshot, convert the latest frame to RGBA:

function toRgba(frame, width, height) {
    const screenshot = Buffer.alloc(width * height * 4);

    for (let source = 0, target = 0; target < screenshot.length;) {
        screenshot[target++] = frame[source++];
        screenshot[target++] = frame[source++];
        screenshot[target++] = frame[source++];
        screenshot[target++] = 255;
        if (frame.length === screenshot.length) {
            source++;
        }
    }

    return screenshot;
}

If you execute node digger.js it will save the screenshot to ./screenshot.png.

Full code of digger.js:

const fs = require("fs");
const jimp = require("jimp");

require("emulators");

const emulators = global.emulators;
emulators.pathPrefix = "./";

const bundle = fs.readFileSync("digger.jsdos");

function toRgba(frame, width, height) {
    const screenshot = Buffer.alloc(width * height * 4);

    for (let source = 0, target = 0; target < screenshot.length;) {
        screenshot[target++] = frame[source++];
        screenshot[target++] = frame[source++];
        screenshot[target++] = frame[source++];
        screenshot[target++] = 255;
        if (frame.length === screenshot.length) {
            source++;
        }
    }

    return screenshot;
}

emulators
    .dosboxDirect(bundle)
    .then((ci) => {
        let frame = new Uint8Array(0);
        ci.events().onFrame((rgb, rgba) => {
            frame = rgb ?? rgba ?? frame;
        });

        // capture the screen after 3 sec
        console.log("Will capture screen after 3 sec...");
        setTimeout(() => {
            const width = ci.width();
            const height = ci.height();
            if (frame.length === 0) {
                throw new Error("No frame received");
            }

            const screenshot = toRgba(frame, width, height);
            new jimp({ data: screenshot, width, height }, (err, image) => {
                image.write("./screenshot.png", () => {
                    ci.exit();
                });
            });
        }, 3000);
    })
    .catch(console.error);

19 июня 2026