venryx/windows-ffi

NodeJS wrappers around Windows p-invoke/dll functions in user32, gdi32, etc. (based on node-ffi-napi)

Windows FFI

NodeJS wrappers around Windows p-invoke/dll functions in user32, gdi32, etc. (based on node-ffi-napi)

Installation

• 1) Install ffi-napi in your project: npm i ffi-napi
  • 1.1) You may need to install the windows-build-tools first for ffi-napi to be able to build: npm install --global --production windows-build-tools
• 2) Install: npm i windows-ffi
  • 2.1) If you're using windows-ffi in symlinked mode (ie. you probably don't need this step!), supply the parent project's copy of the node-ffi libraries using the init code below:

     // Make sure the code below runs before windows-ffi is imported! (example approach: https://stackoverflow.com/a/42817956)
     import ffi from "ffi-napi";
     import ref from "ref-napi";
     import refStructDI from "ref-struct-di";
     import {SupplyConfig} from "windows-ffi/Dist/@UserSupplied/PreImportConfig.js";
    
     SupplyConfig({ffi, ref, refStructDI});
    

Usage

While this library is meant to gradually expand to cover more of the Windows API, it will never be 100%, because it's a "develop as you need it" sort of endeavor.

Some of the most common and/or noteworthy functionalities are shown below.

Capture image-data from a region on-screen

import {VRect, CaptureScreenshot, GetForegroundWindowHandle} from "windows-ffi";

// First capture a screenshot of a section of the screen.
const screenshot = CaptureScreenshot({
	windowHandle: GetForegroundWindowHandle(), // comment to screenshot all windows
	rectToCapture: new VRect(0, 0, 800, 600),
});

// The image-data is now stored in the `screenshot.buffer` Buffer object.
// Access it directly (and cheaply) using the helper functions on `screenshot`.
for (let x = 0; x < 800; x++) {
	console.log(`Pixel color at [${x}, 0] is:`, screenshot.GetPixel(x, 0).ToHex_RGB());
}

Performance:

• Full-screen (2560x1440), all windows (ie. "desktop" window): ~80ms
• Full-screen (2560x1440), single window: ~20ms
• Region (700x200), all windows (ie. "desktop" window): ~50ms
• Region (700x200), single window: ~4ms

Tasks

General:

• Create an accompanying library for Windows-specific functionalities that do not require the ffi-napi dependency. (I've had pains with ffi-related building during NodeJS updates, so things that can be done without that dependency is beneficial to bundle separately)

windows-ffi's Issues

VRect

I don’t understand what I'm doing wrong, I seem to have done everything according to the instructions, but I get an error:
import {VRect, CaptureScreenshot, GetForegroundWindowHandle} from "windows-ffi";
^^^^^
SyntaxError: The requested module 'windows-ffi' does not provide an export named 'VRect'
←[90m at ModuleJob._instantiate (node:internal/modules/esm/module_job:127:21)←[39m
←[90m at async ModuleJob.run (node:internal/modules/esm/module_job:191:5)←[39m
at async Promise.all (index 0)
←[90m at async ESMLoader.import (node:internal/modules/esm/loader:331:24)←[39m
←[90m at async loadESM (node:internal/process/esm_loader:88:5)←[39m
←[90m at async handleMainPromise (node:internal/modules/run_main:65:12)←[39m

custom window handle not work?

Hi, first of all thanks for this repo, much needed given not a lot of resources online and I am not familiar with c/c++..
I have encountered some issue though: when I try the following it works perfectly

	const screenshot = CaptureScreenshot({
		windowHandle: user32.GetDesktopWindow()
	});

However when I try windowHandle: GetForegroundWindowHandle() or windowHandle: user32.FindWindowA(null, "Calculator") it generates blank image, the width/height info are correct but the pixels output from screenshot.GetPixel(x, y).ToHex_RGB() are mostly 000000, I say mostly because I have tried to use it on my Outlook Inbox window, it showed a tiny portion of the window application.

Have you encountered anything like it? I appreciate any pointers/directions, thanks!

screenshot.buffer as .bmp file cannot be opened

code

import {VRect, CaptureScreenshot, GetForegroundWindowHandle} from 'windows-ffi';
import fs from 'fs';
import path from 'path';

async function main() {
    // First capture a screenshot of a section of the screen.
    const screenshot = CaptureScreenshot({
        log: true,
        windowHandle: GetForegroundWindowHandle(), // comment to screenshot all windows
        rectToCapture: new VRect(0, 0, 800, 600)
    });
    console.log('screenshot', screenshot);
    const filePath = path.join('capture.bmp');

    fs.writeFileSync(filePath, screenshot.buffer);
}
main();

result:

.bmp file cannot be opened

CaptureScreen give me always the same ghost image

Hello

I'm at one problem to use your package for my dev.
The problem is that when i try to CaptureScreenshot the foregroung window
Either i get a dark image (when vscode is focused), either i get the same image from my fullscreen game (i can teleport to another place in my game, the screenshot will still be as the first one)
Its seems there is a problem somewhere but i don't know what could cause this

I also check with window detective, nothing is blocking the screenshot for both the game and vscode app

Here is the code used to reproduce the bug

import * as fs from 'fs';

import { Screenshot, VRect } from 'windows-ffi';

import { CaptureScreenshot, GetForegroundWindowHandle } from 'windows-ffi';

import sharp from 'sharp';


let start: number = Date.now();

// First capture a screenshot of a section of the screen.
const screenshot: Screenshot = CaptureScreenshot({
  windowHandle: GetForegroundWindowHandle(), // comment to screenshot all windows
  rectToCapture: new VRect(0, 0, 2560, 1440),
  log: true,
});

console.log(Date.now() - start);
start = Date.now();
const buffer: sharp.Sharp = await sharp(Buffer.from(screenshot.buffer), {
  raw: {
    width: 2560,
    height: 1440,
    channels: 4,
  },
});
fs.writeFileSync('./debug/ffi.jpeg', await buffer.jpeg().toBuffer());
console.log(Date.now() - start);

perhaps i need another/older user32 dll ?

Node version : v19.7.0
Windows 11

Thanks in advance for your help

can you add CreateDesktopA function (winuser.h)?

can you add CreateDesktopA function (winuser.h)?