What is the process for capturing a window screenshot using Node.js?

Question

What is the process for capturing a window screenshot using Node.js?

I am currently conducting research to discover a way to capture a screenshot of a window using Node.js. I have been attempting to achieve this with node-ffi, but I am facing some difficulties at the moment:

var ffi = require('ffi');

var user32 = new ffi.Library("user32", {
      FindWindowA: [ 'uint32' , [ 'string', 'string' ]]
    , PrintWindow: [ 'int32'  , [ 'int32', 'string', 'int32' ]]
});

var IMG;
var windowHandle = user32.FindWindowA(null, "Calculator");
var printWin = user32.PrintWindow(windowHandle, IMG, 0);

console.log(printWin);
console.log(IMG);

The outcome is:

$ node get-print.js
1
undefined

EDITED

I have come across functional C++ code which accomplishes this task:

Bitmap bm = new Bitmap(1024, 768);
Graphics g = Graphics.FromImage(bm);
IntPtr hdc = g.GetHdc();
Form1.PrintWindow(this.Handle, hdc, 0);
g.ReleaseHdc(hdc);
g.Flush();
g.Dispose();
this.pictureBox1.Image = bm;

My goal now is to replicate this functionality in NodeJs,

Is there anyone who can assist me?

javascript node.js npm user32 node-ffi

Answer 1

Answer №1

One way to capture screenshots on your desktop is by utilizing a helpful NPM package called "desktop-screenshot". This tool offers an easy-to-use solution for taking screenshots.

Here's an example implementation using the package:

var screenshot = require('desktop-screenshot');

screenshot("screenshot.png", function(error, complete) {
    if(error)
        console.log("Screenshot failed", error);
    else
        console.log("Screenshot succeeded");
});

For more information about this package, you can visit: https://www.npmjs.com/package/desktop-screenshot

Answer 2

One way to capture screenshots on your desktop is by utilizing a helpful NPM package called "desktop-screenshot". This tool offers an easy-to-use solution for taking screenshots.

Here's an example implementation using the package:

var screenshot = require('desktop-screenshot');

screenshot("screenshot.png", function(error, complete) {
    if(error)
        console.log("Screenshot failed", error);
    else
        console.log("Screenshot succeeded");
});

For more information about this package, you can visit: https://www.npmjs.com/package/desktop-screenshot

Answer 3

Answer №2

Even though I haven't tested this code myself, theoretically if you are able to do so in C++, you can use node-gyp to compile the C++ file into a .node file and then include it in your NodeJS file.

For example, create a binding.gyp file in a new directory with the following code:

{
  "targets": [
    {
        "target_name": "addon",
        "sources": [ 
            "hi.cc"
        ]
    }
  ]
}

In the same directory, create another file named hi.cc and add your C++ code along with additional code to make it a node module. Following the documentation mentioned above, something like this may work (not tested):

/* Include necessary libraries here for Bitmap 
and Graphics functions */

#include <node.h>

using namespace v8;

void GetImage(const FunctionCallbackInfi<Value>& args) {
    // Your code to get image data
}

void Initialize(Local<Object> exports) {
  NODE_SET_METHOD(exports, "hello", GetImage);
}

NODE_MODULE(NODE_GYP_MODULE_NAME, Initialize)

Make sure you have node-gyp and the required build tools installed by running npm i -g node-gyp. Then navigate to build -> Release -> addon.node, copy it to your main NodeJS directory, and create a new NodeJS file or include the following in an existing one:

let addon = require("./addon"),
    pictureData = Buffer.from(addon.hello()/* if returning base64 string, use: ,"base64"*/);

Answer 4

Even though I haven't tested this code myself, theoretically if you are able to do so in C++, you can use node-gyp to compile the C++ file into a .node file and then include it in your NodeJS file.

For example, create a binding.gyp file in a new directory with the following code:

{
  "targets": [
    {
        "target_name": "addon",
        "sources": [ 
            "hi.cc"
        ]
    }
  ]
}

In the same directory, create another file named hi.cc and add your C++ code along with additional code to make it a node module. Following the documentation mentioned above, something like this may work (not tested):

/* Include necessary libraries here for Bitmap 
and Graphics functions */

#include <node.h>

using namespace v8;

void GetImage(const FunctionCallbackInfi<Value>& args) {
    // Your code to get image data
}

void Initialize(Local<Object> exports) {
  NODE_SET_METHOD(exports, "hello", GetImage);
}

NODE_MODULE(NODE_GYP_MODULE_NAME, Initialize)

Make sure you have node-gyp and the required build tools installed by running npm i -g node-gyp. Then navigate to build -> Release -> addon.node, copy it to your main NodeJS directory, and create a new NodeJS file or include the following in an existing one:

let addon = require("./addon"),
    pictureData = Buffer.from(addon.hello()/* if returning base64 string, use: ,"base64"*/);

Answer 5

Answer №3

There is a new Node.js package in development that offers an alternative to the existing one mentioned above. The latest commit was made just 15 days ago, which is a significant contrast to the older package that hasn't been updated since 2015 or 2016. This new package even allows users to select the specific screen they want to capture, a feature not available in the previous version.

Check out the new package here

const screenshot = require('screenshot-desktop');

screenshot.listDisplays().then((displays) => {
  // displays: [{ id, name }, { id, name }]
  screenshot({ screen: displays[displays.length - 1].id })
    .then((img) => {
      // img: Buffer of screenshot of the last display
    });
})

Answer 6

There is a new Node.js package in development that offers an alternative to the existing one mentioned above. The latest commit was made just 15 days ago, which is a significant contrast to the older package that hasn't been updated since 2015 or 2016. This new package even allows users to select the specific screen they want to capture, a feature not available in the previous version.

Check out the new package here

const screenshot = require('screenshot-desktop');

screenshot.listDisplays().then((displays) => {
  // displays: [{ id, name }, { id, name }]
  screenshot({ screen: displays[displays.length - 1].id })
    .then((img) => {
      // img: Buffer of screenshot of the last display
    });
})

Answer 7

Answer №4

If you want to access screenshot data pixel by pixel in NodeJS without having to save it to disk first, you can utilize the CaptureScreenshot function available in my windows-ffi package.

Here's how you can use it:

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

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

// The image data is stored in the `screenshot.buffer` Buffer object.
// Easily access it using the helper functions provided with `screenshot`.
for (let x = 0; x < 800; x++) {
    console.log(`Pixel color at [${x}, 0] is:`, screenshot.GetPixel(x, 0).ToHex_RGB());
}

Keep in mind that this feature is only compatible with Windows operating systems as it leverages the Windows API via ffi-napi.

Answer 8

If you want to access screenshot data pixel by pixel in NodeJS without having to save it to disk first, you can utilize the CaptureScreenshot function available in my windows-ffi package.

Here's how you can use it:

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

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

// The image data is stored in the `screenshot.buffer` Buffer object.
// Easily access it using the helper functions provided with `screenshot`.
for (let x = 0; x < 800; x++) {
    console.log(`Pixel color at [${x}, 0] is:`, screenshot.GetPixel(x, 0).ToHex_RGB());
}

Keep in mind that this feature is only compatible with Windows operating systems as it leverages the Windows API via ffi-napi.

What is the process for capturing a window screenshot using Node.js?

Answer №1

Answer №2

Answer №3

Answer №4

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