ScreenshotResult

Info

Represents the result of a screen capture operation. This interface provides a structured way to access screenshot data, its size, and the image format. The capturePrimaryDisplayPng function returns ScreenshotResult | null.

Interface Definition

interface ScreenshotResult {
  data: Buffer;
  size: number;
  format: 'png';
}

Properties

Property	Type	Description
data	Buffer	Raw PNG image data of the captured screen
size	number	Screenshot data size in bytes
format	'png'	Image format (always 'png')

Usage

The ScreenshotResult interface is returned by the capturePrimaryDisplayPng function.

When the capture fails (e.g., GDI resource exhaustion or invalid display context), the function returns null instead of a ScreenshotResult object. Use getLastError to retrieve the error message in that case.

Tips

Use the size property to check the screenshot data size without accessing the data buffer directly. This is useful for logging or validation before processing.

Note

The format property is always 'png'. The PNG encoding happens inside the Native AOT DLL before the data crosses the FFI boundary.

Example

TypeScript

import { capturePrimaryDisplayPng, ScreenshotResult } from '@eisland/windows-screenshot-helper';

const result: ScreenshotResult | null = capturePrimaryDisplayPng();

if (result) {
  console.log(`Screenshot size: ${result.size} bytes`);
  console.log(`Format: ${result.format}`);

  // Convert to data URL for HTML display
  const dataUrl = `data:image/png;base64,${result.data.toString('base64')}`;

  // Or save to file
  import * as fs from 'fs';
  fs.writeFileSync('screenshot.png', result.data);
} else {
  console.log('Capture failed');
}

JavaScript

const { capturePrimaryDisplayPng } = require('@eisland/windows-screenshot-helper');

const result = capturePrimaryDisplayPng();

if (result) {
  console.log(`Screenshot size: ${result.size} bytes`);
  console.log(`Format: ${result.format}`);

  // Convert to data URL for HTML display
  const dataUrl = `data:image/png;base64,${result.data.toString('base64')}`;

  // Or save to file
  const fs = require('fs');
  fs.writeFileSync('screenshot.png', result.data);
} else {
  console.log('Capture failed');
}

Notes

Important

Always check if the result is null before accessing properties. Screen capture can fail due to GDI resource exhaustion, restricted desktop contexts (e.g., secure desktop), or DLL loading errors.

Warning

The data buffer contains raw PNG bytes of the entire primary display. The buffer size depends on screen resolution and content complexity — it is not a fixed size.

Danger Avoidance

Caution

Do not call capturePrimaryDisplayPng in a tight loop without delay. Each call allocates GDI resources (device context, bitmap) inside the DLL. Rapid successive calls can exhaust GDI handle limits and cause subsequent captures to fail. Add a reasonable delay (e.g., 100ms+) between captures.