swipelab_webp 1.0.0

High-performance WebP image encoding for Dart using native libwebp via FFI. Supports both lossy and lossless compression with configurable quality.

swipelab_webp

High-performance WebP image encoding for Dart using native libwebp via FFI.

Features

• Lossy encoding with configurable quality (0-100)
• Lossless encoding for perfect quality preservation
• High performance native libwebp implementation
• Isolate-friendly with compute() support
• Cross-platform support for Android, iOS, Linux, macOS, and Windows

Installation

Add to your pubspec.yaml:

dependencies:
  swipelab_webp: ^1.0.0

Build Requirements

This package uses Dart's native assets feature to compile libwebp from source during the build process. The following are required:

• Git - to clone the libwebp source code
• C compiler:
  • macOS/iOS: Xcode Command Line Tools (Clang)
  • Linux: GCC (sudo apt install build-essential)
  • Windows: MSVC (Visual Studio Build Tools)
  • Android: NDK (install via Android Studio SDK Manager)

The libwebp source is automatically cloned from swipelab/libwebp on first build:

• macOS/Linux: ~/.cache/swipelab_webp/libwebp
• Windows: %LOCALAPPDATA%\swipelab_webp\libwebp

Usage

Basic Encoding

import 'dart:typed_data';
import 'package:swipelab_webp/swipelab_webp.dart';

void main() {
  // Create RGBA image data (4 bytes per pixel)
  final width = 100;
  final height = 100;
  final rgba = Uint8List(width * height * 4);

  // Fill with red pixels (R=255, G=0, B=0, A=255)
  for (var i = 0; i < rgba.length; i += 4) {
    rgba[i] = 255;     // R
    rgba[i + 1] = 0;   // G
    rgba[i + 2] = 0;   // B
    rgba[i + 3] = 255; // A
  }

  // Lossy encoding (smaller file, slight quality loss)
  final lossy = WebPEncoder.encodeRgba(
    rgba: rgba,
    width: width,
    height: height,
    quality: 80.0, // 0.0 to 100.0
  );

  // Lossless encoding (perfect quality, larger file)
  final lossless = WebPEncoder.encodeRgbaLossless(
    rgba: rgba,
    width: width,
    height: height,
  );

  print('Lossy: ${lossy?.length} bytes');
  print('Lossless: ${lossless?.length} bytes');
}

Using with Isolates

For encoding large images without blocking the UI, use compute():

import 'package:flutter/foundation.dart';
import 'package:swipelab_webp/swipelab_webp.dart';

Future<Uint8List?> encodeInBackground(Uint8List rgba, int width, int height) {
  return compute(
    encodeWebP,
    WebPEncodeInput(
      rgba: rgba,
      width: width,
      height: height,
      quality: 85.0,
      lossless: false,
    ),
  );
}

Version Information

// Get libwebp version
print('libwebp version: ${WebPEncoder.versionString}'); // e.g., "1.4.0"
print('libwebp version (hex): 0x${WebPEncoder.version.toRadixString(16)}');

API Reference

WebPEncoder

Method	Description
encodeRgba()	Encode RGBA data to lossy WebP
encodeRgbaLossless()	Encode RGBA data to lossless WebP
version	Get libwebp version as integer
versionString	Get libwebp version as string

Parameters

Parameter	Type	Description
rgba	Uint8List	Raw RGBA pixel data (4 bytes per pixel)
width	int	Image width in pixels
height	int	Image height in pixels
quality	double	Quality factor 0.0-100.0 (lossy only)

Return Value

Both encoding methods return Uint8List?:

• Valid WebP data on success
• null on encoding error

Performance Tips

• Use lossy encoding with quality 75-85 for photos (best size/quality ratio)
• Use lossless encoding for screenshots, diagrams, or images with text
• For large images, use compute() to avoid blocking the main isolate
• The native library is cached after first build, subsequent builds are fast

License

MIT License - see LICENSE for details.

Credits

This package uses libwebp by Google.