Dart Image Library #

Overview #

The Dart Image Library loads, saves and manipulates images in a variety of image file formats.

It's written in pure Dart with no native dependencies, so it works everywhere Dart does: command-line apps, servers, Flutter on every platform, and the web.

Features include:

• Decoding and encoding many image formats, including animated GIF, PNG and WebP.
• Resizing, cropping, rotating and flipping.
• Dozens of filters for color adjustment, blurring, and effects, plus color quantization and dithering.
• Drawing shapes, lines, text and other images.
• Direct pixel access in 1 to 32-bit integer and 16 to 64-bit floating point formats, with optional palettes.
• EXIF metadata, ICC profiles and HDR images.
• A Command API for running image processing in a separate isolate.

Documentation #

• Tutorial
• Using the library with Flutter
• Performance and memory
• API reference

Supported Image Formats #

Read/Write

• JPEG
• PNG / Animated PNG
• GIF / Animated GIF
• WebP / Animated WebP (lossless and lossy)
• BMP
• TIFF
• TGA
• ICO
• PVR

Read Only

• PSD
• EXR
• PNM (PBM, PGM, PPM)

Write Only

• CUR

Getting started #

dart pub add image

import 'package:image/image.dart' as img;

Examples #

Create an image, set pixel values, and save it as a PNG:

import 'dart:io';
import 'package:image/image.dart' as img;

Future<void> main() async {
  // Create a 256x256 8-bit (default) RGB (default) image.
  final image = img.Image(width: 256, height: 256);
  // Iterate over its pixels.
  for (final pixel in image) {
    pixel
      // Set the red channel to the x position, creating a gradient.
      ..r = pixel.x
      // Set the green channel to the y position.
      ..g = pixel.y;
  }
  // Encode the image to the PNG format.
  final png = img.encodePng(image);
  // Write the PNG data to a file.
  await File('image.png').writeAsBytes(png);
}

Load a JPEG, make a thumbnail, and save it:

import 'dart:io';
import 'package:image/image.dart' as img;

Future<void> main() async {
  final bytes = await File('photo.jpg').readAsBytes();
  // Decode the JPEG. This returns null, or throws an ImageException, if the
  // data isn't a valid JPEG.
  final image = img.decodeJpg(bytes);
  if (image == null) {
    return;
  }
  // Resize to 120 pixels wide, keeping the aspect ratio. The EXIF orientation
  // of the photo is applied.
  final thumbnail = img.copyResize(image, width: 120);
  // Encode as a JPEG and save it.
  await File('thumbnail.jpg').writeAsBytes(img.encodeJpg(thumbnail, quality: 85));
}

Do the same work in a separate isolate with the Command API, so it doesn't block the main isolate:

import 'package:image/image.dart' as img;

Future<void> main(List<String> args) async {
  final path = args.isNotEmpty ? args[0] : 'test.png';
  final cmd = img.Command()
    // Decode the image file at the given path.
    ..decodeImageFile(path)
    // Resize the image to a width of 64 pixels, keeping the aspect ratio.
    ..copyResize(width: 64)
    // Write the image to a PNG file (the format comes from the file extension).
    ..writeToFile('thumbnail.png');
  // On platforms that support isolates, execute the commands on a separate
  // isolate. Otherwise (on the web), they run on the main thread.
  await cmd.executeThread();
}

See the tutorial for more.