图像

Dart Image Library

Overview

The Dart Image Library provides the ability to load, save, and manipulate images in a variety of image file formats.

The library can be used with both dart:io and dart:html, for command-line, Flutter, and web applications.

NOTE: 4.0 is a major revision from the previous version of the library.

Documentation

Supported Image Formats

Read/Write

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

Read Only

• PSD
• EXR
• PNM (PBM, PGM, PPM)

Write Only

• CUR

Examples

Create an image, set pixel values, save it to a PNG.

import 'dart:io';
import 'package:image/image.dart' as img;
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 (var pixel in image) {
    // Set the pixels red value to its x position value, creating a gradient.
    pixel..r = pixel.x
    // Set the pixels green value to its y position value.
    ..g = pixel.y;
  }
  // Encode the resulting image to the PNG image format.
  final png = img.encodePng(image);
  // Write the PNG formatted data to a file.
  await File('image.png').writeAsBytes(png);
}

To asynchronously load an image file, resize it, and save it as a thumbnail:

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

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 and a height that maintains the aspect ratio of the original. 
    ..copyResize(width: 64)
    // Write the image to a PNG file (determined by the suffix of the file path). 
    ..writeToFile('thumbnail.png');
  // On platforms that support Isolates, execute the image commands asynchronously on an isolate thread.
  // Otherwise, the commands will be executed synchronously.
  await cmd.executeThread();
}