颤动/Dart以相同格式重写图像

import 'dart:ui' as ui;
import 'dart:io';
import 'package:flutter/material.dart';

class DitheredImage extends StatelessWidget {
  final String imagePath;

  DitheredImage({required this.imagePath});

  @override
  Widget build(BuildContext context) {
    return FutureBuilder<ui.Image>(
      future: _loadImage(imagePath),
      builder: (context, snapshot) {
        if (snapshot.connectionState == ConnectionState.done) {
          return CustomPaint(
            size: Size(snapshot.data!.width.toDouble(), snapshot.data!.height.toDouble()),
            painter: DitherPainter(image: snapshot.data!),
          );
        } else {
          return Center(child: CircularProgressIndicator());
        }
      },
    );
  }

  Future<ui.Image> _loadImage(String imagePath) async {
    final image = await ImageLoader.load(imagePath);
    return image;
  }
}

class DitherPainter extends CustomPainter {
  final ui.Image image;

  DitherPainter({required this.image});

  @override
  void paint(Canvas canvas, Size size) {
    final paint = Paint();
    final ditherPattern = [
      0, 48, 12, 60, 3, 51, 15, 63,
      32, 16, 44, 28, 35, 19, 47, 31,
      8, 56, 4, 52, 11, 59, 7, 55,
      40, 24, 36, 20, 43, 27, 39, 23,
      2, 50, 14, 62, 1, 49, 13, 61,
      34, 18, 46, 30, 33, 17, 45, 29,
      10, 58, 6, 54, 9, 57, 5, 53,
      42, 26, 38, 22, 41, 25, 37, 21,
    ];

    final codec = await ui.instantiateImageCodec(image.toByteData(format: ui.ImageByteFormat.rawRgba)!);
    final frame = await codec.getNextFrame();
    final pixels = frame.buffer.asUint8List();

    final width = image.width;
    final height = image.height;
    final bytesPerPixel = 4;

    for (int y = 0; y < height; y += 2) {
      for (int x = 0; x < width; x += 2) {
        int index = (y * width + x) * bytesPerPixel;
        int r = pixels[index];
        int g = pixels[index + 1];
        int b = pixels[index + 2];

        int ditherIndex = ditherPattern[(y / 2) * (width / 2) + (x / 2)];
        int rDither = (r + (ditherIndex % 16) * 17) % 256;
        int gDither = (g + (ditherIndex / 16) * 17) % 256;
        int bDither = (b + (ditherIndex % 16) * 17) % 256;

        pixels[index] = rDither;
        pixels[index + 1] = gDither;
        pixels[index + 2] = bDither;
      }
    }

    final newImage = await ui.instantiateImageCodec(pixels.buffer.asUint8List());
    final newFrame = await newImage.getNextFrame();
    final newPixels = newFrame.buffer.asUint8List();

    canvas.drawImage(ui.Image.fromBytes(width, height, newPixels), Offset.zero);
  }

  @override
  bool shouldRepaint(covariant CustomPainter oldDelegate) {
    return false;
  }
}

class ImageLoader {
  static Future<ui.Image> load(String imagePath) async {
    final data = await rootBundle.load(imagePath);
    final codec = await ui.instantiateImageCodec(data.buffer.asUint8List());
    final frame = await codec.getNextFrame();
    return frame.image;
  }
}