floyd-steinberg-dithering/lib/Dither.dart

import 'dart:html';
import 'dart:typed_data';

class Pixed {
  static PixelArray greyscale(PixelArray image) {
    PixelArray pxArr = new PixelArray.fromPixelArray(image);

    for (var y = 0; y < pxArr.getHeight(); y++) {
      for (var x = 0; x < pxArr.getWidth(); x++) {
        var px = pxArr.getPixel(x, y);
        int average = ((px.r+px.g+px.b) / 3).round();
        px.r = average;
        px.g = average;
        px.b = average;
      }
    }
    return pxArr;
  }

  static PixelArray quantize(PixelArray image, [int steps=1]) {
    PixelArray pxArr = new PixelArray.fromPixelArray(image);
    for (var y = 0; y < pxArr.getHeight(); y++) {
      for (var x = 0; x < pxArr.getWidth(); x++) {
        pxArr.setPixel( _quantizePixel(pxArr.getPixel(x, y)) );
      }
    }
    return pxArr;
  }

  static Pixel _quantizePixel(Pixel pixel, [int steps=1]) {
    return new Pixel(
        pixel.x,
        pixel.y,
        (steps * pixel.r / 255).round() * (255 ~/ steps),
        (steps * pixel.g / 255).round() * (255 ~/ steps),
        (steps * pixel.b / 255).round() * (255 ~/ steps),
        pixel.a);
  }

  static PixelArray quantizeError(PixelArray original, PixelArray quantized) {
    PixelArray pxArr = new PixelArray.fromPixelArray(original);
    for (var y = 0; y < pxArr.getHeight(); y++) {
      for (var x = 0; x < pxArr.getWidth(); x++) {
        Pixel px = pxArr.getPixel(x, y);
        Pixel quant = quantized.getPixel(x, y);
        px.r = px.r - quant.r;
        px.g = px.g - quant.g;
        px.b = px.b - quant.b;
      }
    }
    return pxArr;
  }

  static Pixel _quantizeErrorPixel(Pixel original, Pixel quantized) {
    return new Pixel(original.x, original.y,
        original.r - quantized.r,
        original.g - quantized.g,
        original.b - quantized.b,
        original.a);
  }
}

class Pixel {
  int x;
  int y;
  int r;
  int g;
  int b;
  int a;

  Pixel(this.x, this.y, this.r, this.g, this.b, this.a);

  int getBytePos(int imageWidth) {
    return (x+y*imageWidth)*4;
  }

  void setRGB(int r, int g, int b) {
    this.r = r;
    this.g = g;
    this.b = b;
  }

  @override
  String toString() {
    return 'Pixel at $x, $y: {r: $r, g: $g, b: $b, a: $a}';
  }


}

class PixelArray {
  //TODO Implement iterable
  List<List<Pixel>> pixels;

  PixelArray(int width, int height) {
    pixels = new List(height);
    for (int y = 0; y < height; y++) {
      pixels[y] = new List(width);
      for (int x = 0; x < width; x++) {
        pixels[y][x] = new Pixel(x, y, 0, 0, 0, 0);
      }
    }
  }

  PixelArray.fromByteArray(Uint8ClampedList array, int imageWidth) {
    pixels = new List(array.length~/imageWidth~/4);
    int y = 0;
    int x = 0;
    pixels[y] = new List(imageWidth);
    for (var pos = 0; pos < array.length; pos = pos + 4) {
      if (x >= imageWidth) {
        x = 0;
        y++;
        pixels[y] = new List(imageWidth);
      }
      pixels[y][x] = new Pixel(x, y, array[pos], array[pos+1], array[pos+2], array[pos+3]);
      x++;
    }
  }

  PixelArray.fromImageData(ImageData imagedata, int imageWidth): this.fromByteArray(imagedata.data, imageWidth);

  PixelArray.fromPixelArray(PixelArray pixelArray) {
    pixels = pixelArray.clone().pixels;
  }

  Uint8ClampedList toByteArray() {
    //TODO: look for longest array, or each line separately. Only gets width from line 1 currently.
    Uint8ClampedList result = new Uint8ClampedList(getHeight()*getWidth()*4);
    int x = 0;
    int y = 0;
    for (var i = 0; i < result.length; i = i + 4) {
      if (x >= getWidth()) {
        y++;
        x = 0;
      }
      result[i] = pixels[y][x].r;
      result[i+1] = pixels[y][x].g;
      result[i+2] = pixels[y][x].b;
      result[i+3] = pixels[y][x].a;

      x++;
    }

    return result;
  }

  ImageData toImageData() {
    return new ImageData(this.toByteArray(), this.getWidth(), this.getHeight());
  }

  Pixel getPixel(int x, int y) {
    return pixels[y][x];
  }

  void setPixel(Pixel pixel, [int x, int y]) {
    if (x != null && y != null && getHeight() < y && getWidth() < x) {
      pixel.x = x;
      pixel.y = y;
      pixels[y][x] = pixel;
      return;
    } else if (getHeight() <= pixel.y || getWidth() <= pixel.x) {
      return;
    } else {
      pixels[pixel.y][pixel.x] = pixel;
      return;
    }
  }

  int getWidth() {
    //TODO find longest/shortest width not at 0 (support for non square img)
    return pixels[0].length;
  }

  int getHeight() {
    return pixels.length;
  }

  PixelArray clone() {
    PixelArray pxArr = new PixelArray(getWidth(), getHeight());
    for (var y = 0; y < getHeight(); y++) {
      for (var x = 0; x < getWidth(); x++) {
        Pixel px = getPixel(x, y);
        Pixel newPix = new Pixel(x, y, px.r, px.g, px.b, px.a);
        pxArr.setPixel( newPix, x, y );
      }
    }
    return pxArr;
  }
}