grayscale function

Implementation

Image grayscale(Image src,
    {num amount = 1, Image? mask, Channel maskChannel = Channel.luminance}) {
  for (final frame in src.frames) {
    if (frame.hasPalette) {
      final p = frame.palette!;
      final numColors = p.numColors;
      for (var i = 0; i < numColors; ++i) {
        final l = getLuminanceRgb(p.getRed(i), p.getGreen(i), p.getBlue(i));
        if (amount != 1) {
          final r = mix(p.getRed(i), l, amount);
          final g = mix(p.getGreen(i), l, amount);
          final b = mix(p.getBlue(i), l, amount);
          p
            ..setRed(i, r)
            ..setGreen(i, g)
            ..setBlue(i, b);
        } else {
          p
            ..setRed(i, l)
            ..setGreen(i, l)
            ..setBlue(i, l);
        }
      }
    } else {
      for (final p in frame) {
        final l = getLuminanceRgb(p.r, p.g, p.b);
        final msk = mask?.getPixel(p.x, p.y).getChannelNormalized(maskChannel);
        final mx = (msk ?? 1) * amount;
        if (mx != 1) {
          p
            ..r = mix(p.r, l, mx)
            ..g = mix(p.g, l, mx)
            ..b = mix(p.b, l, mx);
        } else {
          p
            ..r = l
            ..g = l
            ..b = l;
        }
      }
    }
  }

  return src;
}