filter method

void filter(ImageFilter filter, [ double? value ])

Implementation

void filter(ImageFilter filter, [double? value]) {
  switch (filter) {
    case ImageFilter.threshold:
      assert(value != null);
      _applyPixelTransform(
          this,
          this,
          (_, __, x, y, colorIn) =>
              HSVColor.fromColor(colorIn).value > value! ? const Color(0xFFFFFFFF) : const Color(0xFF000000));
      break;
    case ImageFilter.gray:
      _applyPixelTransform(
          this, this, (_, __, x, y, colorIn) => HSVColor.fromColor(colorIn).withSaturation(0).toColor());
      break;
    case ImageFilter.opaque:
      _applyPixelTransform(this, this, (_, __, x, y, colorIn) => colorIn.withOpacity(1.0));
      break;
    case ImageFilter.invert:
      _applyPixelTransform(
          this,
          this,
          (_, __, x, y, colorIn) => _colorFromPercentARGB(
                colorIn.opacity,
                1.0 - colorIn.redPercent,
                1.0 - colorIn.greenPercent,
                1.0 - colorIn.bluePercent,
              ));
      break;
    case ImageFilter.posterize:
      if (value == null) {
        throw Exception("You must provide a value to posterize an image");
      }
      if (value < 2 || value > 255) {
        throw Exception("The posterize value must be between [2, 255]");
      }

      final level = value.round();

      // Filter code adapted from the P5.js implementation
      _applyPixelTransform(
          this,
          this,
          (_, __, x, y, colorIn) => Color.fromARGB(
                colorIn.alpha,
                (((colorIn.red * level) >> 8) * 255 / (level - 1)).round(),
                (((colorIn.green * level) >> 8) * 255 / (level - 1)).round(),
                (((colorIn.blue * level) >> 8) * 255 / (level - 1)).round(),
              ));
      break;
    case ImageFilter.erode:
      final outBuffer = copy();
      _applyPixelTransform(this, outBuffer, _erode);
      _pixels = outBuffer.pixels;
      break;
    case ImageFilter.dilate:
      final outBuffer = copy();
      _applyPixelTransform(this, outBuffer, _dilate);
      _pixels = outBuffer.pixels;
      break;
    case ImageFilter.blur:
      // TODO: Handle this case.
      throw UnimplementedError();
  }
}