image_filter.dart

// use-case
var colorFilter = CkColorFilter();
var imageFilter = colorFilter.toImageFilter();
var backdropFilter = CkBackdropFilter(imageFilter);
paint.colorFilter = colorFilter;
paint.imageFilter = imageFilter;

paint.imageFilter = colorFilter;

// ui
abstract class ImageFilter {}
abstract class ColorFilter extends ImageFilter {}

// engine
abstract class CkImageFilter<T> extends ManagedSkiaObject<T> implements ui.ImageFilter {
  final bool isColorFilter;
  SkImageFilter get imageFilter => skiaObject;
  
  CkImageFilter(this.isColorFilter);
}

class CkPaint {
  ui.ImageFilter get imageFilter => _imageFilter;
  set imageFilter(ui.ImageFilter filter) {
    _imageFilter = filter;
    if (filter.isCkColorFilter) {
      skPaint.SetImageFilter(filter.imageFilter);
    } else {
      skPaint.SetImageFilter(actualImageFilter.skiaObject);
    }
  }
}

abstract class CkColorFilter extend CkImageFilter<SkColorFilter> implements ui.ColorFilter {
  SkImageFilter _imageFilter;
  SkImageFilter get imageFilter => _imageFilter ?? (_imageFilter = convert(skiaObject));

  @override
  void delete() {
    rawSkiaObject.delete();
    _imageFilter?.delete();
    _imageFilter = null;
  }
}

class CkDeletableImageFilter extends CkImageFilter<SkImageFilter> {
  @override
  void delete() {
    rawSkiaObject.delete();
  }
}

class CkBlurImageFilter extends CkDeletableImageFilter {
}
class CkMatrixImageFilter extends CkDeletableImageFilter {
}

class CkLinearToSrgbGammaColorFilter extends CkColorFilter {
}
class CkMatrixColorFilter extends CkColorFilter {
}