static std::shared_ptr< ColorFilterContents > MakeBlend(BlendMode blend_mode, FilterInput::Vector inputs, std::optional< Color > foreground_color=std::nullopt)
the [inputs] are expected to be in the order of dst, src.
static std::shared_ptr< FilterContents > MakeMatrixFilter(FilterInput::Ref input, const Matrix &matrix, const SamplerDescriptor &desc)