[FEATURE] Expose SkImageFilters::RuntimeShader()

[RedyG]

I want to use SKCanvas.SaveLayer(), and then apply a shader ( or a tree of shaders ) to the content of that layer on SKCanvas.Restore(). I found out about SkImageFilters::RuntimeShader() but it seems like it's not yet exposed in SkiaSharp.

The code would look something like:

var effect = SKRuntimeEffect.Create("...", out string errors);
SKShader shader = effect.ToShader(false);
var imageFilter = SKImageFilter.CreateShader(shader, ...);
var paint = new SKPaint
{
    ImageFilter = imageFilter
};

canvas.SaveLayer(paint);
// draw stuff
canvas.Restore();

I would like the API the expose a SKImageFilter.CreateShader() or SKImageFilter.CreateRuntimeShader() method

Mentioned here

[cyraid]

I'm wanting to do shaders too, but it seems there's a large lack of support. @mattleibow Think we could have some better uniform setting support too? :) (instead of just WriteTo with a byte span). Just passing a simple color to an effect shader seems to be a lot of boiler plate! Let alone passing floats, etc.

Edit Edit: By better support I mean, uniform.Set(float), uniform.Set(float[]), uniform.Set(SKColorF), etc. For those coming in not knowing there's implicit operator overrides.

Edit: I found out I can set the SKRuntimeEffectUniform and it'll accept Span, so anyone coming here wondering an easy way to do it?

ColorF color = new SKColorF(1, 0, 0, 1); // 100% Red, with 100% alpha
Span<float> colorSpan = stackalloc float[4] { color.Red, color.Green, color.Blue, color.Alpha };
SKRuntimeEffectUniform colorUniform = colorSpan;

or without stackalloc:

ColorF color = new SKColorF(1, 0, 0, 1); // 100% Red, with 100% alpha
Span<float> colorFloats = new float[4] { color.Red, color.Green, color.Blue, color.Alpha };
SKRuntimeEffectUniform colorUniform = colorFloats;

[mattleibow]

Superseded by #3776 which tracks the full SkSL image filter API including SKRuntimeEffect.ToImageFilter() and SKRuntimeImageFilterBuilder. PR #3778 is in progress.