OptionalalphaOptionalcolorValue to add to each channel.
OptionalcolorFactor to apply to each channel. Try to keep them summing to 1.
OptionalditherWhether to dither the gradient output.
OptionalrampThe color ramp to use.
OptionalunpremultiplyWhether to unpremultiply color data before processing it.
How much of the effect to blend over the original.