SkShaders Namespace Reference

Classes
class	MatrixRec

Functions
SK_API sk_sp< SkShader >	MakeFractalNoise (SkScalar baseFrequencyX, SkScalar baseFrequencyY, int numOctaves, SkScalar seed, const SkISize *tileSize=nullptr)
SK_API sk_sp< SkShader >	MakeTurbulence (SkScalar baseFrequencyX, SkScalar baseFrequencyY, int numOctaves, SkScalar seed, const SkISize *tileSize=nullptr)

Function Documentation

MakeFractalNoise()

sk_sp< SkShader > SkShaders::MakeFractalNoise	(	SkScalar	baseFrequencyX,
		SkScalar	baseFrequencyY,
		int	numOctaves,
		SkScalar	seed,
		const SkISize *	tileSize = nullptr
	)

This will construct Perlin noise of the given type (Fractal Noise or Turbulence).

Both base frequencies (X and Y) have a usual range of (0..1) and must be non-negative.

The number of octaves provided should be fairly small, with a limit of 255 enforced. Each octave doubles the frequency, so 10 octaves would produce noise from baseFrequency * 1, * 2, * 4, ..., * 512, which quickly yields insignificantly small periods and resembles regular unstructured noise rather than Perlin noise.

If tileSize isn't NULL or an empty size, the tileSize parameter will be used to modify the frequencies so that the noise will be tileable for the given tile size. If tileSize is NULL or an empty size, the frequencies will be used as is without modification.

Definition at line 135 of file SkPerlinNoiseShaderImpl.cpp.

                                                          {
    if (!valid_input(baseFrequencyX, baseFrequencyY, numOctaves, tileSize, seed)) {
        return nullptr;
    }
 
    if (0 == numOctaves) {
        // For kFractalNoise, w/o any octaves, the entire shader collapses to:
        //    [0,0,0,0] * 0.5 + 0.5
        constexpr SkColor4f kTransparentGray = {0.5f, 0.5f, 0.5f, 0.5f};
 
        return SkShaders::Color(kTransparentGray, /* colorSpace= */ nullptr);
    }
 
    return sk_sp<SkShader>(new SkPerlinNoiseShader(SkPerlinNoiseShaderType::kFractalNoise,
                                                   baseFrequencyX,
                                                   baseFrequencyY,
                                                   numOctaves,
                                                   seed,
                                                   tileSize));
}

MakeTurbulence()

sk_sp< SkShader > SkShaders::MakeTurbulence	(	SkScalar	baseFrequencyX,
		SkScalar	baseFrequencyY,
		int	numOctaves,
		SkScalar	seed,
		const SkISize *	tileSize = nullptr
	)

Definition at line 160 of file SkPerlinNoiseShaderImpl.cpp.

                                                        {
    if (!valid_input(baseFrequencyX, baseFrequencyY, numOctaves, tileSize, seed)) {
        return nullptr;
    }
 
    if (0 == numOctaves) {
        // For kTurbulence, w/o any octaves, the entire shader collapses to: [0,0,0,0]
        return SkShaders::Color(SkColors::kTransparent, /* colorSpace= */ nullptr);
    }
 
    return sk_sp<SkShader>(new SkPerlinNoiseShader(SkPerlinNoiseShaderType::kTurbulence,
                                                   baseFrequencyX,
                                                   baseFrequencyY,
                                                   numOctaves,
                                                   seed,
                                                   tileSize));
}