xref: /aosp_15_r20/external/skia/include/effects/SkPerlinNoiseShader.h (revision c8dee2aa9b3f27cf6c858bd81872bdeb2c07ed17)

/*
 * Copyright 2013 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkPerlinNoiseShader_DEFINED
#define SkPerlinNoiseShader_DEFINED

#include "include/core/SkRefCnt.h"
#include "include/core/SkScalar.h"
#include "include/core/SkShader.h" // IWYU pragma: keep
#include "include/private/base/SkAPI.h"

struct SkISize;

/** \class SkPerlinNoiseShader

    SkPerlinNoiseShader creates an image using the Perlin turbulence function.

    It can produce tileable noise if asked to stitch tiles and provided a tile size.
    In order to fill a large area with repeating noise, set the stitchTiles flag to
    true, and render exactly a single tile of noise. Without this flag, the result
    will contain visible seams between tiles.

    The algorithm used is described here :
    http://www.w3.org/TR/SVG/filters.html#feTurbulenceElement
*/
namespace SkShaders {
/**
 *  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.
 */
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);
}  // namespace SkShaders

#endif