1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
|
/*
* 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 "SkShader.h"
/** \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
*/
class SK_API SkPerlinNoiseShader {
public:
/**
* 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.
*/
static sk_sp<SkShader> MakeFractalNoise(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
int numOctaves, SkScalar seed,
const SkISize* tileSize = nullptr);
static sk_sp<SkShader> MakeTurbulence(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
int numOctaves, SkScalar seed,
const SkISize* tileSize = nullptr);
/**
* Creates an Improved Perlin Noise shader. The z value is roughly equivalent to the seed of the
* other two types, but minor variations to z will only slightly change the noise.
*/
static sk_sp<SkShader> MakeImprovedNoise(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
int numOctaves, SkScalar z);
static void InitializeFlattenables();
private:
SkPerlinNoiseShader() = delete;
};
#endif
|
