1/*
2 * Copyright 2012 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#ifndef GrConvolutionEffect_DEFINED
9#define GrConvolutionEffect_DEFINED
10
11#include "Gr1DKernelEffect.h"
12#include "GrInvariantOutput.h"
13
14/**
15 * A convolution effect. The kernel is specified as an array of 2 * half-width
16 * + 1 weights. Each texel is multiplied by it's weight and summed to determine
17 * the output color. The output color is modulated by the input color.
18 */
19class GrConvolutionEffect : public Gr1DKernelEffect {
20
21public:
22
23    /// Convolve with an arbitrary user-specified kernel
24    static GrFragmentProcessor* Create(GrTexture* tex,
25                                       Direction dir,
26                                       int halfWidth,
27                                       const float* kernel,
28                                       bool useBounds,
29                                       float bounds[2]) {
30        return new GrConvolutionEffect(tex, dir, halfWidth, kernel, useBounds, bounds);
31    }
32
33    /// Convolve with a Gaussian kernel
34    static GrFragmentProcessor* CreateGaussian(GrTexture* tex,
35                                               Direction dir,
36                                               int halfWidth,
37                                               float gaussianSigma,
38                                               bool useBounds,
39                                               float bounds[2]) {
40        return new GrConvolutionEffect(tex, dir, halfWidth, gaussianSigma, useBounds, bounds);
41    }
42
43    virtual ~GrConvolutionEffect();
44
45    const float* kernel() const { return fKernel; }
46
47    const float* bounds() const { return fBounds; }
48    bool useBounds() const { return fUseBounds; }
49
50    const char* name() const override { return "Convolution"; }
51
52    enum {
53        // This was decided based on the min allowed value for the max texture
54        // samples per fragment program run in DX9SM2 (32). A sigma param of 4.0
55        // on a blur filter gives a kernel width of 25 while a sigma of 5.0
56        // would exceed a 32 wide kernel.
57        kMaxKernelRadius = 12,
58        // With a C++11 we could have a constexpr version of WidthFromRadius()
59        // and not have to duplicate this calculation.
60        kMaxKernelWidth = 2 * kMaxKernelRadius + 1,
61    };
62
63protected:
64
65    float fKernel[kMaxKernelWidth];
66    bool fUseBounds;
67    float fBounds[2];
68
69private:
70    GrConvolutionEffect(GrTexture*, Direction,
71                        int halfWidth,
72                        const float* kernel,
73                        bool useBounds,
74                        float bounds[2]);
75
76    /// Convolve with a Gaussian kernel
77    GrConvolutionEffect(GrTexture*, Direction,
78                        int halfWidth,
79                        float gaussianSigma,
80                        bool useBounds,
81                        float bounds[2]);
82
83    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override;
84
85    void onGetGLSLProcessorKey(const GrGLSLCaps&, GrProcessorKeyBuilder*) const override;
86
87    bool onIsEqual(const GrFragmentProcessor&) const override;
88
89    void onComputeInvariantOutput(GrInvariantOutput* inout) const override {
90        // If the texture was opaque we could know that the output color if we knew the sum of the
91        // kernel values.
92        inout->mulByUnknownFourComponents();
93    }
94
95    GR_DECLARE_FRAGMENT_PROCESSOR_TEST;
96
97    typedef Gr1DKernelEffect INHERITED;
98};
99
100#endif
101