GrBicubicEffect.cpp revision 5af9ea399d5e0344cc4b7da4e97b5dc5b3c74f64 
1/*
2 * Copyright 2014 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#include "GrBicubicEffect.h"
9
10#include "GrTexture.h"
11#include "glsl/GrGLSLColorSpaceXformHelper.h"
12#include "glsl/GrGLSLFragmentShaderBuilder.h"
13#include "glsl/GrGLSLProgramDataManager.h"
14#include "glsl/GrGLSLUniformHandler.h"
15#include "../private/GrGLSL.h"
16
17class GrGLBicubicEffect : public GrGLSLFragmentProcessor {
18public:
19    void emitCode(EmitArgs&) override;
20
21    static inline void GenKey(const GrProcessor& effect, const GrShaderCaps&,
22                              GrProcessorKeyBuilder* b) {
23        const GrBicubicEffect& bicubicEffect = effect.cast<GrBicubicEffect>();
24        b->add32(GrTextureDomain::GLDomain::DomainKey(bicubicEffect.domain()));
25        b->add32(GrColorSpaceXform::XformKey(bicubicEffect.colorSpaceXform()));
26    }
27
28protected:
29    void onSetData(const GrGLSLProgramDataManager&, const GrFragmentProcessor&) override;
30
31private:
32    typedef GrGLSLProgramDataManager::UniformHandle UniformHandle;
33
34    UniformHandle               fImageIncrementUni;
35    GrGLSLColorSpaceXformHelper fColorSpaceHelper;
36    GrTextureDomain::GLDomain   fDomain;
37
38    typedef GrGLSLFragmentProcessor INHERITED;
39};
40
41void GrGLBicubicEffect::emitCode(EmitArgs& args) {
42    const GrBicubicEffect& bicubicEffect = args.fFp.cast<GrBicubicEffect>();
43
44    GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
45    fImageIncrementUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
46                                                    kVec2f_GrSLType, kDefault_GrSLPrecision,
47                                                    "ImageIncrement");
48
49    const char* imgInc = uniformHandler->getUniformCStr(fImageIncrementUni);
50
51    fColorSpaceHelper.emitCode(uniformHandler, bicubicEffect.colorSpaceXform());
52
53    GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
54    SkString coords2D = fragBuilder->ensureCoords2D(args.fTransformedCoords[0]);
55
56    /*
57     * Filter weights come from Don Mitchell & Arun Netravali's 'Reconstruction Filters in Computer
58     * Graphics', ACM SIGGRAPH Computer Graphics 22, 4 (Aug. 1988).
59     * ACM DL: http://dl.acm.org/citation.cfm?id=378514
60     * Free  : http://www.cs.utexas.edu/users/fussell/courses/cs384g/lectures/mitchell/Mitchell.pdf
61     *
62     * The authors define a family of cubic filters with two free parameters (B and C):
63     *
64     *            { (12 - 9B - 6C)|x|^3 + (-18 + 12B + 6C)|x|^2 + (6 - 2B)          if |x| < 1
65     * k(x) = 1/6 { (-B - 6C)|x|^3 + (6B + 30C)|x|^2 + (-12B - 48C)|x| + (8B + 24C) if 1 <= |x| < 2
66     *            { 0                                                               otherwise
67     *
68     * Various well-known cubic splines can be generated, and the authors select (1/3, 1/3) as their
69     * favorite overall spline - this is now commonly known as the Mitchell filter, and is the
70     * source of the specific weights below.
71     *
72     * This is GLSL, so the matrix is column-major (transposed from standard matrix notation).
73     */
74    fragBuilder->codeAppend("float4x4 kMitchellCoefficients = float4x4("
75                            " 1.0 / 18.0,  16.0 / 18.0,   1.0 / 18.0,  0.0 / 18.0,"
76                            "-9.0 / 18.0,   0.0 / 18.0,   9.0 / 18.0,  0.0 / 18.0,"
77                            "15.0 / 18.0, -36.0 / 18.0,  27.0 / 18.0, -6.0 / 18.0,"
78                            "-7.0 / 18.0,  21.0 / 18.0, -21.0 / 18.0,  7.0 / 18.0);");
79    fragBuilder->codeAppendf("float2 coord = %s - %s * float2(0.5);", coords2D.c_str(), imgInc);
80    // We unnormalize the coord in order to determine our fractional offset (f) within the texel
81    // We then snap coord to a texel center and renormalize. The snap prevents cases where the
82    // starting coords are near a texel boundary and accumulations of imgInc would cause us to skip/
83    // double hit a texel.
84    fragBuilder->codeAppendf("coord /= %s;", imgInc);
85    fragBuilder->codeAppend("float2 f = fract(coord);");
86    fragBuilder->codeAppendf("coord = (coord - f + float2(0.5)) * %s;", imgInc);
87    fragBuilder->codeAppend("float4 wx = kMitchellCoefficients * float4(1.0, f.x, f.x * f.x, f.x * f.x * f.x);");
88    fragBuilder->codeAppend("float4 wy = kMitchellCoefficients * float4(1.0, f.y, f.y * f.y, f.y * f.y * f.y);");
89    fragBuilder->codeAppend("float4 rowColors[4];");
90    for (int y = 0; y < 4; ++y) {
91        for (int x = 0; x < 4; ++x) {
92            SkString coord;
93            coord.printf("coord + %s * float2(%d, %d)", imgInc, x - 1, y - 1);
94            SkString sampleVar;
95            sampleVar.printf("rowColors[%d]", x);
96            fDomain.sampleTexture(fragBuilder,
97                                  args.fUniformHandler,
98                                  args.fShaderCaps,
99                                  bicubicEffect.domain(),
100                                  sampleVar.c_str(),
101                                  coord,
102                                  args.fTexSamplers[0]);
103        }
104        fragBuilder->codeAppendf(
105            "float4 s%d = wx.x * rowColors[0] + wx.y * rowColors[1] + wx.z * rowColors[2] + wx.w * rowColors[3];",
106            y);
107    }
108    SkString bicubicColor("(wy.x * s0 + wy.y * s1 + wy.z * s2 + wy.w * s3)");
109    if (fColorSpaceHelper.isValid()) {
110        SkString xformedColor;
111        fragBuilder->appendColorGamutXform(&xformedColor, bicubicColor.c_str(), &fColorSpaceHelper);
112        bicubicColor.swap(xformedColor);
113    }
114    fragBuilder->codeAppendf("%s = %s * %s;", args.fOutputColor, bicubicColor.c_str(),
115                             args.fInputColor);
116}
117
118void GrGLBicubicEffect::onSetData(const GrGLSLProgramDataManager& pdman,
119                                  const GrFragmentProcessor& processor) {
120    const GrBicubicEffect& bicubicEffect = processor.cast<GrBicubicEffect>();
121    GrSurfaceProxy* proxy = processor.textureSampler(0).proxy();
122    GrTexture* texture = proxy->priv().peekTexture();
123
124    float imageIncrement[2];
125    imageIncrement[0] = 1.0f / texture->width();
126    imageIncrement[1] = 1.0f / texture->height();
127    pdman.set2fv(fImageIncrementUni, 1, imageIncrement);
128    fDomain.setData(pdman, bicubicEffect.domain(), proxy);
129    if (SkToBool(bicubicEffect.colorSpaceXform())) {
130        fColorSpaceHelper.setData(pdman, bicubicEffect.colorSpaceXform());
131    }
132}
133
134GrBicubicEffect::GrBicubicEffect(sk_sp<GrTextureProxy> proxy,
135                                 sk_sp<GrColorSpaceXform> colorSpaceXform,
136                                 const SkMatrix& matrix,
137                                 const SkShader::TileMode tileModes[2])
138        : INHERITED{ModulateByConfigOptimizationFlags(proxy->config())}
139        , fCoordTransform(matrix, proxy.get())
140        , fDomain(GrTextureDomain::IgnoredDomain())
141        , fTextureSampler(std::move(proxy),
142                          GrSamplerParams(tileModes, GrSamplerParams::kNone_FilterMode))
143        , fColorSpaceXform(std::move(colorSpaceXform)) {
144    this->initClassID<GrBicubicEffect>();
145    this->addCoordTransform(&fCoordTransform);
146    this->addTextureSampler(&fTextureSampler);
147}
148
149GrBicubicEffect::GrBicubicEffect(sk_sp<GrTextureProxy> proxy,
150                                 sk_sp<GrColorSpaceXform> colorSpaceXform,
151                                 const SkMatrix& matrix,
152                                 const SkRect& domain)
153        : INHERITED(ModulateByConfigOptimizationFlags(proxy->config()))
154        , fCoordTransform(matrix, proxy.get())
155        , fDomain(proxy.get(), domain, GrTextureDomain::kClamp_Mode)
156        , fTextureSampler(std::move(proxy))
157        , fColorSpaceXform(std::move(colorSpaceXform)) {
158    this->initClassID<GrBicubicEffect>();
159    this->addCoordTransform(&fCoordTransform);
160    this->addTextureSampler(&fTextureSampler);
161}
162
163GrBicubicEffect::GrBicubicEffect(const GrBicubicEffect& that)
164        : INHERITED(that.optimizationFlags())
165        , fCoordTransform(that.fCoordTransform)
166        , fDomain(that.fDomain)
167        , fTextureSampler(that.fTextureSampler)
168        , fColorSpaceXform(that.fColorSpaceXform) {
169    this->initClassID<GrBicubicEffect>();
170    this->addCoordTransform(&fCoordTransform);
171    this->addTextureSampler(&fTextureSampler);
172}
173
174void GrBicubicEffect::onGetGLSLProcessorKey(const GrShaderCaps& caps,
175                                            GrProcessorKeyBuilder* b) const {
176    GrGLBicubicEffect::GenKey(*this, caps, b);
177}
178
179GrGLSLFragmentProcessor* GrBicubicEffect::onCreateGLSLInstance() const  {
180    return new GrGLBicubicEffect;
181}
182
183bool GrBicubicEffect::onIsEqual(const GrFragmentProcessor& sBase) const {
184    const GrBicubicEffect& s = sBase.cast<GrBicubicEffect>();
185    return fDomain == s.fDomain;
186}
187
188GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrBicubicEffect);
189
190#if GR_TEST_UTILS
191sk_sp<GrFragmentProcessor> GrBicubicEffect::TestCreate(GrProcessorTestData* d) {
192    int texIdx = d->fRandom->nextBool() ? GrProcessorUnitTest::kSkiaPMTextureIdx
193                                        : GrProcessorUnitTest::kAlphaTextureIdx;
194    sk_sp<GrColorSpaceXform> colorSpaceXform = GrTest::TestColorXform(d->fRandom);
195    static const SkShader::TileMode kClampClamp[] =
196        { SkShader::kClamp_TileMode, SkShader::kClamp_TileMode };
197    return GrBicubicEffect::Make(d->textureProxy(texIdx), std::move(colorSpaceXform),
198                                 SkMatrix::I(), kClampClamp);
199}
200#endif
201
202//////////////////////////////////////////////////////////////////////////////
203
204bool GrBicubicEffect::ShouldUseBicubic(const SkMatrix& matrix,
205                                       GrSamplerParams::FilterMode* filterMode) {
206    if (matrix.isIdentity()) {
207        *filterMode = GrSamplerParams::kNone_FilterMode;
208        return false;
209    }
210
211    SkScalar scales[2];
212    if (!matrix.getMinMaxScales(scales) || scales[0] < SK_Scalar1) {
213        // Bicubic doesn't handle arbitrary minimization well, as src texels can be skipped
214        // entirely,
215        *filterMode = GrSamplerParams::kMipMap_FilterMode;
216        return false;
217    }
218    // At this point if scales[1] == SK_Scalar1 then the matrix doesn't do any scaling.
219    if (scales[1] == SK_Scalar1) {
220        if (matrix.rectStaysRect() && SkScalarIsInt(matrix.getTranslateX()) &&
221            SkScalarIsInt(matrix.getTranslateY())) {
222            *filterMode = GrSamplerParams::kNone_FilterMode;
223        } else {
224            // Use bilerp to handle rotation or fractional translation.
225            *filterMode = GrSamplerParams::kBilerp_FilterMode;
226        }
227        return false;
228    }
229    // When we use the bicubic filtering effect each sample is read from the texture using
230    // nearest neighbor sampling.
231    *filterMode = GrSamplerParams::kNone_FilterMode;
232    return true;
233}
234