GrBicubicEffect.cpp revision 467022b1861033d968195687da15270c208279ff 
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 "GrProxyMove.h"
11#include "GrTexture.h"
12#include "GrTextureProxy.h"
13#include "glsl/GrGLSLColorSpaceXformHelper.h"
14#include "glsl/GrGLSLFragmentShaderBuilder.h"
15#include "glsl/GrGLSLProgramDataManager.h"
16#include "glsl/GrGLSLUniformHandler.h"
17#include "../private/GrGLSL.h"
18
19class GrGLBicubicEffect : public GrGLSLFragmentProcessor {
20public:
21    void emitCode(EmitArgs&) override;
22
23    static inline void GenKey(const GrProcessor& effect, const GrShaderCaps&,
24                              GrProcessorKeyBuilder* b) {
25        const GrBicubicEffect& bicubicEffect = effect.cast<GrBicubicEffect>();
26        b->add32(GrTextureDomain::GLDomain::DomainKey(bicubicEffect.domain()));
27        b->add32(GrColorSpaceXform::XformKey(bicubicEffect.colorSpaceXform()));
28    }
29
30protected:
31    void onSetData(const GrGLSLProgramDataManager&, const GrFragmentProcessor&) override;
32
33private:
34    typedef GrGLSLProgramDataManager::UniformHandle UniformHandle;
35
36    UniformHandle               fImageIncrementUni;
37    GrGLSLColorSpaceXformHelper fColorSpaceHelper;
38    GrTextureDomain::GLDomain   fDomain;
39
40    typedef GrGLSLFragmentProcessor INHERITED;
41};
42
43void GrGLBicubicEffect::emitCode(EmitArgs& args) {
44    const GrBicubicEffect& bicubicEffect = args.fFp.cast<GrBicubicEffect>();
45
46    GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
47    fImageIncrementUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
48                                                    kVec2f_GrSLType, kDefault_GrSLPrecision,
49                                                    "ImageIncrement");
50
51    const char* imgInc = uniformHandler->getUniformCStr(fImageIncrementUni);
52
53    fColorSpaceHelper.emitCode(uniformHandler, bicubicEffect.colorSpaceXform());
54
55    GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
56    SkString coords2D = fragBuilder->ensureCoords2D(args.fTransformedCoords[0]);
57
58    /*
59     * Filter weights come from Don Mitchell & Arun Netravali's 'Reconstruction Filters in Computer
60     * Graphics', ACM SIGGRAPH Computer Graphics 22, 4 (Aug. 1988).
61     * ACM DL: http://dl.acm.org/citation.cfm?id=378514
62     * Free  : http://www.cs.utexas.edu/users/fussell/courses/cs384g/lectures/mitchell/Mitchell.pdf
63     *
64     * The authors define a family of cubic filters with two free parameters (B and C):
65     *
66     *            { (12 - 9B - 6C)|x|^3 + (-18 + 12B + 6C)|x|^2 + (6 - 2B)          if |x| < 1
67     * k(x) = 1/6 { (-B - 6C)|x|^3 + (6B + 30C)|x|^2 + (-12B - 48C)|x| + (8B + 24C) if 1 <= |x| < 2
68     *            { 0                                                               otherwise
69     *
70     * Various well-known cubic splines can be generated, and the authors select (1/3, 1/3) as their
71     * favorite overall spline - this is now commonly known as the Mitchell filter, and is the
72     * source of the specific weights below.
73     *
74     * This is GLSL, so the matrix is column-major (transposed from standard matrix notation).
75     */
76    fragBuilder->codeAppend("mat4 kMitchellCoefficients = mat4("
77                            " 1.0 / 18.0,  16.0 / 18.0,   1.0 / 18.0,  0.0 / 18.0,"
78                            "-9.0 / 18.0,   0.0 / 18.0,   9.0 / 18.0,  0.0 / 18.0,"
79                            "15.0 / 18.0, -36.0 / 18.0,  27.0 / 18.0, -6.0 / 18.0,"
80                            "-7.0 / 18.0,  21.0 / 18.0, -21.0 / 18.0,  7.0 / 18.0);");
81    fragBuilder->codeAppendf("vec2 coord = %s - %s * vec2(0.5);", coords2D.c_str(), imgInc);
82    // We unnormalize the coord in order to determine our fractional offset (f) within the texel
83    // We then snap coord to a texel center and renormalize. The snap prevents cases where the
84    // starting coords are near a texel boundary and accumulations of imgInc would cause us to skip/
85    // double hit a texel.
86    fragBuilder->codeAppendf("coord /= %s;", imgInc);
87    fragBuilder->codeAppend("vec2 f = fract(coord);");
88    fragBuilder->codeAppendf("coord = (coord - f + vec2(0.5)) * %s;", imgInc);
89    fragBuilder->codeAppend("vec4 wx = kMitchellCoefficients * vec4(1.0, f.x, f.x * f.x, f.x * f.x * f.x);");
90    fragBuilder->codeAppend("vec4 wy = kMitchellCoefficients * vec4(1.0, f.y, f.y * f.y, f.y * f.y * f.y);");
91    fragBuilder->codeAppend("vec4 rowColors[4];");
92    for (int y = 0; y < 4; ++y) {
93        for (int x = 0; x < 4; ++x) {
94            SkString coord;
95            coord.printf("coord + %s * vec2(%d, %d)", imgInc, x - 1, y - 1);
96            SkString sampleVar;
97            sampleVar.printf("rowColors[%d]", x);
98            fDomain.sampleTexture(fragBuilder,
99                                  args.fUniformHandler,
100                                  args.fShaderCaps,
101                                  bicubicEffect.domain(),
102                                  sampleVar.c_str(),
103                                  coord,
104                                  args.fTexSamplers[0]);
105        }
106        fragBuilder->codeAppendf(
107            "vec4 s%d = wx.x * rowColors[0] + wx.y * rowColors[1] + wx.z * rowColors[2] + wx.w * rowColors[3];",
108            y);
109    }
110    SkString bicubicColor("(wy.x * s0 + wy.y * s1 + wy.z * s2 + wy.w * s3)");
111    if (fColorSpaceHelper.isValid()) {
112        SkString xformedColor;
113        fragBuilder->appendColorGamutXform(&xformedColor, bicubicColor.c_str(), &fColorSpaceHelper);
114        bicubicColor.swap(xformedColor);
115    }
116    fragBuilder->codeAppendf("%s = %s * %s;", args.fOutputColor, bicubicColor.c_str(),
117                             args.fInputColor);
118}
119
120void GrGLBicubicEffect::onSetData(const GrGLSLProgramDataManager& pdman,
121                                  const GrFragmentProcessor& processor) {
122    const GrBicubicEffect& bicubicEffect = processor.cast<GrBicubicEffect>();
123    GrSurfaceProxy* proxy = processor.textureSampler(0).proxy();
124    GrTexture* texture = proxy->priv().peekTexture();
125
126    float imageIncrement[2];
127    imageIncrement[0] = 1.0f / texture->width();
128    imageIncrement[1] = 1.0f / texture->height();
129    pdman.set2fv(fImageIncrementUni, 1, imageIncrement);
130    fDomain.setData(pdman, bicubicEffect.domain(), proxy);
131    if (SkToBool(bicubicEffect.colorSpaceXform())) {
132        fColorSpaceHelper.setData(pdman, bicubicEffect.colorSpaceXform());
133    }
134}
135
136GrBicubicEffect::GrBicubicEffect(sk_sp<GrTextureProxy> proxy,
137                                 sk_sp<GrColorSpaceXform> colorSpaceXform,
138                                 const SkMatrix &matrix,
139                                 const SkShader::TileMode tileModes[2])
140        : INHERITED{ModulationFlags(proxy->config()),
141                    GR_PROXY_MOVE(proxy),
142                    std::move(colorSpaceXform),
143                    matrix,
144                    GrSamplerParams(tileModes, GrSamplerParams::kNone_FilterMode)}
145        , fDomain(GrTextureDomain::IgnoredDomain()) {
146    this->initClassID<GrBicubicEffect>();
147}
148
149GrBicubicEffect::GrBicubicEffect(sk_sp<GrTextureProxy> proxy,
150                                 sk_sp<GrColorSpaceXform> colorSpaceXform,
151                                 const SkMatrix &matrix,
152                                 const SkRect& domain)
153        : INHERITED(ModulationFlags(proxy->config()), proxy,
154                    std::move(colorSpaceXform), matrix,
155                    GrSamplerParams(SkShader::kClamp_TileMode, GrSamplerParams::kNone_FilterMode))
156        , fDomain(proxy.get(), domain, GrTextureDomain::kClamp_Mode) {
157    this->initClassID<GrBicubicEffect>();
158}
159
160GrBicubicEffect::~GrBicubicEffect() {
161}
162
163void GrBicubicEffect::onGetGLSLProcessorKey(const GrShaderCaps& caps,
164                                            GrProcessorKeyBuilder* b) const {
165    GrGLBicubicEffect::GenKey(*this, caps, b);
166}
167
168GrGLSLFragmentProcessor* GrBicubicEffect::onCreateGLSLInstance() const  {
169    return new GrGLBicubicEffect;
170}
171
172bool GrBicubicEffect::onIsEqual(const GrFragmentProcessor& sBase) const {
173    const GrBicubicEffect& s = sBase.cast<GrBicubicEffect>();
174    return fDomain == s.fDomain;
175}
176
177GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrBicubicEffect);
178
179#if GR_TEST_UTILS
180sk_sp<GrFragmentProcessor> GrBicubicEffect::TestCreate(GrProcessorTestData* d) {
181    int texIdx = d->fRandom->nextBool() ? GrProcessorUnitTest::kSkiaPMTextureIdx
182                                        : GrProcessorUnitTest::kAlphaTextureIdx;
183    sk_sp<GrColorSpaceXform> colorSpaceXform = GrTest::TestColorXform(d->fRandom);
184    static const SkShader::TileMode kClampClamp[] =
185        { SkShader::kClamp_TileMode, SkShader::kClamp_TileMode };
186    return GrBicubicEffect::Make(d->textureProxy(texIdx), std::move(colorSpaceXform),
187                                 SkMatrix::I(), kClampClamp);
188}
189#endif
190
191//////////////////////////////////////////////////////////////////////////////
192
193bool GrBicubicEffect::ShouldUseBicubic(const SkMatrix& matrix,
194                                       GrSamplerParams::FilterMode* filterMode) {
195    if (matrix.isIdentity()) {
196        *filterMode = GrSamplerParams::kNone_FilterMode;
197        return false;
198    }
199
200    SkScalar scales[2];
201    if (!matrix.getMinMaxScales(scales) || scales[0] < SK_Scalar1) {
202        // Bicubic doesn't handle arbitrary minimization well, as src texels can be skipped
203        // entirely,
204        *filterMode = GrSamplerParams::kMipMap_FilterMode;
205        return false;
206    }
207    // At this point if scales[1] == SK_Scalar1 then the matrix doesn't do any scaling.
208    if (scales[1] == SK_Scalar1) {
209        if (matrix.rectStaysRect() && SkScalarIsInt(matrix.getTranslateX()) &&
210            SkScalarIsInt(matrix.getTranslateY())) {
211            *filterMode = GrSamplerParams::kNone_FilterMode;
212        } else {
213            // Use bilerp to handle rotation or fractional translation.
214            *filterMode = GrSamplerParams::kBilerp_FilterMode;
215        }
216        return false;
217    }
218    // When we use the bicubic filtering effect each sample is read from the texture using
219    // nearest neighbor sampling.
220    *filterMode = GrSamplerParams::kNone_FilterMode;
221    return true;
222}
223