Hard code bicubic coefficients in the shader

BUG=skia:

Change-Id: Ie231a9bd2ea2083005a595e9e426590da740b2ed
Reviewed-on: https://skia-review.googlesource.com/6619
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

diff --git a/src/gpu/effects/GrBicubicEffect.cpp b/src/gpu/effects/GrBicubicEffect.cpp
index de93aaacc610ca66b1267356734c8aa439845b8e..9d8e728efcef156f74998792505fc5ab9c05bd82 100644 (file)
--- a/src/gpu/effects/GrBicubicEffect.cpp
+++ b/src/gpu/effects/GrBicubicEffect.cpp
@@ -13,32 +13,6 @@
 #include "glsl/GrGLSLUniformHandler.h"
 #include "../private/GrGLSL.h"
 
-/*
- * Filter weights come from Don Mitchell & Arun Netravali's 'Reconstruction Filters in Computer
- * Graphics', ACM SIGGRAPH Computer Graphics 22, 4 (Aug. 1988).
- * ACM DL: http://dl.acm.org/citation.cfm?id=378514
- * Free  : http://www.cs.utexas.edu/users/fussell/courses/cs384g/lectures/mitchell/Mitchell.pdf
- *
- * The authors define a family of cubic filters with two free parameters (B and C):
- *
- *            { (12 - 9B - 6C)|x|^3 + (-18 + 12B + 6C)|x|^2 + (6 - 2B)            if |x| < 1
- * k(x) = 1/6 { (-B - 6C)|x|^3 + (6B + 30C)|x|^2 + (-12B - 48C)|x| + (8B + 24C)   if 1 <= |x| < 2
- *            { 0                                                                 otherwise
- *
- * Various well-known cubic splines can be generated, and the authors select (1/3, 1/3) as their
- * favorite overall spline - this is now commonly known as the Mitchell filter, and is the source
- * of the specific weights below.
- *
- * These weights are in column-major order (ie this matrix is transposed from what you'd expect),
- * so we can upload them directly via setMatrix4f.
- */
-static constexpr float kMitchellCoefficients[16] = {
-     1.0f / 18.0f,  16.0f / 18.0f,   1.0f / 18.0f,  0.0f / 18.0f,
-    -9.0f / 18.0f,   0.0f / 18.0f,   9.0f / 18.0f,  0.0f / 18.0f,
-    15.0f / 18.0f, -36.0f / 18.0f,  27.0f / 18.0f, -6.0f / 18.0f,
-    -7.0f / 18.0f,  21.0f / 18.0f, -21.0f / 18.0f,  7.0f / 18.0f,
-};
-
 class GrGLBicubicEffect : public GrGLSLFragmentProcessor {
 public:
     void emitCode(EmitArgs&) override;
@@ -56,7 +30,6 @@ protected:
 private:
     typedef GrGLSLProgramDataManager::UniformHandle UniformHandle;
 
-    UniformHandle               fCoefficientsUni;
     UniformHandle               fImageIncrementUni;
     UniformHandle               fColorSpaceXformUni;
     GrTextureDomain::GLDomain   fDomain;
@@ -68,48 +41,52 @@ void GrGLBicubicEffect::emitCode(EmitArgs& args) {
     const GrBicubicEffect& bicubicEffect = args.fFp.cast<GrBicubicEffect>();
 
     GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
-    fCoefficientsUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
-                                                  kMat44f_GrSLType, kDefault_GrSLPrecision,
-                                                  "Coefficients");
     fImageIncrementUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                                     kVec2f_GrSLType, kDefault_GrSLPrecision,
                                                     "ImageIncrement");
 
     const char* imgInc = uniformHandler->getUniformCStr(fImageIncrementUni);
-    const char* coeff = uniformHandler->getUniformCStr(fCoefficientsUni);
 
     GrGLSLColorSpaceXformHelper colorSpaceHelper(uniformHandler, bicubicEffect.colorSpaceXform(),
                                                  &fColorSpaceXformUni);
 
-    SkString cubicBlendName;
-
-    static const GrShaderVar gCubicBlendArgs[] = {
-        GrShaderVar("coefficients",  kMat44f_GrSLType),
-        GrShaderVar("t",             kFloat_GrSLType),
-        GrShaderVar("c0",            kVec4f_GrSLType),
-        GrShaderVar("c1",            kVec4f_GrSLType),
-        GrShaderVar("c2",            kVec4f_GrSLType),
-        GrShaderVar("c3",            kVec4f_GrSLType),
-    };
     GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
     SkString coords2D = fragBuilder->ensureCoords2D(args.fTransformedCoords[0]);
-    fragBuilder->emitFunction(kVec4f_GrSLType,
-                              "cubicBlend",
-                              SK_ARRAY_COUNT(gCubicBlendArgs),
-                              gCubicBlendArgs,
-                              "\tvec4 ts = vec4(1.0, t, t * t, t * t * t);\n"
-                              "\tvec4 c = coefficients * ts;\n"
-                              "\treturn c.x * c0 + c.y * c1 + c.z * c2 + c.w * c3;\n",
-                              &cubicBlendName);
-    fragBuilder->codeAppendf("\tvec2 coord = %s - %s * vec2(0.5);\n", coords2D.c_str(), imgInc);
+
+    /*
+     * Filter weights come from Don Mitchell & Arun Netravali's 'Reconstruction Filters in Computer
+     * Graphics', ACM SIGGRAPH Computer Graphics 22, 4 (Aug. 1988).
+     * ACM DL: http://dl.acm.org/citation.cfm?id=378514
+     * Free  : http://www.cs.utexas.edu/users/fussell/courses/cs384g/lectures/mitchell/Mitchell.pdf
+     *
+     * The authors define a family of cubic filters with two free parameters (B and C):
+     *
+     *            { (12 - 9B - 6C)|x|^3 + (-18 + 12B + 6C)|x|^2 + (6 - 2B)          if |x| < 1
+     * k(x) = 1/6 { (-B - 6C)|x|^3 + (6B + 30C)|x|^2 + (-12B - 48C)|x| + (8B + 24C) if 1 <= |x| < 2
+     *            { 0                                                               otherwise
+     *
+     * Various well-known cubic splines can be generated, and the authors select (1/3, 1/3) as their
+     * favorite overall spline - this is now commonly known as the Mitchell filter, and is the
+     * source of the specific weights below.
+     *
+     * This is GLSL, so the matrix is column-major (transposed from standard matrix notation).
+     */
+    fragBuilder->codeAppend("mat4 kMitchellCoefficients = mat4("
+                            " 1.0 / 18.0,  16.0 / 18.0,   1.0 / 18.0,  0.0 / 18.0,"
+                            "-9.0 / 18.0,   0.0 / 18.0,   9.0 / 18.0,  0.0 / 18.0,"
+                            "15.0 / 18.0, -36.0 / 18.0,  27.0 / 18.0, -6.0 / 18.0,"
+                            "-7.0 / 18.0,  21.0 / 18.0, -21.0 / 18.0,  7.0 / 18.0);");
+    fragBuilder->codeAppendf("vec2 coord = %s - %s * vec2(0.5);", coords2D.c_str(), imgInc);
     // We unnormalize the coord in order to determine our fractional offset (f) within the texel
     // We then snap coord to a texel center and renormalize. The snap prevents cases where the
     // starting coords are near a texel boundary and accumulations of imgInc would cause us to skip/
     // double hit a texel.
-    fragBuilder->codeAppendf("\tcoord /= %s;\n", imgInc);
-    fragBuilder->codeAppend("\tvec2 f = fract(coord);\n");
-    fragBuilder->codeAppendf("\tcoord = (coord - f + vec2(0.5)) * %s;\n", imgInc);
-    fragBuilder->codeAppend("\tvec4 rowColors[4];\n");
+    fragBuilder->codeAppendf("coord /= %s;", imgInc);
+    fragBuilder->codeAppend("vec2 f = fract(coord);");
+    fragBuilder->codeAppendf("coord = (coord - f + vec2(0.5)) * %s;", imgInc);
+    fragBuilder->codeAppend("vec4 wx = kMitchellCoefficients * vec4(1.0, f.x, f.x * f.x, f.x * f.x * f.x);");
+    fragBuilder->codeAppend("vec4 wy = kMitchellCoefficients * vec4(1.0, f.y, f.y * f.y, f.y * f.y * f.y);");
+    fragBuilder->codeAppend("vec4 rowColors[4];");
     for (int y = 0; y < 4; ++y) {
         for (int x = 0; x < 4; ++x) {
             SkString coord;
@@ -125,17 +102,16 @@ void GrGLBicubicEffect::emitCode(EmitArgs& args) {
                                   args.fTexSamplers[0]);
         }
         fragBuilder->codeAppendf(
-            "\tvec4 s%d = %s(%s, f.x, rowColors[0], rowColors[1], rowColors[2], rowColors[3]);\n",
-            y, cubicBlendName.c_str(), coeff);
+            "vec4 s%d = wx.x * rowColors[0] + wx.y * rowColors[1] + wx.z * rowColors[2] + wx.w * rowColors[3];",
+            y);
     }
-    SkString bicubicColor;
-    bicubicColor.printf("%s(%s, f.y, s0, s1, s2, s3)", cubicBlendName.c_str(), coeff);
+    SkString bicubicColor("(wy.x * s0 + wy.y * s1 + wy.z * s2 + wy.w * s3)");
     if (colorSpaceHelper.getXformMatrix()) {
         SkString xformedColor;
         fragBuilder->appendColorGamutXform(&xformedColor, bicubicColor.c_str(), &colorSpaceHelper);
         bicubicColor.swap(xformedColor);
     }
-    fragBuilder->codeAppendf("\t%s = %s;\n",
+    fragBuilder->codeAppendf("%s = %s;",
                              args.fOutputColor, (GrGLSLExpr4(bicubicColor.c_str()) *
                                                  GrGLSLExpr4(args.fInputColor)).c_str());
 }
@@ -148,7 +124,6 @@ void GrGLBicubicEffect::onSetData(const GrGLSLProgramDataManager& pdman,
     imageIncrement[0] = 1.0f / texture->width();
     imageIncrement[1] = 1.0f / texture->height();
     pdman.set2fv(fImageIncrementUni, 1, imageIncrement);
-    pdman.setMatrix4f(fCoefficientsUni, kMitchellCoefficients);
     fDomain.setData(pdman, bicubicEffect.domain(), texture->origin());
     if (SkToBool(bicubicEffect.colorSpaceXform())) {
         pdman.setSkMatrix44(fColorSpaceXformUni, bicubicEffect.colorSpaceXform()->srcToDst());