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