Improve quality of distance field rendering

src/gpu/effects/GrDistanceFieldTextureEffect.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrDistanceFieldTextureEffect.h"
 #include "gl/builders/GrGLProgramBuilder.h"
 #include "gl/GrGLProcessor.h"
 #include "gl/GrGLSL.h"
 #include "gl/GrGLTexture.h"
 #include "gl/GrGLGeometryProcessor.h"
 #include "GrTBackendProcessorFactory.h"
 #include "GrTexture.h"
 
 #include "SkDistanceFieldGen.h"
 
-// To get optical sizes people don't complain about when we blit correctly,
-// we need to slightly bold each glyph. On the Mac, we need a larger bold value.
-#if defined(SK_BUILD_FOR_MAC)
-#define SK_DistanceFieldLCDFactor    "0.33"
-#define SK_DistanceFieldNonLCDFactor "0.25"
-#else
-#define SK_DistanceFieldLCDFactor    "0.05"
-#define SK_DistanceFieldNonLCDFactor "0.05"
-#endif
-
 // Assuming a radius of the diagonal of the fragment, hence a factor of sqrt(2)/2
 #define SK_DistanceFieldAAFactor     "0.7071"
 
 class GrGLDistanceFieldTextureEffect : public GrGLGeometryProcessor {
 public:
     GrGLDistanceFieldTextureEffect(const GrBackendProcessorFactory& factory,
                                    const GrProcessor&)
         : INHERITED (factory)
         , fTextureSize(SkISize::Make(-1,-1))
 #ifdef SK_GAMMA_APPLY_TO_A8
@@ skipping 20 matching lines @@
         fTextureSizeUni = args.fPB->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                                kVec2f_GrSLType, "TextureSize",
                                                &textureSizeUniName);
 
         fsBuilder->codeAppend("\tvec4 texColor = ");
         fsBuilder->appendTextureLookup(args.fSamplers[0],
                                        v.fsIn(),
                                        kVec2f_GrSLType);
         fsBuilder->codeAppend(";\n");
         fsBuilder->codeAppend("\tfloat distance = "
-                          SK_DistanceFieldMultiplier "*(texColor.r - " SK_DistanceFieldThreshold ")"
-                          "+ " SK_DistanceFieldNonLCDFactor ";\n");
+                       SK_DistanceFieldMultiplier "*(texColor.r - " SK_DistanceFieldThreshold ");");
 
         // we adjust for the effect of the transformation on the distance by using
         // the length of the gradient of the texture coordinates. We use st coordinates
         // to ensure we're mapping 1:1 from texel space to pixel space.
         fsBuilder->codeAppendf("\tvec2 uv = %s;\n", v.fsIn());
         fsBuilder->codeAppendf("\tvec2 st = uv*%s;\n", textureSizeUniName);
         fsBuilder->codeAppend("\tfloat afwidth;\n");
         if (dfTexEffect.getFlags() & kSimilarity_DistanceFieldEffectFlag) {
             // this gives us a smooth step across approximately one fragment
             fsBuilder->codeAppend("\tafwidth = abs(" SK_DistanceFieldAAFactor "*dFdx(st.x));\n");
@@ skipping 377 matching lines @@
         fsBuilder->codeAppend(";\n");
         fsBuilder->codeAppend("\tdistance.x = texColor.r;\n");
         // blue is distance to right offset
         fsBuilder->codeAppend("\tuv_adjusted = uv + offset;\n");
         fsBuilder->codeAppend("\ttexColor = ");
         fsBuilder->appendTextureLookup(args.fSamplers[0], "uv_adjusted", kVec2f_GrSLType);
         fsBuilder->codeAppend(";\n");
         fsBuilder->codeAppend("\tdistance.z = texColor.r;\n");
 
         fsBuilder->codeAppend("\tdistance = "
-            "vec3(" SK_DistanceFieldMultiplier ")*(distance - vec3(" SK_DistanceFieldThreshold"))"
-            "+ vec3(" SK_DistanceFieldLCDFactor ");\n");
+           "vec3(" SK_DistanceFieldMultiplier ")*(distance - vec3(" SK_DistanceFieldThreshold"));");
 
         // we adjust for the effect of the transformation on the distance by using
         // the length of the gradient of the texture coordinates. We use st coordinates
         // to ensure we're mapping 1:1 from texel space to pixel space.
 
         // To be strictly correct, we should compute the anti-aliasing factor separately
         // for each color component. However, this is only important when using perspective
         // transformations, and even then using a single factor seems like a reasonable
         // trade-off between quality and speed.
         fsBuilder->codeAppend("\tfloat afwidth;\n");
@@ skipping 164 matching lines @@
                                         random->nextULessThan(256),
                                         random->nextULessThan(256));
     uint32_t flags = kUseLCD_DistanceFieldEffectFlag;
     flags |= random->nextBool() ? kUniformScale_DistanceFieldEffectMask : 0;
     flags |= random->nextBool() ? kBGR_DistanceFieldEffectFlag : 0;
     return GrDistanceFieldLCDTextureEffect::Create(textures[texIdx], params,
                                                    textures[texIdx2], params2,
                                                    textColor,
                                                    flags);
 }