| |
| /* |
| * Copyright 2011 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| #include "SkFontHost.h" |
| #include <math.h> |
| |
| // define this to use pre-compiled tables for gamma. This is slightly faster, |
| // and doesn't create any RW global memory, but means we cannot change the |
| // gamma at runtime. |
| //#define USE_PREDEFINED_GAMMA_TABLES |
| |
| #ifndef USE_PREDEFINED_GAMMA_TABLES |
| // define this if you want to spew out the "C" code for the tables, given |
| // the current values for SK_BLACK_GAMMA and SK_WHITE_GAMMA. |
| #define DUMP_GAMMA_TABLESx |
| #endif |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| |
| #include "SkGraphics.h" |
| |
| // declared here, so we can link against it elsewhere |
| void skia_set_text_gamma(float blackGamma, float whiteGamma); |
| |
| #ifdef USE_PREDEFINED_GAMMA_TABLES |
| |
| #include "sk_predefined_gamma.h" |
| |
| void skia_set_text_gamma(float blackGamma, float whiteGamma) {} |
| |
| #else // use writable globals for gamma tables |
| |
| static void build_power_table(uint8_t table[], float ee) { |
| // SkDebugf("------ build_power_table %g\n", ee); |
| for (int i = 0; i < 256; i++) { |
| float x = i / 255.f; |
| // printf(" %d %g", i, x); |
| x = powf(x, ee); |
| // printf(" %g", x); |
| int xx = SkScalarRound(SkFloatToScalar(x * 255)); |
| // printf(" %d\n", xx); |
| table[i] = SkToU8(xx); |
| } |
| } |
| |
| static bool gGammaIsBuilt; |
| static uint8_t gBlackGamma[256], gWhiteGamma[256]; |
| |
| static float gBlackGammaCoeff = 1.4f; |
| static float gWhiteGammaCoeff = 1/1.4f; |
| |
| void skia_set_text_gamma(float blackGamma, float whiteGamma) { |
| gBlackGammaCoeff = blackGamma; |
| gWhiteGammaCoeff = whiteGamma; |
| gGammaIsBuilt = false; |
| SkGraphics::PurgeFontCache(); |
| build_power_table(gBlackGamma, gBlackGammaCoeff); |
| build_power_table(gWhiteGamma, gWhiteGammaCoeff); |
| } |
| |
| #ifdef DUMP_GAMMA_TABLES |
| |
| #include "SkString.h" |
| |
| static void dump_a_table(const char name[], const uint8_t table[], |
| float gamma) { |
| SkDebugf("\n"); |
| SkDebugf("\/\/ Gamma table for %g\n", gamma); |
| SkDebugf("static const uint8_t %s[] = {\n", name); |
| for (int y = 0; y < 16; y++) { |
| SkString line, tmp; |
| for (int x = 0; x < 16; x++) { |
| tmp.printf("0x%02X, ", *table++); |
| line.append(tmp); |
| } |
| SkDebugf(" %s\n", line.c_str()); |
| } |
| SkDebugf("};\n"); |
| } |
| |
| #endif |
| |
| #endif |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| |
| void SkFontHost::GetGammaTables(const uint8_t* tables[2]) { |
| #ifndef USE_PREDEFINED_GAMMA_TABLES |
| if (!gGammaIsBuilt) { |
| build_power_table(gBlackGamma, gBlackGammaCoeff); |
| build_power_table(gWhiteGamma, gWhiteGammaCoeff); |
| gGammaIsBuilt = true; |
| |
| #ifdef DUMP_GAMMA_TABLES |
| dump_a_table("gBlackGamma", gBlackGamma, gBlackGammaCoeff); |
| dump_a_table("gWhiteGamma", gWhiteGamma, gWhiteGammaCoeff); |
| #endif |
| } |
| #endif |
| tables[0] = gBlackGamma; |
| tables[1] = gWhiteGamma; |
| } |
| |
| // If the luminance is <= this value, then apply the black gamma table |
| #define BLACK_GAMMA_THRESHOLD 0x40 |
| |
| // If the luminance is >= this value, then apply the white gamma table |
| #define WHITE_GAMMA_THRESHOLD 0xC0 |
| |
| int SkFontHost::ComputeGammaFlag(const SkPaint& paint) { |
| if (paint.getShader() == NULL) { |
| SkColor c = paint.getColor(); |
| int r = SkColorGetR(c); |
| int g = SkColorGetG(c); |
| int b = SkColorGetB(c); |
| int luminance = (r * 2 + g * 5 + b) >> 3; |
| |
| if (luminance <= BLACK_GAMMA_THRESHOLD) { |
| // printf("------ black gamma for [%d %d %d]\n", r, g, b); |
| return SkScalerContext::kGammaForBlack_Flag; |
| } |
| if (luminance >= WHITE_GAMMA_THRESHOLD) { |
| // printf("------ white gamma for [%d %d %d]\n", r, g, b); |
| return SkScalerContext::kGammaForWhite_Flag; |
| } |
| } |
| return 0; |
| } |
| |