1 2/* 3 * Copyright 2011 Google Inc. 4 * 5 * Use of this source code is governed by a BSD-style license that can be 6 * found in the LICENSE file. 7 */ 8#include "SkFontHost.h" 9#include <math.h> 10 11// define this to use pre-compiled tables for gamma. This is slightly faster, 12// and doesn't create any RW global memory, but means we cannot change the 13// gamma at runtime. 14//#define USE_PREDEFINED_GAMMA_TABLES 15 16#ifndef USE_PREDEFINED_GAMMA_TABLES 17 // define this if you want to spew out the "C" code for the tables, given 18 // the current values for SK_BLACK_GAMMA and SK_WHITE_GAMMA. 19 #define DUMP_GAMMA_TABLESx 20#endif 21 22/////////////////////////////////////////////////////////////////////////////// 23 24#include "SkGraphics.h" 25 26// declared here, so we can link against it elsewhere 27void skia_set_text_gamma(float blackGamma, float whiteGamma); 28 29#ifdef USE_PREDEFINED_GAMMA_TABLES 30 31#include "sk_predefined_gamma.h" 32 33void skia_set_text_gamma(float blackGamma, float whiteGamma) {} 34 35#else // use writable globals for gamma tables 36 37static void build_power_table(uint8_t table[], float ee) { 38// SkDebugf("------ build_power_table %g\n", ee); 39 for (int i = 0; i < 256; i++) { 40 float x = i / 255.f; 41 // printf(" %d %g", i, x); 42 x = powf(x, ee); 43 // printf(" %g", x); 44 int xx = SkScalarRound(SkFloatToScalar(x * 255)); 45 // printf(" %d\n", xx); 46 table[i] = SkToU8(xx); 47 } 48} 49 50static bool gGammaIsBuilt; 51static uint8_t gBlackGamma[256], gWhiteGamma[256]; 52 53static float gBlackGammaCoeff = 1.4f; 54static float gWhiteGammaCoeff = 1/1.4f; 55 56void skia_set_text_gamma(float blackGamma, float whiteGamma) { 57 gBlackGammaCoeff = blackGamma; 58 gWhiteGammaCoeff = whiteGamma; 59 gGammaIsBuilt = false; 60 SkGraphics::PurgeFontCache(); 61 build_power_table(gBlackGamma, gBlackGammaCoeff); 62 build_power_table(gWhiteGamma, gWhiteGammaCoeff); 63} 64 65#ifdef DUMP_GAMMA_TABLES 66 67#include "SkString.h" 68 69static void dump_a_table(const char name[], const uint8_t table[], 70 float gamma) { 71 SkDebugf("\n"); 72 SkDebugf("\/\/ Gamma table for %g\n", gamma); 73 SkDebugf("static const uint8_t %s[] = {\n", name); 74 for (int y = 0; y < 16; y++) { 75 SkString line, tmp; 76 for (int x = 0; x < 16; x++) { 77 tmp.printf("0x%02X, ", *table++); 78 line.append(tmp); 79 } 80 SkDebugf(" %s\n", line.c_str()); 81 } 82 SkDebugf("};\n"); 83} 84 85#endif 86 87#endif 88 89/////////////////////////////////////////////////////////////////////////////// 90 91void SkFontHost::GetGammaTables(const uint8_t* tables[2]) { 92#ifndef USE_PREDEFINED_GAMMA_TABLES 93 if (!gGammaIsBuilt) { 94 build_power_table(gBlackGamma, gBlackGammaCoeff); 95 build_power_table(gWhiteGamma, gWhiteGammaCoeff); 96 gGammaIsBuilt = true; 97 98#ifdef DUMP_GAMMA_TABLES 99 dump_a_table("gBlackGamma", gBlackGamma, gBlackGammaCoeff); 100 dump_a_table("gWhiteGamma", gWhiteGamma, gWhiteGammaCoeff); 101#endif 102 } 103#endif 104 tables[0] = gBlackGamma; 105 tables[1] = gWhiteGamma; 106} 107 108