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
27 void skia_set_text_gamma(float blackGamma, float whiteGamma);
28
29 #ifdef USE_PREDEFINED_GAMMA_TABLES
30
31 #include "sk_predefined_gamma.h"
32
skia_set_text_gamma(float blackGamma,float whiteGamma)33 void skia_set_text_gamma(float blackGamma, float whiteGamma) {}
34
35 #else // use writable globals for gamma tables
36
build_power_table(uint8_t table[],float ee)37 static 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
50 static bool gGammaIsBuilt;
51 static uint8_t gBlackGamma[256], gWhiteGamma[256];
52
53 static float gBlackGammaCoeff = 1.4f;
54 static float gWhiteGammaCoeff = 1/1.4f;
55
skia_set_text_gamma(float blackGamma,float whiteGamma)56 void 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
dump_a_table(const char name[],const uint8_t table[],float gamma)69 static 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
GetGammaTables(const uint8_t * tables[2])91 void 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