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path: root/libavutil/color_utils.c (plain)
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1/*
2 * Copyright (c) 2015 Kevin Wheatley <kevin.j.wheatley@gmail.com>
3 *
4 * This file is part of FFmpeg.
5 *
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * FFmpeg is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
21#include <stddef.h>
22#include <math.h>
23
24#include "common.h"
25#include "libavutil/color_utils.h"
26#include "libavutil/pixfmt.h"
27
28double avpriv_get_gamma_from_trc(enum AVColorTransferCharacteristic trc)
29{
30 double gamma;
31 switch (trc) {
32 case AVCOL_TRC_BT709:
33 case AVCOL_TRC_SMPTE170M:
34 case AVCOL_TRC_SMPTE240M:
35 case AVCOL_TRC_BT1361_ECG:
36 case AVCOL_TRC_BT2020_10:
37 case AVCOL_TRC_BT2020_12:
38 /* these share a segmented TRC, but gamma 1.961 is a close
39 approximation, and also more correct for decoding content */
40 gamma = 1.961;
41 break;
42 case AVCOL_TRC_GAMMA22:
43 case AVCOL_TRC_IEC61966_2_1:
44 gamma = 2.2;
45 break;
46 case AVCOL_TRC_GAMMA28:
47 gamma = 2.8;
48 break;
49 case AVCOL_TRC_LINEAR:
50 gamma = 1.0;
51 break;
52 default:
53 gamma = 0.0; // Unknown value representation
54 }
55 return gamma;
56}
57
58#define BT709_alpha 1.099296826809442
59#define BT709_beta 0.018053968510807
60
61static double avpriv_trc_bt709(double Lc)
62{
63 const double a = BT709_alpha;
64 const double b = BT709_beta;
65
66 return (0.0 > Lc) ? 0.0
67 : ( b > Lc) ? 4.500 * Lc
68 : a * pow(Lc, 0.45) - (a - 1.0);
69}
70
71static double avpriv_trc_gamma22(double Lc)
72{
73 return (0.0 > Lc) ? 0.0 : pow(Lc, 1.0/ 2.2);
74}
75
76static double avpriv_trc_gamma28(double Lc)
77{
78 return (0.0 > Lc) ? 0.0 : pow(Lc, 1.0/ 2.8);
79}
80
81static double avpriv_trc_smpte240M(double Lc)
82{
83 const double a = 1.1115;
84 const double b = 0.0228;
85
86 return (0.0 > Lc) ? 0.0
87 : ( b > Lc) ? 4.000 * Lc
88 : a * pow(Lc, 0.45) - (a - 1.0);
89}
90
91static double avpriv_trc_linear(double Lc)
92{
93 return Lc;
94}
95
96static double avpriv_trc_log(double Lc)
97{
98 return (0.01 > Lc) ? 0.0 : 1.0 + log10(Lc) / 2.0;
99}
100
101static double avpriv_trc_log_sqrt(double Lc)
102{
103 // sqrt(10) / 1000
104 return (0.00316227766 > Lc) ? 0.0 : 1.0 + log10(Lc) / 2.5;
105}
106
107static double avpriv_trc_iec61966_2_4(double Lc)
108{
109 const double a = BT709_alpha;
110 const double b = BT709_beta;
111
112 return (-b >= Lc) ? -a * pow(-Lc, 0.45) + (a - 1.0)
113 : ( b > Lc) ? 4.500 * Lc
114 : a * pow( Lc, 0.45) - (a - 1.0);
115}
116
117static double avpriv_trc_bt1361(double Lc)
118{
119 const double a = BT709_alpha;
120 const double b = BT709_beta;
121
122 return (-0.0045 >= Lc) ? -(a * pow(-4.0 * Lc, 0.45) + (a - 1.0)) / 4.0
123 : ( b > Lc) ? 4.500 * Lc
124 : a * pow( Lc, 0.45) - (a - 1.0);
125}
126
127static double avpriv_trc_iec61966_2_1(double Lc)
128{
129 const double a = 1.055;
130 const double b = 0.0031308;
131
132 return (0.0 > Lc) ? 0.0
133 : ( b > Lc) ? 12.92 * Lc
134 : a * pow(Lc, 1.0 / 2.4) - (a - 1.0);
135}
136
137static double avpriv_trc_smpte_st2084(double Lc)
138{
139 const double c1 = 3424.0 / 4096.0; // c3-c2 + 1
140 const double c2 = 32.0 * 2413.0 / 4096.0;
141 const double c3 = 32.0 * 2392.0 / 4096.0;
142 const double m = 128.0 * 2523.0 / 4096.0;
143 const double n = 0.25 * 2610.0 / 4096.0;
144 const double L = Lc / 10000.0;
145 const double Ln = pow(L, n);
146
147 return (0.0 > Lc) ? 0.0
148 : pow((c1 + c2 * Ln) / (1.0 + c3 * Ln), m);
149
150}
151
152static double avpriv_trc_smpte_st428_1(double Lc)
153{
154 return (0.0 > Lc) ? 0.0
155 : pow(48.0 * Lc / 52.37, 1.0 / 2.6);
156}
157
158
159static double avpriv_trc_arib_std_b67(double Lc) {
160 // The function uses the definition from HEVC, which assumes that the peak
161 // white is input level = 1. (this is equivalent to scaling E = Lc * 12 and
162 // using the definition from the ARIB STD-B67 spec)
163 const double a = 0.17883277;
164 const double b = 0.28466892;
165 const double c = 0.55991073;
166 return (0.0 > Lc) ? 0.0 :
167 (Lc <= 1.0 / 12.0 ? sqrt(3.0 * Lc) : a * log(12.0 * Lc - b) + c);
168}
169
170avpriv_trc_function avpriv_get_trc_function_from_trc(enum AVColorTransferCharacteristic trc)
171{
172 avpriv_trc_function func = NULL;
173 switch (trc) {
174 case AVCOL_TRC_BT709:
175 case AVCOL_TRC_SMPTE170M:
176 case AVCOL_TRC_BT2020_10:
177 case AVCOL_TRC_BT2020_12:
178 func = avpriv_trc_bt709;
179 break;
180
181 case AVCOL_TRC_GAMMA22:
182 func = avpriv_trc_gamma22;
183 break;
184 case AVCOL_TRC_GAMMA28:
185 func = avpriv_trc_gamma28;
186 break;
187
188 case AVCOL_TRC_SMPTE240M:
189 func = avpriv_trc_smpte240M;
190 break;
191
192 case AVCOL_TRC_LINEAR:
193 func = avpriv_trc_linear;
194 break;
195
196 case AVCOL_TRC_LOG:
197 func = avpriv_trc_log;
198 break;
199
200 case AVCOL_TRC_LOG_SQRT:
201 func = avpriv_trc_log_sqrt;
202 break;
203
204 case AVCOL_TRC_IEC61966_2_4:
205 func = avpriv_trc_iec61966_2_4;
206 break;
207
208 case AVCOL_TRC_BT1361_ECG:
209 func = avpriv_trc_bt1361;
210 break;
211
212 case AVCOL_TRC_IEC61966_2_1:
213 func = avpriv_trc_iec61966_2_1;
214 break;
215
216 case AVCOL_TRC_SMPTEST2084:
217 func = avpriv_trc_smpte_st2084;
218 break;
219
220 case AVCOL_TRC_SMPTEST428_1:
221 func = avpriv_trc_smpte_st428_1;
222 break;
223
224 case AVCOL_TRC_ARIB_STD_B67:
225 func = avpriv_trc_arib_std_b67;
226 break;
227
228 case AVCOL_TRC_RESERVED0:
229 case AVCOL_TRC_UNSPECIFIED:
230 case AVCOL_TRC_RESERVED:
231 default:
232 break;
233 }
234 return func;
235}
236
generated by cgit at 2024-05-17 02:28:57 (GMT)