1/*
2 * Copyright 2018 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#pragma once
9
10// skcms.h contains the entire public API for skcms.
11
12#ifndef SKCMS_API
13 #define SKCMS_API
14#endif
15
16#include <stdbool.h>
17#include <stddef.h>
18#include <stdint.h>
19#include <string.h>
20
21#ifdef __cplusplus
22extern "C" {
23#endif
24
25// A row-major 3x3 matrix (ie vals[row][col])
26typedef struct skcms_Matrix3x3 {
27 float vals[3][3];
28} skcms_Matrix3x3;
29
30// It is _not_ safe to alias the pointers to invert in-place.
31SKCMS_API bool skcms_Matrix3x3_invert(const skcms_Matrix3x3*, skcms_Matrix3x3*);
32SKCMS_API skcms_Matrix3x3 skcms_Matrix3x3_concat(const skcms_Matrix3x3*, const skcms_Matrix3x3*);
33
34// A row-major 3x4 matrix (ie vals[row][col])
35typedef struct skcms_Matrix3x4 {
36 float vals[3][4];
37} skcms_Matrix3x4;
38
39// A transfer function mapping encoded values to linear values,
40// represented by this 7-parameter piecewise function:
41//
42// linear = sign(encoded) * (c*|encoded| + f) , 0 <= |encoded| < d
43// = sign(encoded) * ((a*|encoded| + b)^g + e), d <= |encoded|
44//
45// (A simple gamma transfer function sets g to gamma and a to 1.)
46typedef struct skcms_TransferFunction {
47 float g, a,b,c,d,e,f;
48} skcms_TransferFunction;
49
50SKCMS_API float skcms_TransferFunction_eval (const skcms_TransferFunction*, float);
51SKCMS_API bool skcms_TransferFunction_invert(const skcms_TransferFunction*,
52 skcms_TransferFunction*);
53
54// We can jam a couple alternate transfer function forms into skcms_TransferFunction,
55// including those matching the general forms of the SMPTE ST 2084 PQ function or HLG.
56//
57// PQish:
58// max(A + B|encoded|^C, 0)
59// linear = sign(encoded) * (------------------------) ^ F
60// D + E|encoded|^C
61SKCMS_API bool skcms_TransferFunction_makePQish(skcms_TransferFunction*,
62 float A, float B, float C,
63 float D, float E, float F);
64// HLGish:
65// { sign(encoded) * ( (R|encoded|)^G ) when 0 <= |encoded| <= 1/R
66// linear = { sign(encoded) * ( e^(a(|encoded|-c)) + b ) when 1/R < |encoded|
67SKCMS_API bool skcms_TransferFunction_makeHLGish(skcms_TransferFunction*,
68 float R, float G,
69 float a, float b, float c);
70
71// PQ mapping encoded [0,1] to linear [0,1].
72static inline bool skcms_TransferFunction_makePQ(skcms_TransferFunction* tf) {
73 return skcms_TransferFunction_makePQish(tf, -107/128.0f, 1.0f, 32/2523.0f
74 , 2413/128.0f, -2392/128.0f, 8192/1305.0f);
75}
76// HLG mapping encoded [0,1] to linear [0,12].
77static inline bool skcms_TransferFunction_makeHLG(skcms_TransferFunction* tf) {
78 return skcms_TransferFunction_makeHLGish(tf, 2.0f, 2.0f
79 , 1/0.17883277f, 0.28466892f, 0.55991073f);
80}
81
82// Unified representation of 'curv' or 'para' tag data, or a 1D table from 'mft1' or 'mft2'
83typedef union skcms_Curve {
84 struct {
85 uint32_t alias_of_table_entries;
86 skcms_TransferFunction parametric;
87 };
88 struct {
89 uint32_t table_entries;
90 const uint8_t* table_8;
91 const uint8_t* table_16;
92 };
93} skcms_Curve;
94
95typedef struct skcms_A2B {
96 // Optional: N 1D curves, followed by an N-dimensional CLUT.
97 // If input_channels == 0, these curves and CLUT are skipped,
98 // Otherwise, input_channels must be in [1, 4].
99 uint32_t input_channels;
100 skcms_Curve input_curves[4];
101 uint8_t grid_points[4];
102 const uint8_t* grid_8;
103 const uint8_t* grid_16;
104
105 // Optional: 3 1D curves, followed by a color matrix.
106 // If matrix_channels == 0, these curves and matrix are skipped,
107 // Otherwise, matrix_channels must be 3.
108 uint32_t matrix_channels;
109 skcms_Curve matrix_curves[3];
110 skcms_Matrix3x4 matrix;
111
112 // Required: 3 1D curves. Always present, and output_channels must be 3.
113 uint32_t output_channels;
114 skcms_Curve output_curves[3];
115} skcms_A2B;
116
117typedef struct skcms_ICCProfile {
118 const uint8_t* buffer;
119
120 uint32_t size;
121 uint32_t data_color_space;
122 uint32_t pcs;
123 uint32_t tag_count;
124
125 // skcms_Parse() will set commonly-used fields for you when possible:
126
127 // If we can parse red, green and blue transfer curves from the profile,
128 // trc will be set to those three curves, and has_trc will be true.
129 bool has_trc;
130 skcms_Curve trc[3];
131
132 // If this profile's gamut can be represented by a 3x3 transform to XYZD50,
133 // skcms_Parse() sets toXYZD50 to that transform and has_toXYZD50 to true.
134 bool has_toXYZD50;
135 skcms_Matrix3x3 toXYZD50;
136
137 // If the profile has a valid A2B0 tag, skcms_Parse() sets A2B to that data,
138 // and has_A2B to true.
139 bool has_A2B;
140 skcms_A2B A2B;
141} skcms_ICCProfile;
142
143// The sRGB color profile is so commonly used that we offer a canonical skcms_ICCProfile for it.
144SKCMS_API const skcms_ICCProfile* skcms_sRGB_profile(void);
145// Ditto for XYZD50, the most common profile connection space.
146SKCMS_API const skcms_ICCProfile* skcms_XYZD50_profile(void);
147
148SKCMS_API const skcms_TransferFunction* skcms_sRGB_TransferFunction(void);
149SKCMS_API const skcms_TransferFunction* skcms_sRGB_Inverse_TransferFunction(void);
150SKCMS_API const skcms_TransferFunction* skcms_Identity_TransferFunction(void);
151
152// Practical equality test for two skcms_ICCProfiles.
153// The implementation is subject to change, but it will always try to answer
154// "can I substitute A for B?" and "can I skip transforming from A to B?".
155SKCMS_API bool skcms_ApproximatelyEqualProfiles(const skcms_ICCProfile* A,
156 const skcms_ICCProfile* B);
157
158// Practical test that answers: Is curve roughly the inverse of inv_tf? Typically used by passing
159// the inverse of a known parametric transfer function (like sRGB), to determine if a particular
160// curve is very close to sRGB.
161SKCMS_API bool skcms_AreApproximateInverses(const skcms_Curve* curve,
162 const skcms_TransferFunction* inv_tf);
163
164// Similar to above, answering the question for all three TRC curves of the given profile. Again,
165// passing skcms_sRGB_InverseTransferFunction as inv_tf will answer the question:
166// "Does this profile have a transfer function that is very close to sRGB?"
167SKCMS_API bool skcms_TRCs_AreApproximateInverse(const skcms_ICCProfile* profile,
168 const skcms_TransferFunction* inv_tf);
169
170// Parse an ICC profile and return true if possible, otherwise return false.
171// The buffer is not copied, it must remain valid as long as the skcms_ICCProfile
172// will be used.
173SKCMS_API bool skcms_Parse(const void*, size_t, skcms_ICCProfile*);
174
175SKCMS_API bool skcms_ApproximateCurve(const skcms_Curve* curve,
176 skcms_TransferFunction* approx,
177 float* max_error);
178
179SKCMS_API bool skcms_GetCHAD(const skcms_ICCProfile*, skcms_Matrix3x3*);
180SKCMS_API bool skcms_GetWTPT(const skcms_ICCProfile*, float xyz[3]);
181
182// These are common ICC signature values
183enum {
184 // data_color_space
185 skcms_Signature_CMYK = 0x434D594B,
186 skcms_Signature_Gray = 0x47524159,
187 skcms_Signature_RGB = 0x52474220,
188
189 // pcs
190 skcms_Signature_Lab = 0x4C616220,
191 skcms_Signature_XYZ = 0x58595A20,
192};
193
194typedef enum skcms_PixelFormat {
195 skcms_PixelFormat_A_8,
196 skcms_PixelFormat_A_8_,
197 skcms_PixelFormat_G_8,
198 skcms_PixelFormat_G_8_,
199 skcms_PixelFormat_RGBA_8888_Palette8,
200 skcms_PixelFormat_BGRA_8888_Palette8,
201
202 skcms_PixelFormat_RGB_565,
203 skcms_PixelFormat_BGR_565,
204
205 skcms_PixelFormat_ABGR_4444,
206 skcms_PixelFormat_ARGB_4444,
207
208 skcms_PixelFormat_RGB_888,
209 skcms_PixelFormat_BGR_888,
210 skcms_PixelFormat_RGBA_8888,
211 skcms_PixelFormat_BGRA_8888,
212 skcms_PixelFormat_RGBA_8888_sRGB, // Automatic sRGB encoding / decoding.
213 skcms_PixelFormat_BGRA_8888_sRGB, // (Generally used with linear transfer functions.)
214
215 skcms_PixelFormat_RGBA_1010102,
216 skcms_PixelFormat_BGRA_1010102,
217
218 skcms_PixelFormat_RGB_161616LE, // Little-endian. Pointers must be 16-bit aligned.
219 skcms_PixelFormat_BGR_161616LE,
220 skcms_PixelFormat_RGBA_16161616LE,
221 skcms_PixelFormat_BGRA_16161616LE,
222
223 skcms_PixelFormat_RGB_161616BE, // Big-endian. Pointers must be 16-bit aligned.
224 skcms_PixelFormat_BGR_161616BE,
225 skcms_PixelFormat_RGBA_16161616BE,
226 skcms_PixelFormat_BGRA_16161616BE,
227
228 skcms_PixelFormat_RGB_hhh_Norm, // 1-5-10 half-precision float in [0,1]
229 skcms_PixelFormat_BGR_hhh_Norm, // Pointers must be 16-bit aligned.
230 skcms_PixelFormat_RGBA_hhhh_Norm,
231 skcms_PixelFormat_BGRA_hhhh_Norm,
232
233 skcms_PixelFormat_RGB_hhh, // 1-5-10 half-precision float.
234 skcms_PixelFormat_BGR_hhh, // Pointers must be 16-bit aligned.
235 skcms_PixelFormat_RGBA_hhhh,
236 skcms_PixelFormat_BGRA_hhhh,
237
238 skcms_PixelFormat_RGB_fff, // 1-8-23 single-precision float (the normal kind).
239 skcms_PixelFormat_BGR_fff, // Pointers must be 32-bit aligned.
240 skcms_PixelFormat_RGBA_ffff,
241 skcms_PixelFormat_BGRA_ffff,
242} skcms_PixelFormat;
243
244// We always store any alpha channel linearly. In the chart below, tf-1() is the inverse
245// transfer function for the given color profile (applying the transfer function linearizes).
246
247// We treat opaque as a strong requirement, not just a performance hint: we will ignore
248// any source alpha and treat it as 1.0, and will make sure that any destination alpha
249// channel is filled with the equivalent of 1.0.
250
251// We used to offer multiple types of premultiplication, but now just one, PremulAsEncoded.
252// This is the premul you're probably used to working with.
253
254typedef enum skcms_AlphaFormat {
255 skcms_AlphaFormat_Opaque, // alpha is always opaque
256 // tf-1(r), tf-1(g), tf-1(b), 1.0
257 skcms_AlphaFormat_Unpremul, // alpha and color are unassociated
258 // tf-1(r), tf-1(g), tf-1(b), a
259 skcms_AlphaFormat_PremulAsEncoded, // premultiplied while encoded
260 // tf-1(r)*a, tf-1(g)*a, tf-1(b)*a, a
261} skcms_AlphaFormat;
262
263// Convert npixels pixels from src format and color profile to dst format and color profile
264// and return true, otherwise return false. It is safe to alias dst == src if dstFmt == srcFmt.
265SKCMS_API bool skcms_Transform(const void* src,
266 skcms_PixelFormat srcFmt,
267 skcms_AlphaFormat srcAlpha,
268 const skcms_ICCProfile* srcProfile,
269 void* dst,
270 skcms_PixelFormat dstFmt,
271 skcms_AlphaFormat dstAlpha,
272 const skcms_ICCProfile* dstProfile,
273 size_t npixels);
274
275// As skcms_Transform(), supporting srcFmts with a palette.
276SKCMS_API bool skcms_TransformWithPalette(const void* src,
277 skcms_PixelFormat srcFmt,
278 skcms_AlphaFormat srcAlpha,
279 const skcms_ICCProfile* srcProfile,
280 void* dst,
281 skcms_PixelFormat dstFmt,
282 skcms_AlphaFormat dstAlpha,
283 const skcms_ICCProfile* dstProfile,
284 size_t npixels,
285 const void* palette);
286
287// If profile can be used as a destination in skcms_Transform, return true. Otherwise, attempt to
288// rewrite it with approximations where reasonable. If successful, return true. If no reasonable
289// approximation exists, leave the profile unchanged and return false.
290SKCMS_API bool skcms_MakeUsableAsDestination(skcms_ICCProfile* profile);
291
292// If profile can be used as a destination with a single parametric transfer function (ie for
293// rasterization), return true. Otherwise, attempt to rewrite it with approximations where
294// reasonable. If successful, return true. If no reasonable approximation exists, leave the
295// profile unchanged and return false.
296SKCMS_API bool skcms_MakeUsableAsDestinationWithSingleCurve(skcms_ICCProfile* profile);
297
298// Returns a matrix to adapt XYZ color from given the whitepoint to D50.
299SKCMS_API bool skcms_AdaptToXYZD50(float wx, float wy,
300 skcms_Matrix3x3* toXYZD50);
301
302// Returns a matrix to convert RGB color into XYZ adapted to D50, given the
303// primaries and whitepoint of the RGB model.
304SKCMS_API bool skcms_PrimariesToXYZD50(float rx, float ry,
305 float gx, float gy,
306 float bx, float by,
307 float wx, float wy,
308 skcms_Matrix3x3* toXYZD50);
309
310// Utilities for programmatically constructing profiles
311static inline void skcms_Init(skcms_ICCProfile* p) {
312 memset(p, 0, sizeof(*p));
313 p->data_color_space = skcms_Signature_RGB;
314 p->pcs = skcms_Signature_XYZ;
315}
316
317static inline void skcms_SetTransferFunction(skcms_ICCProfile* p,
318 const skcms_TransferFunction* tf) {
319 p->has_trc = true;
320 for (int i = 0; i < 3; ++i) {
321 p->trc[i].table_entries = 0;
322 p->trc[i].parametric = *tf;
323 }
324}
325
326static inline void skcms_SetXYZD50(skcms_ICCProfile* p, const skcms_Matrix3x3* m) {
327 p->has_toXYZD50 = true;
328 p->toXYZD50 = *m;
329}
330
331#ifdef __cplusplus
332}
333#endif
334