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
54typedef enum skcms_TFType {
55 skcms_TFType_Invalid,
56 skcms_TFType_sRGBish,
57 skcms_TFType_PQish,
58 skcms_TFType_HLGish,
59 skcms_TFType_HLGinvish,
60} skcms_TFType;
61
62// Identify which kind of transfer function is encoded in an skcms_TransferFunction
63SKCMS_API skcms_TFType skcms_TransferFunction_getType(const skcms_TransferFunction*);
64
65// We can jam a couple alternate transfer function forms into skcms_TransferFunction,
66// including those matching the general forms of the SMPTE ST 2084 PQ function or HLG.
67//
68// PQish:
69// max(A + B|encoded|^C, 0)
70// linear = sign(encoded) * (------------------------) ^ F
71// D + E|encoded|^C
72SKCMS_API bool skcms_TransferFunction_makePQish(skcms_TransferFunction*,
73 float A, float B, float C,
74 float D, float E, float F);
75// HLGish:
76// { K * sign(encoded) * ( (R|encoded|)^G ) when 0 <= |encoded| <= 1/R
77// linear = { K * sign(encoded) * ( e^(a(|encoded|-c)) + b ) when 1/R < |encoded|
78SKCMS_API bool skcms_TransferFunction_makeScaledHLGish(skcms_TransferFunction*,
79 float K, float R, float G,
80 float a, float b, float c);
81
82// Compatibility shim with K=1 for old callers.
83static inline bool skcms_TransferFunction_makeHLGish(skcms_TransferFunction* fn,
84 float R, float G,
85 float a, float b, float c) {
86 return skcms_TransferFunction_makeScaledHLGish(fn, K: 1.0f, R,G, a,b,c);
87}
88
89// PQ mapping encoded [0,1] to linear [0,1].
90static inline bool skcms_TransferFunction_makePQ(skcms_TransferFunction* tf) {
91 return skcms_TransferFunction_makePQish(tf, A: -107/128.0f, B: 1.0f, C: 32/2523.0f
92 , D: 2413/128.0f, E: -2392/128.0f, F: 8192/1305.0f);
93}
94// HLG mapping encoded [0,1] to linear [0,12].
95static inline bool skcms_TransferFunction_makeHLG(skcms_TransferFunction* tf) {
96 return skcms_TransferFunction_makeHLGish(fn: tf, R: 2.0f, G: 2.0f
97 , a: 1/0.17883277f, b: 0.28466892f, c: 0.55991073f);
98}
99
100// Is this an ordinary sRGB-ish transfer function, or one of the HDR forms we support?
101SKCMS_API bool skcms_TransferFunction_isSRGBish(const skcms_TransferFunction*);
102SKCMS_API bool skcms_TransferFunction_isPQish (const skcms_TransferFunction*);
103SKCMS_API bool skcms_TransferFunction_isHLGish (const skcms_TransferFunction*);
104
105// Unified representation of 'curv' or 'para' tag data, or a 1D table from 'mft1' or 'mft2'
106typedef union skcms_Curve {
107 struct {
108 uint32_t alias_of_table_entries;
109 skcms_TransferFunction parametric;
110 };
111 struct {
112 uint32_t table_entries;
113 const uint8_t* table_8;
114 const uint8_t* table_16;
115 };
116} skcms_Curve;
117
118// Complex transforms between device space (A) and profile connection space (B):
119// A2B: device -> [ "A" curves -> CLUT ] -> [ "M" curves -> matrix ] -> "B" curves -> PCS
120// B2A: device <- [ "A" curves <- CLUT ] <- [ "M" curves <- matrix ] <- "B" curves <- PCS
121
122typedef struct skcms_A2B {
123 // Optional: N 1D "A" curves, followed by an N-dimensional CLUT.
124 // If input_channels == 0, these curves and CLUT are skipped,
125 // Otherwise, input_channels must be in [1, 4].
126 uint32_t input_channels;
127 skcms_Curve input_curves[4];
128 uint8_t grid_points[4];
129 const uint8_t* grid_8;
130 const uint8_t* grid_16;
131
132 // Optional: 3 1D "M" curves, followed by a color matrix.
133 // If matrix_channels == 0, these curves and matrix are skipped,
134 // Otherwise, matrix_channels must be 3.
135 uint32_t matrix_channels;
136 skcms_Curve matrix_curves[3];
137 skcms_Matrix3x4 matrix;
138
139 // Required: 3 1D "B" curves. Always present, and output_channels must be 3.
140 uint32_t output_channels;
141 skcms_Curve output_curves[3];
142} skcms_A2B;
143
144typedef struct skcms_B2A {
145 // Required: 3 1D "B" curves. Always present, and input_channels must be 3.
146 uint32_t input_channels;
147 skcms_Curve input_curves[3];
148
149 // Optional: a color matrix, followed by 3 1D "M" curves.
150 // If matrix_channels == 0, this matrix and these curves are skipped,
151 // Otherwise, matrix_channels must be 3.
152 uint32_t matrix_channels;
153 skcms_Matrix3x4 matrix;
154 skcms_Curve matrix_curves[3];
155
156 // Optional: an N-dimensional CLUT, followed by N 1D "A" curves.
157 // If output_channels == 0, this CLUT and these curves are skipped,
158 // Otherwise, output_channels must be in [1, 4].
159 uint32_t output_channels;
160 uint8_t grid_points[4];
161 const uint8_t* grid_8;
162 const uint8_t* grid_16;
163 skcms_Curve output_curves[4];
164} skcms_B2A;
165
166typedef struct skcms_CICP {
167 uint8_t color_primaries;
168 uint8_t transfer_characteristics;
169 uint8_t matrix_coefficients;
170 uint8_t video_full_range_flag;
171} skcms_CICP;
172
173typedef struct skcms_ICCProfile {
174 const uint8_t* buffer;
175
176 uint32_t size;
177 uint32_t data_color_space;
178 uint32_t pcs;
179 uint32_t tag_count;
180
181 // skcms_Parse() will set commonly-used fields for you when possible:
182
183 // If we can parse red, green and blue transfer curves from the profile,
184 // trc will be set to those three curves, and has_trc will be true.
185 bool has_trc;
186 skcms_Curve trc[3];
187
188 // If this profile's gamut can be represented by a 3x3 transform to XYZD50,
189 // skcms_Parse() sets toXYZD50 to that transform and has_toXYZD50 to true.
190 bool has_toXYZD50;
191 skcms_Matrix3x3 toXYZD50;
192
193 // If the profile has a valid A2B0 or A2B1 tag, skcms_Parse() sets A2B to
194 // that data, and has_A2B to true. skcms_ParseWithA2BPriority() does the
195 // same following any user-provided prioritization of A2B0, A2B1, or A2B2.
196 bool has_A2B;
197 skcms_A2B A2B;
198
199 // If the profile has a valid B2A0 or B2A1 tag, skcms_Parse() sets B2A to
200 // that data, and has_B2A to true. skcms_ParseWithA2BPriority() does the
201 // same following any user-provided prioritization of B2A0, B2A1, or B2A2.
202 bool has_B2A;
203 skcms_B2A B2A;
204
205 // If the profile has a valid CICP tag, skcms_Parse() sets CICP to that data,
206 // and has_CICP to true.
207 bool has_CICP;
208 skcms_CICP CICP;
209} skcms_ICCProfile;
210
211// The sRGB color profile is so commonly used that we offer a canonical skcms_ICCProfile for it.
212SKCMS_API const skcms_ICCProfile* skcms_sRGB_profile(void);
213// Ditto for XYZD50, the most common profile connection space.
214SKCMS_API const skcms_ICCProfile* skcms_XYZD50_profile(void);
215
216SKCMS_API const skcms_TransferFunction* skcms_sRGB_TransferFunction(void);
217SKCMS_API const skcms_TransferFunction* skcms_sRGB_Inverse_TransferFunction(void);
218SKCMS_API const skcms_TransferFunction* skcms_Identity_TransferFunction(void);
219
220// Practical equality test for two skcms_ICCProfiles.
221// The implementation is subject to change, but it will always try to answer
222// "can I substitute A for B?" and "can I skip transforming from A to B?".
223SKCMS_API bool skcms_ApproximatelyEqualProfiles(const skcms_ICCProfile* A,
224 const skcms_ICCProfile* B);
225
226// Practical test that answers: Is curve roughly the inverse of inv_tf? Typically used by passing
227// the inverse of a known parametric transfer function (like sRGB), to determine if a particular
228// curve is very close to sRGB.
229SKCMS_API bool skcms_AreApproximateInverses(const skcms_Curve* curve,
230 const skcms_TransferFunction* inv_tf);
231
232// Similar to above, answering the question for all three TRC curves of the given profile. Again,
233// passing skcms_sRGB_InverseTransferFunction as inv_tf will answer the question:
234// "Does this profile have a transfer function that is very close to sRGB?"
235SKCMS_API bool skcms_TRCs_AreApproximateInverse(const skcms_ICCProfile* profile,
236 const skcms_TransferFunction* inv_tf);
237
238// Parse an ICC profile and return true if possible, otherwise return false.
239// Selects an A2B profile (if present) according to priority list (each entry 0-2).
240// The buffer is not copied; it must remain valid as long as the skcms_ICCProfile will be used.
241SKCMS_API bool skcms_ParseWithA2BPriority(const void*, size_t,
242 const int priority[], int priorities,
243 skcms_ICCProfile*);
244
245static inline bool skcms_Parse(const void* buf, size_t len, skcms_ICCProfile* profile) {
246 // For continuity of existing user expectations,
247 // prefer A2B0 (perceptual) over A2B1 (relative colormetric), and ignore A2B2 (saturation).
248 const int priority[] = {0,1};
249 return skcms_ParseWithA2BPriority(buf, len,
250 priority, priorities: sizeof(priority)/sizeof(*priority),
251 profile);
252}
253
254SKCMS_API bool skcms_ApproximateCurve(const skcms_Curve* curve,
255 skcms_TransferFunction* approx,
256 float* max_error);
257
258SKCMS_API bool skcms_GetCHAD(const skcms_ICCProfile*, skcms_Matrix3x3*);
259SKCMS_API bool skcms_GetWTPT(const skcms_ICCProfile*, float xyz[3]);
260
261// These are common ICC signature values
262enum {
263 // data_color_space
264 skcms_Signature_CMYK = 0x434D594B,
265 skcms_Signature_Gray = 0x47524159,
266 skcms_Signature_RGB = 0x52474220,
267
268 // pcs
269 skcms_Signature_Lab = 0x4C616220,
270 skcms_Signature_XYZ = 0x58595A20,
271};
272
273typedef enum skcms_PixelFormat {
274 skcms_PixelFormat_A_8,
275 skcms_PixelFormat_A_8_,
276 skcms_PixelFormat_G_8,
277 skcms_PixelFormat_G_8_,
278 skcms_PixelFormat_RGBA_8888_Palette8,
279 skcms_PixelFormat_BGRA_8888_Palette8,
280
281 skcms_PixelFormat_RGB_565,
282 skcms_PixelFormat_BGR_565,
283
284 skcms_PixelFormat_ABGR_4444,
285 skcms_PixelFormat_ARGB_4444,
286
287 skcms_PixelFormat_RGB_888,
288 skcms_PixelFormat_BGR_888,
289 skcms_PixelFormat_RGBA_8888,
290 skcms_PixelFormat_BGRA_8888,
291 skcms_PixelFormat_RGBA_8888_sRGB, // Automatic sRGB encoding / decoding.
292 skcms_PixelFormat_BGRA_8888_sRGB, // (Generally used with linear transfer functions.)
293
294 skcms_PixelFormat_RGBA_1010102,
295 skcms_PixelFormat_BGRA_1010102,
296
297 skcms_PixelFormat_RGB_161616LE, // Little-endian. Pointers must be 16-bit aligned.
298 skcms_PixelFormat_BGR_161616LE,
299 skcms_PixelFormat_RGBA_16161616LE,
300 skcms_PixelFormat_BGRA_16161616LE,
301
302 skcms_PixelFormat_RGB_161616BE, // Big-endian. Pointers must be 16-bit aligned.
303 skcms_PixelFormat_BGR_161616BE,
304 skcms_PixelFormat_RGBA_16161616BE,
305 skcms_PixelFormat_BGRA_16161616BE,
306
307 skcms_PixelFormat_RGB_hhh_Norm, // 1-5-10 half-precision float in [0,1]
308 skcms_PixelFormat_BGR_hhh_Norm, // Pointers must be 16-bit aligned.
309 skcms_PixelFormat_RGBA_hhhh_Norm,
310 skcms_PixelFormat_BGRA_hhhh_Norm,
311
312 skcms_PixelFormat_RGB_hhh, // 1-5-10 half-precision float.
313 skcms_PixelFormat_BGR_hhh, // Pointers must be 16-bit aligned.
314 skcms_PixelFormat_RGBA_hhhh,
315 skcms_PixelFormat_BGRA_hhhh,
316
317 skcms_PixelFormat_RGB_fff, // 1-8-23 single-precision float (the normal kind).
318 skcms_PixelFormat_BGR_fff, // Pointers must be 32-bit aligned.
319 skcms_PixelFormat_RGBA_ffff,
320 skcms_PixelFormat_BGRA_ffff,
321
322 skcms_PixelFormat_RGB_101010x_XR, // Note: This is located here to signal no clamping.
323 skcms_PixelFormat_BGR_101010x_XR, // Compatible with MTLPixelFormatBGR10_XR.
324} skcms_PixelFormat;
325
326// We always store any alpha channel linearly. In the chart below, tf-1() is the inverse
327// transfer function for the given color profile (applying the transfer function linearizes).
328
329// We treat opaque as a strong requirement, not just a performance hint: we will ignore
330// any source alpha and treat it as 1.0, and will make sure that any destination alpha
331// channel is filled with the equivalent of 1.0.
332
333// We used to offer multiple types of premultiplication, but now just one, PremulAsEncoded.
334// This is the premul you're probably used to working with.
335
336typedef enum skcms_AlphaFormat {
337 skcms_AlphaFormat_Opaque, // alpha is always opaque
338 // tf-1(r), tf-1(g), tf-1(b), 1.0
339 skcms_AlphaFormat_Unpremul, // alpha and color are unassociated
340 // tf-1(r), tf-1(g), tf-1(b), a
341 skcms_AlphaFormat_PremulAsEncoded, // premultiplied while encoded
342 // tf-1(r)*a, tf-1(g)*a, tf-1(b)*a, a
343} skcms_AlphaFormat;
344
345// Convert npixels pixels from src format and color profile to dst format and color profile
346// and return true, otherwise return false. It is safe to alias dst == src if dstFmt == srcFmt.
347SKCMS_API bool skcms_Transform(const void* src,
348 skcms_PixelFormat srcFmt,
349 skcms_AlphaFormat srcAlpha,
350 const skcms_ICCProfile* srcProfile,
351 void* dst,
352 skcms_PixelFormat dstFmt,
353 skcms_AlphaFormat dstAlpha,
354 const skcms_ICCProfile* dstProfile,
355 size_t npixels);
356
357// As skcms_Transform(), supporting srcFmts with a palette.
358SKCMS_API bool skcms_TransformWithPalette(const void* src,
359 skcms_PixelFormat srcFmt,
360 skcms_AlphaFormat srcAlpha,
361 const skcms_ICCProfile* srcProfile,
362 void* dst,
363 skcms_PixelFormat dstFmt,
364 skcms_AlphaFormat dstAlpha,
365 const skcms_ICCProfile* dstProfile,
366 size_t npixels,
367 const void* palette);
368
369// If profile can be used as a destination in skcms_Transform, return true. Otherwise, attempt to
370// rewrite it with approximations where reasonable. If successful, return true. If no reasonable
371// approximation exists, leave the profile unchanged and return false.
372SKCMS_API bool skcms_MakeUsableAsDestination(skcms_ICCProfile* profile);
373
374// If profile can be used as a destination with a single parametric transfer function (ie for
375// rasterization), return true. Otherwise, attempt to rewrite it with approximations where
376// reasonable. If successful, return true. If no reasonable approximation exists, leave the
377// profile unchanged and return false.
378SKCMS_API bool skcms_MakeUsableAsDestinationWithSingleCurve(skcms_ICCProfile* profile);
379
380// Returns a matrix to adapt XYZ color from given the whitepoint to D50.
381SKCMS_API bool skcms_AdaptToXYZD50(float wx, float wy,
382 skcms_Matrix3x3* toXYZD50);
383
384// Returns a matrix to convert RGB color into XYZ adapted to D50, given the
385// primaries and whitepoint of the RGB model.
386SKCMS_API bool skcms_PrimariesToXYZD50(float rx, float ry,
387 float gx, float gy,
388 float bx, float by,
389 float wx, float wy,
390 skcms_Matrix3x3* toXYZD50);
391
392// Call before your first call to skcms_Transform() to skip runtime CPU detection.
393SKCMS_API void skcms_DisableRuntimeCPUDetection(void);
394
395// Utilities for programmatically constructing profiles
396static inline void skcms_Init(skcms_ICCProfile* p) {
397 memset(s: p, c: 0, n: sizeof(*p));
398 p->data_color_space = skcms_Signature_RGB;
399 p->pcs = skcms_Signature_XYZ;
400}
401
402static inline void skcms_SetTransferFunction(skcms_ICCProfile* p,
403 const skcms_TransferFunction* tf) {
404 p->has_trc = true;
405 for (int i = 0; i < 3; ++i) {
406 p->trc[i].table_entries = 0;
407 p->trc[i].parametric = *tf;
408 }
409}
410
411static inline void skcms_SetXYZD50(skcms_ICCProfile* p, const skcms_Matrix3x3* m) {
412 p->has_toXYZD50 = true;
413 p->toXYZD50 = *m;
414}
415
416#ifdef __cplusplus
417}
418#endif
419

source code of flutter_engine/third_party/skia/modules/skcms/skcms.h