skcms.h - skcms - Git at Google

 /*
  * Copyright 2018 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */

 #pragma once

 // skcms.h contains the entire public API for skcms.

 #ifndef SKCMS_API
     #define SKCMS_API
 #endif

 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <string.h>

 #ifdef __cplusplus
 extern "C" {
 #endif

 // A row-major 3x3 matrix (ie vals[row][col])
 typedef struct skcms_Matrix3x3 {
     float vals[3][3];
 } skcms_Matrix3x3;

 // It is _not_ safe to alias the pointers to invert in-place.
 SKCMS_API bool            skcms_Matrix3x3_invert(const skcms_Matrix3x3*, skcms_Matrix3x3*);
 SKCMS_API skcms_Matrix3x3 skcms_Matrix3x3_concat(const skcms_Matrix3x3*, const skcms_Matrix3x3*);

 // A row-major 3x4 matrix (ie vals[row][col])
 typedef struct skcms_Matrix3x4 {
     float vals[3][4];
 } skcms_Matrix3x4;

 // A transfer function mapping encoded values to linear values,
 // represented by this 7-parameter piecewise function:
 //
 //   linear = sign(encoded) *  (c*|encoded| + f)       , 0 <= |encoded| < d
 //          = sign(encoded) * ((a*|encoded| + b)^g + e), d <= |encoded|
 //
 // (A simple gamma transfer function sets g to gamma and a to 1.)
 typedef struct skcms_TransferFunction {
     float g, a,b,c,d,e,f;
 } skcms_TransferFunction;

 SKCMS_API float skcms_TransferFunction_eval  (const skcms_TransferFunction*, float);
 SKCMS_API bool  skcms_TransferFunction_invert(const skcms_TransferFunction*,
                                               skcms_TransferFunction*);

 // We can jam a couple alternate transfer function forms into skcms_TransferFunction,
 // including those matching the general forms of the SMPTE ST 2084 PQ function or HLG.
 //
 // PQish:
 //                              max(A + B|encoded|^C, 0)
 //    linear = sign(encoded) * (------------------------) ^ F
 //                                  D + E|encoded|^C
 SKCMS_API bool skcms_TransferFunction_makePQish(skcms_TransferFunction*,
                                                 float A, float B, float C,
                                                 float D, float E, float F);
 // HLGish:
 //            { K * sign(encoded) * ( (R|encoded|)^G )          when 0   <= |encoded| <= 1/R
 //   linear = { K * sign(encoded) * ( e^(a(|encoded|-c)) + b )  when 1/R <  |encoded|
 SKCMS_API bool skcms_TransferFunction_makeScaledHLGish(skcms_TransferFunction*,
                                                        float K, float R, float G,
                                                        float a, float b, float c);

 // Compatibility shim with K=1 for old callers.
 static inline bool skcms_TransferFunction_makeHLGish(skcms_TransferFunction* fn,
                                                      float R, float G,
                                                      float a, float b, float c) {
     return skcms_TransferFunction_makeScaledHLGish(fn, 1.0f, R,G, a,b,c);
 }

 // PQ mapping encoded [0,1] to linear [0,1].
 static inline bool skcms_TransferFunction_makePQ(skcms_TransferFunction* tf) {
     return skcms_TransferFunction_makePQish(tf, -107/128.0f,         1.0f,   32/2523.0f
                                               , 2413/128.0f, -2392/128.0f, 8192/1305.0f);
 }
 // HLG mapping encoded [0,1] to linear [0,12].
 static inline bool skcms_TransferFunction_makeHLG(skcms_TransferFunction* tf) {
     return skcms_TransferFunction_makeHLGish(tf, 2.0f, 2.0f
                                                , 1/0.17883277f, 0.28466892f, 0.55991073f);
 }

 // Is this an ordinary sRGB-ish transfer function, or one of the HDR forms we support?
 SKCMS_API bool skcms_TransferFunction_isSRGBish(const skcms_TransferFunction*);
 SKCMS_API bool skcms_TransferFunction_isPQish  (const skcms_TransferFunction*);
 SKCMS_API bool skcms_TransferFunction_isHLGish (const skcms_TransferFunction*);

 // Unified representation of 'curv' or 'para' tag data, or a 1D table from 'mft1' or 'mft2'
 typedef union skcms_Curve {
     struct {
         uint32_t alias_of_table_entries;
         skcms_TransferFunction parametric;
     };
     struct {
         uint32_t table_entries;
         const uint8_t* table_8;
         const uint8_t* table_16;
     };
 } skcms_Curve;

 // Complex transforms between device space (A) and profile connection space (B):
 //   A2B:  device -> [ "A" curves -> CLUT ] -> [ "M" curves -> matrix ] -> "B" curves -> PCS
 //   B2A:  device <- [ "A" curves <- CLUT ] <- [ "M" curves <- matrix ] <- "B" curves <- PCS

 typedef struct skcms_A2B {
     // Optional: N 1D "A" curves, followed by an N-dimensional CLUT.
     // If input_channels == 0, these curves and CLUT are skipped,
     // Otherwise, input_channels must be in [1, 4].
     uint32_t        input_channels;
     skcms_Curve     input_curves[4];
     uint8_t         grid_points[4];
     const uint8_t*  grid_8;
     const uint8_t*  grid_16;

     // Optional: 3 1D "M" curves, followed by a color matrix.
     // If matrix_channels == 0, these curves and matrix are skipped,
     // Otherwise, matrix_channels must be 3.
     uint32_t        matrix_channels;
     skcms_Curve     matrix_curves[3];
     skcms_Matrix3x4 matrix;

     // Required: 3 1D "B" curves. Always present, and output_channels must be 3.
     uint32_t        output_channels;
     skcms_Curve     output_curves[3];
 } skcms_A2B;

 typedef struct skcms_B2A {
     // Required: 3 1D "B" curves. Always present, and input_channels must be 3.
     uint32_t        input_channels;
     skcms_Curve     input_curves[3];

     // Optional: a color matrix, followed by 3 1D "M" curves.
     // If matrix_channels == 0, this matrix and these curves are skipped,
     // Otherwise, matrix_channels must be 3.
     uint32_t        matrix_channels;
     skcms_Matrix3x4 matrix;
     skcms_Curve     matrix_curves[3];

     // Optional: an N-dimensional CLUT, followed by N 1D "A" curves.
     // If output_channels == 0, this CLUT and these curves are skipped,
     // Otherwise, output_channels must be in [1, 4].
     uint32_t        output_channels;
     uint8_t         grid_points[4];
     const uint8_t*  grid_8;
     const uint8_t*  grid_16;
     skcms_Curve     output_curves[4];
 } skcms_B2A;


 typedef struct skcms_ICCProfile {
     const uint8_t* buffer;

     uint32_t size;
     uint32_t data_color_space;
     uint32_t pcs;
     uint32_t tag_count;

     // skcms_Parse() will set commonly-used fields for you when possible:

     // If we can parse red, green and blue transfer curves from the profile,
     // trc will be set to those three curves, and has_trc will be true.
     bool                   has_trc;
     skcms_Curve            trc[3];

     // If this profile's gamut can be represented by a 3x3 transform to XYZD50,
     // skcms_Parse() sets toXYZD50 to that transform and has_toXYZD50 to true.
     bool                   has_toXYZD50;
     skcms_Matrix3x3        toXYZD50;

     // If the profile has a valid A2B0 or A2B1 tag, skcms_Parse() sets A2B to
     // that data, and has_A2B to true.  skcms_ParseWithA2BPriority() does the
     // same following any user-provided prioritization of A2B0, A2B1, or A2B2.
     bool                   has_A2B;
     skcms_A2B              A2B;

     // If the profile has a valid B2A0 or B2A1 tag, skcms_Parse() sets B2A to
     // that data, and has_B2A to true.  skcms_ParseWithA2BPriority() does the
     // same following any user-provided prioritization of B2A0, B2A1, or B2A2.
     bool                   has_B2A;
     skcms_B2A              B2A;

 } skcms_ICCProfile;

 // The sRGB color profile is so commonly used that we offer a canonical skcms_ICCProfile for it.
 SKCMS_API const skcms_ICCProfile* skcms_sRGB_profile(void);
 // Ditto for XYZD50, the most common profile connection space.
 SKCMS_API const skcms_ICCProfile* skcms_XYZD50_profile(void);

 SKCMS_API const skcms_TransferFunction* skcms_sRGB_TransferFunction(void);
 SKCMS_API const skcms_TransferFunction* skcms_sRGB_Inverse_TransferFunction(void);
 SKCMS_API const skcms_TransferFunction* skcms_Identity_TransferFunction(void);

 // Practical equality test for two skcms_ICCProfiles.
 // The implementation is subject to change, but it will always try to answer
 // "can I substitute A for B?" and "can I skip transforming from A to B?".
 SKCMS_API bool skcms_ApproximatelyEqualProfiles(const skcms_ICCProfile* A,
                                                 const skcms_ICCProfile* B);

 // Practical test that answers: Is curve roughly the inverse of inv_tf? Typically used by passing
 // the inverse of a known parametric transfer function (like sRGB), to determine if a particular
 // curve is very close to sRGB.
 SKCMS_API bool skcms_AreApproximateInverses(const skcms_Curve* curve,
                                             const skcms_TransferFunction* inv_tf);

 // Similar to above, answering the question for all three TRC curves of the given profile. Again,
 // passing skcms_sRGB_InverseTransferFunction as inv_tf will answer the question:
 // "Does this profile have a transfer function that is very close to sRGB?"
 SKCMS_API bool skcms_TRCs_AreApproximateInverse(const skcms_ICCProfile* profile,
                                                 const skcms_TransferFunction* inv_tf);

 // Parse an ICC profile and return true if possible, otherwise return false.
 // Selects an A2B profile (if present) according to priority list (each entry 0-2).
 // The buffer is not copied; it must remain valid as long as the skcms_ICCProfile will be used.
 SKCMS_API bool skcms_ParseWithA2BPriority(const void*, size_t,
                                           const int priority[], int priorities,
                                           skcms_ICCProfile*);

 static inline bool skcms_Parse(const void* buf, size_t len, skcms_ICCProfile* profile) {
     // For continuity of existing user expectations,
     // prefer A2B0 (perceptual) over A2B1 (relative colormetric), and ignore A2B2 (saturation).
     const int priority[] = {0,1};
     return skcms_ParseWithA2BPriority(buf, len,
                                       priority, sizeof(priority)/sizeof(*priority),
                                       profile);
 }

 SKCMS_API bool skcms_ApproximateCurve(const skcms_Curve* curve,
                                       skcms_TransferFunction* approx,
                                       float* max_error);

 SKCMS_API bool skcms_GetCHAD(const skcms_ICCProfile*, skcms_Matrix3x3*);
 SKCMS_API bool skcms_GetWTPT(const skcms_ICCProfile*, float xyz[3]);

 // These are common ICC signature values
 enum {
     // data_color_space
     skcms_Signature_CMYK = 0x434D594B,
     skcms_Signature_Gray = 0x47524159,
     skcms_Signature_RGB  = 0x52474220,

     // pcs
     skcms_Signature_Lab  = 0x4C616220,
     skcms_Signature_XYZ  = 0x58595A20,
 };

 typedef enum skcms_PixelFormat {
     skcms_PixelFormat_A_8,
     skcms_PixelFormat_A_8_,
     skcms_PixelFormat_G_8,
     skcms_PixelFormat_G_8_,
     skcms_PixelFormat_RGBA_8888_Palette8,
     skcms_PixelFormat_BGRA_8888_Palette8,

     skcms_PixelFormat_RGB_565,
     skcms_PixelFormat_BGR_565,

     skcms_PixelFormat_ABGR_4444,
     skcms_PixelFormat_ARGB_4444,

     skcms_PixelFormat_RGB_888,
     skcms_PixelFormat_BGR_888,
     skcms_PixelFormat_RGBA_8888,
     skcms_PixelFormat_BGRA_8888,
     skcms_PixelFormat_RGBA_8888_sRGB,   // Automatic sRGB encoding / decoding.
     skcms_PixelFormat_BGRA_8888_sRGB,   // (Generally used with linear transfer functions.)

     skcms_PixelFormat_RGBA_1010102,
     skcms_PixelFormat_BGRA_1010102,

     skcms_PixelFormat_RGB_161616LE,     // Little-endian.  Pointers must be 16-bit aligned.
     skcms_PixelFormat_BGR_161616LE,
     skcms_PixelFormat_RGBA_16161616LE,
     skcms_PixelFormat_BGRA_16161616LE,

     skcms_PixelFormat_RGB_161616BE,     // Big-endian.  Pointers must be 16-bit aligned.
     skcms_PixelFormat_BGR_161616BE,
     skcms_PixelFormat_RGBA_16161616BE,
     skcms_PixelFormat_BGRA_16161616BE,

     skcms_PixelFormat_RGB_hhh_Norm,   // 1-5-10 half-precision float in [0,1]
     skcms_PixelFormat_BGR_hhh_Norm,   // Pointers must be 16-bit aligned.
     skcms_PixelFormat_RGBA_hhhh_Norm,
     skcms_PixelFormat_BGRA_hhhh_Norm,

     skcms_PixelFormat_RGB_hhh,        // 1-5-10 half-precision float.
     skcms_PixelFormat_BGR_hhh,        // Pointers must be 16-bit aligned.
     skcms_PixelFormat_RGBA_hhhh,
     skcms_PixelFormat_BGRA_hhhh,

     skcms_PixelFormat_RGB_fff,        // 1-8-23 single-precision float (the normal kind).
     skcms_PixelFormat_BGR_fff,        // Pointers must be 32-bit aligned.
     skcms_PixelFormat_RGBA_ffff,
     skcms_PixelFormat_BGRA_ffff,
 } skcms_PixelFormat;

 // We always store any alpha channel linearly.  In the chart below, tf-1() is the inverse
 // transfer function for the given color profile (applying the transfer function linearizes).

 // We treat opaque as a strong requirement, not just a performance hint: we will ignore
 // any source alpha and treat it as 1.0, and will make sure that any destination alpha
 // channel is filled with the equivalent of 1.0.

 // We used to offer multiple types of premultiplication, but now just one, PremulAsEncoded.
 // This is the premul you're probably used to working with.

 typedef enum skcms_AlphaFormat {
     skcms_AlphaFormat_Opaque,          // alpha is always opaque
                                        //   tf-1(r),   tf-1(g),   tf-1(b),   1.0
     skcms_AlphaFormat_Unpremul,        // alpha and color are unassociated
                                        //   tf-1(r),   tf-1(g),   tf-1(b),   a
     skcms_AlphaFormat_PremulAsEncoded, // premultiplied while encoded
                                        //   tf-1(r)*a, tf-1(g)*a, tf-1(b)*a, a
 } skcms_AlphaFormat;

 // Convert npixels pixels from src format and color profile to dst format and color profile
 // and return true, otherwise return false.  It is safe to alias dst == src if dstFmt == srcFmt.
 SKCMS_API bool skcms_Transform(const void*             src,
                                skcms_PixelFormat       srcFmt,
                                skcms_AlphaFormat       srcAlpha,
                                const skcms_ICCProfile* srcProfile,
                                void*                   dst,
                                skcms_PixelFormat       dstFmt,
                                skcms_AlphaFormat       dstAlpha,
                                const skcms_ICCProfile* dstProfile,
                                size_t                  npixels);

 // As skcms_Transform(), supporting srcFmts with a palette.
 SKCMS_API bool skcms_TransformWithPalette(const void*             src,
                                           skcms_PixelFormat       srcFmt,
                                           skcms_AlphaFormat       srcAlpha,
                                           const skcms_ICCProfile* srcProfile,
                                           void*                   dst,
                                           skcms_PixelFormat       dstFmt,
                                           skcms_AlphaFormat       dstAlpha,
                                           const skcms_ICCProfile* dstProfile,
                                           size_t                  npixels,
                                           const void*             palette);

 // If profile can be used as a destination in skcms_Transform, return true. Otherwise, attempt to
 // rewrite it with approximations where reasonable. If successful, return true. If no reasonable
 // approximation exists, leave the profile unchanged and return false.
 SKCMS_API bool skcms_MakeUsableAsDestination(skcms_ICCProfile* profile);

 // If profile can be used as a destination with a single parametric transfer function (ie for
 // rasterization), return true. Otherwise, attempt to rewrite it with approximations where
 // reasonable. If successful, return true. If no reasonable approximation exists, leave the
 // profile unchanged and return false.
 SKCMS_API bool skcms_MakeUsableAsDestinationWithSingleCurve(skcms_ICCProfile* profile);

 // Returns a matrix to adapt XYZ color from given the whitepoint to D50.
 SKCMS_API bool skcms_AdaptToXYZD50(float wx, float wy,
                                    skcms_Matrix3x3* toXYZD50);

 // Returns a matrix to convert RGB color into XYZ adapted to D50, given the
 // primaries and whitepoint of the RGB model.
 SKCMS_API bool skcms_PrimariesToXYZD50(float rx, float ry,
                                        float gx, float gy,
                                        float bx, float by,
                                        float wx, float wy,
                                        skcms_Matrix3x3* toXYZD50);

 // Call before your first call to skcms_Transform() to skip runtime CPU detection.
 SKCMS_API void skcms_DisableRuntimeCPUDetection(void);

 // Utilities for programmatically constructing profiles
 static inline void skcms_Init(skcms_ICCProfile* p) {
     memset(p, 0, sizeof(*p));
     p->data_color_space = skcms_Signature_RGB;
     p->pcs = skcms_Signature_XYZ;
 }

 static inline void skcms_SetTransferFunction(skcms_ICCProfile* p,
                                              const skcms_TransferFunction* tf) {
     p->has_trc = true;
     for (int i = 0; i < 3; ++i) {
         p->trc[i].table_entries = 0;
         p->trc[i].parametric = *tf;
     }
 }

 static inline void skcms_SetXYZD50(skcms_ICCProfile* p, const skcms_Matrix3x3* m) {
     p->has_toXYZD50 = true;
     p->toXYZD50 = *m;
 }

 #ifdef __cplusplus
 }
 #endif
	/*
	* Copyright 2018 Google Inc.
	*
	* Use of this source code is governed by a BSD-style license that can be
	* found in the LICENSE file.
	*/

	#pragma once

	// skcms.h contains the entire public API for skcms.

	#ifndef SKCMS_API
	#define SKCMS_API
	#endif

	#include <stdbool.h>
	#include <stddef.h>
	#include <stdint.h>
	#include <string.h>

	#ifdef __cplusplus
	extern "C" {
	#endif

	// A row-major 3x3 matrix (ie vals[row][col])
	typedef struct skcms_Matrix3x3 {
	float vals[3][3];
	} skcms_Matrix3x3;

	// It is _not_ safe to alias the pointers to invert in-place.
	SKCMS_API bool skcms_Matrix3x3_invert(const skcms_Matrix3x3, skcms_Matrix3x3);
	SKCMS_API skcms_Matrix3x3 skcms_Matrix3x3_concat(const skcms_Matrix3x3, const skcms_Matrix3x3);

	// A row-major 3x4 matrix (ie vals[row][col])
	typedef struct skcms_Matrix3x4 {
	float vals[3][4];
	} skcms_Matrix3x4;

	// A transfer function mapping encoded values to linear values,
	// represented by this 7-parameter piecewise function:
	//
	// linear = sign(encoded) * (c*\|encoded\| + f) , 0 <= \|encoded\| < d
	// = sign(encoded) * ((a*\|encoded\| + b)^g + e), d <= \|encoded\|
	//
	// (A simple gamma transfer function sets g to gamma and a to 1.)
	typedef struct skcms_TransferFunction {
	float g, a,b,c,d,e,f;
	} skcms_TransferFunction;

	SKCMS_API float skcms_TransferFunction_eval (const skcms_TransferFunction*, float);
	SKCMS_API bool skcms_TransferFunction_invert(const skcms_TransferFunction*,
	skcms_TransferFunction*);

	// We can jam a couple alternate transfer function forms into skcms_TransferFunction,
	// including those matching the general forms of the SMPTE ST 2084 PQ function or HLG.
	//
	// PQish:
	// max(A + B\|encoded\|^C, 0)
	// linear = sign(encoded) * (------------------------) ^ F
	// D + E\|encoded\|^C
	SKCMS_API bool skcms_TransferFunction_makePQish(skcms_TransferFunction*,
	float A, float B, float C,
	float D, float E, float F);
	// HLGish:
	// { K * sign(encoded) * ( (R\|encoded\|)^G ) when 0 <= \|encoded\| <= 1/R
	// linear = { K * sign(encoded) * ( e^(a(\|encoded\|-c)) + b ) when 1/R < \|encoded\|
	SKCMS_API bool skcms_TransferFunction_makeScaledHLGish(skcms_TransferFunction*,
	float K, float R, float G,
	float a, float b, float c);

	// Compatibility shim with K=1 for old callers.
	static inline bool skcms_TransferFunction_makeHLGish(skcms_TransferFunction* fn,
	float R, float G,
	float a, float b, float c) {
	return skcms_TransferFunction_makeScaledHLGish(fn, 1.0f, R,G, a,b,c);
	}

	// PQ mapping encoded [0,1] to linear [0,1].
	static inline bool skcms_TransferFunction_makePQ(skcms_TransferFunction* tf) {
	return skcms_TransferFunction_makePQish(tf, -107/128.0f, 1.0f, 32/2523.0f
	, 2413/128.0f, -2392/128.0f, 8192/1305.0f);
	}
	// HLG mapping encoded [0,1] to linear [0,12].
	static inline bool skcms_TransferFunction_makeHLG(skcms_TransferFunction* tf) {
	return skcms_TransferFunction_makeHLGish(tf, 2.0f, 2.0f
	, 1/0.17883277f, 0.28466892f, 0.55991073f);
	}

	// Is this an ordinary sRGB-ish transfer function, or one of the HDR forms we support?
	SKCMS_API bool skcms_TransferFunction_isSRGBish(const skcms_TransferFunction*);
	SKCMS_API bool skcms_TransferFunction_isPQish (const skcms_TransferFunction*);
	SKCMS_API bool skcms_TransferFunction_isHLGish (const skcms_TransferFunction*);

	// Unified representation of 'curv' or 'para' tag data, or a 1D table from 'mft1' or 'mft2'
	typedef union skcms_Curve {
	struct {
	uint32_t alias_of_table_entries;
	skcms_TransferFunction parametric;
	};
	struct {
	uint32_t table_entries;
	const uint8_t* table_8;
	const uint8_t* table_16;
	};
	} skcms_Curve;

	// Complex transforms between device space (A) and profile connection space (B):
	// A2B: device -> [ "A" curves -> CLUT ] -> [ "M" curves -> matrix ] -> "B" curves -> PCS
	// B2A: device <- [ "A" curves <- CLUT ] <- [ "M" curves <- matrix ] <- "B" curves <- PCS

	typedef struct skcms_A2B {
	// Optional: N 1D "A" curves, followed by an N-dimensional CLUT.
	// If input_channels == 0, these curves and CLUT are skipped,
	// Otherwise, input_channels must be in [1, 4].
	uint32_t input_channels;
	skcms_Curve input_curves[4];
	uint8_t grid_points[4];
	const uint8_t* grid_8;
	const uint8_t* grid_16;

	// Optional: 3 1D "M" curves, followed by a color matrix.
	// If matrix_channels == 0, these curves and matrix are skipped,
	// Otherwise, matrix_channels must be 3.
	uint32_t matrix_channels;
	skcms_Curve matrix_curves[3];
	skcms_Matrix3x4 matrix;

	// Required: 3 1D "B" curves. Always present, and output_channels must be 3.
	uint32_t output_channels;
	skcms_Curve output_curves[3];
	} skcms_A2B;

	typedef struct skcms_B2A {
	// Required: 3 1D "B" curves. Always present, and input_channels must be 3.
	uint32_t input_channels;
	skcms_Curve input_curves[3];

	// Optional: a color matrix, followed by 3 1D "M" curves.
	// If matrix_channels == 0, this matrix and these curves are skipped,
	// Otherwise, matrix_channels must be 3.
	uint32_t matrix_channels;
	skcms_Matrix3x4 matrix;
	skcms_Curve matrix_curves[3];

	// Optional: an N-dimensional CLUT, followed by N 1D "A" curves.
	// If output_channels == 0, this CLUT and these curves are skipped,
	// Otherwise, output_channels must be in [1, 4].
	uint32_t output_channels;
	uint8_t grid_points[4];
	const uint8_t* grid_8;
	const uint8_t* grid_16;
	skcms_Curve output_curves[4];
	} skcms_B2A;


	typedef struct skcms_ICCProfile {
	const uint8_t* buffer;

	uint32_t size;
	uint32_t data_color_space;
	uint32_t pcs;
	uint32_t tag_count;

	// skcms_Parse() will set commonly-used fields for you when possible:

	// If we can parse red, green and blue transfer curves from the profile,
	// trc will be set to those three curves, and has_trc will be true.
	bool has_trc;
	skcms_Curve trc[3];

	// If this profile's gamut can be represented by a 3x3 transform to XYZD50,
	// skcms_Parse() sets toXYZD50 to that transform and has_toXYZD50 to true.
	bool has_toXYZD50;
	skcms_Matrix3x3 toXYZD50;

	// If the profile has a valid A2B0 or A2B1 tag, skcms_Parse() sets A2B to
	// that data, and has_A2B to true. skcms_ParseWithA2BPriority() does the
	// same following any user-provided prioritization of A2B0, A2B1, or A2B2.
	bool has_A2B;
	skcms_A2B A2B;

	// If the profile has a valid B2A0 or B2A1 tag, skcms_Parse() sets B2A to
	// that data, and has_B2A to true. skcms_ParseWithA2BPriority() does the
	// same following any user-provided prioritization of B2A0, B2A1, or B2A2.
	bool has_B2A;
	skcms_B2A B2A;

	} skcms_ICCProfile;

	// The sRGB color profile is so commonly used that we offer a canonical skcms_ICCProfile for it.
	SKCMS_API const skcms_ICCProfile* skcms_sRGB_profile(void);
	// Ditto for XYZD50, the most common profile connection space.
	SKCMS_API const skcms_ICCProfile* skcms_XYZD50_profile(void);

	SKCMS_API const skcms_TransferFunction* skcms_sRGB_TransferFunction(void);
	SKCMS_API const skcms_TransferFunction* skcms_sRGB_Inverse_TransferFunction(void);
	SKCMS_API const skcms_TransferFunction* skcms_Identity_TransferFunction(void);

	// Practical equality test for two skcms_ICCProfiles.
	// The implementation is subject to change, but it will always try to answer
	// "can I substitute A for B?" and "can I skip transforming from A to B?".
	SKCMS_API bool skcms_ApproximatelyEqualProfiles(const skcms_ICCProfile* A,
	const skcms_ICCProfile* B);

	// Practical test that answers: Is curve roughly the inverse of inv_tf? Typically used by passing
	// the inverse of a known parametric transfer function (like sRGB), to determine if a particular
	// curve is very close to sRGB.
	SKCMS_API bool skcms_AreApproximateInverses(const skcms_Curve* curve,
	const skcms_TransferFunction* inv_tf);

	// Similar to above, answering the question for all three TRC curves of the given profile. Again,
	// passing skcms_sRGB_InverseTransferFunction as inv_tf will answer the question:
	// "Does this profile have a transfer function that is very close to sRGB?"
	SKCMS_API bool skcms_TRCs_AreApproximateInverse(const skcms_ICCProfile* profile,
	const skcms_TransferFunction* inv_tf);

	// Parse an ICC profile and return true if possible, otherwise return false.
	// Selects an A2B profile (if present) according to priority list (each entry 0-2).
	// The buffer is not copied; it must remain valid as long as the skcms_ICCProfile will be used.
	SKCMS_API bool skcms_ParseWithA2BPriority(const void*, size_t,
	const int priority[], int priorities,
	skcms_ICCProfile*);

	static inline bool skcms_Parse(const void* buf, size_t len, skcms_ICCProfile* profile) {
	// For continuity of existing user expectations,
	// prefer A2B0 (perceptual) over A2B1 (relative colormetric), and ignore A2B2 (saturation).
	const int priority[] = {0,1};
	return skcms_ParseWithA2BPriority(buf, len,
	priority, sizeof(priority)/sizeof(*priority),
	profile);
	}

	SKCMS_API bool skcms_ApproximateCurve(const skcms_Curve* curve,
	skcms_TransferFunction* approx,
	float* max_error);

	SKCMS_API bool skcms_GetCHAD(const skcms_ICCProfile, skcms_Matrix3x3);
	SKCMS_API bool skcms_GetWTPT(const skcms_ICCProfile*, float xyz[3]);

	// These are common ICC signature values
	enum {
	// data_color_space
	skcms_Signature_CMYK = 0x434D594B,
	skcms_Signature_Gray = 0x47524159,
	skcms_Signature_RGB = 0x52474220,

	// pcs
	skcms_Signature_Lab = 0x4C616220,
	skcms_Signature_XYZ = 0x58595A20,
	};

	typedef enum skcms_PixelFormat {
	skcms_PixelFormat_A_8,
	skcms_PixelFormat_A_8_,
	skcms_PixelFormat_G_8,
	skcms_PixelFormat_G_8_,
	skcms_PixelFormat_RGBA_8888_Palette8,
	skcms_PixelFormat_BGRA_8888_Palette8,

	skcms_PixelFormat_RGB_565,
	skcms_PixelFormat_BGR_565,

	skcms_PixelFormat_ABGR_4444,
	skcms_PixelFormat_ARGB_4444,

	skcms_PixelFormat_RGB_888,
	skcms_PixelFormat_BGR_888,
	skcms_PixelFormat_RGBA_8888,
	skcms_PixelFormat_BGRA_8888,
	skcms_PixelFormat_RGBA_8888_sRGB, // Automatic sRGB encoding / decoding.
	skcms_PixelFormat_BGRA_8888_sRGB, // (Generally used with linear transfer functions.)

	skcms_PixelFormat_RGBA_1010102,
	skcms_PixelFormat_BGRA_1010102,

	skcms_PixelFormat_RGB_161616LE, // Little-endian. Pointers must be 16-bit aligned.
	skcms_PixelFormat_BGR_161616LE,
	skcms_PixelFormat_RGBA_16161616LE,
	skcms_PixelFormat_BGRA_16161616LE,

	skcms_PixelFormat_RGB_161616BE, // Big-endian. Pointers must be 16-bit aligned.
	skcms_PixelFormat_BGR_161616BE,
	skcms_PixelFormat_RGBA_16161616BE,
	skcms_PixelFormat_BGRA_16161616BE,

	skcms_PixelFormat_RGB_hhh_Norm, // 1-5-10 half-precision float in [0,1]
	skcms_PixelFormat_BGR_hhh_Norm, // Pointers must be 16-bit aligned.
	skcms_PixelFormat_RGBA_hhhh_Norm,
	skcms_PixelFormat_BGRA_hhhh_Norm,

	skcms_PixelFormat_RGB_hhh, // 1-5-10 half-precision float.
	skcms_PixelFormat_BGR_hhh, // Pointers must be 16-bit aligned.
	skcms_PixelFormat_RGBA_hhhh,
	skcms_PixelFormat_BGRA_hhhh,

	skcms_PixelFormat_RGB_fff, // 1-8-23 single-precision float (the normal kind).
	skcms_PixelFormat_BGR_fff, // Pointers must be 32-bit aligned.
	skcms_PixelFormat_RGBA_ffff,
	skcms_PixelFormat_BGRA_ffff,
	} skcms_PixelFormat;

	// We always store any alpha channel linearly. In the chart below, tf-1() is the inverse
	// transfer function for the given color profile (applying the transfer function linearizes).

	// We treat opaque as a strong requirement, not just a performance hint: we will ignore
	// any source alpha and treat it as 1.0, and will make sure that any destination alpha
	// channel is filled with the equivalent of 1.0.

	// We used to offer multiple types of premultiplication, but now just one, PremulAsEncoded.
	// This is the premul you're probably used to working with.

	typedef enum skcms_AlphaFormat {
	skcms_AlphaFormat_Opaque, // alpha is always opaque
	// tf-1(r), tf-1(g), tf-1(b), 1.0
	skcms_AlphaFormat_Unpremul, // alpha and color are unassociated
	// tf-1(r), tf-1(g), tf-1(b), a
	skcms_AlphaFormat_PremulAsEncoded, // premultiplied while encoded
	// tf-1(r)a, tf-1(g)a, tf-1(b)*a, a
	} skcms_AlphaFormat;

	// Convert npixels pixels from src format and color profile to dst format and color profile
	// and return true, otherwise return false. It is safe to alias dst == src if dstFmt == srcFmt.
	SKCMS_API bool skcms_Transform(const void* src,
	skcms_PixelFormat srcFmt,
	skcms_AlphaFormat srcAlpha,
	const skcms_ICCProfile* srcProfile,
	void* dst,
	skcms_PixelFormat dstFmt,
	skcms_AlphaFormat dstAlpha,
	const skcms_ICCProfile* dstProfile,
	size_t npixels);

	// As skcms_Transform(), supporting srcFmts with a palette.
	SKCMS_API bool skcms_TransformWithPalette(const void* src,
	skcms_PixelFormat srcFmt,
	skcms_AlphaFormat srcAlpha,
	const skcms_ICCProfile* srcProfile,
	void* dst,
	skcms_PixelFormat dstFmt,
	skcms_AlphaFormat dstAlpha,
	const skcms_ICCProfile* dstProfile,
	size_t npixels,
	const void* palette);

	// If profile can be used as a destination in skcms_Transform, return true. Otherwise, attempt to
	// rewrite it with approximations where reasonable. If successful, return true. If no reasonable
	// approximation exists, leave the profile unchanged and return false.
	SKCMS_API bool skcms_MakeUsableAsDestination(skcms_ICCProfile* profile);

	// If profile can be used as a destination with a single parametric transfer function (ie for
	// rasterization), return true. Otherwise, attempt to rewrite it with approximations where
	// reasonable. If successful, return true. If no reasonable approximation exists, leave the
	// profile unchanged and return false.
	SKCMS_API bool skcms_MakeUsableAsDestinationWithSingleCurve(skcms_ICCProfile* profile);

	// Returns a matrix to adapt XYZ color from given the whitepoint to D50.
	SKCMS_API bool skcms_AdaptToXYZD50(float wx, float wy,
	skcms_Matrix3x3* toXYZD50);

	// Returns a matrix to convert RGB color into XYZ adapted to D50, given the
	// primaries and whitepoint of the RGB model.
	SKCMS_API bool skcms_PrimariesToXYZD50(float rx, float ry,
	float gx, float gy,
	float bx, float by,
	float wx, float wy,
	skcms_Matrix3x3* toXYZD50);

	// Call before your first call to skcms_Transform() to skip runtime CPU detection.
	SKCMS_API void skcms_DisableRuntimeCPUDetection(void);

	// Utilities for programmatically constructing profiles
	static inline void skcms_Init(skcms_ICCProfile* p) {
	memset(p, 0, sizeof(*p));
	p->data_color_space = skcms_Signature_RGB;
	p->pcs = skcms_Signature_XYZ;
	}

	static inline void skcms_SetTransferFunction(skcms_ICCProfile* p,
	const skcms_TransferFunction* tf) {
	p->has_trc = true;
	for (int i = 0; i < 3; ++i) {
	p->trc[i].table_entries = 0;
	p->trc[i].parametric = *tf;
	}
	}

	static inline void skcms_SetXYZD50(skcms_ICCProfile* p, const skcms_Matrix3x3* m) {
	p->has_toXYZD50 = true;
	p->toXYZD50 = *m;
	}

	#ifdef __cplusplus
	}
	#endif