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;

 // 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;

 // 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;

 typedef struct skcms_A2B {
     // Optional: N 1D 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 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 curves. Always present, and output_channels must be 3.
     uint32_t        output_channels;
     skcms_Curve     output_curves[3];
 } skcms_A2B;

 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 tag, skcms_Parse() sets A2B to that data,
     // and has_A2B to true.
     bool                   has_A2B;
     skcms_A2B              A2B;
 } 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.
 // The buffer is not copied, it must remain valid as long as the skcms_ICCProfile
 // will be used.
 SKCMS_API bool skcms_Parse(const void*, size_t, skcms_ICCProfile*);

 // No-op, to be removed.
 static inline void skcms_OptimizeForSpeed(skcms_ICCProfile* p) { (void)p; }

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

 typedef struct skcms_ICCTag {
     uint32_t       signature;
     uint32_t       type;
     uint32_t       size;
     const uint8_t* buf;
 } skcms_ICCTag;

 SKCMS_API void skcms_GetTagByIndex    (const skcms_ICCProfile*, uint32_t idx, skcms_ICCTag*);
 SKCMS_API bool skcms_GetTagBySignature(const skcms_ICCProfile*, uint32_t sig, skcms_ICCTag*);

 // 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_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_1010102,
     skcms_PixelFormat_BGRA_1010102,

     skcms_PixelFormat_RGB_161616,     // Big-endian.  Pointers must be 16-bit aligned.
     skcms_PixelFormat_BGR_161616,
     skcms_PixelFormat_RGBA_16161616,
     skcms_PixelFormat_BGRA_16161616,

     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.

 // When premultiplying and/or using a non-linear transfer function, it's important
 // that we know the order the operations are applied.  If you're used to working
 // with non-color-managed drawing systems, PremulAsEncoded is probably the "premul"
 // you're looking for; if you want linear blending, PremulLinear is the choice for you.

 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_PremulLinear,    // premultiplied while linear
                                        //   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);

 // 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);

 SKCMS_API bool skcms_PrimariesToXYZD50(float rx, float ry,
                                        float gx, float gy,
                                        float bx, float by,
                                        float wx, float wy,
                                        skcms_Matrix3x3* toXYZD50);

 // 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;

	// 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;

	// 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;

	typedef struct skcms_A2B {
	// Optional: N 1D 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 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 curves. Always present, and output_channels must be 3.
	uint32_t output_channels;
	skcms_Curve output_curves[3];
	} skcms_A2B;

	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 tag, skcms_Parse() sets A2B to that data,
	// and has_A2B to true.
	bool has_A2B;
	skcms_A2B A2B;
	} 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.
	// The buffer is not copied, it must remain valid as long as the skcms_ICCProfile
	// will be used.
	SKCMS_API bool skcms_Parse(const void, size_t, skcms_ICCProfile);

	// No-op, to be removed.
	static inline void skcms_OptimizeForSpeed(skcms_ICCProfile* p) { (void)p; }

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

	typedef struct skcms_ICCTag {
	uint32_t signature;
	uint32_t type;
	uint32_t size;
	const uint8_t* buf;
	} skcms_ICCTag;

	SKCMS_API void skcms_GetTagByIndex (const skcms_ICCProfile, uint32_t idx, skcms_ICCTag);
	SKCMS_API bool skcms_GetTagBySignature(const skcms_ICCProfile, uint32_t sig, skcms_ICCTag);

	// 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_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_1010102,
	skcms_PixelFormat_BGRA_1010102,

	skcms_PixelFormat_RGB_161616, // Big-endian. Pointers must be 16-bit aligned.
	skcms_PixelFormat_BGR_161616,
	skcms_PixelFormat_RGBA_16161616,
	skcms_PixelFormat_BGRA_16161616,

	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.

	// When premultiplying and/or using a non-linear transfer function, it's important
	// that we know the order the operations are applied. If you're used to working
	// with non-color-managed drawing systems, PremulAsEncoded is probably the "premul"
	// you're looking for; if you want linear blending, PremulLinear is the choice for you.

	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_PremulLinear, // premultiplied while linear
	// tf-1(ra), tf-1(ga), 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);

	// 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);

	SKCMS_API bool skcms_PrimariesToXYZD50(float rx, float ry,
	float gx, float gy,
	float bx, float by,
	float wx, float wy,
	skcms_Matrix3x3* toXYZD50);

	// 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