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- /*
- * 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*);
- // 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*);
- 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_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_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);
- 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
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