/* * 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 #include #include #include #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