/* * 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. #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; // 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. extern const skcms_ICCProfile skcms_sRGB_profile; // Ditto for XYZD50, the most common profile connection space. extern const skcms_ICCProfile skcms_XYZD50_profile; // 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?". bool skcms_ApproximatelyEqualProfiles(const skcms_ICCProfile* A, const skcms_ICCProfile* B); // 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. bool skcms_Parse(const void*, size_t, skcms_ICCProfile*); // skcms_Parse() creates a profile that directs skcms_Transform() to favor accuracy. // If you want to trade a little accuracy for a big speedup, call skcms_OptimizeForSpeed(). void skcms_OptimizeForSpeed(skcms_ICCProfile*); bool skcms_ApproximateCurve(const skcms_Curve* curve, skcms_TransferFunction* approx, float* max_error); // What is the best single transfer function to use for the given profile? Note that there is // no real upper bound on the error of this transfer function. skcms_TransferFunction skcms_BestSingleCurve(const skcms_ICCProfile*); typedef struct skcms_ICCTag { uint32_t signature; uint32_t type; uint32_t size; const uint8_t* buf; } skcms_ICCTag; void skcms_GetTagByIndex (const skcms_ICCProfile*, uint32_t idx, skcms_ICCTag*); bool skcms_GetTagBySignature(const skcms_ICCProfile*, uint32_t sig, skcms_ICCTag*); typedef enum skcms_PixelFormat { skcms_PixelFormat_RGB_565, skcms_PixelFormat_BGR_565, 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. 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 cannot be used as a destination profile in skcms_Transform(), // rewrite it with approximations where reasonable or by pulling from fallback // (e.g. skcms_sRGB_profile) where not. void skcms_EnsureUsableAsDestination(skcms_ICCProfile* profile, const skcms_ICCProfile* fallback); // If profile cannot be used as a destination profile with a single parametric transfer function, // (ie for rasterization), rewrite it with approximations where reasonable or by pulling from // fallback (e.g. skcms_sRGB_profile) where not. void skcms_EnsureUsableAsDestinationWithSingleCurve(skcms_ICCProfile* profile, const skcms_ICCProfile* fallback); #ifdef __cplusplus } #endif