305 lines
12 KiB
C
305 lines
12 KiB
C
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/*
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* Copyright 2018 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#pragma once
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// skcms.h contains the entire public API for skcms.
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#ifndef SKCMS_API
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#define SKCMS_API
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#endif
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#include <stdbool.h>
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#include <stddef.h>
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#include <stdint.h>
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#include <string.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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// A row-major 3x3 matrix (ie vals[row][col])
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typedef struct skcms_Matrix3x3 {
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float vals[3][3];
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} skcms_Matrix3x3;
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// It is _not_ safe to alias the pointers to invert in-place.
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SKCMS_API bool skcms_Matrix3x3_invert(const skcms_Matrix3x3*, skcms_Matrix3x3*);
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SKCMS_API skcms_Matrix3x3 skcms_Matrix3x3_concat(const skcms_Matrix3x3*, const skcms_Matrix3x3*);
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// A row-major 3x4 matrix (ie vals[row][col])
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typedef struct skcms_Matrix3x4 {
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float vals[3][4];
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} skcms_Matrix3x4;
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// A transfer function mapping encoded values to linear values,
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// represented by this 7-parameter piecewise function:
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//
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// linear = sign(encoded) * (c*|encoded| + f) , 0 <= |encoded| < d
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// = sign(encoded) * ((a*|encoded| + b)^g + e), d <= |encoded|
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//
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// (A simple gamma transfer function sets g to gamma and a to 1.)
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typedef struct skcms_TransferFunction {
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float g, a,b,c,d,e,f;
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} skcms_TransferFunction;
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SKCMS_API float skcms_TransferFunction_eval (const skcms_TransferFunction*, float);
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SKCMS_API bool skcms_TransferFunction_invert(const skcms_TransferFunction*,
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skcms_TransferFunction*);
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// Unified representation of 'curv' or 'para' tag data, or a 1D table from 'mft1' or 'mft2'
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typedef union skcms_Curve {
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struct {
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uint32_t alias_of_table_entries;
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skcms_TransferFunction parametric;
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};
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struct {
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uint32_t table_entries;
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const uint8_t* table_8;
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const uint8_t* table_16;
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};
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} skcms_Curve;
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typedef struct skcms_A2B {
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// Optional: N 1D curves, followed by an N-dimensional CLUT.
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// If input_channels == 0, these curves and CLUT are skipped,
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// Otherwise, input_channels must be in [1, 4].
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uint32_t input_channels;
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skcms_Curve input_curves[4];
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uint8_t grid_points[4];
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const uint8_t* grid_8;
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const uint8_t* grid_16;
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// Optional: 3 1D curves, followed by a color matrix.
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// If matrix_channels == 0, these curves and matrix are skipped,
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// Otherwise, matrix_channels must be 3.
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uint32_t matrix_channels;
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skcms_Curve matrix_curves[3];
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skcms_Matrix3x4 matrix;
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// Required: 3 1D curves. Always present, and output_channels must be 3.
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uint32_t output_channels;
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skcms_Curve output_curves[3];
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} skcms_A2B;
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typedef struct skcms_ICCProfile {
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const uint8_t* buffer;
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uint32_t size;
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uint32_t data_color_space;
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uint32_t pcs;
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uint32_t tag_count;
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// skcms_Parse() will set commonly-used fields for you when possible:
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// If we can parse red, green and blue transfer curves from the profile,
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// trc will be set to those three curves, and has_trc will be true.
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bool has_trc;
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skcms_Curve trc[3];
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// If this profile's gamut can be represented by a 3x3 transform to XYZD50,
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// skcms_Parse() sets toXYZD50 to that transform and has_toXYZD50 to true.
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bool has_toXYZD50;
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skcms_Matrix3x3 toXYZD50;
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// If the profile has a valid A2B0 tag, skcms_Parse() sets A2B to that data,
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// and has_A2B to true.
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bool has_A2B;
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skcms_A2B A2B;
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} skcms_ICCProfile;
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// The sRGB color profile is so commonly used that we offer a canonical skcms_ICCProfile for it.
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SKCMS_API const skcms_ICCProfile* skcms_sRGB_profile(void);
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// Ditto for XYZD50, the most common profile connection space.
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SKCMS_API const skcms_ICCProfile* skcms_XYZD50_profile(void);
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SKCMS_API const skcms_TransferFunction* skcms_sRGB_TransferFunction(void);
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SKCMS_API const skcms_TransferFunction* skcms_sRGB_Inverse_TransferFunction(void);
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SKCMS_API const skcms_TransferFunction* skcms_Identity_TransferFunction(void);
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// Practical equality test for two skcms_ICCProfiles.
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// The implementation is subject to change, but it will always try to answer
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// "can I substitute A for B?" and "can I skip transforming from A to B?".
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SKCMS_API bool skcms_ApproximatelyEqualProfiles(const skcms_ICCProfile* A,
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const skcms_ICCProfile* B);
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// Practical test that answers: Is curve roughly the inverse of inv_tf? Typically used by passing
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// the inverse of a known parametric transfer function (like sRGB), to determine if a particular
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// curve is very close to sRGB.
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SKCMS_API bool skcms_AreApproximateInverses(const skcms_Curve* curve,
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const skcms_TransferFunction* inv_tf);
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// Similar to above, answering the question for all three TRC curves of the given profile. Again,
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// passing skcms_sRGB_InverseTransferFunction as inv_tf will answer the question:
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// "Does this profile have a transfer function that is very close to sRGB?"
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SKCMS_API bool skcms_TRCs_AreApproximateInverse(const skcms_ICCProfile* profile,
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const skcms_TransferFunction* inv_tf);
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// Parse an ICC profile and return true if possible, otherwise return false.
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// The buffer is not copied, it must remain valid as long as the skcms_ICCProfile
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// will be used.
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SKCMS_API bool skcms_Parse(const void*, size_t, skcms_ICCProfile*);
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SKCMS_API bool skcms_ApproximateCurve(const skcms_Curve* curve,
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skcms_TransferFunction* approx,
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float* max_error);
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typedef struct skcms_ICCTag {
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uint32_t signature;
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uint32_t type;
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uint32_t size;
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const uint8_t* buf;
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} skcms_ICCTag;
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SKCMS_API void skcms_GetTagByIndex (const skcms_ICCProfile*, uint32_t idx, skcms_ICCTag*);
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SKCMS_API bool skcms_GetTagBySignature(const skcms_ICCProfile*, uint32_t sig, skcms_ICCTag*);
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// These are common ICC signature values
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enum {
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// data_color_space
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skcms_Signature_CMYK = 0x434D594B,
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skcms_Signature_Gray = 0x47524159,
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skcms_Signature_RGB = 0x52474220,
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// pcs
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skcms_Signature_Lab = 0x4C616220,
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skcms_Signature_XYZ = 0x58595A20,
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};
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typedef enum skcms_PixelFormat {
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skcms_PixelFormat_A_8,
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skcms_PixelFormat_A_8_,
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skcms_PixelFormat_G_8,
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skcms_PixelFormat_G_8_,
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skcms_PixelFormat_RGBA_8888_Palette8,
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skcms_PixelFormat_BGRA_8888_Palette8,
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skcms_PixelFormat_RGB_565,
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skcms_PixelFormat_BGR_565,
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skcms_PixelFormat_ABGR_4444,
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skcms_PixelFormat_ARGB_4444,
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skcms_PixelFormat_RGB_888,
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skcms_PixelFormat_BGR_888,
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skcms_PixelFormat_RGBA_8888,
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skcms_PixelFormat_BGRA_8888,
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skcms_PixelFormat_RGBA_1010102,
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skcms_PixelFormat_BGRA_1010102,
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skcms_PixelFormat_RGB_161616LE, // Little-endian. Pointers must be 16-bit aligned.
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skcms_PixelFormat_BGR_161616LE,
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skcms_PixelFormat_RGBA_16161616LE,
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skcms_PixelFormat_BGRA_16161616LE,
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skcms_PixelFormat_RGB_161616BE, // Big-endian. Pointers must be 16-bit aligned.
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skcms_PixelFormat_BGR_161616BE,
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skcms_PixelFormat_RGBA_16161616BE,
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skcms_PixelFormat_BGRA_16161616BE,
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skcms_PixelFormat_RGB_hhh_Norm, // 1-5-10 half-precision float in [0,1]
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skcms_PixelFormat_BGR_hhh_Norm, // Pointers must be 16-bit aligned.
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skcms_PixelFormat_RGBA_hhhh_Norm,
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skcms_PixelFormat_BGRA_hhhh_Norm,
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skcms_PixelFormat_RGB_hhh, // 1-5-10 half-precision float.
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skcms_PixelFormat_BGR_hhh, // Pointers must be 16-bit aligned.
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skcms_PixelFormat_RGBA_hhhh,
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skcms_PixelFormat_BGRA_hhhh,
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skcms_PixelFormat_RGB_fff, // 1-8-23 single-precision float (the normal kind).
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skcms_PixelFormat_BGR_fff, // Pointers must be 32-bit aligned.
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skcms_PixelFormat_RGBA_ffff,
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skcms_PixelFormat_BGRA_ffff,
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} skcms_PixelFormat;
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// We always store any alpha channel linearly. In the chart below, tf-1() is the inverse
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// transfer function for the given color profile (applying the transfer function linearizes).
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// We treat opaque as a strong requirement, not just a performance hint: we will ignore
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// any source alpha and treat it as 1.0, and will make sure that any destination alpha
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// channel is filled with the equivalent of 1.0.
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// We used to offer multiple types of premultiplication, but now just one, PremulAsEncoded.
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// This is the premul you're probably used to working with.
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typedef enum skcms_AlphaFormat {
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skcms_AlphaFormat_Opaque, // alpha is always opaque
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// tf-1(r), tf-1(g), tf-1(b), 1.0
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skcms_AlphaFormat_Unpremul, // alpha and color are unassociated
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// tf-1(r), tf-1(g), tf-1(b), a
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skcms_AlphaFormat_PremulAsEncoded, // premultiplied while encoded
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// tf-1(r)*a, tf-1(g)*a, tf-1(b)*a, a
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} skcms_AlphaFormat;
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// Convert npixels pixels from src format and color profile to dst format and color profile
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// and return true, otherwise return false. It is safe to alias dst == src if dstFmt == srcFmt.
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SKCMS_API bool skcms_Transform(const void* src,
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skcms_PixelFormat srcFmt,
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skcms_AlphaFormat srcAlpha,
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const skcms_ICCProfile* srcProfile,
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void* dst,
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skcms_PixelFormat dstFmt,
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skcms_AlphaFormat dstAlpha,
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const skcms_ICCProfile* dstProfile,
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size_t npixels);
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// As skcms_Transform(), supporting srcFmts with a palette.
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SKCMS_API bool skcms_TransformWithPalette(const void* src,
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skcms_PixelFormat srcFmt,
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skcms_AlphaFormat srcAlpha,
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const skcms_ICCProfile* srcProfile,
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void* dst,
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skcms_PixelFormat dstFmt,
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skcms_AlphaFormat dstAlpha,
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const skcms_ICCProfile* dstProfile,
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size_t npixels,
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const void* palette);
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// If profile can be used as a destination in skcms_Transform, return true. Otherwise, attempt to
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// rewrite it with approximations where reasonable. If successful, return true. If no reasonable
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// approximation exists, leave the profile unchanged and return false.
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SKCMS_API bool skcms_MakeUsableAsDestination(skcms_ICCProfile* profile);
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// If profile can be used as a destination with a single parametric transfer function (ie for
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// rasterization), return true. Otherwise, attempt to rewrite it with approximations where
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// reasonable. If successful, return true. If no reasonable approximation exists, leave the
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// profile unchanged and return false.
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SKCMS_API bool skcms_MakeUsableAsDestinationWithSingleCurve(skcms_ICCProfile* profile);
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SKCMS_API bool skcms_PrimariesToXYZD50(float rx, float ry,
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float gx, float gy,
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float bx, float by,
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float wx, float wy,
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skcms_Matrix3x3* toXYZD50);
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// Utilities for programmatically constructing profiles
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static inline void skcms_Init(skcms_ICCProfile* p) {
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memset(p, 0, sizeof(*p));
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p->data_color_space = skcms_Signature_RGB;
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p->pcs = skcms_Signature_XYZ;
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}
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static inline void skcms_SetTransferFunction(skcms_ICCProfile* p,
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const skcms_TransferFunction* tf) {
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p->has_trc = true;
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for (int i = 0; i < 3; ++i) {
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p->trc[i].table_entries = 0;
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p->trc[i].parametric = *tf;
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}
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}
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static inline void skcms_SetXYZD50(skcms_ICCProfile* p, const skcms_Matrix3x3* m) {
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p->has_toXYZD50 = true;
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p->toXYZD50 = *m;
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}
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#ifdef __cplusplus
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}
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#endif
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