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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*);
+
+typedef enum skcms_TFType {
+ skcms_TFType_Invalid,
+ skcms_TFType_sRGBish,
+ skcms_TFType_PQish,
+ skcms_TFType_HLGish,
+ skcms_TFType_HLGinvish,
+} skcms_TFType;
+
+// Identify which kind of transfer function is encoded in an skcms_TransferFunction
+SKCMS_API skcms_TFType skcms_TransferFunction_getType(const 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_CICP {
+ uint8_t color_primaries;
+ uint8_t transfer_characteristics;
+ uint8_t matrix_coefficients;
+ uint8_t video_full_range_flag;
+} skcms_CICP;
+
+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;
+
+ // If the profile has a valid CICP tag, skcms_Parse() sets CICP to that data,
+ // and has_CICP to true.
+ bool has_CICP;
+ skcms_CICP CICP;
+} 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_RGB_101010x_XR, // Note: This is located here to signal no clamping.
+ skcms_PixelFormat_BGR_101010x_XR, // Compatible with MTLPixelFormatBGR10_XR.
+} 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
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