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ced1d35bc5
skia2/third_party/skcms/skcms.cc
skia-autoroll ced1d35bc5 Roll skcms from 65de465d622d to b9593d4e39ea (1 revision) 
https://skia.googlesource.com/skcms.git/+log/65de465d622d..b9593d4e39ea

2021-03-25 mtklein@google.com inclusivity in comments

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/skcms-skia-autoroll
Please CC reed@google.com,mtklein@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/master/autoroll/README.md

Cq-Include-Trybots: luci.chromium.try:linux-blink-rel
Tbr: reed@google.com,mtklein@google.com
Change-Id: I7e5a4e221e5442d663fee36a214b3f46b5acb6cc
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/389198
Reviewed-by: skia-autoroll <skia-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: skia-autoroll <skia-autoroll@skia-public.iam.gserviceaccount.com>
2021-03-25 19:25:41 +00:00

2678 lines
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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.
*/
#include "skcms.h"
#include "skcms_internal.h"
#include <assert.h>
#include <float.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#if defined(__ARM_NEON)
#include <arm_neon.h>
#elif defined(__SSE__)
#include <immintrin.h>
#if defined(__clang__)
// That #include <immintrin.h> is usually enough, but Clang's headers
// "helpfully" skip including the whole kitchen sink when _MSC_VER is
// defined, because lots of programs on Windows would include that and
// it'd be a lot slower. But we want all those headers included so we
// can use their features after runtime checks later.
#include <smmintrin.h>
#include <avxintrin.h>
#include <avx2intrin.h>
#include <avx512fintrin.h>
#include <avx512dqintrin.h>
#endif
#endif
static bool runtime_cpu_detection = true;
void skcms_DisableRuntimeCPUDetection() {
runtime_cpu_detection = false;
}
// sizeof(x) will return size_t, which is 32-bit on some machines and 64-bit on others.
// We have better testing on 64-bit machines, so force 32-bit machines to behave like 64-bit.
//
// Please do not use sizeof() directly, and size_t only when required.
// (We have no way of enforcing these requests...)
#define SAFE_SIZEOF(x) ((uint64_t)sizeof(x))
// Same sort of thing for _Layout structs with a variable sized array at the end (named "variable").
#define SAFE_FIXED_SIZE(type) ((uint64_t)offsetof(type, variable))
static const union {
uint32_t bits;
float f;
} inf_ = { 0x7f800000 };
#define INFINITY_ inf_.f
#if defined(__clang__) || defined(__GNUC__)
#define small_memcpy __builtin_memcpy
#else
#define small_memcpy memcpy
#endif
static float log2f_(float x) {
// The first approximation of log2(x) is its exponent 'e', minus 127.
int32_t bits;
small_memcpy(&bits, &x, sizeof(bits));
float e = (float)bits * (1.0f / (1<<23));
// If we use the mantissa too we can refine the error signficantly.
int32_t m_bits = (bits & 0x007fffff) | 0x3f000000;
float m;
small_memcpy(&m, &m_bits, sizeof(m));
return (e - 124.225514990f
- 1.498030302f*m
- 1.725879990f/(0.3520887068f + m));
}
static float logf_(float x) {
const float ln2 = 0.69314718f;
return ln2*log2f_(x);
}
static float exp2f_(float x) {
float fract = x - floorf_(x);
float fbits = (1.0f * (1<<23)) * (x + 121.274057500f
- 1.490129070f*fract
+ 27.728023300f/(4.84252568f - fract));
// Before we cast fbits to int32_t, check for out of range values to pacify UBSAN.
// INT_MAX is not exactly representable as a float, so exclude it as effectively infinite.
// Negative values are effectively underflow - we'll end up returning a (different) negative
// value, which makes no sense. So clamp to zero.
if (fbits >= (float)INT_MAX) {
return INFINITY_;
} else if (fbits < 0) {
return 0;
}
int32_t bits = (int32_t)fbits;
small_memcpy(&x, &bits, sizeof(x));
return x;
}
// Not static, as it's used by some test tools.
float powf_(float x, float y) {
assert (x >= 0);
return (x == 0) || (x == 1) ? x
: exp2f_(log2f_(x) * y);
}
static float expf_(float x) {
const float log2_e = 1.4426950408889634074f;
return exp2f_(log2_e * x);
}
static float fmaxf_(float x, float y) { return x > y ? x : y; }
static float fminf_(float x, float y) { return x < y ? x : y; }
static bool isfinitef_(float x) { return 0 == x*0; }
static float minus_1_ulp(float x) {
int32_t bits;
memcpy(&bits, &x, sizeof(bits));
bits = bits - 1;
memcpy(&x, &bits, sizeof(bits));
return x;
}
// Most transfer functions we work with are sRGBish.
// For exotic HDR transfer functions, we encode them using a tf.g that makes no sense,
// and repurpose the other fields to hold the parameters of the HDR functions.
enum TFKind { Bad, sRGBish, PQish, HLGish, HLGinvish };
struct TF_PQish { float A,B,C,D,E,F; };
struct TF_HLGish { float R,G,a,b,c,K_minus_1; };
// We didn't originally support a scale factor K for HLG, and instead just stored 0 in
// the unused `f` field of skcms_TransferFunction for HLGish and HLGInvish transfer functions.
// By storing f=K-1, those old unusued f=0 values now mean K=1, a noop scale factor.
static float TFKind_marker(TFKind kind) {
// We'd use different NaNs, but those aren't guaranteed to be preserved by WASM.
return -(float)kind;
}
static TFKind classify(const skcms_TransferFunction& tf, TF_PQish* pq = nullptr
, TF_HLGish* hlg = nullptr) {
if (tf.g < 0 && (int)tf.g == tf.g) {
// TODO: soundness checks for PQ/HLG like we do for sRGBish?
switch ((int)tf.g) {
case -PQish: if (pq ) { memcpy(pq , &tf.a, sizeof(*pq )); } return PQish;
case -HLGish: if (hlg) { memcpy(hlg, &tf.a, sizeof(*hlg)); } return HLGish;
case -HLGinvish: if (hlg) { memcpy(hlg, &tf.a, sizeof(*hlg)); } return HLGinvish;
}
return Bad;
}
// Basic soundness checks for sRGBish transfer functions.
if (isfinitef_(tf.a + tf.b + tf.c + tf.d + tf.e + tf.f + tf.g)
// a,c,d,g should be non-negative to make any sense.
&& tf.a >= 0
&& tf.c >= 0
&& tf.d >= 0
&& tf.g >= 0
// Raising a negative value to a fractional tf->g produces complex numbers.
&& tf.a * tf.d + tf.b >= 0) {
return sRGBish;
}
return Bad;
}
bool skcms_TransferFunction_isSRGBish(const skcms_TransferFunction* tf) {
return classify(*tf) == sRGBish;
}
bool skcms_TransferFunction_isPQish(const skcms_TransferFunction* tf) {
return classify(*tf) == PQish;
}
bool skcms_TransferFunction_isHLGish(const skcms_TransferFunction* tf) {
return classify(*tf) == HLGish;
}
bool skcms_TransferFunction_makePQish(skcms_TransferFunction* tf,
float A, float B, float C,
float D, float E, float F) {
*tf = { TFKind_marker(PQish), A,B,C,D,E,F };
assert(skcms_TransferFunction_isPQish(tf));
return true;
}
bool skcms_TransferFunction_makeScaledHLGish(skcms_TransferFunction* tf,
float K, float R, float G,
float a, float b, float c) {
*tf = { TFKind_marker(HLGish), R,G, a,b,c, K-1.0f };
assert(skcms_TransferFunction_isHLGish(tf));
return true;
}
float skcms_TransferFunction_eval(const skcms_TransferFunction* tf, float x) {
float sign = x < 0 ? -1.0f : 1.0f;
x *= sign;
TF_PQish pq;
TF_HLGish hlg;
switch (classify(*tf, &pq, &hlg)) {
case Bad: break;
case HLGish: {
const float K = hlg.K_minus_1 + 1.0f;
return K * sign * (x*hlg.R <= 1 ? powf_(x*hlg.R, hlg.G)
: expf_((x-hlg.c)*hlg.a) + hlg.b);
}
// skcms_TransferFunction_invert() inverts R, G, and a for HLGinvish so this math is fast.
case HLGinvish: {
const float K = hlg.K_minus_1 + 1.0f;
x /= K;
return sign * (x <= 1 ? hlg.R * powf_(x, hlg.G)
: hlg.a * logf_(x - hlg.b) + hlg.c);
}
case sRGBish: return sign * (x < tf->d ? tf->c * x + tf->f
: powf_(tf->a * x + tf->b, tf->g) + tf->e);
case PQish: return sign * powf_(fmaxf_(pq.A + pq.B * powf_(x, pq.C), 0)
/ (pq.D + pq.E * powf_(x, pq.C)),
pq.F);
}
return 0;
}
static float eval_curve(const skcms_Curve* curve, float x) {
if (curve->table_entries == 0) {
return skcms_TransferFunction_eval(&curve->parametric, x);
}
float ix = fmaxf_(0, fminf_(x, 1)) * (curve->table_entries - 1);
int lo = (int) ix ,
hi = (int)(float)minus_1_ulp(ix + 1.0f);
float t = ix - (float)lo;
float l, h;
if (curve->table_8) {
l = curve->table_8[lo] * (1/255.0f);
h = curve->table_8[hi] * (1/255.0f);
} else {
uint16_t be_l, be_h;
memcpy(&be_l, curve->table_16 + 2*lo, 2);
memcpy(&be_h, curve->table_16 + 2*hi, 2);
uint16_t le_l = ((be_l << 8) | (be_l >> 8)) & 0xffff;
uint16_t le_h = ((be_h << 8) | (be_h >> 8)) & 0xffff;
l = le_l * (1/65535.0f);
h = le_h * (1/65535.0f);
}
return l + (h-l)*t;
}
float skcms_MaxRoundtripError(const skcms_Curve* curve, const skcms_TransferFunction* inv_tf) {
uint32_t N = curve->table_entries > 256 ? curve->table_entries : 256;
const float dx = 1.0f / (N - 1);
float err = 0;
for (uint32_t i = 0; i < N; i++) {
float x = i * dx,
y = eval_curve(curve, x);
err = fmaxf_(err, fabsf_(x - skcms_TransferFunction_eval(inv_tf, y)));
}
return err;
}
bool skcms_AreApproximateInverses(const skcms_Curve* curve, const skcms_TransferFunction* inv_tf) {
return skcms_MaxRoundtripError(curve, inv_tf) < (1/512.0f);
}
// Additional ICC signature values that are only used internally
enum {
// File signature
skcms_Signature_acsp = 0x61637370,
// Tag signatures
skcms_Signature_rTRC = 0x72545243,
skcms_Signature_gTRC = 0x67545243,
skcms_Signature_bTRC = 0x62545243,
skcms_Signature_kTRC = 0x6B545243,
skcms_Signature_rXYZ = 0x7258595A,
skcms_Signature_gXYZ = 0x6758595A,
skcms_Signature_bXYZ = 0x6258595A,
skcms_Signature_A2B0 = 0x41324230,
skcms_Signature_A2B1 = 0x41324231,
skcms_Signature_mAB = 0x6D414220,
skcms_Signature_CHAD = 0x63686164,
skcms_Signature_WTPT = 0x77747074,
// Type signatures
skcms_Signature_curv = 0x63757276,
skcms_Signature_mft1 = 0x6D667431,
skcms_Signature_mft2 = 0x6D667432,
skcms_Signature_para = 0x70617261,
skcms_Signature_sf32 = 0x73663332,
// XYZ is also a PCS signature, so it's defined in skcms.h
// skcms_Signature_XYZ = 0x58595A20,
};
static uint16_t read_big_u16(const uint8_t* ptr) {
uint16_t be;
memcpy(&be, ptr, sizeof(be));
#if defined(_MSC_VER)
return _byteswap_ushort(be);
#else
return __builtin_bswap16(be);
#endif
}
static uint32_t read_big_u32(const uint8_t* ptr) {
uint32_t be;
memcpy(&be, ptr, sizeof(be));
#if defined(_MSC_VER)
return _byteswap_ulong(be);
#else
return __builtin_bswap32(be);
#endif
}
static int32_t read_big_i32(const uint8_t* ptr) {
return (int32_t)read_big_u32(ptr);
}
static float read_big_fixed(const uint8_t* ptr) {
return read_big_i32(ptr) * (1.0f / 65536.0f);
}
// Maps to an in-memory profile so that fields line up to the locations specified
// in ICC.1:2010, section 7.2
typedef struct {
uint8_t size [ 4];
uint8_t cmm_type [ 4];
uint8_t version [ 4];
uint8_t profile_class [ 4];
uint8_t data_color_space [ 4];
uint8_t pcs [ 4];
uint8_t creation_date_time [12];
uint8_t signature [ 4];
uint8_t platform [ 4];
uint8_t flags [ 4];
uint8_t device_manufacturer [ 4];
uint8_t device_model [ 4];
uint8_t device_attributes [ 8];
uint8_t rendering_intent [ 4];
uint8_t illuminant_X [ 4];
uint8_t illuminant_Y [ 4];
uint8_t illuminant_Z [ 4];
uint8_t creator [ 4];
uint8_t profile_id [16];
uint8_t reserved [28];
uint8_t tag_count [ 4]; // Technically not part of header, but required
} header_Layout;
typedef struct {
uint8_t signature [4];
uint8_t offset [4];
uint8_t size [4];
} tag_Layout;
static const tag_Layout* get_tag_table(const skcms_ICCProfile* profile) {
return (const tag_Layout*)(profile->buffer + SAFE_SIZEOF(header_Layout));
}
// s15Fixed16ArrayType is technically variable sized, holding N values. However, the only valid
// use of the type is for the CHAD tag that stores exactly nine values.
typedef struct {
uint8_t type [ 4];
uint8_t reserved [ 4];
uint8_t values [36];
} sf32_Layout;
bool skcms_GetCHAD(const skcms_ICCProfile* profile, skcms_Matrix3x3* m) {
skcms_ICCTag tag;
if (!skcms_GetTagBySignature(profile, skcms_Signature_CHAD, &tag)) {
return false;
}
if (tag.type != skcms_Signature_sf32 || tag.size < SAFE_SIZEOF(sf32_Layout)) {
return false;
}
const sf32_Layout* sf32Tag = (const sf32_Layout*)tag.buf;
const uint8_t* values = sf32Tag->values;
for (int r = 0; r < 3; ++r)
for (int c = 0; c < 3; ++c, values += 4) {
m->vals[r][c] = read_big_fixed(values);
}
return true;
}
// XYZType is technically variable sized, holding N XYZ triples. However, the only valid uses of
// the type are for tags/data that store exactly one triple.
typedef struct {
uint8_t type [4];
uint8_t reserved [4];
uint8_t X [4];
uint8_t Y [4];
uint8_t Z [4];
} XYZ_Layout;
static bool read_tag_xyz(const skcms_ICCTag* tag, float* x, float* y, float* z) {
if (tag->type != skcms_Signature_XYZ || tag->size < SAFE_SIZEOF(XYZ_Layout)) {
return false;
}
const XYZ_Layout* xyzTag = (const XYZ_Layout*)tag->buf;
*x = read_big_fixed(xyzTag->X);
*y = read_big_fixed(xyzTag->Y);
*z = read_big_fixed(xyzTag->Z);
return true;
}
bool skcms_GetWTPT(const skcms_ICCProfile* profile, float xyz[3]) {
skcms_ICCTag tag;
return skcms_GetTagBySignature(profile, skcms_Signature_WTPT, &tag) &&
read_tag_xyz(&tag, &xyz[0], &xyz[1], &xyz[2]);
}
static bool read_to_XYZD50(const skcms_ICCTag* rXYZ, const skcms_ICCTag* gXYZ,
const skcms_ICCTag* bXYZ, skcms_Matrix3x3* toXYZ) {
return read_tag_xyz(rXYZ, &toXYZ->vals[0][0], &toXYZ->vals[1][0], &toXYZ->vals[2][0]) &&
read_tag_xyz(gXYZ, &toXYZ->vals[0][1], &toXYZ->vals[1][1], &toXYZ->vals[2][1]) &&
read_tag_xyz(bXYZ, &toXYZ->vals[0][2], &toXYZ->vals[1][2], &toXYZ->vals[2][2]);
}
typedef struct {
uint8_t type [4];
uint8_t reserved_a [4];
uint8_t function_type [2];
uint8_t reserved_b [2];
uint8_t variable [1/*variable*/]; // 1, 3, 4, 5, or 7 s15.16, depending on function_type
} para_Layout;
static bool read_curve_para(const uint8_t* buf, uint32_t size,
skcms_Curve* curve, uint32_t* curve_size) {
if (size < SAFE_FIXED_SIZE(para_Layout)) {
return false;
}
const para_Layout* paraTag = (const para_Layout*)buf;
enum { kG = 0, kGAB = 1, kGABC = 2, kGABCD = 3, kGABCDEF = 4 };
uint16_t function_type = read_big_u16(paraTag->function_type);
if (function_type > kGABCDEF) {
return false;
}
static const uint32_t curve_bytes[] = { 4, 12, 16, 20, 28 };
if (size < SAFE_FIXED_SIZE(para_Layout) + curve_bytes[function_type]) {
return false;
}
if (curve_size) {
*curve_size = SAFE_FIXED_SIZE(para_Layout) + curve_bytes[function_type];
}
curve->table_entries = 0;
curve->parametric.a = 1.0f;
curve->parametric.b = 0.0f;
curve->parametric.c = 0.0f;
curve->parametric.d = 0.0f;
curve->parametric.e = 0.0f;
curve->parametric.f = 0.0f;
curve->parametric.g = read_big_fixed(paraTag->variable);
switch (function_type) {
case kGAB:
curve->parametric.a = read_big_fixed(paraTag->variable + 4);
curve->parametric.b = read_big_fixed(paraTag->variable + 8);
if (curve->parametric.a == 0) {
return false;
}
curve->parametric.d = -curve->parametric.b / curve->parametric.a;
break;
case kGABC:
curve->parametric.a = read_big_fixed(paraTag->variable + 4);
curve->parametric.b = read_big_fixed(paraTag->variable + 8);
curve->parametric.e = read_big_fixed(paraTag->variable + 12);
if (curve->parametric.a == 0) {
return false;
}
curve->parametric.d = -curve->parametric.b / curve->parametric.a;
curve->parametric.f = curve->parametric.e;
break;
case kGABCD:
curve->parametric.a = read_big_fixed(paraTag->variable + 4);
curve->parametric.b = read_big_fixed(paraTag->variable + 8);
curve->parametric.c = read_big_fixed(paraTag->variable + 12);
curve->parametric.d = read_big_fixed(paraTag->variable + 16);
break;
case kGABCDEF:
curve->parametric.a = read_big_fixed(paraTag->variable + 4);
curve->parametric.b = read_big_fixed(paraTag->variable + 8);
curve->parametric.c = read_big_fixed(paraTag->variable + 12);
curve->parametric.d = read_big_fixed(paraTag->variable + 16);
curve->parametric.e = read_big_fixed(paraTag->variable + 20);
curve->parametric.f = read_big_fixed(paraTag->variable + 24);
break;
}
return skcms_TransferFunction_isSRGBish(&curve->parametric);
}
typedef struct {
uint8_t type [4];
uint8_t reserved [4];
uint8_t value_count [4];
uint8_t variable [1/*variable*/]; // value_count, 8.8 if 1, uint16 (n*65535) if > 1
} curv_Layout;
static bool read_curve_curv(const uint8_t* buf, uint32_t size,
skcms_Curve* curve, uint32_t* curve_size) {
if (size < SAFE_FIXED_SIZE(curv_Layout)) {
return false;
}
const curv_Layout* curvTag = (const curv_Layout*)buf;
uint32_t value_count = read_big_u32(curvTag->value_count);
if (size < SAFE_FIXED_SIZE(curv_Layout) + value_count * SAFE_SIZEOF(uint16_t)) {
return false;
}
if (curve_size) {
*curve_size = SAFE_FIXED_SIZE(curv_Layout) + value_count * SAFE_SIZEOF(uint16_t);
}
if (value_count < 2) {
curve->table_entries = 0;
curve->parametric.a = 1.0f;
curve->parametric.b = 0.0f;
curve->parametric.c = 0.0f;
curve->parametric.d = 0.0f;
curve->parametric.e = 0.0f;
curve->parametric.f = 0.0f;
if (value_count == 0) {
// Empty tables are a shorthand for an identity curve
curve->parametric.g = 1.0f;
} else {
// Single entry tables are a shorthand for simple gamma
curve->parametric.g = read_big_u16(curvTag->variable) * (1.0f / 256.0f);
}
} else {
curve->table_8 = nullptr;
curve->table_16 = curvTag->variable;
curve->table_entries = value_count;
}
return true;
}
// Parses both curveType and parametricCurveType data. Ensures that at most 'size' bytes are read.
// If curve_size is not nullptr, writes the number of bytes used by the curve in (*curve_size).
static bool read_curve(const uint8_t* buf, uint32_t size,
skcms_Curve* curve, uint32_t* curve_size) {
if (!buf || size < 4 || !curve) {
return false;
}
uint32_t type = read_big_u32(buf);
if (type == skcms_Signature_para) {
return read_curve_para(buf, size, curve, curve_size);
} else if (type == skcms_Signature_curv) {
return read_curve_curv(buf, size, curve, curve_size);
}
return false;
}
// mft1 and mft2 share a large chunk of data
typedef struct {
uint8_t type [ 4];
uint8_t reserved_a [ 4];
uint8_t input_channels [ 1];
uint8_t output_channels [ 1];
uint8_t grid_points [ 1];
uint8_t reserved_b [ 1];
uint8_t matrix [36];
} mft_CommonLayout;
typedef struct {
mft_CommonLayout common [1];
uint8_t variable [1/*variable*/];
} mft1_Layout;
typedef struct {
mft_CommonLayout common [1];
uint8_t input_table_entries [2];
uint8_t output_table_entries [2];
uint8_t variable [1/*variable*/];
} mft2_Layout;
static bool read_mft_common(const mft_CommonLayout* mftTag, skcms_A2B* a2b) {
// MFT matrices are applied before the first set of curves, but must be identity unless the
// input is PCSXYZ. We don't support PCSXYZ profiles, so we ignore this matrix. Note that the
// matrix in skcms_A2B is applied later in the pipe, so supporting this would require another
// field/flag.
a2b->matrix_channels = 0;
a2b->input_channels = mftTag->input_channels[0];
a2b->output_channels = mftTag->output_channels[0];
// We require exactly three (ie XYZ/Lab/RGB) output channels
if (a2b->output_channels != ARRAY_COUNT(a2b->output_curves)) {
return false;
}
// We require at least one, and no more than four (ie CMYK) input channels
if (a2b->input_channels < 1 || a2b->input_channels > ARRAY_COUNT(a2b->input_curves)) {
return false;
}
for (uint32_t i = 0; i < a2b->input_channels; ++i) {
a2b->grid_points[i] = mftTag->grid_points[0];
}
// The grid only makes sense with at least two points along each axis
if (a2b->grid_points[0] < 2) {
return false;
}
return true;
}
static bool init_a2b_tables(const uint8_t* table_base, uint64_t max_tables_len, uint32_t byte_width,
uint32_t input_table_entries, uint32_t output_table_entries,
skcms_A2B* a2b) {
// byte_width is 1 or 2, [input|output]_table_entries are in [2, 4096], so no overflow
uint32_t byte_len_per_input_table = input_table_entries * byte_width;
uint32_t byte_len_per_output_table = output_table_entries * byte_width;
// [input|output]_channels are <= 4, so still no overflow
uint32_t byte_len_all_input_tables = a2b->input_channels * byte_len_per_input_table;
uint32_t byte_len_all_output_tables = a2b->output_channels * byte_len_per_output_table;
uint64_t grid_size = a2b->output_channels * byte_width;
for (uint32_t axis = 0; axis < a2b->input_channels; ++axis) {
grid_size *= a2b->grid_points[axis];
}
if (max_tables_len < byte_len_all_input_tables + grid_size + byte_len_all_output_tables) {
return false;
}
for (uint32_t i = 0; i < a2b->input_channels; ++i) {
a2b->input_curves[i].table_entries = input_table_entries;
if (byte_width == 1) {
a2b->input_curves[i].table_8 = table_base + i * byte_len_per_input_table;
a2b->input_curves[i].table_16 = nullptr;
} else {
a2b->input_curves[i].table_8 = nullptr;
a2b->input_curves[i].table_16 = table_base + i * byte_len_per_input_table;
}
}
if (byte_width == 1) {
a2b->grid_8 = table_base + byte_len_all_input_tables;
a2b->grid_16 = nullptr;
} else {
a2b->grid_8 = nullptr;
a2b->grid_16 = table_base + byte_len_all_input_tables;
}
const uint8_t* output_table_base = table_base + byte_len_all_input_tables + grid_size;
for (uint32_t i = 0; i < a2b->output_channels; ++i) {
a2b->output_curves[i].table_entries = output_table_entries;
if (byte_width == 1) {
a2b->output_curves[i].table_8 = output_table_base + i * byte_len_per_output_table;
a2b->output_curves[i].table_16 = nullptr;
} else {
a2b->output_curves[i].table_8 = nullptr;
a2b->output_curves[i].table_16 = output_table_base + i * byte_len_per_output_table;
}
}
return true;
}
static bool read_tag_mft1(const skcms_ICCTag* tag, skcms_A2B* a2b) {
if (tag->size < SAFE_FIXED_SIZE(mft1_Layout)) {
return false;
}
const mft1_Layout* mftTag = (const mft1_Layout*)tag->buf;
if (!read_mft_common(mftTag->common, a2b)) {
return false;
}
uint32_t input_table_entries = 256;
uint32_t output_table_entries = 256;
return init_a2b_tables(mftTag->variable, tag->size - SAFE_FIXED_SIZE(mft1_Layout), 1,
input_table_entries, output_table_entries, a2b);
}
static bool read_tag_mft2(const skcms_ICCTag* tag, skcms_A2B* a2b) {
if (tag->size < SAFE_FIXED_SIZE(mft2_Layout)) {
return false;
}
const mft2_Layout* mftTag = (const mft2_Layout*)tag->buf;
if (!read_mft_common(mftTag->common, a2b)) {
return false;
}
uint32_t input_table_entries = read_big_u16(mftTag->input_table_entries);
uint32_t output_table_entries = read_big_u16(mftTag->output_table_entries);
// ICC spec mandates that 2 <= table_entries <= 4096
if (input_table_entries < 2 || input_table_entries > 4096 ||
output_table_entries < 2 || output_table_entries > 4096) {
return false;
}
return init_a2b_tables(mftTag->variable, tag->size - SAFE_FIXED_SIZE(mft2_Layout), 2,
input_table_entries, output_table_entries, a2b);
}
static bool read_curves(const uint8_t* buf, uint32_t size, uint32_t curve_offset,
uint32_t num_curves, skcms_Curve* curves) {
for (uint32_t i = 0; i < num_curves; ++i) {
if (curve_offset > size) {
return false;
}
uint32_t curve_bytes;
if (!read_curve(buf + curve_offset, size - curve_offset, &curves[i], &curve_bytes)) {
return false;
}
if (curve_bytes > UINT32_MAX - 3) {
return false;
}
curve_bytes = (curve_bytes + 3) & ~3U;
uint64_t new_offset_64 = (uint64_t)curve_offset + curve_bytes;
curve_offset = (uint32_t)new_offset_64;
if (new_offset_64 != curve_offset) {
return false;
}
}
return true;
}
typedef struct {
uint8_t type [ 4];
uint8_t reserved_a [ 4];
uint8_t input_channels [ 1];
uint8_t output_channels [ 1];
uint8_t reserved_b [ 2];
uint8_t b_curve_offset [ 4];
uint8_t matrix_offset [ 4];
uint8_t m_curve_offset [ 4];
uint8_t clut_offset [ 4];
uint8_t a_curve_offset [ 4];
} mAB_Layout;
typedef struct {
uint8_t grid_points [16];
uint8_t grid_byte_width [ 1];
uint8_t reserved [ 3];
uint8_t variable [1/*variable*/];
} mABCLUT_Layout;
static bool read_tag_mab(const skcms_ICCTag* tag, skcms_A2B* a2b, bool pcs_is_xyz) {
if (tag->size < SAFE_SIZEOF(mAB_Layout)) {
return false;
}
const mAB_Layout* mABTag = (const mAB_Layout*)tag->buf;
a2b->input_channels = mABTag->input_channels[0];
a2b->output_channels = mABTag->output_channels[0];
// We require exactly three (ie XYZ/Lab/RGB) output channels
if (a2b->output_channels != ARRAY_COUNT(a2b->output_curves)) {
return false;
}
// We require no more than four (ie CMYK) input channels
if (a2b->input_channels > ARRAY_COUNT(a2b->input_curves)) {
return false;
}
uint32_t b_curve_offset = read_big_u32(mABTag->b_curve_offset);
uint32_t matrix_offset = read_big_u32(mABTag->matrix_offset);
uint32_t m_curve_offset = read_big_u32(mABTag->m_curve_offset);
uint32_t clut_offset = read_big_u32(mABTag->clut_offset);
uint32_t a_curve_offset = read_big_u32(mABTag->a_curve_offset);
// "B" curves must be present
if (0 == b_curve_offset) {
return false;
}
if (!read_curves(tag->buf, tag->size, b_curve_offset, a2b->output_channels,
a2b->output_curves)) {
return false;
}
// "M" curves and Matrix must be used together
if (0 != m_curve_offset) {
if (0 == matrix_offset) {
return false;
}
a2b->matrix_channels = a2b->output_channels;
if (!read_curves(tag->buf, tag->size, m_curve_offset, a2b->matrix_channels,
a2b->matrix_curves)) {
return false;
}
// Read matrix, which is stored as a row-major 3x3, followed by the fourth column
if (tag->size < matrix_offset + 12 * SAFE_SIZEOF(uint32_t)) {
return false;
}
float encoding_factor = pcs_is_xyz ? 65535 / 32768.0f : 1.0f;
const uint8_t* mtx_buf = tag->buf + matrix_offset;
a2b->matrix.vals[0][0] = encoding_factor * read_big_fixed(mtx_buf + 0);
a2b->matrix.vals[0][1] = encoding_factor * read_big_fixed(mtx_buf + 4);
a2b->matrix.vals[0][2] = encoding_factor * read_big_fixed(mtx_buf + 8);
a2b->matrix.vals[1][0] = encoding_factor * read_big_fixed(mtx_buf + 12);
a2b->matrix.vals[1][1] = encoding_factor * read_big_fixed(mtx_buf + 16);
a2b->matrix.vals[1][2] = encoding_factor * read_big_fixed(mtx_buf + 20);
a2b->matrix.vals[2][0] = encoding_factor * read_big_fixed(mtx_buf + 24);
a2b->matrix.vals[2][1] = encoding_factor * read_big_fixed(mtx_buf + 28);
a2b->matrix.vals[2][2] = encoding_factor * read_big_fixed(mtx_buf + 32);
a2b->matrix.vals[0][3] = encoding_factor * read_big_fixed(mtx_buf + 36);
a2b->matrix.vals[1][3] = encoding_factor * read_big_fixed(mtx_buf + 40);
a2b->matrix.vals[2][3] = encoding_factor * read_big_fixed(mtx_buf + 44);
} else {
if (0 != matrix_offset) {
return false;
}
a2b->matrix_channels = 0;
}
// "A" curves and CLUT must be used together
if (0 != a_curve_offset) {
if (0 == clut_offset) {
return false;
}
if (!read_curves(tag->buf, tag->size, a_curve_offset, a2b->input_channels,
a2b->input_curves)) {
return false;
}
if (tag->size < clut_offset + SAFE_FIXED_SIZE(mABCLUT_Layout)) {
return false;
}
const mABCLUT_Layout* clut = (const mABCLUT_Layout*)(tag->buf + clut_offset);
if (clut->grid_byte_width[0] == 1) {
a2b->grid_8 = clut->variable;
a2b->grid_16 = nullptr;
} else if (clut->grid_byte_width[0] == 2) {
a2b->grid_8 = nullptr;
a2b->grid_16 = clut->variable;
} else {
return false;
}
uint64_t grid_size = a2b->output_channels * clut->grid_byte_width[0];
for (uint32_t i = 0; i < a2b->input_channels; ++i) {
a2b->grid_points[i] = clut->grid_points[i];
// The grid only makes sense with at least two points along each axis
if (a2b->grid_points[i] < 2) {
return false;
}
grid_size *= a2b->grid_points[i];
}
if (tag->size < clut_offset + SAFE_FIXED_SIZE(mABCLUT_Layout) + grid_size) {
return false;
}
} else {
if (0 != clut_offset) {
return false;
}
// If there is no CLUT, the number of input and output channels must match
if (a2b->input_channels != a2b->output_channels) {
return false;
}
// Zero out the number of input channels to signal that we're skipping this stage
a2b->input_channels = 0;
}
return true;
}
// If you pass f, we'll fit a possibly-non-zero value for *f.
// If you pass nullptr, we'll assume you want *f to be treated as zero.
static int fit_linear(const skcms_Curve* curve, int N, float tol,
float* c, float* d, float* f = nullptr) {
assert(N > 1);
// We iteratively fit the first points to the TF's linear piece.
// We want the cx + f line to pass through the first and last points we fit exactly.
//
// As we walk along the points we find the minimum and maximum slope of the line before the
// error would exceed our tolerance. We stop when the range [slope_min, slope_max] becomes
// emtpy, when we definitely can't add any more points.
//
// Some points' error intervals may intersect the running interval but not lie fully
// within it. So we keep track of the last point we saw that is a valid end point candidate,
// and once the search is done, back up to build the line through *that* point.
const float dx = 1.0f / (N - 1);
int lin_points = 1;
float f_zero = 0.0f;
if (f) {
*f = eval_curve(curve, 0);
} else {
f = &f_zero;
}
float slope_min = -INFINITY_;
float slope_max = +INFINITY_;
for (int i = 1; i < N; ++i) {
float x = i * dx;
float y = eval_curve(curve, x);
float slope_max_i = (y + tol - *f) / x,
slope_min_i = (y - tol - *f) / x;
if (slope_max_i < slope_min || slope_max < slope_min_i) {
// Slope intervals would no longer overlap.
break;
}
slope_max = fminf_(slope_max, slope_max_i);
slope_min = fmaxf_(slope_min, slope_min_i);
float cur_slope = (y - *f) / x;
if (slope_min <= cur_slope && cur_slope <= slope_max) {
lin_points = i + 1;
*c = cur_slope;
}
}
// Set D to the last point that met our tolerance.
*d = (lin_points - 1) * dx;
return lin_points;
}
static bool read_a2b(const skcms_ICCTag* tag, skcms_A2B* a2b, bool pcs_is_xyz) {
bool ok = false;
if (tag->type == skcms_Signature_mft1) {
ok = read_tag_mft1(tag, a2b);
} else if (tag->type == skcms_Signature_mft2) {
ok = read_tag_mft2(tag, a2b);
} else if (tag->type == skcms_Signature_mAB) {
ok = read_tag_mab(tag, a2b, pcs_is_xyz);
}
if (!ok) {
return false;
}
// Detect and canonicalize identity tables.
skcms_Curve* curves[] = {
a2b->input_channels > 0 ? a2b->input_curves + 0 : nullptr,
a2b->input_channels > 1 ? a2b->input_curves + 1 : nullptr,
a2b->input_channels > 2 ? a2b->input_curves + 2 : nullptr,
a2b->input_channels > 3 ? a2b->input_curves + 3 : nullptr,
a2b->matrix_channels > 0 ? a2b->matrix_curves + 0 : nullptr,
a2b->matrix_channels > 1 ? a2b->matrix_curves + 1 : nullptr,
a2b->matrix_channels > 2 ? a2b->matrix_curves + 2 : nullptr,
a2b->output_channels > 0 ? a2b->output_curves + 0 : nullptr,
a2b->output_channels > 1 ? a2b->output_curves + 1 : nullptr,
a2b->output_channels > 2 ? a2b->output_curves + 2 : nullptr,
};
for (int i = 0; i < ARRAY_COUNT(curves); i++) {
skcms_Curve* curve = curves[i];
if (curve && curve->table_entries && curve->table_entries <= (uint32_t)INT_MAX) {
int N = (int)curve->table_entries;
float c = 0.0f, d = 0.0f, f = 0.0f;
if (N == fit_linear(curve, N, 1.0f/(2*N), &c,&d,&f)
&& c == 1.0f
&& f == 0.0f) {
curve->table_entries = 0;
curve->table_8 = nullptr;
curve->table_16 = nullptr;
curve->parametric = skcms_TransferFunction{1,1,0,0,0,0,0};
}
}
}
return true;
}
void skcms_GetTagByIndex(const skcms_ICCProfile* profile, uint32_t idx, skcms_ICCTag* tag) {
if (!profile || !profile->buffer || !tag) { return; }
if (idx > profile->tag_count) { return; }
const tag_Layout* tags = get_tag_table(profile);
tag->signature = read_big_u32(tags[idx].signature);
tag->size = read_big_u32(tags[idx].size);
tag->buf = read_big_u32(tags[idx].offset) + profile->buffer;
tag->type = read_big_u32(tag->buf);
}
bool skcms_GetTagBySignature(const skcms_ICCProfile* profile, uint32_t sig, skcms_ICCTag* tag) {
if (!profile || !profile->buffer || !tag) { return false; }
const tag_Layout* tags = get_tag_table(profile);
for (uint32_t i = 0; i < profile->tag_count; ++i) {
if (read_big_u32(tags[i].signature) == sig) {
tag->signature = sig;
tag->size = read_big_u32(tags[i].size);
tag->buf = read_big_u32(tags[i].offset) + profile->buffer;
tag->type = read_big_u32(tag->buf);
return true;
}
}
return false;
}
static bool usable_as_src(const skcms_ICCProfile* profile) {
return profile->has_A2B
|| (profile->has_trc && profile->has_toXYZD50);
}
bool skcms_ParseWithA2BPriority(const void* buf, size_t len,
const int priority[], const int priorities,
skcms_ICCProfile* profile) {
assert(SAFE_SIZEOF(header_Layout) == 132);
if (!profile) {
return false;
}
memset(profile, 0, SAFE_SIZEOF(*profile));
if (len < SAFE_SIZEOF(header_Layout)) {
return false;
}
// Byte-swap all header fields
const header_Layout* header = (const header_Layout*)buf;
profile->buffer = (const uint8_t*)buf;
profile->size = read_big_u32(header->size);
uint32_t version = read_big_u32(header->version);
profile->data_color_space = read_big_u32(header->data_color_space);
profile->pcs = read_big_u32(header->pcs);
uint32_t signature = read_big_u32(header->signature);
float illuminant_X = read_big_fixed(header->illuminant_X);
float illuminant_Y = read_big_fixed(header->illuminant_Y);
float illuminant_Z = read_big_fixed(header->illuminant_Z);
profile->tag_count = read_big_u32(header->tag_count);
// Validate signature, size (smaller than buffer, large enough to hold tag table),
// and major version
uint64_t tag_table_size = profile->tag_count * SAFE_SIZEOF(tag_Layout);
if (signature != skcms_Signature_acsp ||
profile->size > len ||
profile->size < SAFE_SIZEOF(header_Layout) + tag_table_size ||
(version >> 24) > 4) {
return false;
}
// Validate that illuminant is D50 white
if (fabsf_(illuminant_X - 0.9642f) > 0.0100f ||
fabsf_(illuminant_Y - 1.0000f) > 0.0100f ||
fabsf_(illuminant_Z - 0.8249f) > 0.0100f) {
return false;
}
// Validate that all tag entries have sane offset + size
const tag_Layout* tags = get_tag_table(profile);
for (uint32_t i = 0; i < profile->tag_count; ++i) {
uint32_t tag_offset = read_big_u32(tags[i].offset);
uint32_t tag_size = read_big_u32(tags[i].size);
uint64_t tag_end = (uint64_t)tag_offset + (uint64_t)tag_size;
if (tag_size < 4 || tag_end > profile->size) {
return false;
}
}
if (profile->pcs != skcms_Signature_XYZ && profile->pcs != skcms_Signature_Lab) {
return false;
}
bool pcs_is_xyz = profile->pcs == skcms_Signature_XYZ;
// Pre-parse commonly used tags.
skcms_ICCTag kTRC;
if (profile->data_color_space == skcms_Signature_Gray &&
skcms_GetTagBySignature(profile, skcms_Signature_kTRC, &kTRC)) {
if (!read_curve(kTRC.buf, kTRC.size, &profile->trc[0], nullptr)) {
// Malformed tag
return false;
}
profile->trc[1] = profile->trc[0];
profile->trc[2] = profile->trc[0];
profile->has_trc = true;
if (pcs_is_xyz) {
profile->toXYZD50.vals[0][0] = illuminant_X;
profile->toXYZD50.vals[1][1] = illuminant_Y;
profile->toXYZD50.vals[2][2] = illuminant_Z;
profile->has_toXYZD50 = true;
}
} else {
skcms_ICCTag rTRC, gTRC, bTRC;
if (skcms_GetTagBySignature(profile, skcms_Signature_rTRC, &rTRC) &&
skcms_GetTagBySignature(profile, skcms_Signature_gTRC, &gTRC) &&
skcms_GetTagBySignature(profile, skcms_Signature_bTRC, &bTRC)) {
if (!read_curve(rTRC.buf, rTRC.size, &profile->trc[0], nullptr) ||
!read_curve(gTRC.buf, gTRC.size, &profile->trc[1], nullptr) ||
!read_curve(bTRC.buf, bTRC.size, &profile->trc[2], nullptr)) {
// Malformed TRC tags
return false;
}
profile->has_trc = true;
}
skcms_ICCTag rXYZ, gXYZ, bXYZ;
if (skcms_GetTagBySignature(profile, skcms_Signature_rXYZ, &rXYZ) &&
skcms_GetTagBySignature(profile, skcms_Signature_gXYZ, &gXYZ) &&
skcms_GetTagBySignature(profile, skcms_Signature_bXYZ, &bXYZ)) {
if (!read_to_XYZD50(&rXYZ, &gXYZ, &bXYZ, &profile->toXYZD50)) {
// Malformed XYZ tags
return false;
}
profile->has_toXYZD50 = true;
}
}
skcms_ICCTag a2b_tag;
for (int i = 0; i < priorities; i++) {
// enum { perceptual, relative_colormetric, saturation }
if (priority[i] < 0 || priority[i] > 2) {
return false;
}
uint32_t sig = skcms_Signature_A2B0 + static_cast<uint32_t>(priority[i]);
if (skcms_GetTagBySignature(profile, sig, &a2b_tag)) {
if (!read_a2b(&a2b_tag, &profile->A2B, pcs_is_xyz)) {
// Malformed A2B tag
return false;
}
profile->has_A2B = true;
break;
}
}
return usable_as_src(profile);
}
const skcms_ICCProfile* skcms_sRGB_profile() {
static const skcms_ICCProfile sRGB_profile = {
nullptr, // buffer, moot here
0, // size, moot here
skcms_Signature_RGB, // data_color_space
skcms_Signature_XYZ, // pcs
0, // tag count, moot here
// We choose to represent sRGB with its canonical transfer function,
// and with its canonical XYZD50 gamut matrix.
true, // has_trc, followed by the 3 trc curves
{
{{0, {2.4f, (float)(1/1.055), (float)(0.055/1.055), (float)(1/12.92), 0.04045f, 0, 0}}},
{{0, {2.4f, (float)(1/1.055), (float)(0.055/1.055), (float)(1/12.92), 0.04045f, 0, 0}}},
{{0, {2.4f, (float)(1/1.055), (float)(0.055/1.055), (float)(1/12.92), 0.04045f, 0, 0}}},
},
true, // has_toXYZD50, followed by 3x3 toXYZD50 matrix
{{
{ 0.436065674f, 0.385147095f, 0.143066406f },
{ 0.222488403f, 0.716873169f, 0.060607910f },
{ 0.013916016f, 0.097076416f, 0.714096069f },
}},
false, // has_A2B, followed by a2b itself which we don't care about.
{
0,
{
{{0, {0,0, 0,0,0,0,0}}},
{{0, {0,0, 0,0,0,0,0}}},
{{0, {0,0, 0,0,0,0,0}}},
{{0, {0,0, 0,0,0,0,0}}},
},
{0,0,0,0},
nullptr,
nullptr,
0,
{
{{0, {0,0, 0,0,0,0,0}}},
{{0, {0,0, 0,0,0,0,0}}},
{{0, {0,0, 0,0,0,0,0}}},
},
{{
{ 0,0,0,0 },
{ 0,0,0,0 },
{ 0,0,0,0 },
}},
0,
{
{{0, {0,0, 0,0,0,0,0}}},
{{0, {0,0, 0,0,0,0,0}}},
{{0, {0,0, 0,0,0,0,0}}},
},
},
};
return &sRGB_profile;
}
const skcms_ICCProfile* skcms_XYZD50_profile() {
// Just like sRGB above, but with identity transfer functions and toXYZD50 matrix.
static const skcms_ICCProfile XYZD50_profile = {
nullptr, // buffer, moot here
0, // size, moot here
skcms_Signature_RGB, // data_color_space
skcms_Signature_XYZ, // pcs
0, // tag count, moot here
true, // has_trc, followed by the 3 trc curves
{
{{0, {1,1, 0,0,0,0,0}}},
{{0, {1,1, 0,0,0,0,0}}},
{{0, {1,1, 0,0,0,0,0}}},
},
true, // has_toXYZD50, followed by 3x3 toXYZD50 matrix
{{
{ 1,0,0 },
{ 0,1,0 },
{ 0,0,1 },
}},
false, // has_A2B, followed by a2b itself which we don't care about.
{
0,
{
{{0, {0,0, 0,0,0,0,0}}},
{{0, {0,0, 0,0,0,0,0}}},
{{0, {0,0, 0,0,0,0,0}}},
{{0, {0,0, 0,0,0,0,0}}},
},
{0,0,0,0},
nullptr,
nullptr,
0,
{
{{0, {0,0, 0,0,0,0,0}}},
{{0, {0,0, 0,0,0,0,0}}},
{{0, {0,0, 0,0,0,0,0}}},
},
{{
{ 0,0,0,0 },
{ 0,0,0,0 },
{ 0,0,0,0 },
}},
0,
{
{{0, {0,0, 0,0,0,0,0}}},
{{0, {0,0, 0,0,0,0,0}}},
{{0, {0,0, 0,0,0,0,0}}},
},
},
};
return &XYZD50_profile;
}
const skcms_TransferFunction* skcms_sRGB_TransferFunction() {
return &skcms_sRGB_profile()->trc[0].parametric;
}
const skcms_TransferFunction* skcms_sRGB_Inverse_TransferFunction() {
static const skcms_TransferFunction sRGB_inv =
{0.416666657f, 1.137283325f, -0.0f, 12.920000076f, 0.003130805f, -0.054969788f, -0.0f};
return &sRGB_inv;
}
const skcms_TransferFunction* skcms_Identity_TransferFunction() {
static const skcms_TransferFunction identity = {1,1,0,0,0,0,0};
return &identity;
}
const uint8_t skcms_252_random_bytes[] = {
8, 179, 128, 204, 253, 38, 134, 184, 68, 102, 32, 138, 99, 39, 169, 215,
119, 26, 3, 223, 95, 239, 52, 132, 114, 74, 81, 234, 97, 116, 244, 205, 30,
154, 173, 12, 51, 159, 122, 153, 61, 226, 236, 178, 229, 55, 181, 220, 191,
194, 160, 126, 168, 82, 131, 18, 180, 245, 163, 22, 246, 69, 235, 252, 57,
108, 14, 6, 152, 240, 255, 171, 242, 20, 227, 177, 238, 96, 85, 16, 211,
70, 200, 149, 155, 146, 127, 145, 100, 151, 109, 19, 165, 208, 195, 164,
137, 254, 182, 248, 64, 201, 45, 209, 5, 147, 207, 210, 113, 162, 83, 225,
9, 31, 15, 231, 115, 37, 58, 53, 24, 49, 197, 56, 120, 172, 48, 21, 214,
129, 111, 11, 50, 187, 196, 34, 60, 103, 71, 144, 47, 203, 77, 80, 232,
140, 222, 250, 206, 166, 247, 139, 249, 221, 72, 106, 27, 199, 117, 54,
219, 135, 118, 40, 79, 41, 251, 46, 93, 212, 92, 233, 148, 28, 121, 63,
123, 158, 105, 59, 29, 42, 143, 23, 0, 107, 176, 87, 104, 183, 156, 193,
189, 90, 188, 65, 190, 17, 198, 7, 186, 161, 1, 124, 78, 125, 170, 133,
174, 218, 67, 157, 75, 101, 89, 217, 62, 33, 141, 228, 25, 35, 91, 230, 4,
2, 13, 73, 86, 167, 237, 84, 243, 44, 185, 66, 130, 110, 150, 142, 216, 88,
112, 36, 224, 136, 202, 76, 94, 98, 175, 213
};
bool skcms_ApproximatelyEqualProfiles(const skcms_ICCProfile* A, const skcms_ICCProfile* B) {
// Test for exactly equal profiles first.
if (A == B || 0 == memcmp(A,B, sizeof(skcms_ICCProfile))) {
return true;
}
// For now this is the essentially the same strategy we use in test_only.c
// for our skcms_Transform() smoke tests:
// 1) transform A to XYZD50
// 2) transform B to XYZD50
// 3) return true if they're similar enough
// Our current criterion in 3) is maximum 1 bit error per XYZD50 byte.
// skcms_252_random_bytes are 252 of a random shuffle of all possible bytes.
// 252 is evenly divisible by 3 and 4. Only 192, 10, 241, and 43 are missing.
// We want to allow otherwise equivalent profiles tagged as grayscale and RGB
// to be treated as equal. But CMYK profiles are a totally different ballgame.
const auto CMYK = skcms_Signature_CMYK;
if ((A->data_color_space == CMYK) != (B->data_color_space == CMYK)) {
return false;
}
// Interpret as RGB_888 if data color space is RGB or GRAY, RGBA_8888 if CMYK.
// TODO: working with RGBA_8888 either way is probably fastest.
skcms_PixelFormat fmt = skcms_PixelFormat_RGB_888;
size_t npixels = 84;
if (A->data_color_space == skcms_Signature_CMYK) {
fmt = skcms_PixelFormat_RGBA_8888;
npixels = 63;
}
// TODO: if A or B is a known profile (skcms_sRGB_profile, skcms_XYZD50_profile),
// use pre-canned results and skip that skcms_Transform() call?
uint8_t dstA[252],
dstB[252];
if (!skcms_Transform(
skcms_252_random_bytes, fmt, skcms_AlphaFormat_Unpremul, A,
dstA, skcms_PixelFormat_RGB_888, skcms_AlphaFormat_Unpremul, skcms_XYZD50_profile(),
npixels)) {
return false;
}
if (!skcms_Transform(
skcms_252_random_bytes, fmt, skcms_AlphaFormat_Unpremul, B,
dstB, skcms_PixelFormat_RGB_888, skcms_AlphaFormat_Unpremul, skcms_XYZD50_profile(),
npixels)) {
return false;
}
// TODO: make sure this final check has reasonable codegen.
for (size_t i = 0; i < 252; i++) {
if (abs((int)dstA[i] - (int)dstB[i]) > 1) {
return false;
}
}
return true;
}
bool skcms_TRCs_AreApproximateInverse(const skcms_ICCProfile* profile,
const skcms_TransferFunction* inv_tf) {
if (!profile || !profile->has_trc) {
return false;
}
return skcms_AreApproximateInverses(&profile->trc[0], inv_tf) &&
skcms_AreApproximateInverses(&profile->trc[1], inv_tf) &&
skcms_AreApproximateInverses(&profile->trc[2], inv_tf);
}
static bool is_zero_to_one(float x) {
return 0 <= x && x <= 1;
}
typedef struct { float vals[3]; } skcms_Vector3;
static skcms_Vector3 mv_mul(const skcms_Matrix3x3* m, const skcms_Vector3* v) {
skcms_Vector3 dst = {{0,0,0}};
for (int row = 0; row < 3; ++row) {
dst.vals[row] = m->vals[row][0] * v->vals[0]
+ m->vals[row][1] * v->vals[1]
+ m->vals[row][2] * v->vals[2];
}
return dst;
}
bool skcms_AdaptToXYZD50(float wx, float wy,
skcms_Matrix3x3* toXYZD50) {
if (!is_zero_to_one(wx) || !is_zero_to_one(wy) ||
!toXYZD50) {
return false;
}
// Assumes that Y is 1.0f.
skcms_Vector3 wXYZ = { { wx / wy, 1, (1 - wx - wy) / wy } };
// Now convert toXYZ matrix to toXYZD50.
skcms_Vector3 wXYZD50 = { { 0.96422f, 1.0f, 0.82521f } };
// Calculate the chromatic adaptation matrix. We will use the Bradford method, thus
// the matrices below. The Bradford method is used by Adobe and is widely considered
// to be the best.
skcms_Matrix3x3 xyz_to_lms = {{
{ 0.8951f, 0.2664f, -0.1614f },
{ -0.7502f, 1.7135f, 0.0367f },
{ 0.0389f, -0.0685f, 1.0296f },
}};
skcms_Matrix3x3 lms_to_xyz = {{
{ 0.9869929f, -0.1470543f, 0.1599627f },
{ 0.4323053f, 0.5183603f, 0.0492912f },
{ -0.0085287f, 0.0400428f, 0.9684867f },
}};
skcms_Vector3 srcCone = mv_mul(&xyz_to_lms, &wXYZ);
skcms_Vector3 dstCone = mv_mul(&xyz_to_lms, &wXYZD50);
*toXYZD50 = {{
{ dstCone.vals[0] / srcCone.vals[0], 0, 0 },
{ 0, dstCone.vals[1] / srcCone.vals[1], 0 },
{ 0, 0, dstCone.vals[2] / srcCone.vals[2] },
}};
*toXYZD50 = skcms_Matrix3x3_concat(toXYZD50, &xyz_to_lms);
*toXYZD50 = skcms_Matrix3x3_concat(&lms_to_xyz, toXYZD50);
return true;
}
bool skcms_PrimariesToXYZD50(float rx, float ry,
float gx, float gy,
float bx, float by,
float wx, float wy,
skcms_Matrix3x3* toXYZD50) {
if (!is_zero_to_one(rx) || !is_zero_to_one(ry) ||
!is_zero_to_one(gx) || !is_zero_to_one(gy) ||
!is_zero_to_one(bx) || !is_zero_to_one(by) ||
!is_zero_to_one(wx) || !is_zero_to_one(wy) ||
!toXYZD50) {
return false;
}
// First, we need to convert xy values (primaries) to XYZ.
skcms_Matrix3x3 primaries = {{
{ rx, gx, bx },
{ ry, gy, by },
{ 1 - rx - ry, 1 - gx - gy, 1 - bx - by },
}};
skcms_Matrix3x3 primaries_inv;
if (!skcms_Matrix3x3_invert(&primaries, &primaries_inv)) {
return false;
}
// Assumes that Y is 1.0f.
skcms_Vector3 wXYZ = { { wx / wy, 1, (1 - wx - wy) / wy } };
skcms_Vector3 XYZ = mv_mul(&primaries_inv, &wXYZ);
skcms_Matrix3x3 toXYZ = {{
{ XYZ.vals[0], 0, 0 },
{ 0, XYZ.vals[1], 0 },
{ 0, 0, XYZ.vals[2] },
}};
toXYZ = skcms_Matrix3x3_concat(&primaries, &toXYZ);
skcms_Matrix3x3 DXtoD50;
if (!skcms_AdaptToXYZD50(wx, wy, &DXtoD50)) {
return false;
}
*toXYZD50 = skcms_Matrix3x3_concat(&DXtoD50, &toXYZ);
return true;
}
bool skcms_Matrix3x3_invert(const skcms_Matrix3x3* src, skcms_Matrix3x3* dst) {
double a00 = src->vals[0][0],
a01 = src->vals[1][0],
a02 = src->vals[2][0],
a10 = src->vals[0][1],
a11 = src->vals[1][1],
a12 = src->vals[2][1],
a20 = src->vals[0][2],
a21 = src->vals[1][2],
a22 = src->vals[2][2];
double b0 = a00*a11 - a01*a10,
b1 = a00*a12 - a02*a10,
b2 = a01*a12 - a02*a11,
b3 = a20,
b4 = a21,
b5 = a22;
double determinant = b0*b5
- b1*b4
+ b2*b3;
if (determinant == 0) {
return false;
}
double invdet = 1.0 / determinant;
if (invdet > +FLT_MAX || invdet < -FLT_MAX || !isfinitef_((float)invdet)) {
return false;
}
b0 *= invdet;
b1 *= invdet;
b2 *= invdet;
b3 *= invdet;
b4 *= invdet;
b5 *= invdet;
dst->vals[0][0] = (float)( a11*b5 - a12*b4 );
dst->vals[1][0] = (float)( a02*b4 - a01*b5 );
dst->vals[2][0] = (float)( + b2 );
dst->vals[0][1] = (float)( a12*b3 - a10*b5 );
dst->vals[1][1] = (float)( a00*b5 - a02*b3 );
dst->vals[2][1] = (float)( - b1 );
dst->vals[0][2] = (float)( a10*b4 - a11*b3 );
dst->vals[1][2] = (float)( a01*b3 - a00*b4 );
dst->vals[2][2] = (float)( + b0 );
for (int r = 0; r < 3; ++r)
for (int c = 0; c < 3; ++c) {
if (!isfinitef_(dst->vals[r][c])) {
return false;
}
}
return true;
}
skcms_Matrix3x3 skcms_Matrix3x3_concat(const skcms_Matrix3x3* A, const skcms_Matrix3x3* B) {
skcms_Matrix3x3 m = { { { 0,0,0 },{ 0,0,0 },{ 0,0,0 } } };
for (int r = 0; r < 3; r++)
for (int c = 0; c < 3; c++) {
m.vals[r][c] = A->vals[r][0] * B->vals[0][c]
+ A->vals[r][1] * B->vals[1][c]
+ A->vals[r][2] * B->vals[2][c];
}
return m;
}
#if defined(__clang__)
[[clang::no_sanitize("float-divide-by-zero")]] // Checked for by classify() on the way out.
#endif
bool skcms_TransferFunction_invert(const skcms_TransferFunction* src, skcms_TransferFunction* dst) {
TF_PQish pq;
TF_HLGish hlg;
switch (classify(*src, &pq, &hlg)) {
case Bad: return false;
case sRGBish: break; // handled below
case PQish:
*dst = { TFKind_marker(PQish), -pq.A, pq.D, 1.0f/pq.F
, pq.B, -pq.E, 1.0f/pq.C};
return true;
case HLGish:
*dst = { TFKind_marker(HLGinvish), 1.0f/hlg.R, 1.0f/hlg.G
, 1.0f/hlg.a, hlg.b, hlg.c
, hlg.K_minus_1 };
return true;
case HLGinvish:
*dst = { TFKind_marker(HLGish), 1.0f/hlg.R, 1.0f/hlg.G
, 1.0f/hlg.a, hlg.b, hlg.c
, hlg.K_minus_1 };
return true;
}
assert (classify(*src) == sRGBish);
// We're inverting this function, solving for x in terms of y.
// y = (cx + f) x < d
// (ax + b)^g + e x ≥ d
// The inverse of this function can be expressed in the same piecewise form.
skcms_TransferFunction inv = {0,0,0,0,0,0,0};
// We'll start by finding the new threshold inv.d.
// In principle we should be able to find that by solving for y at x=d from either side.
// (If those two d values aren't the same, it's a discontinuous transfer function.)
float d_l = src->c * src->d + src->f,
d_r = powf_(src->a * src->d + src->b, src->g) + src->e;
if (fabsf_(d_l - d_r) > 1/512.0f) {
return false;
}
inv.d = d_l; // TODO(mtklein): better in practice to choose d_r?
// When d=0, the linear section collapses to a point. We leave c,d,f all zero in that case.
if (inv.d > 0) {
// Inverting the linear section is pretty straightfoward:
// y = cx + f
// y - f = cx
// (1/c)y - f/c = x
inv.c = 1.0f/src->c;
inv.f = -src->f/src->c;
}
// The interesting part is inverting the nonlinear section:
// y = (ax + b)^g + e.
// y - e = (ax + b)^g
// (y - e)^1/g = ax + b
// (y - e)^1/g - b = ax
// (1/a)(y - e)^1/g - b/a = x
//
// To make that fit our form, we need to move the (1/a) term inside the exponentiation:
// let k = (1/a)^g
// (1/a)( y - e)^1/g - b/a = x
// (ky - ke)^1/g - b/a = x
float k = powf_(src->a, -src->g); // (1/a)^g == a^-g
inv.g = 1.0f / src->g;
inv.a = k;
inv.b = -k * src->e;
inv.e = -src->b / src->a;
// We need to enforce the same constraints here that we do when fitting a curve,
// a >= 0 and ad+b >= 0. These constraints are checked by classify(), so they're true
// of the source function if we're here.
// Just like when fitting the curve, there's really no way to rescue a < 0.
if (inv.a < 0) {
return false;
}
// On the other hand we can rescue an ad+b that's gone slightly negative here.
if (inv.a * inv.d + inv.b < 0) {
inv.b = -inv.a * inv.d;
}
// That should usually make classify(inv) == sRGBish true, but there are a couple situations
// where we might still fail here, like non-finite parameter values.
if (classify(inv) != sRGBish) {
return false;
}
assert (inv.a >= 0);
assert (inv.a * inv.d + inv.b >= 0);
// Now in principle we're done.
// But to preserve the valuable invariant inv(src(1.0f)) == 1.0f, we'll tweak
// e or f of the inverse, depending on which segment contains src(1.0f).
float s = skcms_TransferFunction_eval(src, 1.0f);
if (!isfinitef_(s)) {
return false;
}
float sign = s < 0 ? -1.0f : 1.0f;
s *= sign;
if (s < inv.d) {
inv.f = 1.0f - sign * inv.c * s;
} else {
inv.e = 1.0f - sign * powf_(inv.a * s + inv.b, inv.g);
}
*dst = inv;
return classify(*dst) == sRGBish;
}
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ //
// From here below we're approximating an skcms_Curve with an skcms_TransferFunction{g,a,b,c,d,e,f}:
//
// tf(x) = cx + f x < d
// tf(x) = (ax + b)^g + e x ≥ d
//
// When fitting, we add the additional constraint that both pieces meet at d:
//
// cd + f = (ad + b)^g + e
//
// Solving for e and folding it through gives an alternate formulation of the non-linear piece:
//
// tf(x) = cx + f x < d
// tf(x) = (ax + b)^g - (ad + b)^g + cd + f x ≥ d
//
// Our overall strategy is then:
// For a couple tolerances,
// - fit_linear(): fit c,d,f iteratively to as many points as our tolerance allows
// - invert c,d,f
// - fit_nonlinear(): fit g,a,b using Gauss-Newton given those inverted c,d,f
// (and by constraint, inverted e) to the inverse of the table.
// Return the parameters with least maximum error.
//
// To run Gauss-Newton to find g,a,b, we'll also need the gradient of the residuals
// of round-trip f_inv(x), the inverse of the non-linear piece of f(x).
//
// let y = Table(x)
// r(x) = x - f_inv(y)
//
// ∂r/∂g = ln(ay + b)*(ay + b)^g
// - ln(ad + b)*(ad + b)^g
// ∂r/∂a = yg(ay + b)^(g-1)
// - dg(ad + b)^(g-1)
// ∂r/∂b = g(ay + b)^(g-1)
// - g(ad + b)^(g-1)
// Return the residual of roundtripping skcms_Curve(x) through f_inv(y) with parameters P,
// and fill out the gradient of the residual into dfdP.
static float rg_nonlinear(float x,
const skcms_Curve* curve,
const skcms_TransferFunction* tf,
float dfdP[3]) {
const float y = eval_curve(curve, x);
const float g = tf->g, a = tf->a, b = tf->b,
c = tf->c, d = tf->d, f = tf->f;
const float Y = fmaxf_(a*y + b, 0.0f),
D = a*d + b;
assert (D >= 0);
// The gradient.
dfdP[0] = logf_(Y)*powf_(Y, g)
- logf_(D)*powf_(D, g);
dfdP[1] = y*g*powf_(Y, g-1)
- d*g*powf_(D, g-1);
dfdP[2] = g*powf_(Y, g-1)
- g*powf_(D, g-1);
// The residual.
const float f_inv = powf_(Y, g)
- powf_(D, g)
+ c*d + f;
return x - f_inv;
}
static bool gauss_newton_step(const skcms_Curve* curve,
skcms_TransferFunction* tf,
float x0, float dx, int N) {
// We'll sample x from the range [x0,x1] (both inclusive) N times with even spacing.
//
// Let P = [ tf->g, tf->a, tf->b ] (the three terms that we're adjusting).
//
// We want to do P' = P + (Jf^T Jf)^-1 Jf^T r(P),
// where r(P) is the residual vector
// and Jf is the Jacobian matrix of f(), ∂r/∂P.
//
// Let's review the shape of each of these expressions:
// r(P) is [N x 1], a column vector with one entry per value of x tested
// Jf is [N x 3], a matrix with an entry for each (x,P) pair
// Jf^T is [3 x N], the transpose of Jf
//
// Jf^T Jf is [3 x N] * [N x 3] == [3 x 3], a 3x3 matrix,
// and so is its inverse (Jf^T Jf)^-1
// Jf^T r(P) is [3 x N] * [N x 1] == [3 x 1], a column vector with the same shape as P
//
// Our implementation strategy to get to the final ∆P is
// 1) evaluate Jf^T Jf, call that lhs
// 2) evaluate Jf^T r(P), call that rhs
// 3) invert lhs
// 4) multiply inverse lhs by rhs
//
// This is a friendly implementation strategy because we don't have to have any
// buffers that scale with N, and equally nice don't have to perform any matrix
// operations that are variable size.
//
// Other implementation strategies could trade this off, e.g. evaluating the
// pseudoinverse of Jf ( (Jf^T Jf)^-1 Jf^T ) directly, then multiplying that by
// the residuals. That would probably require implementing singular value
// decomposition, and would create a [3 x N] matrix to be multiplied by the
// [N x 1] residual vector, but on the upside I think that'd eliminate the
// possibility of this gauss_newton_step() function ever failing.
// 0) start off with lhs and rhs safely zeroed.
skcms_Matrix3x3 lhs = {{ {0,0,0}, {0,0,0}, {0,0,0} }};
skcms_Vector3 rhs = { {0,0,0} };
// 1,2) evaluate lhs and evaluate rhs
// We want to evaluate Jf only once, but both lhs and rhs involve Jf^T,
// so we'll have to update lhs and rhs at the same time.
for (int i = 0; i < N; i++) {
float x = x0 + i*dx;
float dfdP[3] = {0,0,0};
float resid = rg_nonlinear(x,curve,tf, dfdP);
for (int r = 0; r < 3; r++) {
for (int c = 0; c < 3; c++) {
lhs.vals[r][c] += dfdP[r] * dfdP[c];
}
rhs.vals[r] += dfdP[r] * resid;
}
}
// If any of the 3 P parameters are unused, this matrix will be singular.
// Detect those cases and fix them up to indentity instead, so we can invert.
for (int k = 0; k < 3; k++) {
if (lhs.vals[0][k]==0 && lhs.vals[1][k]==0 && lhs.vals[2][k]==0 &&
lhs.vals[k][0]==0 && lhs.vals[k][1]==0 && lhs.vals[k][2]==0) {
lhs.vals[k][k] = 1;
}
}
// 3) invert lhs
skcms_Matrix3x3 lhs_inv;
if (!skcms_Matrix3x3_invert(&lhs, &lhs_inv)) {
return false;
}
// 4) multiply inverse lhs by rhs
skcms_Vector3 dP = mv_mul(&lhs_inv, &rhs);
tf->g += dP.vals[0];
tf->a += dP.vals[1];
tf->b += dP.vals[2];
return isfinitef_(tf->g) && isfinitef_(tf->a) && isfinitef_(tf->b);
}
static float max_roundtrip_error_checked(const skcms_Curve* curve,
const skcms_TransferFunction* tf_inv) {
skcms_TransferFunction tf;
if (!skcms_TransferFunction_invert(tf_inv, &tf) || sRGBish != classify(tf)) {
return INFINITY_;
}
skcms_TransferFunction tf_inv_again;
if (!skcms_TransferFunction_invert(&tf, &tf_inv_again)) {
return INFINITY_;
}
return skcms_MaxRoundtripError(curve, &tf_inv_again);
}
// Fit the points in [L,N) to the non-linear piece of tf, or return false if we can't.
static bool fit_nonlinear(const skcms_Curve* curve, int L, int N, skcms_TransferFunction* tf) {
// This enforces a few constraints that are not modeled in gauss_newton_step()'s optimization.
auto fixup_tf = [tf]() {
// a must be non-negative. That ensures the function is monotonically increasing.
// We don't really know how to fix up a if it goes negative.
if (tf->a < 0) {
return false;
}
// ad+b must be non-negative. That ensures we don't end up with complex numbers in powf.
// We feel just barely not uneasy enough to tweak b so ad+b is zero in this case.
if (tf->a * tf->d + tf->b < 0) {
tf->b = -tf->a * tf->d;
}
assert (tf->a >= 0 &&
tf->a * tf->d + tf->b >= 0);
// cd+f must be ~= (ad+b)^g+e. That ensures the function is continuous. We keep e as a free
// parameter so we can guarantee this.
tf->e = tf->c*tf->d + tf->f
- powf_(tf->a*tf->d + tf->b, tf->g);
return true;
};
if (!fixup_tf()) {
return false;
}
// No matter where we start, dx should always represent N even steps from 0 to 1.
const float dx = 1.0f / (N-1);
skcms_TransferFunction best_tf = *tf;
float best_max_error = INFINITY_;
// Need this or several curves get worse... *sigh*
float init_error = max_roundtrip_error_checked(curve, tf);
if (init_error < best_max_error) {
best_max_error = init_error;
best_tf = *tf;
}
// As far as we can tell, 1 Gauss-Newton step won't converge, and 3 steps is no better than 2.
for (int j = 0; j < 8; j++) {
if (!gauss_newton_step(curve, tf, L*dx, dx, N-L) || !fixup_tf()) {
*tf = best_tf;
return isfinitef_(best_max_error);
}
float max_error = max_roundtrip_error_checked(curve, tf);
if (max_error < best_max_error) {
best_max_error = max_error;
best_tf = *tf;
}
}
*tf = best_tf;
return isfinitef_(best_max_error);
}
bool skcms_ApproximateCurve(const skcms_Curve* curve,
skcms_TransferFunction* approx,
float* max_error) {
if (!curve || !approx || !max_error) {
return false;
}
if (curve->table_entries == 0) {
// No point approximating an skcms_TransferFunction with an skcms_TransferFunction!
return false;
}
if (curve->table_entries == 1 || curve->table_entries > (uint32_t)INT_MAX) {
// We need at least two points, and must put some reasonable cap on the maximum number.
return false;
}
int N = (int)curve->table_entries;
const float dx = 1.0f / (N - 1);
*max_error = INFINITY_;
const float kTolerances[] = { 1.5f / 65535.0f, 1.0f / 512.0f };
for (int t = 0; t < ARRAY_COUNT(kTolerances); t++) {
skcms_TransferFunction tf,
tf_inv;
// It's problematic to fit curves with non-zero f, so always force it to zero explicitly.
tf.f = 0.0f;
int L = fit_linear(curve, N, kTolerances[t], &tf.c, &tf.d);
if (L == N) {
// If the entire data set was linear, move the coefficients to the nonlinear portion
// with G == 1. This lets use a canonical representation with d == 0.
tf.g = 1;
tf.a = tf.c;
tf.b = tf.f;
tf.c = tf.d = tf.e = tf.f = 0;
} else if (L == N - 1) {
// Degenerate case with only two points in the nonlinear segment. Solve directly.
tf.g = 1;
tf.a = (eval_curve(curve, (N-1)*dx) -
eval_curve(curve, (N-2)*dx))
/ dx;
tf.b = eval_curve(curve, (N-2)*dx)
- tf.a * (N-2)*dx;
tf.e = 0;
} else {
// Start by guessing a gamma-only curve through the midpoint.
int mid = (L + N) / 2;
float mid_x = mid / (N - 1.0f);
float mid_y = eval_curve(curve, mid_x);
tf.g = log2f_(mid_y) / log2f_(mid_x);
tf.a = 1;
tf.b = 0;
tf.e = tf.c*tf.d + tf.f
- powf_(tf.a*tf.d + tf.b, tf.g);
if (!skcms_TransferFunction_invert(&tf, &tf_inv) ||
!fit_nonlinear(curve, L,N, &tf_inv)) {
continue;
}
// We fit tf_inv, so calculate tf to keep in sync.
// fit_nonlinear() should guarantee invertibility.
if (!skcms_TransferFunction_invert(&tf_inv, &tf)) {
assert(false);
continue;
}
}
// We'd better have a sane, sRGB-ish TF by now.
// Other non-Bad TFs would be fine, but we know we've only ever tried to fit sRGBish;
// anything else is just some accident of math and the way we pun tf.g as a type flag.
// fit_nonlinear() should guarantee this, but the special cases may fail this test.
if (sRGBish != classify(tf)) {
continue;
}
// We find our error by roundtripping the table through tf_inv.
//
// (The most likely use case for this approximation is to be inverted and
// used as the transfer function for a destination color space.)
//
// We've kept tf and tf_inv in sync above, but we can't guarantee that tf is
// invertible, so re-verify that here (and use the new inverse for testing).
// fit_nonlinear() should guarantee this, but the special cases that don't use
// it may fail this test.
if (!skcms_TransferFunction_invert(&tf, &tf_inv)) {
continue;
}
float err = skcms_MaxRoundtripError(curve, &tf_inv);
if (*max_error > err) {
*max_error = err;
*approx = tf;
}
}
return isfinitef_(*max_error);
}
// ~~~~ Impl. of skcms_Transform() ~~~~
typedef enum {
Op_load_a8,
Op_load_g8,
Op_load_8888_palette8,
Op_load_4444,
Op_load_565,
Op_load_888,
Op_load_8888,
Op_load_1010102,
Op_load_161616LE,
Op_load_16161616LE,
Op_load_161616BE,
Op_load_16161616BE,
Op_load_hhh,
Op_load_hhhh,
Op_load_fff,
Op_load_ffff,
Op_swap_rb,
Op_clamp,
Op_invert,
Op_force_opaque,
Op_premul,
Op_unpremul,
Op_matrix_3x3,
Op_matrix_3x4,
Op_lab_to_xyz,
Op_tf_r,
Op_tf_g,
Op_tf_b,
Op_tf_a,
Op_pq_r,
Op_pq_g,
Op_pq_b,
Op_pq_a,
Op_hlg_r,
Op_hlg_g,
Op_hlg_b,
Op_hlg_a,
Op_hlginv_r,
Op_hlginv_g,
Op_hlginv_b,
Op_hlginv_a,
Op_table_r,
Op_table_g,
Op_table_b,
Op_table_a,
Op_clut,
Op_store_a8,
Op_store_g8,
Op_store_4444,
Op_store_565,
Op_store_888,
Op_store_8888,
Op_store_1010102,
Op_store_161616LE,
Op_store_16161616LE,
Op_store_161616BE,
Op_store_16161616BE,
Op_store_hhh,
Op_store_hhhh,
Op_store_fff,
Op_store_ffff,
} Op;
#if defined(__clang__)
template <int N, typename T> using Vec = T __attribute__((ext_vector_type(N)));
#elif defined(__GNUC__)
// For some reason GCC accepts this nonsense, but not the more straightforward version,
// template <int N, typename T> using Vec = T __attribute__((vector_size(N*sizeof(T))));
template <int N, typename T>
struct VecHelper { typedef T __attribute__((vector_size(N*sizeof(T)))) V; };
template <int N, typename T> using Vec = typename VecHelper<N,T>::V;
#endif
// First, instantiate our default exec_ops() implementation using the default compiliation target.
namespace baseline {
#if defined(SKCMS_PORTABLE) || !(defined(__clang__) || defined(__GNUC__)) \
|| (defined(__EMSCRIPTEN_major__) && !defined(__wasm_simd128__))
#define N 1
template <typename T> using V = T;
using Color = float;
#elif defined(__AVX512F__)
#define N 16
template <typename T> using V = Vec<N,T>;
using Color = float;
#elif defined(__AVX__)
#define N 8
template <typename T> using V = Vec<N,T>;
using Color = float;
#elif defined(__ARM_FEATURE_FP16_VECTOR_ARITHMETIC) && defined(SKCMS_OPT_INTO_NEON_FP16)
#define N 8
template <typename T> using V = Vec<N,T>;
using Color = _Float16;
#else
#define N 4
template <typename T> using V = Vec<N,T>;
using Color = float;
#endif
#include "src/Transform_inl.h"
#undef N
}
// Now, instantiate any other versions of run_program() we may want for runtime detection.
#if !defined(SKCMS_PORTABLE) && \
!defined(SKCMS_NO_RUNTIME_CPU_DETECTION) && \
(( defined(__clang__) && __clang_major__ >= 5) || \
(!defined(__clang__) && defined(__GNUC__))) \
&& defined(__x86_64__)
#if !defined(__AVX2__)
#if defined(__clang__)
#pragma clang attribute push(__attribute__((target("avx2,f16c"))), apply_to=function)
#elif defined(__GNUC__)
#pragma GCC push_options
#pragma GCC target("avx2,f16c")
#endif
namespace hsw {
#define USING_AVX
#define USING_AVX_F16C
#define USING_AVX2
#define N 8
template <typename T> using V = Vec<N,T>;
using Color = float;
#include "src/Transform_inl.h"
// src/Transform_inl.h will undefine USING_* for us.
#undef N
}
#if defined(__clang__)
#pragma clang attribute pop
#elif defined(__GNUC__)
#pragma GCC pop_options
#endif
#define TEST_FOR_HSW
#endif
#if !defined(__AVX512F__)
#if defined(__clang__)
#pragma clang attribute push(__attribute__((target("avx512f,avx512dq,avx512cd,avx512bw,avx512vl"))), apply_to=function)
#elif defined(__GNUC__)
#pragma GCC push_options
#pragma GCC target("avx512f,avx512dq,avx512cd,avx512bw,avx512vl")
#endif
namespace skx {
#define USING_AVX512F
#define N 16
template <typename T> using V = Vec<N,T>;
using Color = float;
#include "src/Transform_inl.h"
// src/Transform_inl.h will undefine USING_* for us.
#undef N
}
#if defined(__clang__)
#pragma clang attribute pop
#elif defined(__GNUC__)
#pragma GCC pop_options
#endif
#define TEST_FOR_SKX
#endif
#if defined(TEST_FOR_HSW) || defined(TEST_FOR_SKX)
enum class CpuType { None, HSW, SKX };
static CpuType cpu_type() {
static const CpuType type = []{
if (!runtime_cpu_detection) {
return CpuType::None;
}
// See http://www.sandpile.org/x86/cpuid.htm
// First, a basic cpuid(1) lets us check prerequisites for HSW, SKX.
uint32_t eax, ebx, ecx, edx;
__asm__ __volatile__("cpuid" : "=a"(eax), "=b"(ebx), "=c"(ecx), "=d"(edx)
: "0"(1), "2"(0));
if ((edx & (1u<<25)) && // SSE
(edx & (1u<<26)) && // SSE2
(ecx & (1u<< 0)) && // SSE3
(ecx & (1u<< 9)) && // SSSE3
(ecx & (1u<<12)) && // FMA (N.B. not used, avoided even)
(ecx & (1u<<19)) && // SSE4.1
(ecx & (1u<<20)) && // SSE4.2
(ecx & (1u<<26)) && // XSAVE
(ecx & (1u<<27)) && // OSXSAVE
(ecx & (1u<<28)) && // AVX
(ecx & (1u<<29))) { // F16C
// Call cpuid(7) to check for AVX2 and AVX-512 bits.
__asm__ __volatile__("cpuid" : "=a"(eax), "=b"(ebx), "=c"(ecx), "=d"(edx)
: "0"(7), "2"(0));
// eax from xgetbv(0) will tell us whether XMM, YMM, and ZMM state is saved.
uint32_t xcr0, dont_need_edx;
__asm__ __volatile__("xgetbv" : "=a"(xcr0), "=d"(dont_need_edx) : "c"(0));
if ((xcr0 & (1u<<1)) && // XMM register state saved?
(xcr0 & (1u<<2)) && // YMM register state saved?
(ebx & (1u<<5))) { // AVX2
// At this point we're at least HSW. Continue checking for SKX.
if ((xcr0 & (1u<< 5)) && // Opmasks state saved?
(xcr0 & (1u<< 6)) && // First 16 ZMM registers saved?
(xcr0 & (1u<< 7)) && // High 16 ZMM registers saved?
(ebx & (1u<<16)) && // AVX512F
(ebx & (1u<<17)) && // AVX512DQ
(ebx & (1u<<28)) && // AVX512CD
(ebx & (1u<<30)) && // AVX512BW
(ebx & (1u<<31))) { // AVX512VL
return CpuType::SKX;
}
return CpuType::HSW;
}
}
return CpuType::None;
}();
return type;
}
#endif
#endif
typedef struct {
Op op;
const void* arg;
} OpAndArg;
static OpAndArg select_curve_op(const skcms_Curve* curve, int channel) {
static const struct { Op sRGBish, PQish, HLGish, HLGinvish, table; } ops[] = {
{ Op_tf_r, Op_pq_r, Op_hlg_r, Op_hlginv_r, Op_table_r },
{ Op_tf_g, Op_pq_g, Op_hlg_g, Op_hlginv_g, Op_table_g },
{ Op_tf_b, Op_pq_b, Op_hlg_b, Op_hlginv_b, Op_table_b },
{ Op_tf_a, Op_pq_a, Op_hlg_a, Op_hlginv_a, Op_table_a },
};
const auto& op = ops[channel];
if (curve->table_entries == 0) {
const OpAndArg noop = { Op_load_a8/*doesn't matter*/, nullptr };
const skcms_TransferFunction& tf = curve->parametric;
if (tf.g == 1 && tf.a == 1 &&
tf.b == 0 && tf.c == 0 && tf.d == 0 && tf.e == 0 && tf.f == 0) {
return noop;
}
switch (classify(tf)) {
case Bad: return noop;
case sRGBish: return OpAndArg{op.sRGBish, &tf};
case PQish: return OpAndArg{op.PQish, &tf};
case HLGish: return OpAndArg{op.HLGish, &tf};
case HLGinvish: return OpAndArg{op.HLGinvish, &tf};
}
}
return OpAndArg{op.table, curve};
}
static size_t bytes_per_pixel(skcms_PixelFormat fmt) {
switch (fmt >> 1) { // ignore rgb/bgr
case skcms_PixelFormat_A_8 >> 1: return 1;
case skcms_PixelFormat_G_8 >> 1: return 1;
case skcms_PixelFormat_RGBA_8888_Palette8 >> 1: return 1;
case skcms_PixelFormat_ABGR_4444 >> 1: return 2;
case skcms_PixelFormat_RGB_565 >> 1: return 2;
case skcms_PixelFormat_RGB_888 >> 1: return 3;
case skcms_PixelFormat_RGBA_8888 >> 1: return 4;
case skcms_PixelFormat_RGBA_8888_sRGB >> 1: return 4;
case skcms_PixelFormat_RGBA_1010102 >> 1: return 4;
case skcms_PixelFormat_RGB_161616LE >> 1: return 6;
case skcms_PixelFormat_RGBA_16161616LE >> 1: return 8;
case skcms_PixelFormat_RGB_161616BE >> 1: return 6;
case skcms_PixelFormat_RGBA_16161616BE >> 1: return 8;
case skcms_PixelFormat_RGB_hhh_Norm >> 1: return 6;
case skcms_PixelFormat_RGBA_hhhh_Norm >> 1: return 8;
case skcms_PixelFormat_RGB_hhh >> 1: return 6;
case skcms_PixelFormat_RGBA_hhhh >> 1: return 8;
case skcms_PixelFormat_RGB_fff >> 1: return 12;
case skcms_PixelFormat_RGBA_ffff >> 1: return 16;
}
assert(false);
return 0;
}
static bool prep_for_destination(const skcms_ICCProfile* profile,
skcms_Matrix3x3* fromXYZD50,
skcms_TransferFunction* invR,
skcms_TransferFunction* invG,
skcms_TransferFunction* invB) {
// We only support destinations with parametric transfer functions
// and with gamuts that can be transformed from XYZD50.
return profile->has_trc
&& profile->has_toXYZD50
&& profile->trc[0].table_entries == 0
&& profile->trc[1].table_entries == 0
&& profile->trc[2].table_entries == 0
&& skcms_TransferFunction_invert(&profile->trc[0].parametric, invR)
&& skcms_TransferFunction_invert(&profile->trc[1].parametric, invG)
&& skcms_TransferFunction_invert(&profile->trc[2].parametric, invB)
&& skcms_Matrix3x3_invert(&profile->toXYZD50, fromXYZD50);
}
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) {
return skcms_TransformWithPalette(src, srcFmt, srcAlpha, srcProfile,
dst, dstFmt, dstAlpha, dstProfile,
npixels, nullptr);
}
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 nz,
const void* palette) {
const size_t dst_bpp = bytes_per_pixel(dstFmt),
src_bpp = bytes_per_pixel(srcFmt);
// Let's just refuse if the request is absurdly big.
if (nz * dst_bpp > INT_MAX || nz * src_bpp > INT_MAX) {
return false;
}
int n = (int)nz;
// Null profiles default to sRGB. Passing null for both is handy when doing format conversion.
if (!srcProfile) {
srcProfile = skcms_sRGB_profile();
}
if (!dstProfile) {
dstProfile = skcms_sRGB_profile();
}
// We can't transform in place unless the PixelFormats are the same size.
if (dst == src && dst_bpp != src_bpp) {
return false;
}
// TODO: more careful alias rejection (like, dst == src + 1)?
if (needs_palette(srcFmt) && !palette) {
return false;
}
Op program [32];
const void* arguments[32];
Op* ops = program;
const void** args = arguments;
// These are always parametric curves of some sort.
skcms_Curve dst_curves[3];
dst_curves[0].table_entries =
dst_curves[1].table_entries =
dst_curves[2].table_entries = 0;
skcms_Matrix3x3 from_xyz;
switch (srcFmt >> 1) {
default: return false;
case skcms_PixelFormat_A_8 >> 1: *ops++ = Op_load_a8; break;
case skcms_PixelFormat_G_8 >> 1: *ops++ = Op_load_g8; break;
case skcms_PixelFormat_ABGR_4444 >> 1: *ops++ = Op_load_4444; break;
case skcms_PixelFormat_RGB_565 >> 1: *ops++ = Op_load_565; break;
case skcms_PixelFormat_RGB_888 >> 1: *ops++ = Op_load_888; break;
case skcms_PixelFormat_RGBA_8888 >> 1: *ops++ = Op_load_8888; break;
case skcms_PixelFormat_RGBA_1010102 >> 1: *ops++ = Op_load_1010102; break;
case skcms_PixelFormat_RGB_161616LE >> 1: *ops++ = Op_load_161616LE; break;
case skcms_PixelFormat_RGBA_16161616LE >> 1: *ops++ = Op_load_16161616LE; break;
case skcms_PixelFormat_RGB_161616BE >> 1: *ops++ = Op_load_161616BE; break;
case skcms_PixelFormat_RGBA_16161616BE >> 1: *ops++ = Op_load_16161616BE; break;
case skcms_PixelFormat_RGB_hhh_Norm >> 1: *ops++ = Op_load_hhh; break;
case skcms_PixelFormat_RGBA_hhhh_Norm >> 1: *ops++ = Op_load_hhhh; break;
case skcms_PixelFormat_RGB_hhh >> 1: *ops++ = Op_load_hhh; break;
case skcms_PixelFormat_RGBA_hhhh >> 1: *ops++ = Op_load_hhhh; break;
case skcms_PixelFormat_RGB_fff >> 1: *ops++ = Op_load_fff; break;
case skcms_PixelFormat_RGBA_ffff >> 1: *ops++ = Op_load_ffff; break;
case skcms_PixelFormat_RGBA_8888_Palette8 >> 1: *ops++ = Op_load_8888_palette8;
*args++ = palette;
break;
case skcms_PixelFormat_RGBA_8888_sRGB >> 1:
*ops++ = Op_load_8888;
*ops++ = Op_tf_r; *args++ = skcms_sRGB_TransferFunction();
*ops++ = Op_tf_g; *args++ = skcms_sRGB_TransferFunction();
*ops++ = Op_tf_b; *args++ = skcms_sRGB_TransferFunction();
break;
}
if (srcFmt == skcms_PixelFormat_RGB_hhh_Norm ||
srcFmt == skcms_PixelFormat_RGBA_hhhh_Norm) {
*ops++ = Op_clamp;
}
if (srcFmt & 1) {
*ops++ = Op_swap_rb;
}
skcms_ICCProfile gray_dst_profile;
if ((dstFmt >> 1) == (skcms_PixelFormat_G_8 >> 1)) {
// When transforming to gray, stop at XYZ (by setting toXYZ to identity), then transform
// luminance (Y) by the destination transfer function.
gray_dst_profile = *dstProfile;
skcms_SetXYZD50(&gray_dst_profile, &skcms_XYZD50_profile()->toXYZD50);
dstProfile = &gray_dst_profile;
}
if (srcProfile->data_color_space == skcms_Signature_CMYK) {
// Photoshop creates CMYK images as inverse CMYK.
// These happen to be the only ones we've _ever_ seen.
*ops++ = Op_invert;
// With CMYK, ignore the alpha type, to avoid changing K or conflating CMY with K.
srcAlpha = skcms_AlphaFormat_Unpremul;
}
if (srcAlpha == skcms_AlphaFormat_Opaque) {
*ops++ = Op_force_opaque;
} else if (srcAlpha == skcms_AlphaFormat_PremulAsEncoded) {
*ops++ = Op_unpremul;
}
if (dstProfile != srcProfile) {
if (!prep_for_destination(dstProfile,
&from_xyz,
&dst_curves[0].parametric,
&dst_curves[1].parametric,
&dst_curves[2].parametric)) {
return false;
}
if (srcProfile->has_A2B) {
if (srcProfile->A2B.input_channels) {
for (int i = 0; i < (int)srcProfile->A2B.input_channels; i++) {
OpAndArg oa = select_curve_op(&srcProfile->A2B.input_curves[i], i);
if (oa.arg) {
*ops++ = oa.op;
*args++ = oa.arg;
}
}
*ops++ = Op_clamp;
*ops++ = Op_clut;
*args++ = &srcProfile->A2B;
}
if (srcProfile->A2B.matrix_channels == 3) {
for (int i = 0; i < 3; i++) {
OpAndArg oa = select_curve_op(&srcProfile->A2B.matrix_curves[i], i);
if (oa.arg) {
*ops++ = oa.op;
*args++ = oa.arg;
}
}
static const skcms_Matrix3x4 I = {{
{1,0,0,0},
{0,1,0,0},
{0,0,1,0},
}};
if (0 != memcmp(&I, &srcProfile->A2B.matrix, sizeof(I))) {
*ops++ = Op_matrix_3x4;
*args++ = &srcProfile->A2B.matrix;
}
}
if (srcProfile->A2B.output_channels == 3) {
for (int i = 0; i < 3; i++) {
OpAndArg oa = select_curve_op(&srcProfile->A2B.output_curves[i], i);
if (oa.arg) {
*ops++ = oa.op;
*args++ = oa.arg;
}
}
}
if (srcProfile->pcs == skcms_Signature_Lab) {
*ops++ = Op_lab_to_xyz;
}
} else if (srcProfile->has_trc && srcProfile->has_toXYZD50) {
for (int i = 0; i < 3; i++) {
OpAndArg oa = select_curve_op(&srcProfile->trc[i], i);
if (oa.arg) {
*ops++ = oa.op;
*args++ = oa.arg;
}
}
} else {
return false;
}
// A2B sources should already be in XYZD50 at this point.
// Others still need to be transformed using their toXYZD50 matrix.
// N.B. There are profiles that contain both A2B tags and toXYZD50 matrices.
// If we use the A2B tags, we need to ignore the XYZD50 matrix entirely.
assert (srcProfile->has_A2B || srcProfile->has_toXYZD50);
static const skcms_Matrix3x3 I = {{
{ 1.0f, 0.0f, 0.0f },
{ 0.0f, 1.0f, 0.0f },
{ 0.0f, 0.0f, 1.0f },
}};
const skcms_Matrix3x3* to_xyz = srcProfile->has_A2B ? &I : &srcProfile->toXYZD50;
// There's a chance the source and destination gamuts are identical,
// in which case we can skip the gamut transform.
if (0 != memcmp(&dstProfile->toXYZD50, to_xyz, sizeof(skcms_Matrix3x3))) {
// Concat the entire gamut transform into from_xyz,
// now slightly misnamed but it's a handy spot to stash the result.
from_xyz = skcms_Matrix3x3_concat(&from_xyz, to_xyz);
*ops++ = Op_matrix_3x3;
*args++ = &from_xyz;
}
// Encode back to dst RGB using its parametric transfer functions.
for (int i = 0; i < 3; i++) {
OpAndArg oa = select_curve_op(dst_curves+i, i);
if (oa.arg) {
assert (oa.op != Op_table_r &&
oa.op != Op_table_g &&
oa.op != Op_table_b &&
oa.op != Op_table_a);
*ops++ = oa.op;
*args++ = oa.arg;
}
}
}
// Clamp here before premul to make sure we're clamping to normalized values _and_ gamut,
// not just to values that fit in [0,1].
//
// E.g. r = 1.1, a = 0.5 would fit fine in fixed point after premul (ra=0.55,a=0.5),
// but would be carrying r > 1, which is really unexpected for downstream consumers.
if (dstFmt < skcms_PixelFormat_RGB_hhh) {
*ops++ = Op_clamp;
}
if (dstAlpha == skcms_AlphaFormat_Opaque) {
*ops++ = Op_force_opaque;
} else if (dstAlpha == skcms_AlphaFormat_PremulAsEncoded) {
*ops++ = Op_premul;
}
if (dstFmt & 1) {
*ops++ = Op_swap_rb;
}
switch (dstFmt >> 1) {
default: return false;
case skcms_PixelFormat_A_8 >> 1: *ops++ = Op_store_a8; break;
case skcms_PixelFormat_G_8 >> 1: *ops++ = Op_store_g8; break;
case skcms_PixelFormat_ABGR_4444 >> 1: *ops++ = Op_store_4444; break;
case skcms_PixelFormat_RGB_565 >> 1: *ops++ = Op_store_565; break;
case skcms_PixelFormat_RGB_888 >> 1: *ops++ = Op_store_888; break;
case skcms_PixelFormat_RGBA_8888 >> 1: *ops++ = Op_store_8888; break;
case skcms_PixelFormat_RGBA_1010102 >> 1: *ops++ = Op_store_1010102; break;
case skcms_PixelFormat_RGB_161616LE >> 1: *ops++ = Op_store_161616LE; break;
case skcms_PixelFormat_RGBA_16161616LE >> 1: *ops++ = Op_store_16161616LE; break;
case skcms_PixelFormat_RGB_161616BE >> 1: *ops++ = Op_store_161616BE; break;
case skcms_PixelFormat_RGBA_16161616BE >> 1: *ops++ = Op_store_16161616BE; break;
case skcms_PixelFormat_RGB_hhh_Norm >> 1: *ops++ = Op_store_hhh; break;
case skcms_PixelFormat_RGBA_hhhh_Norm >> 1: *ops++ = Op_store_hhhh; break;
case skcms_PixelFormat_RGB_hhh >> 1: *ops++ = Op_store_hhh; break;
case skcms_PixelFormat_RGBA_hhhh >> 1: *ops++ = Op_store_hhhh; break;
case skcms_PixelFormat_RGB_fff >> 1: *ops++ = Op_store_fff; break;
case skcms_PixelFormat_RGBA_ffff >> 1: *ops++ = Op_store_ffff; break;
case skcms_PixelFormat_RGBA_8888_sRGB >> 1:
*ops++ = Op_tf_r; *args++ = skcms_sRGB_Inverse_TransferFunction();
*ops++ = Op_tf_g; *args++ = skcms_sRGB_Inverse_TransferFunction();
*ops++ = Op_tf_b; *args++ = skcms_sRGB_Inverse_TransferFunction();
*ops++ = Op_store_8888;
break;
}
auto run = baseline::run_program;
#if defined(TEST_FOR_HSW)
switch (cpu_type()) {
case CpuType::None: break;
case CpuType::HSW: run = hsw::run_program; break;
case CpuType::SKX: run = hsw::run_program; break;
}
#endif
#if defined(TEST_FOR_SKX)
switch (cpu_type()) {
case CpuType::None: break;
case CpuType::HSW: break;
case CpuType::SKX: run = skx::run_program; break;
}
#endif
run(program, arguments, (const char*)src, (char*)dst, n, src_bpp,dst_bpp);
return true;
}
static void assert_usable_as_destination(const skcms_ICCProfile* profile) {
#if defined(NDEBUG)
(void)profile;
#else
skcms_Matrix3x3 fromXYZD50;
skcms_TransferFunction invR, invG, invB;
assert(prep_for_destination(profile, &fromXYZD50, &invR, &invG, &invB));
#endif
}
bool skcms_MakeUsableAsDestination(skcms_ICCProfile* profile) {
skcms_Matrix3x3 fromXYZD50;
if (!profile->has_trc || !profile->has_toXYZD50
|| !skcms_Matrix3x3_invert(&profile->toXYZD50, &fromXYZD50)) {
return false;
}
skcms_TransferFunction tf[3];
for (int i = 0; i < 3; i++) {
skcms_TransferFunction inv;
if (profile->trc[i].table_entries == 0
&& skcms_TransferFunction_invert(&profile->trc[i].parametric, &inv)) {
tf[i] = profile->trc[i].parametric;
continue;
}
float max_error;
// Parametric curves from skcms_ApproximateCurve() are guaranteed to be invertible.
if (!skcms_ApproximateCurve(&profile->trc[i], &tf[i], &max_error)) {
return false;
}
}
for (int i = 0; i < 3; ++i) {
profile->trc[i].table_entries = 0;
profile->trc[i].parametric = tf[i];
}
assert_usable_as_destination(profile);
return true;
}
bool skcms_MakeUsableAsDestinationWithSingleCurve(skcms_ICCProfile* profile) {
// Operate on a copy of profile, so we can choose the best TF for the original curves
skcms_ICCProfile result = *profile;
if (!skcms_MakeUsableAsDestination(&result)) {
return false;
}
int best_tf = 0;
float min_max_error = INFINITY_;
for (int i = 0; i < 3; i++) {
skcms_TransferFunction inv;
if (!skcms_TransferFunction_invert(&result.trc[i].parametric, &inv)) {
return false;
}
float err = 0;
for (int j = 0; j < 3; ++j) {
err = fmaxf_(err, skcms_MaxRoundtripError(&profile->trc[j], &inv));
}
if (min_max_error > err) {
min_max_error = err;
best_tf = i;
}
}
for (int i = 0; i < 3; i++) {
result.trc[i].parametric = result.trc[best_tf].parametric;
}
*profile = result;
assert_usable_as_destination(profile);
return true;
}
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