/*
* Copyright 2016 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "SkAutoMalloc.h"
#include "SkColorSpacePriv.h"
#include "SkEndian.h"
#include "SkFixed.h"
#include "SkICC.h"
#include "SkICCPriv.h"
#include "SkMD5.h"
#include "SkUtils.h"
static constexpr char kDescriptionTagBodyPrefix[12] =
{ 'G', 'o', 'o', 'g', 'l', 'e', '/', 'S', 'k', 'i', 'a' , '/'};
static constexpr size_t kICCDescriptionTagSize = 44;
static_assert(kICCDescriptionTagSize ==
sizeof(kDescriptionTagBodyPrefix) + 2 * sizeof(SkMD5::Digest), "");
static constexpr size_t kDescriptionTagBodySize = kICCDescriptionTagSize * 2; // ascii->utf16be
static_assert(SkIsAlign4(kDescriptionTagBodySize), "Description must be aligned to 4-bytes.");
static constexpr uint32_t kDescriptionTagHeader[7] {
SkEndian_SwapBE32(kTAG_TextType), // Type signature
0, // Reserved
SkEndian_SwapBE32(1), // Number of records
SkEndian_SwapBE32(12), // Record size (must be 12)
SkEndian_SwapBE32(SkSetFourByteTag('e', 'n', 'U', 'S')), // English USA
SkEndian_SwapBE32(kDescriptionTagBodySize), // Length of string
SkEndian_SwapBE32(28), // Offset of string
};
static constexpr uint32_t kWhitePointTag[5] {
SkEndian_SwapBE32(kXYZ_PCSSpace),
0,
SkEndian_SwapBE32(0x0000f6d6), // X = 0.96420 (D50)
SkEndian_SwapBE32(0x00010000), // Y = 1.00000 (D50)
SkEndian_SwapBE32(0x0000d32d), // Z = 0.82491 (D50)
};
// Google Inc. 2016 (UTF-16)
static constexpr uint8_t kCopyrightTagBody[] = {
0x00, 0x47, 0x00, 0x6f,
0x00, 0x6f, 0x00, 0x67,
0x00, 0x6c, 0x00, 0x65,
0x00, 0x20, 0x00, 0x49,
0x00, 0x6e, 0x00, 0x63,
0x00, 0x2e, 0x00, 0x20,
0x00, 0x32, 0x00, 0x30,
0x00, 0x31, 0x00, 0x36,
};
static_assert(SkIsAlign4(sizeof(kCopyrightTagBody)), "Copyright must be aligned to 4-bytes.");
static constexpr uint32_t kCopyrightTagHeader[7] {
SkEndian_SwapBE32(kTAG_TextType), // Type signature
0, // Reserved
SkEndian_SwapBE32(1), // Number of records
SkEndian_SwapBE32(12), // Record size (must be 12)
SkEndian_SwapBE32(SkSetFourByteTag('e', 'n', 'U', 'S')), // English USA
SkEndian_SwapBE32(sizeof(kCopyrightTagBody)), // Length of string
SkEndian_SwapBE32(28), // Offset of string
};
// We will write a profile with the minimum nine required tags.
static constexpr uint32_t kICCNumEntries = 9;
static constexpr uint32_t kTAG_desc = SkSetFourByteTag('d', 'e', 's', 'c');
static constexpr uint32_t kTAG_desc_Bytes = sizeof(kDescriptionTagHeader) +
kDescriptionTagBodySize;
static constexpr uint32_t kTAG_desc_Offset = kICCHeaderSize +
kICCNumEntries * kICCTagTableEntrySize;
static constexpr uint32_t kTAG_XYZ_Bytes = 20;
static constexpr uint32_t kTAG_rXYZ_Offset = kTAG_desc_Offset + kTAG_desc_Bytes;
static constexpr uint32_t kTAG_gXYZ_Offset = kTAG_rXYZ_Offset + kTAG_XYZ_Bytes;
static constexpr uint32_t kTAG_bXYZ_Offset = kTAG_gXYZ_Offset + kTAG_XYZ_Bytes;
static constexpr uint32_t kTAG_TRC_Bytes = 40;
static constexpr uint32_t kTAG_rTRC_Offset = kTAG_bXYZ_Offset + kTAG_XYZ_Bytes;
static constexpr uint32_t kTAG_gTRC_Offset = kTAG_rTRC_Offset;
static constexpr uint32_t kTAG_bTRC_Offset = kTAG_rTRC_Offset;
static constexpr uint32_t kTAG_wtpt = SkSetFourByteTag('w', 't', 'p', 't');
static constexpr uint32_t kTAG_wtpt_Offset = kTAG_bTRC_Offset + kTAG_TRC_Bytes;
static constexpr uint32_t kTAG_cprt = SkSetFourByteTag('c', 'p', 'r', 't');
static constexpr uint32_t kTAG_cprt_Bytes = sizeof(kCopyrightTagHeader) +
sizeof(kCopyrightTagBody);
static constexpr uint32_t kTAG_cprt_Offset = kTAG_wtpt_Offset + kTAG_XYZ_Bytes;
static constexpr uint32_t kICCProfileSize = kTAG_cprt_Offset + kTAG_cprt_Bytes;
static constexpr uint32_t kICCHeader[kICCHeaderSize / 4] {
SkEndian_SwapBE32(kICCProfileSize), // Size of the profile
0, // Preferred CMM type (ignored)
SkEndian_SwapBE32(0x02100000), // Version 2.1
SkEndian_SwapBE32(kDisplay_Profile), // Display device profile
SkEndian_SwapBE32(kRGB_ColorSpace), // RGB input color space
SkEndian_SwapBE32(kXYZ_PCSSpace), // XYZ profile connection space
0, 0, 0, // Date and time (ignored)
SkEndian_SwapBE32(kACSP_Signature), // Profile signature
0, // Platform target (ignored)
0x00000000, // Flags: not embedded, can be used independently
0, // Device manufacturer (ignored)
0, // Device model (ignored)
0, 0, // Device attributes (ignored)
SkEndian_SwapBE32(1), // Relative colorimetric rendering intent
SkEndian_SwapBE32(0x0000f6d6), // D50 standard illuminant (X)
SkEndian_SwapBE32(0x00010000), // D50 standard illuminant (Y)
SkEndian_SwapBE32(0x0000d32d), // D50 standard illuminant (Z)
0, // Profile creator (ignored)
0, 0, 0, 0, // Profile id checksum (ignored)
0, 0, 0, 0, 0, 0, 0, // Reserved (ignored)
SkEndian_SwapBE32(kICCNumEntries), // Number of tags
};
static constexpr uint32_t kICCTagTable[3 * kICCNumEntries] {
// Profile description
SkEndian_SwapBE32(kTAG_desc),
SkEndian_SwapBE32(kTAG_desc_Offset),
SkEndian_SwapBE32(kTAG_desc_Bytes),
// rXYZ
SkEndian_SwapBE32(kTAG_rXYZ),
SkEndian_SwapBE32(kTAG_rXYZ_Offset),
SkEndian_SwapBE32(kTAG_XYZ_Bytes),
// gXYZ
SkEndian_SwapBE32(kTAG_gXYZ),
SkEndian_SwapBE32(kTAG_gXYZ_Offset),
SkEndian_SwapBE32(kTAG_XYZ_Bytes),
// bXYZ
SkEndian_SwapBE32(kTAG_bXYZ),
SkEndian_SwapBE32(kTAG_bXYZ_Offset),
SkEndian_SwapBE32(kTAG_XYZ_Bytes),
// rTRC
SkEndian_SwapBE32(kTAG_rTRC),
SkEndian_SwapBE32(kTAG_rTRC_Offset),
SkEndian_SwapBE32(kTAG_TRC_Bytes),
// gTRC
SkEndian_SwapBE32(kTAG_gTRC),
SkEndian_SwapBE32(kTAG_gTRC_Offset),
SkEndian_SwapBE32(kTAG_TRC_Bytes),
// bTRC
SkEndian_SwapBE32(kTAG_bTRC),
SkEndian_SwapBE32(kTAG_bTRC_Offset),
SkEndian_SwapBE32(kTAG_TRC_Bytes),
// White point
SkEndian_SwapBE32(kTAG_wtpt),
SkEndian_SwapBE32(kTAG_wtpt_Offset),
SkEndian_SwapBE32(kTAG_XYZ_Bytes),
// Copyright
SkEndian_SwapBE32(kTAG_cprt),
SkEndian_SwapBE32(kTAG_cprt_Offset),
SkEndian_SwapBE32(kTAG_cprt_Bytes),
};
// This is like SkFloatToFixed, but rounds to nearest, preserving as much accuracy as possible
// when going float -> fixed -> float (it has the same accuracy when going fixed -> float -> fixed).
// The use of double is necessary to accomodate the full potential 32-bit mantissa of the 16.16
// SkFixed value, and so avoiding rounding problems with float. Also, see the comment in SkFixed.h.
static SkFixed float_round_to_fixed(float x) {
return sk_float_saturate2int((float)floor((double)x * SK_Fixed1 + 0.5));
}
static void write_xyz_tag(uint32_t* ptr, const skcms_Matrix3x3& toXYZD50, int col) {
ptr[0] = SkEndian_SwapBE32(kXYZ_PCSSpace);
ptr[1] = 0;
ptr[2] = SkEndian_SwapBE32(float_round_to_fixed(toXYZD50.vals[0][col]));
ptr[3] = SkEndian_SwapBE32(float_round_to_fixed(toXYZD50.vals[1][col]));
ptr[4] = SkEndian_SwapBE32(float_round_to_fixed(toXYZD50.vals[2][col]));
}
static void write_trc_tag(uint32_t* ptr, const skcms_TransferFunction& fn) {
ptr[0] = SkEndian_SwapBE32(kTAG_ParaCurveType);
ptr[1] = 0;
ptr[2] = (uint32_t) (SkEndian_SwapBE16(kGABCDEF_ParaCurveType));
ptr[3] = SkEndian_SwapBE32(float_round_to_fixed(fn.g));
ptr[4] = SkEndian_SwapBE32(float_round_to_fixed(fn.a));
ptr[5] = SkEndian_SwapBE32(float_round_to_fixed(fn.b));
ptr[6] = SkEndian_SwapBE32(float_round_to_fixed(fn.c));
ptr[7] = SkEndian_SwapBE32(float_round_to_fixed(fn.d));
ptr[8] = SkEndian_SwapBE32(float_round_to_fixed(fn.e));
ptr[9] = SkEndian_SwapBE32(float_round_to_fixed(fn.f));
}
static bool nearly_equal(float x, float y) {
// A note on why I chose this tolerance: transfer_fn_almost_equal() uses a
// tolerance of 0.001f, which doesn't seem to be enough to distinguish
// between similar transfer functions, for example: gamma2.2 and sRGB.
//
// If the tolerance is 0.0f, then this we can't distinguish between two
// different encodings of what is clearly the same colorspace. Some
// experimentation with example files lead to this number:
static constexpr float kTolerance = 1.0f / (1 << 11);
return ::fabsf(x - y) <= kTolerance;
}
static bool nearly_equal(const skcms_TransferFunction& u,
const skcms_TransferFunction& v) {
return nearly_equal(u.g, v.g)
&& nearly_equal(u.a, v.a)
&& nearly_equal(u.b, v.b)
&& nearly_equal(u.c, v.c)
&& nearly_equal(u.d, v.d)
&& nearly_equal(u.e, v.e)
&& nearly_equal(u.f, v.f);
}
static bool nearly_equal(const skcms_Matrix3x3& u, const skcms_Matrix3x3& v) {
for (int r = 0; r < 3; r++) {
for (int c = 0; c < 3; c++) {
if (!nearly_equal(u.vals[r][c], v.vals[r][c])) {
return false;
}
}
}
return true;
}
// Return nullptr if the color profile doen't have a special name.
const char* get_color_profile_description(const skcms_TransferFunction& fn,
const skcms_Matrix3x3& toXYZD50) {
bool srgb_xfer = nearly_equal(fn, SkNamedTransferFn::kSRGB);
bool srgb_gamut = nearly_equal(toXYZD50, SkNamedGamut::kSRGB);
if (srgb_xfer && srgb_gamut) {
return "sRGB";
}
bool line_xfer = nearly_equal(fn, SkNamedTransferFn::kLinear);
if (line_xfer && srgb_gamut) {
return "Linear Transfer with sRGB Gamut";
}
bool twoDotTwo = nearly_equal(fn, SkNamedTransferFn::k2Dot2);
if (twoDotTwo && srgb_gamut) {
return "2.2 Transfer with sRGB Gamut";
}
if (twoDotTwo && nearly_equal(toXYZD50, SkNamedGamut::kAdobeRGB)) {
return "AdobeRGB";
}
bool dcip3_gamut = nearly_equal(toXYZD50, SkNamedGamut::kDCIP3);
if (srgb_xfer || line_xfer) {
if (srgb_xfer && dcip3_gamut) {
return "sRGB Transfer with DCI-P3 Gamut";
}
if (line_xfer && dcip3_gamut) {
return "Linear Transfer with DCI-P3 Gamut";
}
bool rec2020 = nearly_equal(toXYZD50, SkNamedGamut::kRec2020);
if (srgb_xfer && rec2020) {
return "sRGB Transfer with Rec-BT-2020 Gamut";
}
if (line_xfer && rec2020) {
return "Linear Transfer with Rec-BT-2020 Gamut";
}
}
return nullptr;
}
static void get_color_profile_tag(char dst[kICCDescriptionTagSize],
const skcms_TransferFunction& fn,
const skcms_Matrix3x3& toXYZD50) {
SkASSERT(dst);
if (const char* description = get_color_profile_description(fn, toXYZD50)) {
SkASSERT(strlen(description) < kICCDescriptionTagSize);
strncpy(dst, description, kICCDescriptionTagSize);
// "If the length of src is less than n, strncpy() writes additional
// null bytes to dest to ensure that a total of n bytes are written."
} else {
strncpy(dst, kDescriptionTagBodyPrefix, sizeof(kDescriptionTagBodyPrefix));
SkMD5 md5;
md5.write(&toXYZD50, sizeof(toXYZD50));
static_assert(sizeof(fn) == sizeof(float) * 7, "packed");
md5.write(&fn, sizeof(fn));
SkMD5::Digest digest;
md5.finish(digest);
char* ptr = dst + sizeof(kDescriptionTagBodyPrefix);
for (unsigned i = 0; i < sizeof(SkMD5::Digest); ++i) {
uint8_t byte = digest.data[i];
*ptr++ = SkHexadecimalDigits::gUpper[byte >> 4];
*ptr++ = SkHexadecimalDigits::gUpper[byte & 0xF];
}
SkASSERT(ptr == dst + kICCDescriptionTagSize);
}
}
sk_sp<SkData> SkWriteICCProfile(const skcms_TransferFunction& fn,
const skcms_Matrix3x3& toXYZD50) {
if (!is_valid_transfer_fn(fn)) {
return nullptr;
}
SkAutoMalloc profile(kICCProfileSize);
uint8_t* ptr = (uint8_t*) profile.get();
// Write profile header
memcpy(ptr, kICCHeader, sizeof(kICCHeader));
ptr += sizeof(kICCHeader);
// Write tag table
memcpy(ptr, kICCTagTable, sizeof(kICCTagTable));
ptr += sizeof(kICCTagTable);
// Write profile description tag
memcpy(ptr, kDescriptionTagHeader, sizeof(kDescriptionTagHeader));
ptr += sizeof(kDescriptionTagHeader);
{
char colorProfileTag[kICCDescriptionTagSize];
get_color_profile_tag(colorProfileTag, fn, toXYZD50);
// ASCII --> big-endian UTF-16.
for (size_t i = 0; i < kICCDescriptionTagSize; i++) {
*ptr++ = 0;
*ptr++ = colorProfileTag[i];
}
}
// Write XYZ tags
write_xyz_tag((uint32_t*) ptr, toXYZD50, 0);
ptr += kTAG_XYZ_Bytes;
write_xyz_tag((uint32_t*) ptr, toXYZD50, 1);
ptr += kTAG_XYZ_Bytes;
write_xyz_tag((uint32_t*) ptr, toXYZD50, 2);
ptr += kTAG_XYZ_Bytes;
// Write TRC tag
write_trc_tag((uint32_t*) ptr, fn);
ptr += kTAG_TRC_Bytes;
// Write white point tag (must be D50)
memcpy(ptr, kWhitePointTag, sizeof(kWhitePointTag));
ptr += sizeof(kWhitePointTag);
// Write copyright tag
memcpy(ptr, kCopyrightTagHeader, sizeof(kCopyrightTagHeader));
ptr += sizeof(kCopyrightTagHeader);
memcpy(ptr, kCopyrightTagBody, sizeof(kCopyrightTagBody));
ptr += sizeof(kCopyrightTagBody);
SkASSERT(kICCProfileSize == ptr - (uint8_t*) profile.get());
return SkData::MakeFromMalloc(profile.release(), kICCProfileSize);
}