SkICC.h File Reference

#include "include/core/SkRefCnt.h"
#include "include/private/base/SkAPI.h"
#include <cstdint>

Go to the source code of this file.

Functions
SK_API sk_sp< SkData >	SkWriteICCProfile (const skcms_TransferFunction &, const skcms_Matrix3x3 &toXYZD50)
SK_API sk_sp< SkData >	SkWriteICCProfile (const skcms_ICCProfile *, const char *description)
SK_API void	SkICCFloatXYZD50ToGrid16Lab (const float *float_xyz, uint8_t *grid16_lab)
SK_API void	SkICCFloatToTable16 (const float f, uint8_t *table_16)

Function Documentation

SkICCFloatToTable16()

SK_API void SkICCFloatToTable16	(	const float	f,
		uint8_t *	table_16
	)

SkICCFloatXYZD50ToGrid16Lab()

SK_API void SkICCFloatXYZD50ToGrid16Lab	(	const float *	float_xyz,
		uint8_t *	grid16_lab
	)

SkWriteICCProfile() [1/2]

SK_API sk_sp< SkData > SkWriteICCProfile	(	const skcms_ICCProfile *	profile,
		const char *	description
	)

Definition at line 545 of file SkICC.cpp.

                                                                                   {
    ICCHeader header;
 
    std::vector<std::pair<uint32_t, sk_sp<SkData>>> tags;
 
    // Compute primaries.
    if (profile->has_toXYZD50) {
        const auto& m = profile->toXYZD50;
        tags.emplace_back(kTAG_rXYZ, write_xyz_tag(m.vals[0][0], m.vals[1][0], m.vals[2][0]));
        tags.emplace_back(kTAG_gXYZ, write_xyz_tag(m.vals[0][1], m.vals[1][1], m.vals[2][1]));
        tags.emplace_back(kTAG_bXYZ, write_xyz_tag(m.vals[0][2], m.vals[1][2], m.vals[2][2]));
    }
 
    // Compute white point tag (must be D50)
    tags.emplace_back(kTAG_wtpt, write_xyz_tag(kD50_x, kD50_y, kD50_z));
 
    // Compute transfer curves.
    if (profile->has_trc) {
        tags.emplace_back(kTAG_rTRC, write_trc_tag(profile->trc[0]));
 
        // Use empty data to indicate that the entry should use the previous tag's
        // data.
        if (!memcmp(&profile->trc[1], &profile->trc[0], sizeof(profile->trc[0]))) {
            tags.emplace_back(kTAG_gTRC, SkData::MakeEmpty());
        } else {
            tags.emplace_back(kTAG_gTRC, write_trc_tag(profile->trc[1]));
        }
 
        if (!memcmp(&profile->trc[2], &profile->trc[1], sizeof(profile->trc[1]))) {
            tags.emplace_back(kTAG_bTRC, SkData::MakeEmpty());
        } else {
            tags.emplace_back(kTAG_bTRC, write_trc_tag(profile->trc[2]));
        }
    }
 
    // Compute CICP.
    if (profile->has_CICP) {
        // The CICP tag is present in ICC 4.4, so update the header's version.
        header.version = SkEndian_SwapBE32(0x04400000);
        tags.emplace_back(kTAG_cicp, write_cicp_tag(profile->CICP));
    }
 
    // Compute A2B0.
    if (profile->has_A2B) {
        const auto& a2b = profile->A2B;
        SkASSERT(a2b.output_channels == kNumChannels);
        auto a2b_data = write_mAB_or_mBA_tag(kTAG_mABType,
                                             a2b.output_curves,
                                             a2b.input_channels ? a2b.input_curves : nullptr,
                                             a2b.input_channels ? a2b.grid_points : nullptr,
                                             a2b.input_channels ? a2b.grid_16 : nullptr,
                                             a2b.matrix_channels ? a2b.matrix_curves : nullptr,
                                             a2b.matrix_channels ? &a2b.matrix : nullptr);
        tags.emplace_back(kTAG_A2B0, std::move(a2b_data));
    }
 
    // Compute B2A0.
    if (profile->has_B2A) {
        const auto& b2a = profile->B2A;
        SkASSERT(b2a.input_channels == kNumChannels);
        auto b2a_data = write_mAB_or_mBA_tag(kTAG_mBAType,
                                             b2a.input_curves,
                                             b2a.output_channels ? b2a.input_curves : nullptr,
                                             b2a.output_channels ? b2a.grid_points : nullptr,
                                             b2a.output_channels ? b2a.grid_16 : nullptr,
                                             b2a.matrix_channels ? b2a.matrix_curves : nullptr,
                                             b2a.matrix_channels ? &b2a.matrix : nullptr);
        tags.emplace_back(kTAG_B2A0, std::move(b2a_data));
    }
 
    // Compute copyright tag
    tags.emplace_back(kTAG_cprt, write_text_tag("Google Inc. 2016"));
 
    // Ensure that the desc isn't empty https://crbug.com/329032158
    std::string generatedDesc;
    if (!desc || *desc == '\0') {
        SkMD5 md5;
        for (const auto& tag : tags) {
            md5.write(&tag.first, sizeof(tag.first));
            md5.write(tag.second->bytes(), tag.second->size());
        }
        SkMD5::Digest digest = md5.finish();
        generatedDesc = std::string("Google/Skia/") + digest.toHexString().c_str();
        desc = generatedDesc.c_str();
    }
    // Compute profile description tag
    tags.emplace(tags.begin(), kTAG_desc, write_text_tag(desc));
 
    // Compute the size of the profile.
    size_t tag_data_size = 0;
    for (const auto& tag : tags) {
        tag_data_size += tag.second->size();
    }
    size_t tag_table_size = kICCTagTableEntrySize * tags.size();
    size_t profile_size = kICCHeaderSize + tag_table_size + tag_data_size;
 
    // Write the header.
    header.data_color_space = SkEndian_SwapBE32(profile->data_color_space);
    header.pcs = SkEndian_SwapBE32(profile->pcs);
    header.size = SkEndian_SwapBE32(profile_size);
    header.tag_count = SkEndian_SwapBE32(tags.size());
 
    SkAutoMalloc profile_data(profile_size);
    uint8_t* ptr = (uint8_t*)profile_data.get();
    memcpy(ptr, &header, sizeof(header));
    ptr += sizeof(header);
 
    // Write the tag table. Track the offset and size of the previous tag to
    // compute each tag's offset. An empty SkData indicates that the previous
    // tag is to be reused.
    size_t last_tag_offset = sizeof(header) + tag_table_size;
    size_t last_tag_size = 0;
    for (const auto& tag : tags) {
        if (!tag.second->isEmpty()) {
            last_tag_offset = last_tag_offset + last_tag_size;
            last_tag_size = tag.second->size();
        }
        uint32_t tag_table_entry[3] = {
                SkEndian_SwapBE32(tag.first),
                SkEndian_SwapBE32(last_tag_offset),
                SkEndian_SwapBE32(last_tag_size),
        };
        memcpy(ptr, tag_table_entry, sizeof(tag_table_entry));
        ptr += sizeof(tag_table_entry);
    }
 
    // Write the tags.
    for (const auto& tag : tags) {
        if (tag.second->isEmpty()) continue;
        memcpy(ptr, tag.second->data(), tag.second->size());
        ptr += tag.second->size();
    }
 
    SkASSERT(profile_size == static_cast<size_t>(ptr - (uint8_t*)profile_data.get()));
    return SkData::MakeFromMalloc(profile_data.release(), profile_size);
}

SkWriteICCProfile() [2/2]

SK_API sk_sp< SkData > SkWriteICCProfile	(	const skcms_TransferFunction &	fn,
		const skcms_Matrix3x3 &	toXYZD50
	)

Definition at line 682 of file SkICC.cpp.

                                                                                                   {
    skcms_ICCProfile profile;
    memset(&profile, 0, sizeof(profile));
    std::vector<uint16_t> trc_table;
    std::vector<uint16_t> a2b_grid;
 
    profile.data_color_space = skcms_Signature_RGB;
    profile.pcs = skcms_Signature_XYZ;
 
    // Populate toXYZD50.
    {
        profile.has_toXYZD50 = true;
        profile.toXYZD50 = toXYZD50;
    }
 
    // Populate the analytic TRC for sRGB-like curves.
    if (skcms_TransferFunction_isSRGBish(&fn)) {
        profile.has_trc = true;
        profile.trc[0].table_entries = 0;
        profile.trc[0].parametric = fn;
        memcpy(&profile.trc[1], &profile.trc[0], sizeof(profile.trc[0]));
        memcpy(&profile.trc[2], &profile.trc[0], sizeof(profile.trc[0]));
    }
 
    // Populate A2B (PQ and HLG only).
    if (skcms_TransferFunction_isPQish(&fn) || skcms_TransferFunction_isHLGish(&fn)) {
        // Populate a 1D curve to perform per-channel conversion to linear and tone mapping.
        constexpr uint32_t kTrcTableSize = 65;
        trc_table.resize(kTrcTableSize);
        for (uint32_t i = 0; i < kTrcTableSize; ++i) {
            float x = i / (kTrcTableSize - 1.f);
            x = hdr_trfn_eval(fn, x);
            x *= tone_map_gain(x);
            trc_table[i] = SkEndian_SwapBE16(float_to_uInt16Number(x, kOne16CurveType));
        }
 
        // Populate the grid with a 3D LUT to do cross-channel tone mapping.
        constexpr uint32_t kGridSize = 11;
        a2b_grid.resize(kGridSize * kGridSize * kGridSize * kNumChannels);
        size_t a2b_grid_index = 0;
        for (uint32_t r_index = 0; r_index < kGridSize; ++r_index) {
            for (uint32_t g_index = 0; g_index < kGridSize; ++g_index) {
                for (uint32_t b_index = 0; b_index < kGridSize; ++b_index) {
                    float rgb[3] = {
                            r_index / (kGridSize - 1.f),
                            g_index / (kGridSize - 1.f),
                            b_index / (kGridSize - 1.f),
                    };
 
                    // Un-apply the per-channel tone mapping.
                    for (auto& c : rgb) {
                        c = tone_map_inverse(c);
                    }
 
                    // For HLG, mix the channels according to the OOTF.
                    if (skcms_TransferFunction_isHLGish(&fn)) {
                        // Scale to [0, 1].
                        for (auto& c : rgb) {
                            c /= kToneMapInputMax;
                        }
 
                        // Un-apply the per-channel OOTF.
                        for (auto& c : rgb) {
                            c = std::pow(c, 1 / 1.2);
                        }
 
                        // Re-apply the cross-channel OOTF.
                        float Y = 0.2627f * rgb[0] + 0.6780f * rgb[1] + 0.0593f * rgb[2];
                        for (auto& c : rgb) {
                            c *= std::pow(Y, 0.2);
                        }
 
                        // Scale back up to 1.0 being 1,000/203.
                        for (auto& c : rgb) {
                            c *= kToneMapInputMax;
                        }
                    }
 
                    // Apply tone mapping to take 1,000/203 to 1.0.
                    {
                        float max_rgb = std::max(std::max(rgb[0], rgb[1]), rgb[2]);
                        for (auto& c : rgb) {
                            c *= tone_map_gain(0.5 * (c + max_rgb));
                            c = std::min(c, 1.f);
                        }
                    }
 
                    // Write the result to the LUT.
                    for (const auto& c : rgb) {
                        a2b_grid[a2b_grid_index++] =
                                SkEndian_SwapBE16(float_to_uInt16Number(c, kOne16XYZ));
                    }
                }
            }
        }
 
        // Populate A2B as this tone mapping.
        profile.has_A2B = true;
        profile.A2B.input_channels = kNumChannels;
        profile.A2B.output_channels = kNumChannels;
        profile.A2B.matrix_channels = kNumChannels;
        for (size_t i = 0; i < kNumChannels; ++i) {
            profile.A2B.grid_points[i] = kGridSize;
            // Set the input curve to convert to linear pre-OOTF space.
            profile.A2B.input_curves[i].table_entries = kTrcTableSize;
            profile.A2B.input_curves[i].table_16 = reinterpret_cast<uint8_t*>(trc_table.data());
            // The output and matrix curves are the identity.
            profile.A2B.output_curves[i].parametric = SkNamedTransferFn::kLinear;
            profile.A2B.matrix_curves[i].parametric = SkNamedTransferFn::kLinear;
            // Set the matrix to convert from the primaries to XYZD50.
            for (size_t j = 0; j < 3; ++j) {
                profile.A2B.matrix.vals[i][j] = toXYZD50.vals[i][j];
            }
            profile.A2B.matrix.vals[i][3] = 0.f;
        }
        profile.A2B.grid_16 = reinterpret_cast<const uint8_t*>(a2b_grid.data());
 
        // Populate B2A as the identity.
        profile.has_B2A = true;
        profile.B2A.input_channels = kNumChannels;
        for (size_t i = 0; i < 3; ++i) {
            profile.B2A.input_curves[i].parametric = SkNamedTransferFn::kLinear;
        }
    }
 
    // Populate CICP.
    if (skcms_TransferFunction_isHLGish(&fn) || skcms_TransferFunction_isPQish(&fn)) {
        profile.has_CICP = true;
        profile.CICP.color_primaries = get_cicp_primaries(toXYZD50);
        profile.CICP.transfer_characteristics = get_cicp_trfn(fn);
        profile.CICP.matrix_coefficients = 0;
        profile.CICP.video_full_range_flag = 1;
        SkASSERT(profile.CICP.color_primaries);
        SkASSERT(profile.CICP.transfer_characteristics);
    }
 
    std::string description = get_desc_string(fn, toXYZD50);
    return SkWriteICCProfile(&profile, description.c_str());
}