icc.cpp

/*
 * Copyright (c) 2022-2023, Nico Weber <thakis@chromium.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/Random.h>
#include <AK/String.h>
#include <AK/StringView.h>
#include <LibCore/ArgsParser.h>
#include <LibCore/DateTime.h>
#include <LibCore/File.h>
#include <LibCore/MappedFile.h>
#include <LibGfx/DeltaE.h>
#include <LibGfx/ICC/BinaryWriter.h>
#include <LibGfx/ICC/Profile.h>
#include <LibGfx/ICC/Tags.h>
#include <LibGfx/ICC/WellKnownProfiles.h>
#include <LibGfx/ImageFormats/ImageDecoder.h>
#include <LibMedia/Color/CodingIndependentCodePoints.h>

template<class T>
static ErrorOr<String> hyperlink(URL::URL const& target, T const& label)
{
    return String::formatted("\033]8;;{}\033\\{}\033]8;;\033\\", target, label);
}

template<class T>
static void out_optional(char const* label, Optional<T> const& optional)
{
    out("{}: ", label);
    if (optional.has_value())
        outln("{}", *optional);
    else
        outln("(not set)");
}

static void out_curve(Gfx::ICC::CurveTagData const& curve, int indent_amount)
{
    if (curve.values().is_empty()) {
        outln("{: >{}}identity curve", "", indent_amount);
    } else if (curve.values().size() == 1) {
        outln("{: >{}}gamma: {}", "", indent_amount, FixedPoint<8, u16>::create_raw(curve.values()[0]));
    } else {
        // FIXME: Maybe print the actual points if -v is passed?
        outln("{: >{}}curve with {} points", "", indent_amount, curve.values().size());
    }
}

static void out_parametric_curve(Gfx::ICC::ParametricCurveTagData const& parametric_curve, int indent_amount)
{
    switch (parametric_curve.function_type()) {
    case Gfx::ICC::ParametricCurveTagData::FunctionType::Type0:
        outln("{: >{}}Y = X**{}", "", indent_amount, parametric_curve.g());
        break;
    case Gfx::ICC::ParametricCurveTagData::FunctionType::Type1:
        outln("{: >{}}Y = ({}*X + {})**{}   if X >= -{}/{}", "", indent_amount,
            parametric_curve.a(), parametric_curve.b(), parametric_curve.g(), parametric_curve.b(), parametric_curve.a());
        outln("{: >{}}Y = 0                                else", "", indent_amount);
        break;
    case Gfx::ICC::ParametricCurveTagData::FunctionType::Type2:
        outln("{: >{}}Y = ({}*X + {})**{} + {}   if X >= -{}/{}", "", indent_amount,
            parametric_curve.a(), parametric_curve.b(), parametric_curve.g(), parametric_curve.c(), parametric_curve.b(), parametric_curve.a());
        outln("{: >{}}Y =  {}                                    else", "", indent_amount, parametric_curve.c());
        break;
    case Gfx::ICC::ParametricCurveTagData::FunctionType::Type3:
        outln("{: >{}}Y = ({}*X + {})**{}   if X >= {}", "", indent_amount,
            parametric_curve.a(), parametric_curve.b(), parametric_curve.g(), parametric_curve.d());
        outln("{: >{}}Y =  {}*X                         else", "", indent_amount, parametric_curve.c());
        break;
    case Gfx::ICC::ParametricCurveTagData::FunctionType::Type4:
        outln("{: >{}}Y = ({}*X + {})**{} + {}   if X >= {}", "", indent_amount,
            parametric_curve.a(), parametric_curve.b(), parametric_curve.g(), parametric_curve.e(), parametric_curve.d());
        outln("{: >{}}Y =  {}*X + {}                             else", "", indent_amount, parametric_curve.c(), parametric_curve.f());
        break;
    }
}

static float curve_distance_u8(Gfx::ICC::TagData const& tag1, Gfx::ICC::TagData const& tag2)
{
    VERIFY(tag1.type() == Gfx::ICC::CurveTagData::Type || tag1.type() == Gfx::ICC::ParametricCurveTagData::Type);
    VERIFY(tag2.type() == Gfx::ICC::CurveTagData::Type || tag2.type() == Gfx::ICC::ParametricCurveTagData::Type);

    float curve1_data[256];
    if (tag1.type() == Gfx::ICC::CurveTagData::Type) {
        auto& curve1 = static_cast<Gfx::ICC::CurveTagData const&>(tag1);
        for (int i = 0; i < 256; ++i)
            curve1_data[i] = curve1.evaluate(i / 255.f);
    } else {
        auto& parametric_curve1 = static_cast<Gfx::ICC::ParametricCurveTagData const&>(tag1);
        for (int i = 0; i < 256; ++i)
            curve1_data[i] = parametric_curve1.evaluate(i / 255.f);
    }

    float curve2_data[256];
    if (tag2.type() == Gfx::ICC::CurveTagData::Type) {
        auto& curve2 = static_cast<Gfx::ICC::CurveTagData const&>(tag2);
        for (int i = 0; i < 256; ++i)
            curve2_data[i] = curve2.evaluate(i / 255.f);
    } else {
        auto& parametric_curve2 = static_cast<Gfx::ICC::ParametricCurveTagData const&>(tag2);
        for (int i = 0; i < 256; ++i)
            curve2_data[i] = parametric_curve2.evaluate(i / 255.f);
    }

    float distance = 0;
    for (int i = 0; i < 256; ++i)
        distance += fabsf(curve1_data[i] - curve2_data[i]);
    return distance;
}

static ErrorOr<void> out_curve_tag(Gfx::ICC::TagData const& tag, int indent_amount)
{
    VERIFY(tag.type() == Gfx::ICC::CurveTagData::Type || tag.type() == Gfx::ICC::ParametricCurveTagData::Type);
    if (tag.type() == Gfx::ICC::CurveTagData::Type)
        out_curve(static_cast<Gfx::ICC::CurveTagData const&>(tag), indent_amount);
    if (tag.type() == Gfx::ICC::ParametricCurveTagData::Type)
        out_parametric_curve(static_cast<Gfx::ICC::ParametricCurveTagData const&>(tag), indent_amount);

    auto sRGB_curve = TRY(Gfx::ICC::sRGB_curve());

    // Some example values (for abs distance summed over the 256 values of an u8):
    // In Compact-ICC-Profiles/profiles:
    //   AdobeCompat-v2.icc: 1.14 (this is a gamma 2.2 curve, so not really sRGB but close)
    //   AdobeCompat-v4.icc: 1.13
    //   AppleCompat-v2.icc: 11.94 (gamma 1.8 curve)
    //   DCI-P3-v4.icc: 8.29 (gamma 2.6 curve)
    //   DisplayP3-v2-magic.icc: 0.000912 (looks sRGB-ish)
    //   DisplayP3-v2-micro.icc: 0.010819
    //   DisplayP3-v4.icc: 0.001062 (yes, definitely sRGB)
    //   Rec2020-g24-v4.icc: 4.119216 (gamma 2.4 curve)
    //   Rec2020-v4.icc: 7.805417 (custom non-sRGB curve)
    //   Rec709-v4.icc: 7.783267 (same custom non-sRGB curve as Rec2020)
    //   sRGB-v2-magic.icc: 0.000912
    //   sRGB-v2-micro.icc: 0.010819
    //   sRGB-v2-nano.icc: 0.052516
    //   sRGB-v4.icc: 0.001062
    //   scRGB-v2.icc: 48.379859 (linear identity curve)
    // Google sRGB IEC61966-2.1 (from a Pixel jpeg, parametric): 0
    // Google sRGB IEC61966-2.1 (from a Pixel jpeg, LUT curve): 0.00096
    // Apple 2015 Display P3 (from iPhone 7, parametric): 0.011427 (has the old, left intersection for switching from linear to exponent)
    // HP sRGB: 0.00096
    // color.org sRGB2014.icc: 0.00096
    // color.org sRGB_ICC_v4_Appearance.icc, AToB1Tag, a curves: 0.441926 -- but this is not _really_ sRGB
    // color.org sRGB_v4_ICC_preference.icc, AToB1Tag, a curves: 2.205453 -- not really sRGB either
    // So `< 0.06` identifies sRGB in practice (for u8 values).
    float u8_distance_to_sRGB = curve_distance_u8(*sRGB_curve, tag);
    if (u8_distance_to_sRGB < 0.06f)
        outln("{: >{}}Looks like sRGB's curve (distance {})", "", indent_amount, u8_distance_to_sRGB);
    else
        outln("{: >{}}Does not look like sRGB's curve (distance: {})", "", indent_amount, u8_distance_to_sRGB);

    return {};
}

static ErrorOr<void> out_curves(Vector<Gfx::ICC::LutCurveType> const& curves)
{
    for (auto const& curve : curves) {
        VERIFY(curve->type() == Gfx::ICC::CurveTagData::Type || curve->type() == Gfx::ICC::ParametricCurveTagData::Type);
        outln("        type {}, relative offset {}, size {}", curve->type(), curve->offset(), curve->size());
        TRY(out_curve_tag(*curve, /*indent=*/12));
    }
    return {};
}

static ErrorOr<void> perform_debug_roundtrip(Gfx::ICC::Profile const& profile)
{
    size_t num_channels = Gfx::ICC::number_of_components_in_color_space(profile.data_color_space());
    Vector<u8, 4> input, output;
    input.resize(num_channels);
    output.resize(num_channels);

    size_t const num_total_roundtrips = 500;
    size_t num_lossless_roundtrips = 0;

    for (size_t i = 0; i < num_total_roundtrips; ++i) {
        for (size_t j = 0; j < num_channels; ++j)
            input[j] = get_random<u8>();
        auto color_in_profile_connection_space = TRY(profile.to_pcs(input));
        TRY(profile.from_pcs(profile, color_in_profile_connection_space, output));
        if (input != output) {
            outln("roundtrip failed for {} -> {}", input, output);
        } else {
            ++num_lossless_roundtrips;
        }
    }
    outln("lossless roundtrips: {} / {}", num_lossless_roundtrips, num_total_roundtrips);
    return {};
}

static ErrorOr<void> print_profile_measurement(Gfx::ICC::Profile const& profile)
{
    auto lab_from_rgb = [&profile](u8 r, u8 g, u8 b) {
        u8 rgb[3] = { r, g, b };
        return profile.to_lab(rgb);
    };
    float largest = -1, smallest = 1000;
    Color largest_color1, largest_color2, smallest_color1, smallest_color2;
    for (u8 r = 0; r < 254; ++r) {
        out("\r{}/254", r + 1);
        fflush(stdout);
        for (u8 g = 0; g < 254; ++g) {
            for (u8 b = 0; b < 254; ++b) {
                auto lab = TRY(lab_from_rgb(r, g, b));
                u8 delta_r[] = { 1, 0, 0 };
                u8 delta_g[] = { 0, 1, 0 };
                u8 delta_b[] = { 0, 0, 1 };
                for (unsigned i = 0; i < sizeof(delta_r); ++i) {
                    auto lab2 = TRY(lab_from_rgb(r + delta_r[i], g + delta_g[i], b + delta_b[i]));
                    float delta = Gfx::DeltaE(lab, lab2);
                    if (delta > largest) {
                        largest = delta;
                        largest_color1 = Color(r, g, b);
                        largest_color2 = Color(r + delta_r[i], g + delta_g[i], b + delta_b[i]);
                    }
                    if (delta < smallest) {
                        smallest = delta;
                        smallest_color1 = Color(r, g, b);
                        smallest_color2 = Color(r + delta_r[i], g + delta_g[i], b + delta_b[i]);
                    }
                }
            }
        }
    }
    outln("\rlargest difference between neighboring colors: {}, between {} and {}", largest, largest_color1, largest_color2);
    outln("smallest difference between neighboring colors: {}, between {} and {}", smallest, smallest_color1, smallest_color2);
    return {};
}

ErrorOr<int> serenity_main(Main::Arguments arguments)
{
    Core::ArgsParser args_parser;

    StringView path;
    args_parser.add_positional_argument(path, "Path to ICC profile or to image containing ICC profile", "FILE", Core::ArgsParser::Required::No);

    StringView name;
    args_parser.add_option(name, "Name of a built-in profile, such as 'sRGB'", "name", 'n', "NAME");

    StringView dump_out_path;
    args_parser.add_option(dump_out_path, "Dump unmodified ICC profile bytes to this path", "dump-to", 0, "FILE");

    StringView reencode_out_path;
    args_parser.add_option(reencode_out_path, "Reencode ICC profile to this path", "reencode-to", 0, "FILE");

    bool debug_roundtrip = false;
    args_parser.add_option(debug_roundtrip, "Check how many u8 colors roundtrip losslessly through the profile. For debugging.", "debug-roundtrip");

    bool measure = false;
    args_parser.add_option(measure, "For RGB ICC profiles, print perceptually smallest and largest color step", "measure");

    bool force_print = false;
    args_parser.add_option(force_print, "Print profile even when writing ICC files", "print");

    args_parser.parse(arguments);

    if (path.is_empty() && name.is_empty()) {
        warnln("need either a path or a profile name");
        return 1;
    }
    if (!path.is_empty() && !name.is_empty()) {
        warnln("can't have both a path and a profile name");
        return 1;
    }
    if (path.is_empty() && !dump_out_path.is_empty()) {
        warnln("--dump-to only valid with path, not with profile name; use --reencode-to instead");
        return 1;
    }

    ReadonlyBytes icc_bytes;
    NonnullRefPtr<Gfx::ICC::Profile> profile = TRY([&]() -> ErrorOr<NonnullRefPtr<Gfx::ICC::Profile>> {
        if (!name.is_empty()) {
            if (name == "sRGB")
                return Gfx::ICC::sRGB();
            return Error::from_string_literal("unknown profile name");
        }
        auto file = TRY(Core::MappedFile::map(path));

        auto decoder = TRY(Gfx::ImageDecoder::try_create_for_raw_bytes(file->bytes()));
        if (decoder) {
            if (auto embedded_icc_bytes = TRY(decoder->icc_data()); embedded_icc_bytes.has_value()) {
                icc_bytes = *embedded_icc_bytes;
            } else {
                outln("image contains no embedded ICC profile");
                exit(1);
            }
        } else {
            icc_bytes = file->bytes();
        }

        if (!dump_out_path.is_empty()) {
            auto output_stream = TRY(Core::File::open(dump_out_path, Core::File::OpenMode::Write));
            TRY(output_stream->write_until_depleted(icc_bytes));
        }
        return Gfx::ICC::Profile::try_load_from_externally_owned_memory(icc_bytes);
    }());

    if (!reencode_out_path.is_empty()) {
        auto reencoded_bytes = TRY(Gfx::ICC::encode(profile));
        auto output_stream = TRY(Core::File::open(reencode_out_path, Core::File::OpenMode::Write));
        TRY(output_stream->write_until_depleted(reencoded_bytes));
    }

    if (debug_roundtrip) {
        TRY(perform_debug_roundtrip(*profile));
        return 0;
    }

    if (measure) {
        if (profile->data_color_space() != Gfx::ICC::ColorSpace::RGB) {
            warnln("--measure only works for RGB ICC profiles");
            return 1;
        }
        TRY(print_profile_measurement(*profile));
    }

    bool do_print = (dump_out_path.is_empty() && reencode_out_path.is_empty() && !measure) || force_print;
    if (!do_print)
        return 0;

    outln("                  size: {} bytes", profile->on_disk_size());
    out_optional("    preferred CMM type", profile->preferred_cmm_type());
    outln("               version: {}", profile->version());
    outln("          device class: {}", Gfx::ICC::device_class_name(profile->device_class()));
    outln("      data color space: {}", Gfx::ICC::data_color_space_name(profile->data_color_space()));
    outln("      connection space: {}", Gfx::ICC::profile_connection_space_name(profile->connection_space()));

    if (auto time = profile->creation_timestamp().to_time_t(); !time.is_error()) {
        // Print in friendly localtime for valid profiles.
        outln("creation date and time: {}", Core::DateTime::from_timestamp(time.release_value()));
    } else {
        outln("creation date and time: {:04}-{:02}-{:02} {:02}:{:02}:{:02} UTC (invalid)",
            profile->creation_timestamp().year, profile->creation_timestamp().month, profile->creation_timestamp().day,
            profile->creation_timestamp().hours, profile->creation_timestamp().minutes, profile->creation_timestamp().seconds);
    }

    out_optional("      primary platform", profile->primary_platform().map([](auto platform) { return primary_platform_name(platform); }));

    auto flags = profile->flags();
    outln("                 flags: {:#08x}", flags.bits());
    outln("                        - {}embedded in file", flags.is_embedded_in_file() ? "" : "not ");
    outln("                        - can{} be used independently of embedded color data", flags.can_be_used_independently_of_embedded_color_data() ? "" : "not");
    if (auto unknown_icc_bits = flags.icc_bits() & ~Gfx::ICC::Flags::KnownBitsMask)
        outln("                        other unknown ICC bits: {:#04x}", unknown_icc_bits);
    if (auto color_management_module_bits = flags.color_management_module_bits())
        outln("                            CMM bits: {:#04x}", color_management_module_bits);

    out_optional("   device manufacturer", TRY(profile->device_manufacturer().map([](auto device_manufacturer) {
        return hyperlink(device_manufacturer_url(device_manufacturer), device_manufacturer);
    })));
    out_optional("          device model", TRY(profile->device_model().map([](auto device_model) {
        return hyperlink(device_model_url(device_model), device_model);
    })));

    auto device_attributes = profile->device_attributes();
    outln("     device attributes: {:#016x}", device_attributes.bits());
    outln("                        media is:");
    outln("                        - {}",
        device_attributes.media_reflectivity() == Gfx::ICC::DeviceAttributes::MediaReflectivity::Reflective ? "reflective" : "transparent");
    outln("                        - {}",
        device_attributes.media_glossiness() == Gfx::ICC::DeviceAttributes::MediaGlossiness::Glossy ? "glossy" : "matte");
    outln("                        - {}",
        device_attributes.media_polarity() == Gfx::ICC::DeviceAttributes::MediaPolarity::Positive ? "of positive polarity" : "of negative polarity");
    outln("                        - {}",
        device_attributes.media_color() == Gfx::ICC::DeviceAttributes::MediaColor::Colored ? "colored" : "black and white");
    VERIFY((flags.icc_bits() & ~Gfx::ICC::DeviceAttributes::KnownBitsMask) == 0);
    if (auto vendor_bits = device_attributes.vendor_bits())
        outln("                        vendor bits: {:#08x}", vendor_bits);

    outln("      rendering intent: {}", Gfx::ICC::rendering_intent_name(profile->rendering_intent()));
    outln("        pcs illuminant: {}", profile->pcs_illuminant());
    out_optional("               creator", profile->creator());
    out_optional("                    id", profile->id());

    size_t profile_disk_size = icc_bytes.size();
    if (profile_disk_size != profile->on_disk_size()) {
        VERIFY(profile_disk_size > profile->on_disk_size());
        outln("{} trailing bytes after profile data", profile_disk_size - profile->on_disk_size());
    }

    outln("");

    outln("tags:");
    HashMap<Gfx::ICC::TagData*, Gfx::ICC::TagSignature> tag_data_to_first_signature;
    TRY(profile->try_for_each_tag([&tag_data_to_first_signature](auto tag_signature, auto tag_data) -> ErrorOr<void> {
        if (auto name = tag_signature_spec_name(tag_signature); name.has_value())
            out("{} ({}): ", *name, tag_signature);
        else
            out("Unknown tag ({}): ", tag_signature);
        outln("type {}, offset {}, size {}", tag_data->type(), tag_data->offset(), tag_data->size());

        // Print tag data only the first time it's seen.
        // (Different sigatures can refer to the same data.)
        auto it = tag_data_to_first_signature.find(tag_data);
        if (it != tag_data_to_first_signature.end()) {
            outln("    (see {} above)", it->value);
            return {};
        }
        tag_data_to_first_signature.set(tag_data, tag_signature);

        if (tag_data->type() == Gfx::ICC::ChromaticityTagData::Type) {
            auto& chromaticity = static_cast<Gfx::ICC::ChromaticityTagData&>(*tag_data);
            outln("    phosphor or colorant type: {}", Gfx::ICC::ChromaticityTagData::phosphor_or_colorant_type_name(chromaticity.phosphor_or_colorant_type()));
            for (auto const& xy : chromaticity.xy_coordinates())
                outln("    x, y: {}, {}", xy.x, xy.y);
        } else if (tag_data->type() == Gfx::ICC::CicpTagData::Type) {
            auto& cicp = static_cast<Gfx::ICC::CicpTagData&>(*tag_data);
            outln("    color primaries: {} - {}", cicp.color_primaries(),
                Media::color_primaries_to_string((Media::ColorPrimaries)cicp.color_primaries()));
            outln("    transfer characteristics: {} - {}", cicp.transfer_characteristics(),
                Media::transfer_characteristics_to_string((Media::TransferCharacteristics)cicp.transfer_characteristics()));
            outln("    matrix coefficients: {} - {}", cicp.matrix_coefficients(),
                Media::matrix_coefficients_to_string((Media::MatrixCoefficients)cicp.matrix_coefficients()));
            outln("    video full range flag: {} - {}", cicp.video_full_range_flag(),
                Media::video_full_range_flag_to_string((Media::VideoFullRangeFlag)cicp.video_full_range_flag()));
        } else if (tag_data->type() == Gfx::ICC::CurveTagData::Type) {
            TRY(out_curve_tag(*tag_data, /*indent=*/4));
        } else if (tag_data->type() == Gfx::ICC::Lut16TagData::Type) {
            auto& lut16 = static_cast<Gfx::ICC::Lut16TagData&>(*tag_data);
            outln("    input table: {} channels x {} entries", lut16.number_of_input_channels(), lut16.number_of_input_table_entries());
            outln("    output table: {} channels x {} entries", lut16.number_of_output_channels(), lut16.number_of_output_table_entries());
            outln("    color lookup table: {} grid points, {} total entries", lut16.number_of_clut_grid_points(), lut16.clut_values().size());

            auto const& e = lut16.e_matrix();
            outln("    e = [ {}, {}, {},", e[0], e[1], e[2]);
            outln("          {}, {}, {},", e[3], e[4], e[5]);
            outln("          {}, {}, {} ]", e[6], e[7], e[8]);
        } else if (tag_data->type() == Gfx::ICC::Lut8TagData::Type) {
            auto& lut8 = static_cast<Gfx::ICC::Lut8TagData&>(*tag_data);
            outln("    input table: {} channels x {} entries", lut8.number_of_input_channels(), lut8.number_of_input_table_entries());
            outln("    output table: {} channels x {} entries", lut8.number_of_output_channels(), lut8.number_of_output_table_entries());
            outln("    color lookup table: {} grid points, {} total entries", lut8.number_of_clut_grid_points(), lut8.clut_values().size());

            auto const& e = lut8.e_matrix();
            outln("    e = [ {}, {}, {},", e[0], e[1], e[2]);
            outln("          {}, {}, {},", e[3], e[4], e[5]);
            outln("          {}, {}, {} ]", e[6], e[7], e[8]);
        } else if (tag_data->type() == Gfx::ICC::LutAToBTagData::Type) {
            auto& a_to_b = static_cast<Gfx::ICC::LutAToBTagData&>(*tag_data);
            outln("    {} input channels, {} output channels", a_to_b.number_of_input_channels(), a_to_b.number_of_output_channels());

            if (auto const& optional_a_curves = a_to_b.a_curves(); optional_a_curves.has_value()) {
                outln("    a curves: {} curves", optional_a_curves->size());
                TRY(out_curves(optional_a_curves.value()));
            } else {
                outln("    a curves: (not set)");
            }

            if (auto const& optional_clut = a_to_b.clut(); optional_clut.has_value()) {
                auto const& clut = optional_clut.value();
                outln("    color lookup table: {} grid points, {}",
                    TRY(String::join(" x "sv, clut.number_of_grid_points_in_dimension)),
                    TRY(clut.values.visit(
                        [](Vector<u8> const& v) { return String::formatted("{} u8 entries", v.size()); },
                        [](Vector<u16> const& v) { return String::formatted("{} u16 entries", v.size()); })));
            } else {
                outln("    color lookup table: (not set)");
            }

            if (auto const& optional_m_curves = a_to_b.m_curves(); optional_m_curves.has_value()) {
                outln("    m curves: {} curves", optional_m_curves->size());
                TRY(out_curves(optional_m_curves.value()));
            } else {
                outln("    m curves: (not set)");
            }

            if (auto const& optional_e = a_to_b.e_matrix(); optional_e.has_value()) {
                auto const& e = optional_e.value();
                outln("    e = [ {}, {}, {}, {},", e[0], e[1], e[2], e[9]);
                outln("          {}, {}, {}, {},", e[3], e[4], e[5], e[10]);
                outln("          {}, {}, {}, {} ]", e[6], e[7], e[8], e[11]);
            } else {
                outln("    e = (not set)");
            }

            outln("    b curves: {} curves", a_to_b.b_curves().size());
            TRY(out_curves(a_to_b.b_curves()));
        } else if (tag_data->type() == Gfx::ICC::LutBToATagData::Type) {
            auto& b_to_a = static_cast<Gfx::ICC::LutBToATagData&>(*tag_data);
            outln("    {} input channels, {} output channels", b_to_a.number_of_input_channels(), b_to_a.number_of_output_channels());

            outln("    b curves: {} curves", b_to_a.b_curves().size());
            TRY(out_curves(b_to_a.b_curves()));

            if (auto const& optional_e = b_to_a.e_matrix(); optional_e.has_value()) {
                auto const& e = optional_e.value();
                outln("    e = [ {}, {}, {}, {},", e[0], e[1], e[2], e[9]);
                outln("          {}, {}, {}, {},", e[3], e[4], e[5], e[10]);
                outln("          {}, {}, {}, {} ]", e[6], e[7], e[8], e[11]);
            } else {
                outln("    e = (not set)");
            }

            if (auto const& optional_m_curves = b_to_a.m_curves(); optional_m_curves.has_value()) {
                outln("    m curves: {} curves", optional_m_curves->size());
                TRY(out_curves(optional_m_curves.value()));
            } else {
                outln("    m curves: (not set)");
            }

            if (auto const& optional_clut = b_to_a.clut(); optional_clut.has_value()) {
                auto const& clut = optional_clut.value();
                outln("    color lookup table: {} grid points, {}",
                    TRY(String::join(" x "sv, clut.number_of_grid_points_in_dimension)),
                    TRY(clut.values.visit(
                        [](Vector<u8> const& v) { return String::formatted("{} u8 entries", v.size()); },
                        [](Vector<u16> const& v) { return String::formatted("{} u16 entries", v.size()); })));
            } else {
                outln("    color lookup table: (not set)");
            }

            if (auto const& optional_a_curves = b_to_a.a_curves(); optional_a_curves.has_value()) {
                outln("    a curves: {} curves", optional_a_curves->size());
                TRY(out_curves(optional_a_curves.value()));
            } else {
                outln("    a curves: (not set)");
            }
        } else if (tag_data->type() == Gfx::ICC::MeasurementTagData::Type) {
            auto& measurement = static_cast<Gfx::ICC::MeasurementTagData&>(*tag_data);
            outln("    standard observer: {}", Gfx::ICC::MeasurementTagData::standard_observer_name(measurement.standard_observer()));
            outln("    tristimulus value for measurement backing: {}", measurement.tristimulus_value_for_measurement_backing());
            outln("    measurement geometry: {}", Gfx::ICC::MeasurementTagData::measurement_geometry_name(measurement.measurement_geometry()));
            outln("    measurement flare: {} %", measurement.measurement_flare() * 100);
            outln("    standard illuminant: {}", Gfx::ICC::MeasurementTagData::standard_illuminant_name(measurement.standard_illuminant()));
        } else if (tag_data->type() == Gfx::ICC::MultiLocalizedUnicodeTagData::Type) {
            auto& multi_localized_unicode = static_cast<Gfx::ICC::MultiLocalizedUnicodeTagData&>(*tag_data);
            for (auto& record : multi_localized_unicode.records()) {
                outln("    {:c}{:c}/{:c}{:c}: \"{}\"",
                    record.iso_639_1_language_code >> 8, record.iso_639_1_language_code & 0xff,
                    record.iso_3166_1_country_code >> 8, record.iso_3166_1_country_code & 0xff,
                    record.text);
            }
        } else if (tag_data->type() == Gfx::ICC::NamedColor2TagData::Type) {
            auto& named_colors = static_cast<Gfx::ICC::NamedColor2TagData&>(*tag_data);
            outln("    vendor specific flag: {:#08x}", named_colors.vendor_specific_flag());
            outln("    common name prefix: \"{}\"", named_colors.prefix());
            outln("    common name suffix: \"{}\"", named_colors.suffix());
            outln("    {} colors:", named_colors.size());
            for (size_t i = 0; i < min(named_colors.size(), 5u); ++i) {
                auto const& pcs = named_colors.pcs_coordinates(i);

                // FIXME: Display decoded values? (See ICC v4 6.3.4.2 and 10.8.)
                out("        \"{}\", PCS coordinates: {:#04x} {:#04x} {:#04x}", TRY(named_colors.color_name(i)), pcs.xyz.x, pcs.xyz.y, pcs.xyz.z);
                if (auto number_of_device_coordinates = named_colors.number_of_device_coordinates(); number_of_device_coordinates > 0) {
                    out(", device coordinates:");
                    for (size_t j = 0; j < number_of_device_coordinates; ++j)
                        out(" {:#04x}", named_colors.device_coordinates(i)[j]);
                }
                outln();
            }
            if (named_colors.size() > 5u)
                outln("        ...");
        } else if (tag_data->type() == Gfx::ICC::ParametricCurveTagData::Type) {
            TRY(out_curve_tag(*tag_data, /*indent=*/4));
        } else if (tag_data->type() == Gfx::ICC::S15Fixed16ArrayTagData::Type) {
            // This tag can contain arbitrarily many fixed-point numbers, but in practice it's
            // exclusively used for the 'chad' tag, where it always contains 9 values that
            // represent a 3x3 matrix.  So print the values in groups of 3.
            auto& fixed_array = static_cast<Gfx::ICC::S15Fixed16ArrayTagData&>(*tag_data);
            out("    [");
            int i = 0;
            for (auto value : fixed_array.values()) {
                if (i > 0) {
                    out(",");
                    if (i % 3 == 0) {
                        outln();
                        out("     ");
                    }
                }
                out(" {}", value);
                i++;
            }
            outln(" ]");
        } else if (tag_data->type() == Gfx::ICC::SignatureTagData::Type) {
            auto& signature = static_cast<Gfx::ICC::SignatureTagData&>(*tag_data);

            if (auto name = signature.name_for_tag(tag_signature); name.has_value()) {
                outln("    signature: {}", name.value());
            } else {
                outln("    signature: Unknown ('{:c}{:c}{:c}{:c}' / {:#08x})",
                    signature.signature() >> 24, (signature.signature() >> 16) & 0xff, (signature.signature() >> 8) & 0xff, signature.signature() & 0xff,
                    signature.signature());
            }
        } else if (tag_data->type() == Gfx::ICC::TextDescriptionTagData::Type) {
            auto& text_description = static_cast<Gfx::ICC::TextDescriptionTagData&>(*tag_data);
            outln("    ascii: \"{}\"", text_description.ascii_description());
            out_optional("    unicode", TRY(text_description.unicode_description().map([](auto description) { return String::formatted("\"{}\"", description); })));
            outln("    unicode language code: 0x{}", text_description.unicode_language_code());
            out_optional("    macintosh", TRY(text_description.macintosh_description().map([](auto description) { return String::formatted("\"{}\"", description); })));
        } else if (tag_data->type() == Gfx::ICC::TextTagData::Type) {
            outln("    text: \"{}\"", static_cast<Gfx::ICC::TextTagData&>(*tag_data).text());
        } else if (tag_data->type() == Gfx::ICC::ViewingConditionsTagData::Type) {
            auto& viewing_conditions = static_cast<Gfx::ICC::ViewingConditionsTagData&>(*tag_data);
            outln("    unnormalized CIEXYZ values for illuminant (in which Y is in cd/m²): {}", viewing_conditions.unnormalized_ciexyz_values_for_illuminant());
            outln("    unnormalized CIEXYZ values for surround (in which Y is in cd/m²): {}", viewing_conditions.unnormalized_ciexyz_values_for_surround());
            outln("    illuminant type: {}", Gfx::ICC::MeasurementTagData::standard_illuminant_name(viewing_conditions.illuminant_type()));
        } else if (tag_data->type() == Gfx::ICC::XYZTagData::Type) {
            for (auto& xyz : static_cast<Gfx::ICC::XYZTagData&>(*tag_data).xyzs())
                outln("    {}", xyz);
        }
        return {};
    }));

    return 0;
}