LibGfx+icc: Read viewingConditionsType

Not terribly useful in practice either and also mostly for
completionism. But with this, we can dump all types present
in Lightroom Classic-exported jpegs :^)

Userland/Libraries/LibGfx/ICC/Profile.cpp

@@ -600,6 +600,8 @@ ErrorOr<NonnullRefPtr<TagData>> Profile::read_tag(ReadonlyBytes bytes, u32 offse
         return TextDescriptionTagData::from_bytes(tag_bytes, offset_to_beginning_of_tag_data_element, size_of_tag_data_element);
     case TextTagData::Type:
         return TextTagData::from_bytes(tag_bytes, offset_to_beginning_of_tag_data_element, size_of_tag_data_element);
+    case ViewingConditionsTagData::Type:
+        return ViewingConditionsTagData::from_bytes(tag_bytes, offset_to_beginning_of_tag_data_element, size_of_tag_data_element);
     case XYZTagData::Type:
         return XYZTagData::from_bytes(tag_bytes, offset_to_beginning_of_tag_data_element, size_of_tag_data_element);
     default:
@@ -1259,7 +1261,8 @@ ErrorOr<void> Profile::check_tag_types()
 
     // ICC v4, 9.2.51 viewingConditionsTag
     // "Permitted tag types: viewingConditionsType"
-    // FIXME
+    if (!has_type(viewingConditionsTag, { ViewingConditionsTagData::Type }, {}))
+        return Error::from_string_literal("ICC::Profile: viewingConditionsTag has unexpected type");
 
     // FIXME: Add validation for v2-only tags:
     // - ICC v2, 6.4.14 crdInfoTag

Userland/Libraries/LibGfx/ICC/TagTypes.cpp

@@ -934,6 +934,31 @@ ErrorOr<NonnullRefPtr<TextTagData>> TextTagData::from_bytes(ReadonlyBytes bytes,
     return adopt_ref(*new TextTagData(offset, size, TRY(String::from_utf8(StringView(text_data, length - 1)))));
 }
 
+ErrorOr<NonnullRefPtr<ViewingConditionsTagData>> ViewingConditionsTagData::from_bytes(ReadonlyBytes bytes, u32 offset, u32 size)
+{
+    // ICC v4, 10.30 viewingConditionsType
+    VERIFY(tag_type(bytes) == Type);
+    TRY(check_reserved(bytes));
+
+    // Table 84 — viewingConditionsType encoding
+    struct ViewingConditionsHeader {
+        XYZNumber unnormalized_ciexyz_values_for_illuminant; // "(in which Y is in cd/m2)"
+        XYZNumber unnormalized_ciexyz_values_for_surround;   // "(in which Y is in cd/m2)"
+        BigEndian<MeasurementTagData::StandardIlluminant> illuminant_type;
+    };
+    static_assert(AssertSize<ViewingConditionsHeader, 28>());
+
+    if (bytes.size() < 2 * sizeof(u32) + sizeof(ViewingConditionsHeader))
+        return Error::from_string_literal("ICC::Profile: viewingConditionsType has not enough data");
+
+    auto& header = *bit_cast<ViewingConditionsHeader const*>(bytes.data() + 8);
+
+    TRY(MeasurementTagData::validate_standard_illuminant(header.illuminant_type));
+
+    return adopt_ref(*new ViewingConditionsTagData(offset, size, header.unnormalized_ciexyz_values_for_illuminant,
+        header.unnormalized_ciexyz_values_for_surround, header.illuminant_type));
+}
+
 ErrorOr<NonnullRefPtr<XYZTagData>> XYZTagData::from_bytes(ReadonlyBytes bytes, u32 offset, u32 size)
 {
     // ICC v4, 10.31 XYZType

Userland/Libraries/LibGfx/ICC/TagTypes.h

@@ -679,6 +679,32 @@ private:
     String m_text;
 };
 
+// ICC v4, 10.30 viewingConditionsType
+class ViewingConditionsTagData : public TagData {
+public:
+    static constexpr TagTypeSignature Type { 0x76696577 }; // 'view'
+
+    static ErrorOr<NonnullRefPtr<ViewingConditionsTagData>> from_bytes(ReadonlyBytes, u32 offset, u32 size);
+
+    ViewingConditionsTagData(u32 offset, u32 size, XYZ const& unnormalized_ciexyz_values_for_illuminant,
+        XYZ const& unnormalized_ciexyz_values_for_surround, MeasurementTagData::StandardIlluminant illuminant_type)
+        : TagData(offset, size, Type)
+        , m_unnormalized_ciexyz_values_for_illuminant(unnormalized_ciexyz_values_for_illuminant)
+        , m_unnormalized_ciexyz_values_for_surround(unnormalized_ciexyz_values_for_surround)
+        , m_illuminant_type(illuminant_type)
+    {
+    }
+
+    XYZ const& unnormalized_ciexyz_values_for_illuminant() const { return m_unnormalized_ciexyz_values_for_illuminant; }
+    XYZ const& unnormalized_ciexyz_values_for_surround() const { return m_unnormalized_ciexyz_values_for_surround; }
+    MeasurementTagData::StandardIlluminant illuminant_type() const { return m_illuminant_type; }
+
+private:
+    XYZ m_unnormalized_ciexyz_values_for_illuminant; // "(in which Y is in cd/m2)"
+    XYZ m_unnormalized_ciexyz_values_for_surround;   // "(in which Y is in cd/m2)"
+    MeasurementTagData::StandardIlluminant m_illuminant_type;
+};
+
 // ICC v4, 10.31 XYZType
 class XYZTagData : public TagData {
 public:

Userland/Utilities/icc.cpp

@@ -311,6 +311,11 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
             out_optional("    macintosh", MUST(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);