From ececea9a1c343a9a8b50580194bb27402f70e1d6 Mon Sep 17 00:00:00 2001
From: Nico Weber <thakis@chromium.org>
Date: Fri, 17 Feb 2023 20:56:24 -0500
Subject: [PATCH] LibGfx: Implement serialization of ParametricCurveTagData

With this, simple v4 matrix profiles using parametric curves, such as
Compact-ICC-Profiles/profiles/sRGB-v4.icc, can be completely serialized
and the serialized file can be read again by `icc` :^)
---
 .../Libraries/LibGfx/ICC/BinaryWriter.cpp     | 19 +++++++++++++++++++
 Userland/Libraries/LibGfx/ICC/TagTypes.h      |  7 +++++++
 2 files changed, 26 insertions(+)

diff --git a/Userland/Libraries/LibGfx/ICC/BinaryWriter.cpp b/Userland/Libraries/LibGfx/ICC/BinaryWriter.cpp
index 8467f7a894..72bb31d2ca 100644
--- a/Userland/Libraries/LibGfx/ICC/BinaryWriter.cpp
+++ b/Userland/Libraries/LibGfx/ICC/BinaryWriter.cpp
@@ -60,6 +60,23 @@ static ErrorOr<ByteBuffer> encode_multi_localized_unicode(MultiLocalizedUnicodeT
     return bytes;
 }
 
+static ErrorOr<ByteBuffer> encode_parametric_curve(ParametricCurveTagData const& tag_data)
+{
+    // ICC v4, 10.18 parametricCurveType
+    auto bytes = TRY(ByteBuffer::create_uninitialized(2 * sizeof(u32) + 2 * sizeof(u16) + tag_data.parameter_count() * sizeof(s15Fixed16Number)));
+    *bit_cast<BigEndian<u32>*>(bytes.data()) = (u32)ParametricCurveTagData::Type;
+    *bit_cast<BigEndian<u32>*>(bytes.data() + 4) = 0;
+
+    *bit_cast<BigEndian<u16>*>(bytes.data() + 8) = (u16)tag_data.function_type();
+    *bit_cast<BigEndian<u16>*>(bytes.data() + 10) = 0;
+
+    auto* parameters = bit_cast<BigEndian<s15Fixed16Number>*>(bytes.data() + 12);
+    for (size_t i = 0; i < tag_data.parameter_count(); ++i)
+        parameters[i] = tag_data.parameter(i).raw();
+
+    return bytes;
+}
+
 static ErrorOr<ByteBuffer> encode_s15_fixed_array(S15Fixed16ArrayTagData const& tag_data)
 {
     // ICC v4, 10.22 s15Fixed16ArrayType
@@ -93,6 +110,8 @@ static ErrorOr<ByteBuffer> encode_tag_data(TagData const& tag_data)
     switch (tag_data.type()) {
     case MultiLocalizedUnicodeTagData::Type:
         return encode_multi_localized_unicode(static_cast<MultiLocalizedUnicodeTagData const&>(tag_data));
+    case ParametricCurveTagData::Type:
+        return encode_parametric_curve(static_cast<ParametricCurveTagData const&>(tag_data));
     case S15Fixed16ArrayTagData::Type:
         return encode_s15_fixed_array(static_cast<S15Fixed16ArrayTagData const&>(tag_data));
     case XYZTagData::Type:
diff --git a/Userland/Libraries/LibGfx/ICC/TagTypes.h b/Userland/Libraries/LibGfx/ICC/TagTypes.h
index 2e4ac26e58..b936e7e672 100644
--- a/Userland/Libraries/LibGfx/ICC/TagTypes.h
+++ b/Userland/Libraries/LibGfx/ICC/TagTypes.h
@@ -626,6 +626,13 @@ public:
 
     static unsigned parameter_count(FunctionType);
 
+    unsigned parameter_count() const { return parameter_count(function_type()); }
+    S15Fixed16 parameter(size_t i) const
+    {
+        VERIFY(i < parameter_count());
+        return m_parameters[i];
+    }
+
     S15Fixed16 g() const { return m_parameters[0]; }
     S15Fixed16 a() const
     {