Merge pull request #30 from B3zaleel/implement-KHR_texture_transform-…

…extension

Implement KHR_texture_transform Gltf extension

src/ThreeDModels/Format/Gltf/Extensions/KHR_texture_transform.cs

@@ -0,0 +1,114 @@
+using System.Text.Json;
+using ThreeDModels.Format.Gltf.Elements;
+using ThreeDModels.Format.Gltf.IO;
+using static ThreeDModels.Format.Gltf.IO.Utf8JsonReaderHelpers;
+
+namespace ThreeDModels.Format.Gltf.Extensions;
+
+public class KHR_texture_transform : IGltfProperty
+{
+    /// <summary>
+    /// The offset of the UV coordinate origin as a factor of the texture dimensions.
+    /// </summary>
+    public required float[] Offset { get; set; }
+    /// <summary>
+    /// Rotate the UVs by this many radians counter-clockwise around the origin.
+    /// </summary>
+    public float Rotation { get; set; }
+    /// <summary>
+    /// The scale factor applied to the components of the UV coordinates.
+    /// </summary>
+    public required float[] Scale { get; set; }
+    /// <summary>
+    /// Overrides the textureInfo texCoord value if supplied, and if this extension is supported.
+    /// </summary>
+    public int? TexCoord { get; set; }
+    public Dictionary<string, object?>? Extensions { get; set; }
+    public object? Extras { get; set; }
+}
+
+public class KhrTextureTransformExtension : IGltfExtension
+{
+    public string Name => nameof(KHR_texture_transform);
+    public static readonly float[] Default_Offset = [0.0f, 0.0f];
+    public const float Default_Rotation = 0.0f;
+    public static readonly float[] Default_Scale = [1.0f, 1.0f];
+
+    public object? Read(ref Utf8JsonReader jsonReader, GltfReaderContext context, Type parentType)
+    {
+        if (parentType != typeof(TextureInfo))
+        {
+            throw new InvalidDataException("KHR_texture_transform must be used in a TextureInfo.");
+        }
+        float[]? offset = null;
+        float? rotation = null;
+        float[]? scale = null;
+        int? texCoord = null;
+        Dictionary<string, object?>? extensions = null;
+        object? extras = null;
+        if (jsonReader.TokenType == JsonTokenType.PropertyName && jsonReader.Read())
+        {
+        }
+        if (jsonReader.TokenType == JsonTokenType.Null)
+        {
+            return null;
+        }
+        else if (jsonReader.TokenType != JsonTokenType.StartObject)
+        {
+            throw new InvalidDataException("Failed to find start of property.");
+        }
+        while (jsonReader.Read())
+        {
+            if (jsonReader.TokenType == JsonTokenType.EndObject)
+            {
+                break;
+            }
+            var propertyName = jsonReader.GetString();
+            if (propertyName == nameof(offset))
+            {
+                offset = ReadFloatList(ref jsonReader, context)?.ToArray();
+            }
+            else if (propertyName == nameof(rotation))
+            {
+                rotation = ReadFloat(ref jsonReader);
+            }
+            else if (propertyName == nameof(scale))
+            {
+                scale = ReadFloatList(ref jsonReader, context)?.ToArray();
+            }
+            else if (propertyName == nameof(texCoord))
+            {
+                texCoord = ReadInteger(ref jsonReader);
+            }
+            else if (propertyName == nameof(extensions))
+            {
+                extensions = ExtensionsSerialization.Read<KHR_texture_transform>(ref jsonReader, context);
+            }
+            else if (propertyName == nameof(extras))
+            {
+                extras = JsonSerialization.Read(ref jsonReader, context);
+            }
+            else
+            {
+                throw new InvalidDataException($"Unknown property: {propertyName}");
+            }
+        }
+        if (offset != null && offset.Length != 2)
+        {
+            throw new InvalidDataException("KHR_texture_transform.offset must have 2 items.");
+        }
+        if (scale != null && scale.Length != 2)
+        {
+            throw new InvalidDataException("KHR_texture_transform.scale must have 2 items.");
+        }
+        return new KHR_texture_transform()
+        {
+            Offset = offset ?? Default_Offset,
+            Rotation = rotation ?? Default_Rotation,
+            Scale = scale ?? Default_Scale,
+            TexCoord = texCoord,
+            Extensions = extensions,
+            Extras = extras,
+        };
+    }
+}