Enhance metadata conversion

Author: JimBobSquarePants

src/ImageSharp/Formats/Exr/ExrMetadata.cs

@@ -95,14 +95,52 @@ public PixelTypeInfo GetPixelTypeInfo()
     }
 
     /// <inheritdoc/>
-    public FormatConnectingMetadata ToFormatConnectingMetadata() => new()
+    public FormatConnectingMetadata ToFormatConnectingMetadata()
     {
-        EncodingType = this.Compression is ExrCompression.B44 or ExrCompression.B44A or ExrCompression.Pxr24 ? EncodingType.Lossy : EncodingType.Lossless,
-        PixelTypeInfo = this.GetPixelTypeInfo()
-    };
+        EncodingType type = this.Compression is ExrCompression.B44 or ExrCompression.B44A or ExrCompression.Pxr24
+            ? EncodingType.Lossy
+            : EncodingType.Lossless;
+
+        return new()
+        {
+            EncodingType = type,
+            PixelTypeInfo = this.GetPixelTypeInfo()
+        };
+    }
 
     /// <inheritdoc/>
-    public static ExrMetadata FromFormatConnectingMetadata(FormatConnectingMetadata metadata) => new() { PixelType = ExrPixelType.Half };
+    public static ExrMetadata FromFormatConnectingMetadata(FormatConnectingMetadata metadata)
+    {
+        PixelTypeInfo pixelTypeInfo = metadata.PixelTypeInfo;
+        PixelComponentInfo? info = pixelTypeInfo.ComponentInfo;
+        PixelColorType colorType = pixelTypeInfo.ColorType;
+
+        int bitsPerComponent = info?.GetMaximumComponentPrecision()
+            ?? (pixelTypeInfo.BitsPerPixel <= 16 ? 16 : 32);
+
+        int componentCount = info?.ComponentCount ?? 0;
+        ExrImageDataType imageDataType = colorType switch
+        {
+            PixelColorType.Luminance => ExrImageDataType.Gray,
+            PixelColorType.RGB or PixelColorType.BGR => ExrImageDataType.Rgb,
+            PixelColorType.RGB | PixelColorType.Alpha
+                or PixelColorType.BGR | PixelColorType.Alpha
+                or PixelColorType.Luminance | PixelColorType.Alpha => ExrImageDataType.Rgba,
+            _ => componentCount switch
+            {
+                >= 4 => ExrImageDataType.Rgba,
+                >= 3 => ExrImageDataType.Rgb,
+                1 => ExrImageDataType.Gray,
+                _ => ExrImageDataType.Unknown,
+            }
+        };
+
+        return new()
+        {
+            PixelType = bitsPerComponent <= 16 ? ExrPixelType.Half : ExrPixelType.Float,
+            ImageDataType = imageDataType,
+        };
+    }
 
     /// <inheritdoc/>
     ExrMetadata IDeepCloneable<ExrMetadata>.DeepClone() => new(this);

tests/ImageSharp.Tests/Formats/Exr/ExrMetadataTests.cs

@@ -1,8 +1,10 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Formats.Exr;
 using SixLabors.ImageSharp.Formats.Exr.Constants;
+using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp.Tests.Formats.Exr;
 
@@ -85,4 +87,32 @@ public void Identify_DetectsCorrectCompression(string imagePath, ExrCompression
         Assert.NotNull(metadata);
         Assert.Equal(expectedCompression, metadata.Compression);
     }
+
+    [Theory]
+    [InlineData(PixelColorType.Binary, 1, ExrImageDataType.Unknown, ExrPixelType.Half)]
+    [InlineData(PixelColorType.Indexed, 8, ExrImageDataType.Unknown, ExrPixelType.Half)]
+    [InlineData(PixelColorType.Luminance, 16, ExrImageDataType.Gray, ExrPixelType.Half)]
+    [InlineData(PixelColorType.RGB, 48, ExrImageDataType.Rgb, ExrPixelType.Float)]
+    [InlineData(PixelColorType.BGR, 48, ExrImageDataType.Rgb, ExrPixelType.Float)]
+    [InlineData(PixelColorType.RGB | PixelColorType.Alpha, 64, ExrImageDataType.Rgba, ExrPixelType.Float)]
+    [InlineData(PixelColorType.BGR | PixelColorType.Alpha, 64, ExrImageDataType.Rgba, ExrPixelType.Float)]
+    [InlineData(PixelColorType.Luminance | PixelColorType.Alpha, 32, ExrImageDataType.Rgba, ExrPixelType.Float)]
+    [InlineData(PixelColorType.YCbCr, 48, ExrImageDataType.Unknown, ExrPixelType.Float)]
+    [InlineData(PixelColorType.CMYK, 64, ExrImageDataType.Unknown, ExrPixelType.Float)]
+    [InlineData(PixelColorType.YCCK, 64, ExrImageDataType.Unknown, ExrPixelType.Float)]
+    public void FromFormatConnectingMetadata_ConvertColorTypeAsExpected(PixelColorType pixelColorType, int bitsPerPixel, ExrImageDataType expectedImageDataType, ExrPixelType expectedPixelType)
+    {
+        FormatConnectingMetadata formatConnectingMetadata = new()
+        {
+            PixelTypeInfo = new PixelTypeInfo(bitsPerPixel)
+            {
+                ColorType = pixelColorType,
+            },
+        };
+
+        ExrMetadata actual = ExrMetadata.FromFormatConnectingMetadata(formatConnectingMetadata);
+
+        Assert.Equal(expectedImageDataType, actual.ImageDataType);
+        Assert.Equal(expectedPixelType, actual.PixelType);
+    }
 }