Implement GetPixelTypeInfo() for EXR

src/ImageSharp/Formats/Exr/Constants/ExrImageDataType.cs

@@ -3,13 +3,28 @@
 
 namespace SixLabors.ImageSharp.Formats.Exr.Constants;
 
-internal enum ExrImageDataType
+/// <summary>
+/// This enum represents the type of pixel data in the EXR image.
+/// </summary>
+public enum ExrImageDataType
 {
+    /// <summary>
+    /// The pixel data is unknown.
+    /// </summary>
     Unknown = 0,
 
+    /// <summary>
+    /// The pixel data has 3 channels: red, green and blue.
+    /// </summary>
     Rgb = 1,
 
+    /// <summary>
+    /// The pixel data has four channels: red, green, blue and a alpha channel.
+    /// </summary>
     Rgba = 2,
 
+    /// <summary>
+    /// There is only one channel with the luminance.
+    /// </summary>
     Gray = 3,
 }

src/ImageSharp/Formats/Exr/ExrDecoderCore.cs

@@ -79,6 +79,11 @@ internal sealed class ExrDecoderCore : ImageDecoderCore
     /// </summary>
     private ExrCompression Compression { get; set; }
 
+    /// <summary>
+    /// Gets or sets the image data type, either RGB, RGBA or gray.
+    /// </summary>
+    private ExrImageDataType ImageDataType { get; set; }
+
     /// <summary>
     /// Gets or sets the pixel type.
     /// </summary>
@@ -403,6 +408,59 @@ internal sealed class ExrDecoderCore : ImageDecoderCore
         return pixelType;
     }
 
+    private ExrImageDataType ReadImageDataType()
+    {
+        bool hasRedChannel = false;
+        bool hasGreenChannel = false;
+        bool hasBlueChannel = false;
+        bool hasAlphaChannel = false;
+        bool hasLuminance = false;
+        foreach (ExrChannelInfo channelInfo in this.Channels)
+        {
+            if (channelInfo.ChannelName.Equals("A", StringComparison.Ordinal))
+            {
+                hasAlphaChannel = true;
+            }
+
+            if (channelInfo.ChannelName.Equals("R", StringComparison.Ordinal))
+            {
+                hasRedChannel = true;
+            }
+
+            if (channelInfo.ChannelName.Equals("G", StringComparison.Ordinal))
+            {
+                hasGreenChannel = true;
+            }
+
+            if (channelInfo.ChannelName.Equals("B", StringComparison.Ordinal))
+            {
+                hasBlueChannel = true;
+            }
+
+            if (channelInfo.ChannelName.Equals("Y", StringComparison.Ordinal))
+            {
+                hasLuminance = true;
+            }
+        }
+
+        if (hasRedChannel && hasGreenChannel && hasBlueChannel && hasAlphaChannel)
+        {
+            return ExrImageDataType.Rgba;
+        }
+
+        if (hasRedChannel && hasGreenChannel && hasBlueChannel)
+        {
+            return ExrImageDataType.Rgb;
+        }
+
+        if (hasLuminance && this.Channels.Count == 1)
+        {
+            return ExrImageDataType.Gray;
+        }
+
+        return ExrImageDataType.Unknown;
+    }
+
     private ExrHeaderAttributes ReadExrHeader(BufferedReadStream stream)
     {
         // Skip over the magick bytes, we already know its an EXR image.
@@ -431,11 +489,13 @@ internal sealed class ExrDecoderCore : ImageDecoderCore
         this.Channels = this.HeaderAttributes.Channels;
         this.Compression = this.HeaderAttributes.Compression;
         this.PixelType = this.ValidateChannels();
+        this.ImageDataType = this.ReadImageDataType();
 
         this.metadata = new ImageMetadata();
 
         this.exrMetadata = this.metadata.GetExrMetadata();
         this.exrMetadata.PixelType = this.PixelType;
+        this.exrMetadata.ImageDataType = this.ImageDataType;
 
         return this.HeaderAttributes;
     }

src/ImageSharp/Formats/Exr/ExrMetadata.cs

@@ -30,12 +30,69 @@ public class ExrMetadata : IFormatMetadata<ExrMetadata>
     /// </summary>
     public ExrPixelType PixelType { get; set; } = ExrPixelType.Half;
 
+    /// <summary>
+    /// Gets or sets the image data type, either RGB, RGBA or gray.
+    /// </summary>
+    public ExrImageDataType ImageDataType { get; set; } = ExrImageDataType.Unknown;
+
     /// <inheritdoc/>
-    public void AfterImageApply<TPixel>(Image<TPixel> destination, Matrix4x4 matrix)
+    public PixelTypeInfo GetPixelTypeInfo()
-        where TPixel : unmanaged, IPixel<TPixel> => throw new NotImplementedException();
+    {
+        bool hasAlpha = this.ImageDataType is ExrImageDataType.Rgba;
+
+        int bitsPerComponent = 32;
+        int bitsPerPixel = hasAlpha ? bitsPerComponent * 4 : bitsPerComponent * 3;
+        if (this.PixelType == ExrPixelType.Half)
+        {
+            bitsPerComponent = 16;
+            bitsPerPixel = hasAlpha ? bitsPerComponent * 4 : bitsPerComponent * 3;
+        }
+
+        PixelAlphaRepresentation alpha = hasAlpha ? PixelAlphaRepresentation.Unassociated : PixelAlphaRepresentation.None;
+        PixelColorType color = PixelColorType.RGB;
+
+        int componentsCount = 0;
+        int[] precision = [];
+        switch (this.ImageDataType)
+        {
+            case ExrImageDataType.Rgb:
+                color = PixelColorType.RGB;
+                componentsCount = 3;
+                precision = new int[componentsCount];
+                precision[0] = bitsPerComponent;
+                precision[1] = bitsPerComponent;
+                precision[2] = bitsPerComponent;
+                break;
+            case ExrImageDataType.Rgba:
+                color = PixelColorType.RGB | PixelColorType.Alpha;
+                componentsCount = 4;
+                precision = new int[componentsCount];
+                precision[0] = bitsPerComponent;
+                precision[1] = bitsPerComponent;
+                precision[2] = bitsPerComponent;
+                precision[3] = bitsPerComponent;
+                break;
+            case ExrImageDataType.Gray:
+                color = PixelColorType.Luminance;
+                componentsCount = 1;
+                precision = new int[componentsCount];
+                precision[0] = bitsPerComponent;
+                break;
+        }
+
+        PixelComponentInfo info = PixelComponentInfo.Create(componentsCount, bitsPerPixel, precision);
+        return new PixelTypeInfo(bitsPerPixel)
+        {
+            AlphaRepresentation = alpha,
+            ComponentInfo = info,
+            ColorType = color
+        };
+    }
+
 
     /// <inheritdoc/>
-    public PixelTypeInfo GetPixelTypeInfo() => throw new NotImplementedException();
+    public void AfterImageApply<TPixel>(Image<TPixel> destination, Matrix4x4 matrix)
+        where TPixel : unmanaged, IPixel<TPixel> => throw new NotImplementedException();
 
     /// <inheritdoc/>
     public FormatConnectingMetadata ToFormatConnectingMetadata() => throw new NotImplementedException();

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

@@ -30,7 +30,20 @@ public class ExrDecoderTests
 
     [Theory]
     [InlineData(TestImages.Exr.Uncompressed)]
-    public void ExrDecoder_Identify_DetectsCorrectPixelType<TPixel>(string imagePath)
+    public void ExrDecoder_Identify_DetectsCorrectPixelType_Half<TPixel>(string imagePath)
+    {
+        TestFile testFile = TestFile.Create(imagePath);
+        using MemoryStream stream = new(testFile.Bytes, false);
+        ImageInfo imageInfo = Image.Identify(stream);
+        ExrMetadata exrMetaData = imageInfo.Metadata.GetExrMetadata();
+
+        Assert.NotNull(imageInfo);
+        Assert.Equal(ExrPixelType.Half, exrMetaData.PixelType);
+    }
+
+    [Theory]
+    [InlineData(TestImages.Exr.UncompressedFloatRgb)]
+    public void ExrDecoder_Identify_DetectsCorrectPixelType_Float<TPixel>(string imagePath)
     {
         TestFile testFile = TestFile.Create(imagePath);
         using MemoryStream stream = new(testFile.Bytes, false);
@@ -41,6 +54,19 @@ public class ExrDecoderTests
         Assert.Equal(ExrPixelType.Float, exrMetaData.PixelType);
     }
 
+    [Theory]
+    [InlineData(TestImages.Exr.UncompressedUintRgb)]
+    public void ExrDecoder_Identify_DetectsCorrectPixelType_Int<TPixel>(string imagePath)
+    {
+        TestFile testFile = TestFile.Create(imagePath);
+        using MemoryStream stream = new(testFile.Bytes, false);
+        ImageInfo imageInfo = Image.Identify(stream);
+        ExrMetadata exrMetaData = imageInfo.Metadata.GetExrMetadata();
+
+        Assert.NotNull(imageInfo);
+        Assert.Equal(ExrPixelType.UnsignedInt, exrMetaData.PixelType);
+    }
+
     [Theory]
     [WithFile(TestImages.Exr.Uncompressed, PixelTypes.Rgba32)]
     public void ExrDecoder_CanDecode_Uncompressed_Rgba_ExrPixelType_Half<TPixel>(TestImageProvider<TPixel> provider)