Merge pull request #3159 from SixLabors/fix/3145-preserve-tiff-icc-profile

Clone TIFF profiles into image metadata

src/ImageSharp/Formats/Tiff/TiffDecoderMetadataCreator.cs

@@ -22,8 +22,6 @@ internal static class TiffDecoderMetadataCreator
             TiffThrowHelper.ThrowImageFormatException("Expected at least one frame.");
         }
 
-        ImageMetadata imageMetaData = Create(byteOrder, isBigTiff, frames[0]);
-
         if (!ignoreMetadata)
         {
             for (int i = 0; i < frames.Count; i++)
@@ -43,12 +41,24 @@ internal static class TiffDecoderMetadataCreator
             }
         }
 
-        return imageMetaData;
+        // IPTC and XMP are materialized from IFD tags above, so image-level metadata
+        // must be created after all frame profiles are available.
+        return Create(byteOrder, isBigTiff, frames[0]);
     }
 
     private static ImageMetadata Create(ByteOrder byteOrder, bool isBigTiff, ImageFrameMetadata rootFrameMetadata)
     {
-        ImageMetadata imageMetaData = new();
+        // TIFF stores metadata per IFD, while ImageMetadata is the source used by single-frame encoders.
+        // Mirror the root IFD profiles at image scope so cross-format encoding preserves them. Each profile
+        // is cloned because image-level and frame-level metadata are independently mutable public APIs.
+        ImageMetadata imageMetaData = new()
+        {
+            ExifProfile = rootFrameMetadata.ExifProfile?.DeepClone(),
+            IccProfile = rootFrameMetadata.IccProfile?.DeepClone(),
+            IptcProfile = rootFrameMetadata.IptcProfile?.DeepClone(),
+            XmpProfile = rootFrameMetadata.XmpProfile?.DeepClone()
+        };
+
         SetResolution(imageMetaData, rootFrameMetadata.ExifProfile);
 
         TiffMetadata tiffMetadata = imageMetaData.GetTiffMetadata();

src/ImageSharp/Metadata/Profiles/Exif/ExifWriter.cs

@@ -403,6 +403,13 @@ internal sealed class ExifWriter
                     return WriteUInt32((uint)longNumber, destination, offset);
                 }
 
+                // ExifLong8Array retains ulong storage but reports Long when every value fits
+                // in 32 bits, allowing BigTIFF offsets to be serialized by classic EXIF writers.
+                if (value is ulong long8Value)
+                {
+                    return WriteUInt32((uint)long8Value, destination, offset);
+                }
+
                 return WriteUInt32((uint)value, destination, offset);
             case ExifDataType.Long8:
                 return WriteUInt64((ulong)value, destination, offset);

tests/ImageSharp.Tests/Formats/Tiff/BigTiffMetadataTests.cs

@@ -88,6 +88,21 @@ public class BigTiffMetadataTests
         Assert.Equal(ExifDataType.Long8, long8.DataType);
     }
 
+    [Fact]
+    public void ExifLong8Array_CanWriteValuesAsLong()
+    {
+        ExifLong8Array long8 = new(ExifTagValue.StripOffsets);
+        Assert.True(long8.TrySetValue(new long[] { 1, uint.MaxValue }));
+        Assert.Equal(ExifDataType.Long, long8.DataType);
+
+        byte[] buffer = new byte[8];
+        int written = ExifWriter.WriteValue(long8, buffer, 0);
+
+        Assert.Equal(buffer.Length, written);
+        Assert.Equal(1U, BinaryPrimitives.ReadUInt32LittleEndian(buffer));
+        Assert.Equal(uint.MaxValue, BinaryPrimitives.ReadUInt32LittleEndian(buffer.AsSpan(4)));
+    }
+
     [Fact]
     public void ExifSignedLong8Array()
     {

tests/ImageSharp.Tests/Formats/Tiff/TiffDecoderTests.cs

@@ -370,6 +370,22 @@ public class TiffDecoderTests : TiffDecoderBaseTester
         Assert.Null(image.Metadata.IccProfile);
     }
 
+    [Theory]
+    [WithFile(Icc.PerceptualRgb8, PixelTypes.Rgba32)]
+    [WithFile(Icc.PerceptualRgb16, PixelTypes.Rgba32)]
+    public void Decode_WhenColorProfileHandlingIsPreserve_PreservesIccProfile<TPixel>(TestImageProvider<TPixel> provider)
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        DecoderOptions options = new() { ColorProfileHandling = ColorProfileHandling.Preserve };
+        using Image<TPixel> image = provider.GetImage(TiffDecoder.Instance, options);
+
+        Assert.NotNull(image.Metadata.IccProfile);
+        Assert.NotSame(image.Frames.RootFrame.Metadata.IccProfile, image.Metadata.IccProfile);
+        Assert.Equal(
+            image.Frames.RootFrame.Metadata.IccProfile.ToByteArray(),
+            image.Metadata.IccProfile.ToByteArray());
+    }
+
     [Theory]
     [WithFile(Issues2454_A, PixelTypes.Rgba32)]
     [WithFile(Issues2454_B, PixelTypes.Rgba32)]

tests/ImageSharp.Tests/Formats/Tiff/TiffMetadataTests.cs

@@ -150,13 +150,22 @@ public class TiffMetadataTests
         Assert.NotNull(meta);
         if (ignoreMetadata)
         {
+            Assert.Null(image.Metadata.XmpProfile);
+            Assert.Null(image.Metadata.ExifProfile);
             Assert.Null(rootFrameMetaData.XmpProfile);
             Assert.Null(rootFrameMetaData.ExifProfile);
         }
         else
         {
+            Assert.NotNull(image.Metadata.XmpProfile);
+            Assert.NotNull(image.Metadata.ExifProfile);
             Assert.NotNull(rootFrameMetaData.XmpProfile);
             Assert.NotNull(rootFrameMetaData.ExifProfile);
+
+            Assert.NotSame(rootFrameMetaData.XmpProfile, image.Metadata.XmpProfile);
+            Assert.NotSame(rootFrameMetaData.ExifProfile, image.Metadata.ExifProfile);
+            Assert.Equal(rootFrameMetaData.XmpProfile.Data, image.Metadata.XmpProfile.Data);
+            Assert.Equal(rootFrameMetaData.ExifProfile.ToByteArray(), image.Metadata.ExifProfile.ToByteArray());
             Assert.Equal(2596, rootFrameMetaData.XmpProfile.Data.Length); // padding bytes are trimmed
             Assert.Equal(25, rootFrameMetaData.ExifProfile.Values.Count);
         }
@@ -171,6 +180,10 @@ public class TiffMetadataTests
 
         IptcProfile iptcProfile = image.Frames.RootFrame.Metadata.IptcProfile;
         Assert.NotNull(iptcProfile);
+        Assert.NotNull(image.Metadata.IptcProfile);
+        Assert.NotSame(iptcProfile, image.Metadata.IptcProfile);
+        Assert.Equal(iptcProfile.Data, image.Metadata.IptcProfile.Data);
+
         IptcValue byline = iptcProfile.Values.FirstOrDefault(data => data.Tag == IptcTag.Byline);
         Assert.NotNull(byline);
         Assert.Equal("Studio Mantyniemi", byline.Value);