Fix small deviation to the spec when encoding tiff images

src/ImageSharp/Formats/Tiff/TiffEncoderCore.cs

@@ -244,6 +244,12 @@ private long WriteFrame<TPixel>(
         entriesCollector.ProcessFrameInfo(frame, imageMetadata);
         entriesCollector.ProcessImageFormat(this);
 
+        if (writer.Position % 2 != 0)
+        {
+            // Write padding byte, because the tiff spec requires ifd offset to begin on a word boundary.
+            writer.Write(0);
+        }
+
         this.frameMarkers.Add((ifdOffset, (uint)writer.Position));
 
         return this.WriteIfd(writer, entriesCollector.Entries);

src/ImageSharp/Formats/Tiff/TiffEncoderEntriesCollector.cs

@@ -178,7 +178,7 @@ private void ProcessProfiles(ImageMetadata imageMetadata, bool skipMetadata, Exi
                     Value = imageMetadata.IptcProfile.Data
                 };
 
-                this.Collector.Add(iptc);
+                this.Collector.AddOrReplace(iptc);
             }
             else
             {
@@ -192,7 +192,7 @@ private void ProcessProfiles(ImageMetadata imageMetadata, bool skipMetadata, Exi
                     Value = imageMetadata.IccProfile.ToByteArray()
                 };
 
-                this.Collector.Add(icc);
+                this.Collector.AddOrReplace(icc);
             }
             else
             {
@@ -206,7 +206,7 @@ private void ProcessProfiles(ImageMetadata imageMetadata, bool skipMetadata, Exi
                     Value = xmpProfile.Data
                 };
 
-                this.Collector.Add(xmp);
+                this.Collector.AddOrReplace(xmp);
             }
             else
             {
@@ -278,7 +278,7 @@ public void Process(TiffEncoderCore encoder)
                 Value = (ushort)TiffPlanarConfiguration.Chunky
             };
 
-            ExifLong samplesPerPixel = new(ExifTagValue.SamplesPerPixel)
+            ExifShort samplesPerPixel = new(ExifTagValue.SamplesPerPixel)
             {
                 Value = GetSamplesPerPixel(encoder)
             };
@@ -317,7 +317,7 @@ TiffPhotometricInterpretation.PaletteColor or
             }
         }
 
-        private static uint GetSamplesPerPixel(TiffEncoderCore encoder)
+        private static ushort GetSamplesPerPixel(TiffEncoderCore encoder)
             => encoder.PhotometricInterpretation switch
             {
                 TiffPhotometricInterpretation.PaletteColor or

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

@@ -246,6 +246,25 @@ public void TiffEncoder_PreservesPredictor<TPixel>(TestImageProvider<TPixel> pro
         Assert.Equal(expectedPredictor, frameMetadata.Predictor);
     }
 
+    // https://github.com/SixLabors/ImageSharp/issues/2297
+    [Fact]
+    public void TiffEncoder_WritesIfdOffsetAtWordBoundary()
+    {
+        // arrange
+        var tiffEncoder = new TiffEncoder();
+        using var memStream = new MemoryStream();
+        using Image<Rgba32> image = new(1, 1);
+        byte[] expectedIfdOffsetBytes = { 12, 0 };
+
+        // act
+        image.Save(memStream, tiffEncoder);
+
+        // assert
+        byte[] imageBytes = memStream.ToArray();
+        Assert.Equal(imageBytes[4], expectedIfdOffsetBytes[0]);
+        Assert.Equal(imageBytes[5], expectedIfdOffsetBytes[1]);
+    }
+
     [Theory]
     [WithFile(RgbUncompressed, PixelTypes.Rgba32, TiffCompression.CcittGroup3Fax, TiffCompression.CcittGroup3Fax)]
     [WithFile(RgbUncompressed, PixelTypes.Rgba32, TiffCompression.CcittGroup4Fax, TiffCompression.CcittGroup4Fax)]

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

@@ -71,7 +71,6 @@ private static void VerifyExpectedTiffFrameMetaDataIsPresent(TiffFrameMetadata f
         Assert.Equal(TiffBitsPerPixel.Bit4, frameMetaData.BitsPerPixel);
         Assert.Equal(TiffCompression.Lzw, frameMetaData.Compression);
         Assert.Equal(TiffPhotometricInterpretation.PaletteColor, frameMetaData.PhotometricInterpretation);
-        Assert.Equal(TiffPredictor.None, frameMetaData.Predictor);
     }
 
     [Theory]
@@ -129,7 +128,7 @@ public void MetadataProfiles<TPixel>(TestImageProvider<TPixel> provider, bool ig
             Assert.NotNull(rootFrameMetaData.XmpProfile);
             Assert.NotNull(rootFrameMetaData.ExifProfile);
             Assert.Equal(2599, rootFrameMetaData.XmpProfile.Data.Length);
-            Assert.Equal(26, rootFrameMetaData.ExifProfile.Values.Count);
+            Assert.Equal(25, rootFrameMetaData.ExifProfile.Values.Count);
         }
     }
 
@@ -163,38 +162,33 @@ public void BaselineTags<TPixel>(TestImageProvider<TPixel> provider)
         TiffFrameMetadata tiffFrameMetadata = rootFrame.Metadata.GetTiffMetadata();
         Assert.NotNull(exifProfile);
 
-        // The original exifProfile has 30 values, but 4 of those values will be stored in the TiffFrameMetaData
-        // and removed from the profile on decode.
-        Assert.Equal(26, exifProfile.Values.Count);
+        Assert.Equal(25, exifProfile.Values.Count);
         Assert.Equal(TiffBitsPerPixel.Bit4, tiffFrameMetadata.BitsPerPixel);
         Assert.Equal(TiffCompression.Lzw, tiffFrameMetadata.Compression);
-        Assert.Equal("This is Название", exifProfile.GetValue(ExifTag.ImageDescription).Value);
-        Assert.Equal("This is Изготовитель камеры", exifProfile.GetValue(ExifTag.Make).Value);
-        Assert.Equal("This is Модель камеры", exifProfile.GetValue(ExifTag.Model).Value);
-        Assert.Equal("IrfanView", exifProfile.GetValue(ExifTag.Software).Value);
+        Assert.Equal("ImageDescription", exifProfile.GetValue(ExifTag.ImageDescription).Value);
+        Assert.Equal("Make", exifProfile.GetValue(ExifTag.Make).Value);
+        Assert.Equal("Model", exifProfile.GetValue(ExifTag.Model).Value);
+        Assert.Equal("ImageSharp", exifProfile.GetValue(ExifTag.Software).Value);
         Assert.Null(exifProfile.GetValue(ExifTag.DateTime)?.Value);
-        Assert.Equal("This is author1;Author2", exifProfile.GetValue(ExifTag.Artist).Value);
+        Assert.Equal("Artist", exifProfile.GetValue(ExifTag.Artist).Value);
         Assert.Null(exifProfile.GetValue(ExifTag.HostComputer)?.Value);
-        Assert.Equal("This is Авторские права", exifProfile.GetValue(ExifTag.Copyright).Value);
+        Assert.Equal("Copyright", exifProfile.GetValue(ExifTag.Copyright).Value);
         Assert.Equal(4, exifProfile.GetValue(ExifTag.Rating).Value);
         Assert.Equal(75, exifProfile.GetValue(ExifTag.RatingPercent).Value);
-        var expectedResolution = new Rational(10000, 1000, simplify: false);
+        var expectedResolution = new Rational(10, 1, simplify: false);
         Assert.Equal(expectedResolution, exifProfile.GetValue(ExifTag.XResolution).Value);
         Assert.Equal(expectedResolution, exifProfile.GetValue(ExifTag.YResolution).Value);
         Assert.Equal(new Number[] { 8u }, exifProfile.GetValue(ExifTag.StripOffsets)?.Value, new NumberComparer());
-        Assert.Equal(new Number[] { 297u }, exifProfile.GetValue(ExifTag.StripByteCounts)?.Value, new NumberComparer());
+        Assert.Equal(new Number[] { 285u }, exifProfile.GetValue(ExifTag.StripByteCounts)?.Value, new NumberComparer());
         Assert.Null(exifProfile.GetValue(ExifTag.ExtraSamples)?.Value);
         Assert.Equal(32u, exifProfile.GetValue(ExifTag.RowsPerStrip).Value);
         Assert.Null(exifProfile.GetValue(ExifTag.SampleFormat));
-        Assert.Equal(TiffPredictor.None, tiffFrameMetadata.Predictor);
         Assert.Equal(PixelResolutionUnit.PixelsPerInch, UnitConverter.ExifProfileToResolutionUnit(exifProfile));
         ushort[] colorMap = exifProfile.GetValue(ExifTag.ColorMap)?.Value;
         Assert.NotNull(colorMap);
         Assert.Equal(48, colorMap.Length);
-        Assert.Equal(10537, colorMap[0]);
-        Assert.Equal(14392, colorMap[1]);
-        Assert.Equal(58596, colorMap[46]);
-        Assert.Equal(3855, colorMap[47]);
+        Assert.Equal(4369, colorMap[0]);
+        Assert.Equal(8738, colorMap[1]);
         Assert.Equal(TiffPhotometricInterpretation.PaletteColor, tiffFrameMetadata.PhotometricInterpretation);
         Assert.Equal(1u, exifProfile.GetValue(ExifTag.SamplesPerPixel).Value);
 
@@ -238,7 +232,7 @@ public void Encode_PreservesMetadata<TPixel>(TestImageProvider<TPixel> provider)
     {
         // Load Tiff image
         DecoderOptions options = new() { SkipMetadata = false };
-        using Image<TPixel> image = provider.GetImage(new TiffDecoder(), options);
+        using Image<TPixel> image = provider.GetImage(TiffDecoder, options);
 
         ImageMetadata inputMetaData = image.Metadata;
         ImageFrame<TPixel> rootFrameInput = image.Frames.RootFrame;
@@ -284,17 +278,15 @@ public void Encode_PreservesMetadata<TPixel>(TestImageProvider<TPixel> provider)
         Assert.NotNull(encodedImageXmpProfile);
         Assert.Equal(xmpProfileInput.Data, encodedImageXmpProfile.Data);
 
-        Assert.Equal("IrfanView", exifProfileInput.GetValue(ExifTag.Software).Value);
-        Assert.Equal("This is Название", exifProfileInput.GetValue(ExifTag.ImageDescription).Value);
-        Assert.Equal("This is Изготовитель камеры", exifProfileInput.GetValue(ExifTag.Make).Value);
-        Assert.Equal("This is Авторские права", exifProfileInput.GetValue(ExifTag.Copyright).Value);
-
+        Assert.Equal(exifProfileInput.GetValue(ExifTag.Software).Value, encodedImageExifProfile.GetValue(ExifTag.Software).Value);
         Assert.Equal(exifProfileInput.GetValue(ExifTag.ImageDescription).Value, encodedImageExifProfile.GetValue(ExifTag.ImageDescription).Value);
         Assert.Equal(exifProfileInput.GetValue(ExifTag.Make).Value, encodedImageExifProfile.GetValue(ExifTag.Make).Value);
         Assert.Equal(exifProfileInput.GetValue(ExifTag.Copyright).Value, encodedImageExifProfile.GetValue(ExifTag.Copyright).Value);
+        Assert.Equal(exifProfileInput.GetValue(ExifTag.Artist).Value, encodedImageExifProfile.GetValue(ExifTag.Artist).Value);
+        Assert.Equal(exifProfileInput.GetValue(ExifTag.Orientation).Value, encodedImageExifProfile.GetValue(ExifTag.Orientation).Value);
+        Assert.Equal(exifProfileInput.GetValue(ExifTag.Model).Value, encodedImageExifProfile.GetValue(ExifTag.Model).Value);
 
-        // Note that the encoded profile has PlanarConfiguration explicitly set, which is missing in the original image profile.
         Assert.Equal((ushort)TiffPlanarConfiguration.Chunky, encodedImageExifProfile.GetValue(ExifTag.PlanarConfiguration)?.Value);
-        Assert.Equal(exifProfileInput.Values.Count + 1, encodedImageExifProfile.Values.Count);
+        Assert.Equal(exifProfileInput.Values.Count, encodedImageExifProfile.Values.Count);
     }
 }