Refactor TIFF metadata reading into separate method

src/ImageSharp/Formats/Tiff/TiffDecoderCore.cs

@@ -208,6 +208,25 @@ namespace ImageSharp.Formats
 
             Image<TPixel> image = new Image<TPixel>(this.configuration, width, height);
 
+            this.ReadMetadata(ifd, image);
+            this.ReadImageFormat(ifd);
+
+            if (ifd.TryGetIfdEntry(TiffTags.RowsPerStrip, out TiffIfdEntry rowsPerStripEntry)
+                && ifd.TryGetIfdEntry(TiffTags.StripOffsets, out TiffIfdEntry stripOffsetsEntry)
+                && ifd.TryGetIfdEntry(TiffTags.StripByteCounts, out TiffIfdEntry stripByteCountsEntry))
+            {
+                int rowsPerStrip = (int)this.ReadUnsignedInteger(ref rowsPerStripEntry);
+                uint[] stripOffsets = this.ReadUnsignedIntegerArray(ref stripOffsetsEntry);
+                uint[] stripByteCounts = this.ReadUnsignedIntegerArray(ref stripByteCountsEntry);
+                this.DecodeImageStrips(image, rowsPerStrip, stripOffsets, stripByteCounts);
+            }
+
+            return image;
+        }
+
+        public void ReadMetadata<TPixel>(TiffIfd ifd, Image<TPixel> image)
+            where TPixel : struct, IPixel<TPixel>
+        {
             TiffResolutionUnit resolutionUnit = (TiffResolutionUnit)this.ReadUnsignedInteger(ifd, TiffTags.ResolutionUnit, (uint)TiffResolutionUnit.Inch);
 
             if (resolutionUnit != TiffResolutionUnit.None)
@@ -226,20 +245,6 @@ namespace ImageSharp.Formats
                     image.MetaData.VerticalResolution = yResolution.ToDouble() * resolutionUnitFactor;
                 }
             }
-
-            this.ReadImageFormat(ifd);
-
-            if (ifd.TryGetIfdEntry(TiffTags.RowsPerStrip, out TiffIfdEntry rowsPerStripEntry)
-                && ifd.TryGetIfdEntry(TiffTags.StripOffsets, out TiffIfdEntry stripOffsetsEntry)
-                && ifd.TryGetIfdEntry(TiffTags.StripByteCounts, out TiffIfdEntry stripByteCountsEntry))
-            {
-                int rowsPerStrip = (int)this.ReadUnsignedInteger(ref rowsPerStripEntry);
-                uint[] stripOffsets = this.ReadUnsignedIntegerArray(ref stripOffsetsEntry);
-                uint[] stripByteCounts = this.ReadUnsignedIntegerArray(ref stripByteCountsEntry);
-                this.DecodeImageStrips(image, rowsPerStrip, stripOffsets, stripByteCounts);
-            }
-
-            return image;
         }
 
         /// <summary>

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

@@ -16,8 +16,6 @@ namespace ImageSharp.Tests
     {
         public const int ImageWidth = 200;
         public const int ImageHeight = 150;
-        public const int XResolution = 100;
-        public const int YResolution = 200;
 
         public static object[][] IsLittleEndianValues = new[] { new object[] { false },
                                                                 new object[] { true } };
@@ -37,57 +35,6 @@ namespace ImageSharp.Tests
             Assert.Equal(ImageHeight, image.Height);
         }
 
-        [Theory]
-        [InlineData(false, 150u, 1u, 200u, 1u, 2u /* Inch */, 150.0, 200.0)]
-        [InlineData(false, 150u, 1u, 200u, 1u, 3u /* Cm */, 150.0 * 2.54, 200.0 * 2.54)]
-        [InlineData(false, 150u, 1u, 200u, 1u, 1u /* None */, 96.0, 96.0)]
-        [InlineData(false, 150u, 1u, 200u, 1u, null /* Inch */, 150.0, 200.0)]
-        [InlineData(false, 5u, 2u, 9u, 4u, 2u /* Inch */, 2.5, 2.25)]
-        [InlineData(false, null, null, null, null, null /* Inch */, 96.0, 96.0)]
-        [InlineData(false, 150u, 1u, null, null, 2u /* Inch */, 150.0, 96.0)]
-        [InlineData(false, null, null, 200u, 1u, 2u /* Inch */, 96.0, 200.0)]
-        [InlineData(true, 150u, 1u, 200u, 1u, 2u /* Inch */, 150.0, 200.0)]
-        [InlineData(true, 150u, 1u, 200u, 1u, 3u /* Cm */, 150.0 * 2.54, 200.0 * 2.54)]
-        [InlineData(true, 150u, 1u, 200u, 1u, 1u /* None */, 96.0, 96.0)]
-        [InlineData(true, 5u, 2u, 9u, 4u, 2u /* Inch */, 2.5, 2.25)]
-        [InlineData(true, 150u, 1u, 200u, 1u, null /* Inch */, 150.0, 200.0)]
-        [InlineData(true, null, null, null, null, null /* Inch */, 96.0, 96.0)]
-        [InlineData(true, 150u, 1u, null, null, 2u /* Inch */, 150.0, 96.0)]
-        [InlineData(true, null, null, 200u, 1u, 2u /* Inch */, 96.0, 200.0)]
-        public void DecodeImage_SetsImageResolution(bool isLittleEndian, uint? xResolutionNumerator, uint? xResolutionDenominator,
-            uint? yResolutionNumerator, uint? yResolutionDenominator, uint? resolutionUnit,
-            double expectedHorizonalResolution, double expectedVerticalResolution)
-        {
-            TiffGenIfd ifdGen = CreateTiffGenIfd()
-                                .WithoutEntry(TiffTags.XResolution)
-                                .WithoutEntry(TiffTags.YResolution)
-                                .WithoutEntry(TiffTags.ResolutionUnit);
-
-            if (xResolutionNumerator != null)
-            {
-                ifdGen.WithEntry(TiffGenEntry.Rational(TiffTags.XResolution, xResolutionNumerator.Value, xResolutionDenominator.Value));
-            }
-
-            if (yResolutionNumerator != null)
-            {
-                ifdGen.WithEntry(TiffGenEntry.Rational(TiffTags.YResolution, yResolutionNumerator.Value, yResolutionDenominator.Value));
-            }
-
-            if (resolutionUnit != null)
-            {
-                ifdGen.WithEntry(TiffGenEntry.Integer(TiffTags.ResolutionUnit, TiffType.Short, resolutionUnit.Value));
-            }
-
-            Stream stream = ifdGen.ToStream(isLittleEndian);
-
-            TiffDecoderCore decoder = new TiffDecoderCore(stream, isLittleEndian, null, null);
-            TiffIfd ifd = decoder.ReadIfd(0);
-            Image<Rgba32> image = decoder.DecodeImage<Rgba32>(ifd);
-
-            Assert.Equal(expectedHorizonalResolution, image.MetaData.HorizontalResolution, 10);
-            Assert.Equal(expectedVerticalResolution, image.MetaData.VerticalResolution, 10);
-        }
-
         [Theory]
         [MemberData(nameof(IsLittleEndianValues))]
         public void DecodeImage_ThrowsException_WithMissingImageWidth(bool isLittleEndian)
@@ -551,8 +498,8 @@ namespace ImageSharp.Tests
                         {
                             TiffGenEntry.Integer(TiffTags.ImageWidth, TiffType.Long, ImageWidth),
                             TiffGenEntry.Integer(TiffTags.ImageLength, TiffType.Long, ImageHeight),
-                            TiffGenEntry.Rational(TiffTags.XResolution, XResolution, 1),
+                            TiffGenEntry.Rational(TiffTags.XResolution, 100, 1),
-                            TiffGenEntry.Rational(TiffTags.YResolution, YResolution, 1),
+                            TiffGenEntry.Rational(TiffTags.YResolution, 200, 1),
                             TiffGenEntry.Integer(TiffTags.ResolutionUnit, TiffType.Short, 2),
                             TiffGenEntry.Integer(TiffTags.PhotometricInterpretation, TiffType.Short, (int)TiffPhotometricInterpretation.WhiteIsZero),
                             TiffGenEntry.Integer(TiffTags.BitsPerSample, TiffType.Short, new int[] { 8 }),

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

@@ -0,0 +1,70 @@
+// <copyright file="TiffDecoderMetadataTests.cs" company="James Jackson-South">
+// Copyright (c) James Jackson-South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageSharp.Tests
+{
+    using System;
+    using System.IO;
+    using Xunit;
+
+    using ImageSharp.Formats;
+    using ImageSharp.Formats.Tiff;
+
+    public class TiffDecoderMetadataTests
+    {
+        public static object[][] IsLittleEndianValues = new[] { new object[] { false },
+                                                                new object[] { true } };
+
+        [Theory]
+        [InlineData(false, 150u, 1u, 200u, 1u, 2u /* Inch */, 150.0, 200.0)]
+        [InlineData(false, 150u, 1u, 200u, 1u, 3u /* Cm */, 150.0 * 2.54, 200.0 * 2.54)]
+        [InlineData(false, 150u, 1u, 200u, 1u, 1u /* None */, 96.0, 96.0)]
+        [InlineData(false, 150u, 1u, 200u, 1u, null /* Inch */, 150.0, 200.0)]
+        [InlineData(false, 5u, 2u, 9u, 4u, 2u /* Inch */, 2.5, 2.25)]
+        [InlineData(false, null, null, null, null, null /* Inch */, 96.0, 96.0)]
+        [InlineData(false, 150u, 1u, null, null, 2u /* Inch */, 150.0, 96.0)]
+        [InlineData(false, null, null, 200u, 1u, 2u /* Inch */, 96.0, 200.0)]
+        [InlineData(true, 150u, 1u, 200u, 1u, 2u /* Inch */, 150.0, 200.0)]
+        [InlineData(true, 150u, 1u, 200u, 1u, 3u /* Cm */, 150.0 * 2.54, 200.0 * 2.54)]
+        [InlineData(true, 150u, 1u, 200u, 1u, 1u /* None */, 96.0, 96.0)]
+        [InlineData(true, 5u, 2u, 9u, 4u, 2u /* Inch */, 2.5, 2.25)]
+        [InlineData(true, 150u, 1u, 200u, 1u, null /* Inch */, 150.0, 200.0)]
+        [InlineData(true, null, null, null, null, null /* Inch */, 96.0, 96.0)]
+        [InlineData(true, 150u, 1u, null, null, 2u /* Inch */, 150.0, 96.0)]
+        [InlineData(true, null, null, 200u, 1u, 2u /* Inch */, 96.0, 200.0)]
+        public void DecodeImage_SetsImageResolution(bool isLittleEndian, uint? xResolutionNumerator, uint? xResolutionDenominator,
+            uint? yResolutionNumerator, uint? yResolutionDenominator, uint? resolutionUnit,
+            double expectedHorizonalResolution, double expectedVerticalResolution)
+        {
+            TiffGenIfd ifdGen = new TiffGenIfd();
+
+            if (xResolutionNumerator != null)
+            {
+                ifdGen.WithEntry(TiffGenEntry.Rational(TiffTags.XResolution, xResolutionNumerator.Value, xResolutionDenominator.Value));
+            }
+
+            if (yResolutionNumerator != null)
+            {
+                ifdGen.WithEntry(TiffGenEntry.Rational(TiffTags.YResolution, yResolutionNumerator.Value, yResolutionDenominator.Value));
+            }
+
+            if (resolutionUnit != null)
+            {
+                ifdGen.WithEntry(TiffGenEntry.Integer(TiffTags.ResolutionUnit, TiffType.Short, resolutionUnit.Value));
+            }
+
+            Stream stream = ifdGen.ToStream(isLittleEndian);
+
+            TiffDecoderCore decoder = new TiffDecoderCore(stream, isLittleEndian, null, null);
+            TiffIfd ifd = decoder.ReadIfd(0);
+            Image<Rgba32> image = new Image<Rgba32>(null, 20, 20);
+
+            decoder.ReadMetadata<Rgba32>(ifd, image);
+
+            Assert.Equal(expectedHorizonalResolution, image.MetaData.HorizontalResolution, 10);
+            Assert.Equal(expectedVerticalResolution, image.MetaData.VerticalResolution, 10);
+        }
+    }
+}