Add Tiff implementation of IImageFormat

src/ImageSharp.Formats.Tiff/TiffConstants.cs

@@ -0,0 +1,30 @@
+// <copyright file="TiffConstants.cs" company="James Jackson-South">
+// Copyright (c) James Jackson-South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageSharp.Formats
+{
+    using System.Text;
+
+    /// <summary>
+    /// Defines constants defined in the TIFF specification.
+    /// </summary>
+    internal static class GifConstants
+    {
+        /// <summary>
+        /// Byte order markers for indicating little endian encoding.
+        /// </summary>
+        public const ushort ByteOrderLittleEndian = 0x4949;
+
+        /// <summary>
+        /// Byte order markers for indicating big endian encoding.
+        /// </summary>
+        public const ushort ByteOrderBigEndian = 0x4D4D;
+
+        /// <summary>
+        /// Magic number used within the image file header to identify a TIFF format file.
+        /// </summary>
+        public const ushort HeaderMagicNumber = 42;
+    }
+}

src/ImageSharp.Formats.Tiff/TiffFormat.cs

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+// <copyright file="TiffFormat.cs" company="James Jackson-South">
+// Copyright (c) James Jackson-South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageSharp.Formats
+{
+    using System.Collections.Generic;
+
+    /// <summary>
+    /// Encapsulates the means to encode and decode Tiff images.
+    /// </summary>
+    public class TiffFormat //: IImageFormat
+    {
+        /// <inheritdoc/>
+        public string MimeType => "image/tiff";
+
+        /// <inheritdoc/>
+        public string Extension => "tif";
+
+        /// <inheritdoc/>
+        public IEnumerable<string> SupportedExtensions => new string[] { "tif", "tiff" };
+
+        /// <inheritdoc/>
+        //public IImageDecoder Decoder => new TiffDecoder();
+
+        /// <inheritdoc/>
+        //public IImageEncoder Encoder => throw new System.NotImplementedException();
+
+        /// <inheritdoc/>
+        public int HeaderSize => 4;
+
+        /// <inheritdoc/>
+        public bool IsSupportedFileFormat(byte[] header)
+        {
+            return header.Length >= this.HeaderSize &&
+                   ((header[0] == 0x49 && header[1] == 0x49 && header[2] == 0x2A && header[3] == 0x00) ||  // Little-endian
+                    (header[0] == 0x4D && header[1] == 0x4D && header[2] == 0x00 && header[3] == 0x2A));   // Big-endian
+        }
+    }
+}

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

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+// <copyright file="TiffFormatTests.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.Linq;
+    using Xunit;
+
+    using ImageSharp.Formats;
+
+    public class TiffFormatTests
+    {
+        public static object[][] IsLittleEndianValues = new[] { new object[] { false },
+                                                                new object[] { true } };
+
+        [Theory]
+        [MemberData(nameof(IsLittleEndianValues))]
+        public void IsSupportedFileFormat_ReturnsTrue_ForValidFile(bool isLittleEndian)
+        {
+            byte[] bytes = new TiffGenHeader()
+                            {
+                                FirstIfd = new TiffGenIfd()
+                            }
+                            .ToBytes(isLittleEndian);
+
+            TiffFormat tiffFormat = new TiffFormat();
+            byte[] headerBytes = bytes.Take(tiffFormat.HeaderSize).ToArray();
+            bool isSupported = tiffFormat.IsSupportedFileFormat(headerBytes);
+
+            Assert.True(isSupported);
+        }
+
+        [Theory]
+        [MemberData(nameof(IsLittleEndianValues))]
+        public void IsSupportedFileFormat_ReturnsFalse_WithInvalidByteOrderMarkers(bool isLittleEndian)
+        {
+            byte[] bytes = new TiffGenHeader()
+                            {
+                                FirstIfd = new TiffGenIfd(),
+                                ByteOrderMarker = 0x1234
+                            }
+                            .ToBytes(isLittleEndian);
+
+            TiffFormat tiffFormat = new TiffFormat();
+            byte[] headerBytes = bytes.Take(tiffFormat.HeaderSize).ToArray();
+            bool isSupported = tiffFormat.IsSupportedFileFormat(headerBytes);
+
+            Assert.False(isSupported);
+        }
+
+        [Theory]
+        [MemberData(nameof(IsLittleEndianValues))]
+        public void IsSupportedFileFormat_ReturnsFalse_WithIncorrectMagicNumber(bool isLittleEndian)
+        {
+            byte[] bytes = new TiffGenHeader()
+                            {
+                                FirstIfd = new TiffGenIfd(),
+                                MagicNumber = 32
+                            }
+                            .ToBytes(isLittleEndian);
+
+            TiffFormat tiffFormat = new TiffFormat();
+            byte[] headerBytes = bytes.Take(tiffFormat.HeaderSize).ToArray();
+            bool isSupported = tiffFormat.IsSupportedFileFormat(headerBytes);
+
+            Assert.False(isSupported);
+        }
+
+        [Theory]
+        [MemberData(nameof(IsLittleEndianValues))]
+        public void IsSupportedFileFormat_ReturnsFalse_WithShortHeader(bool isLittleEndian)
+        {
+            byte[] bytes = new TiffGenHeader()
+                            {
+                                FirstIfd = new TiffGenIfd()
+                            }
+                            .ToBytes(isLittleEndian);
+
+            TiffFormat tiffFormat = new TiffFormat();
+            byte[] headerBytes = bytes.Take(tiffFormat.HeaderSize - 1).ToArray();
+            bool isSupported = tiffFormat.IsSupportedFileFormat(headerBytes);
+
+            Assert.False(isSupported);
+        }
+    }
+}