add TiffFormatType enum

src/ImageSharp/Formats/Tiff/TiffDecoderMetadataCreator.cs

@@ -57,7 +57,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff
 
             TiffMetadata tiffMetadata = imageMetaData.GetTiffMetadata();
             tiffMetadata.ByteOrder = byteOrder;
-            tiffMetadata.IsBigTiff = isBigTiff;
+            tiffMetadata.FormatType = isBigTiff ? TiffFormatType.BigTIFF : TiffFormatType.Default;
 
             return imageMetaData;
         }

src/ImageSharp/Formats/Tiff/TiffFormatType.cs

@@ -0,0 +1,21 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+namespace SixLabors.ImageSharp.Formats.Tiff
+{
+    /// <summary>
+    /// The TIFF format type enum.
+    /// </summary>
+    public enum TiffFormatType
+    {
+        /// <summary>
+        /// The TIFF file format type.
+        /// </summary>
+        Default,
+
+        /// <summary>
+        /// The BigTIFF format type.
+        /// </summary>
+        BigTIFF
+    }
+}

src/ImageSharp/Formats/Tiff/TiffMetadata.cs

@@ -27,12 +27,9 @@ namespace SixLabors.ImageSharp.Formats.Tiff
         public ByteOrder ByteOrder { get; set; }
 
         /// <summary>
-        /// Gets or sets a value indicating whether this instance is BigTiff format.
+        /// Gets or sets the format type.
         /// </summary>
-        /// <value>
-        ///   <c>true</c> if this instance BigTiff format; otherwise, <c>false</c>.
-        /// </value>
-        public bool IsBigTiff { get; set; }
+        public TiffFormatType FormatType { get; set; }
 
         /// <inheritdoc/>
         public IDeepCloneable DeepClone() => new TiffMetadata(this);

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

@@ -5,6 +5,7 @@
 using System;
 using System.IO;
 using System.Linq;
+using SixLabors.ImageSharp.Formats.Tiff;
 using SixLabors.ImageSharp.Metadata;
 using SixLabors.ImageSharp.Metadata.Profiles.Exif;
 using SixLabors.ImageSharp.PixelFormats;
@@ -80,9 +81,9 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff
                 Assert.Equal(expectedVResolution, info.Metadata.VerticalResolution);
                 Assert.Equal(expectedResolutionUnit, info.Metadata.ResolutionUnits);
 
-                ImageSharp.Formats.Tiff.TiffMetadata tiffmeta = info.Metadata.GetTiffMetadata();
+                TiffMetadata tiffmeta = info.Metadata.GetTiffMetadata();
                 Assert.NotNull(tiffmeta);
-                Assert.True(tiffmeta.IsBigTiff);
+                Assert.Equal(TiffFormatType.BigTIFF, tiffmeta.FormatType);
             }
         }