Do not register Tiff in the default config: The user must do this manually as long as this feature is considered experimental

src/ImageSharp/Configuration.cs

@@ -95,9 +95,9 @@ namespace SixLabors.ImageSharp
         }
 
         /// <summary>
-        /// Gets a set of properties for the Congiguration.
+        /// Gets a set of properties for the Configuration.
         /// </summary>
-        /// <remarks>This can be used for storing global settings and defaults to be accessable to processors.</remarks>
+        /// <remarks>This can be used for storing global settings and defaults to be accessible to processors.</remarks>
         public IDictionary<object, object> Properties { get; } = new ConcurrentDictionary<object, object>();
 
         /// <summary>
@@ -191,8 +191,7 @@ namespace SixLabors.ImageSharp
                 new JpegConfigurationModule(),
                 new GifConfigurationModule(),
                 new BmpConfigurationModule(),
-                new TgaConfigurationModule(),
-                new TiffConfigurationModule());
+                new TgaConfigurationModule());
         }
     }
 }

src/ImageSharp/Formats/Tiff/TiffDecoder.cs

@@ -9,7 +9,7 @@ using SixLabors.ImageSharp.PixelFormats;
 namespace SixLabors.ImageSharp.Formats.Experimental.Tiff
 {
     /// <summary>
-    /// Image decoder for generating an image out of a TIFF stream.
+    /// EXPERIMENTAL! Image decoder for generating an image out of a TIFF stream.
     /// </summary>
     public class TiffDecoder : IImageDecoder, ITiffDecoderOptions, IImageInfoDetector
     {

src/ImageSharp/Formats/Tiff/TiffEncoder.cs

@@ -13,7 +13,7 @@ using SixLabors.ImageSharp.Processing.Processors.Quantization;
 namespace SixLabors.ImageSharp.Formats.Experimental.Tiff
 {
     /// <summary>
-    /// Encoder for writing the data image to a stream in TIFF format.
+    /// EXPERIMENTAL! Encoder for writing the data image to a stream in TIFF format.
     /// </summary>
     public class TiffEncoder : IImageEncoder, ITiffEncoderOptions
     {

src/ImageSharp/Formats/Tiff/TiffEncoderCore.cs

@@ -308,13 +308,13 @@ namespace SixLabors.ImageSharp.Formats.Experimental.Tiff
 
             var xResolution = new ExifRational(ExifTagValue.XResolution)
             {
-                // TODO: what to use here as a default?
+                // TODO: This field is required according to the spec, what to use here as a default?
                 Value = Rational.FromDouble(1.0d)
             };
 
             var yResolution = new ExifRational(ExifTagValue.YResolution)
             {
-                // TODO: what to use here as a default?
+                // TODO: This field is required according to the spec, what to use here as a default?
                 Value = Rational.FromDouble(1.0d)
             };
 

tests/ImageSharp.Tests/ConfigurationTests.cs

@@ -21,7 +21,7 @@ namespace SixLabors.ImageSharp.Tests
 
         public Configuration DefaultConfiguration { get; }
 
-        private readonly int expectedDefaultConfigurationCount = 6;
+        private readonly int expectedDefaultConfigurationCount = 5;
 
         public ConfigurationTests()
         {

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

@@ -13,6 +13,14 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff
     [Trait("Format", "Tiff")]
     public class ImageExtensionsTest
     {
+        public ImageExtensionsTest()
+        {
+            Configuration.Default.ImageFormatsManager.AddImageFormat(TiffFormat.Instance);
+            Configuration.Default.ImageFormatsManager.AddImageFormatDetector(new TiffImageFormatDetector());
+            Configuration.Default.ImageFormatsManager.SetDecoder(TiffFormat.Instance, new TiffDecoder());
+            Configuration.Default.ImageFormatsManager.SetEncoder(TiffFormat.Instance, new TiffEncoder());
+        }
+
         [Fact]
         public void SaveAsTiff_Path()
         {

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

@@ -28,6 +28,13 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff
 
         private static MagickReferenceDecoder ReferenceDecoder => new MagickReferenceDecoder();
 
+        public TiffDecoderTests()
+        {
+            Configuration.Default.ImageFormatsManager.AddImageFormat(TiffFormat.Instance);
+            Configuration.Default.ImageFormatsManager.AddImageFormatDetector(new TiffImageFormatDetector());
+            Configuration.Default.ImageFormatsManager.SetDecoder(TiffFormat.Instance, new TiffDecoder());
+        }
+
         [Theory]
         [WithFileCollection(nameof(NotSupportedImages), PixelTypes.Rgba32)]
         public void ThrowsNotSupported<TPixel>(TestImageProvider<TPixel> provider)

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

@@ -29,6 +29,14 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff
                 { RgbUncompressed, TiffBitsPerPixel.Pixel24 },
             };
 
+        public TiffEncoderTests()
+        {
+            Configuration.Default.ImageFormatsManager.AddImageFormat(TiffFormat.Instance);
+            Configuration.Default.ImageFormatsManager.AddImageFormatDetector(new TiffImageFormatDetector());
+            Configuration.Default.ImageFormatsManager.SetDecoder(TiffFormat.Instance, new TiffDecoder());
+            Configuration.Default.ImageFormatsManager.SetEncoder(TiffFormat.Instance, new TiffEncoder());
+        }
+
         [Theory]
         [InlineData(TiffEncodingMode.Default, TiffEncoderCompression.None, TiffBitsPerPixel.Pixel24, TiffCompression.None)]
         [InlineData(TiffEncodingMode.Rgb, TiffEncoderCompression.None, TiffBitsPerPixel.Pixel24, TiffCompression.None)]