Tiff Decoder option to decode only first frame

src/ImageSharp/Formats/Gif/GifDecoder.cs

@@ -5,7 +5,6 @@
 using System.Threading;
 using System.Threading.Tasks;
 using SixLabors.ImageSharp.IO;
-using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.Metadata;
 using SixLabors.ImageSharp.PixelFormats;
 

src/ImageSharp/Formats/Tiff/ITiffDecoderOptions.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
+using SixLabors.ImageSharp.Metadata;
+
 namespace SixLabors.ImageSharp.Formats.Tiff
 {
     /// <summary>
@@ -12,5 +14,10 @@ internal interface ITiffDecoderOptions
         /// Gets a value indicating whether the metadata should be ignored when the image is being decoded.
         /// </summary>
         bool IgnoreMetadata { get; }
+
+        /// <summary>
+        /// Gets the decoding mode for multi-frame images.
+        /// </summary>
+        FrameDecodingMode DecodingMode { get; }
     }
 }

src/ImageSharp/Formats/Tiff/README.md

@@ -25,7 +25,7 @@
 
 ## Implementation Status
 
-- The Decoder currently only supports a single frame per image.
+- The Decoder currently only supports decoding multiframe images, which have the same dimensions.
 - Some compression formats are not yet supported. See the list below.
 
 ### Deviations from the TIFF spec (to be fixed)

src/ImageSharp/Formats/Tiff/TiffDecoder.cs

@@ -4,6 +4,7 @@
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
+using SixLabors.ImageSharp.Metadata;
 using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp.Formats.Tiff
@@ -18,6 +19,11 @@ public class TiffDecoder : IImageDecoder, ITiffDecoderOptions, IImageInfoDetecto
         /// </summary>
         public bool IgnoreMetadata { get; set; }
 
+        /// <summary>
+        /// Gets or sets the decoding mode for multi-frame images.
+        /// </summary>
+        public FrameDecodingMode DecodingMode { get; set; }
+
         /// <inheritdoc/>
         public Image<TPixel> Decode<TPixel>(Configuration configuration, Stream stream)
             where TPixel : unmanaged, IPixel<TPixel>

src/ImageSharp/Formats/Tiff/TiffDecoderCore.cs

@@ -13,7 +13,6 @@
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.Metadata;
 using SixLabors.ImageSharp.Metadata.Profiles.Exif;
-using SixLabors.ImageSharp.Metadata.Profiles.Xmp;
 using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp.Formats.Tiff
@@ -33,6 +32,11 @@ internal class TiffDecoderCore : IImageDecoderInternals
         /// </summary>
         private readonly bool ignoreMetadata;
 
+        /// <summary>
+        /// Gets the decoding mode for multi-frame images
+        /// </summary>
+        private FrameDecodingMode decodingMode;
+
         /// <summary>
         /// The stream to decode from.
         /// </summary>
@@ -59,6 +63,7 @@ public TiffDecoderCore(Configuration configuration, ITiffDecoderOptions options)
 
             this.Configuration = configuration ?? Configuration.Default;
             this.ignoreMetadata = options.IgnoreMetadata;
+            this.decodingMode = options.DecodingMode;
             this.memoryAllocator = this.Configuration.MemoryAllocator;
         }
 
@@ -160,11 +165,16 @@ public Image<TPixel> Decode<TPixel>(BufferedReadStream stream, CancellationToken
                 cancellationToken.ThrowIfCancellationRequested();
                 ImageFrame<TPixel> frame = this.DecodeFrame<TPixel>(ifd, cancellationToken);
                 frames.Add(frame);
+
+                if (this.decodingMode is FrameDecodingMode.First)
+                {
+                    break;
+                }
             }
 
             ImageMetadata metadata = TiffDecoderMetadataCreator.Create(frames, this.ignoreMetadata, reader.ByteOrder, reader.IsBigTiff);
 
-            // TODO: Tiff frames can have different sizes
+            // TODO: Tiff frames can have different sizes.
             ImageFrame<TPixel> root = frames[0];
             this.Dimensions = root.Size();
             foreach (ImageFrame<TPixel> frame in frames)

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

@@ -4,6 +4,7 @@
 // ReSharper disable InconsistentNaming
 using System;
 using System.IO;
+using SixLabors.ImageSharp.Formats.Tiff;
 using SixLabors.ImageSharp.Metadata;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Tests.TestUtilities.ImageComparison;
@@ -365,6 +366,17 @@ public void TiffDecoder_CanDecode_Compressed_LowerOrderBitsFirst<TPixel>(TestIma
         public void TiffDecoder_CanDecode_PackBitsCompressed<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : unmanaged, IPixel<TPixel> => TestTiffDecoder(provider);
 
+        [Theory]
+        [WithFile(MultiFrameMipMap, PixelTypes.Rgba32)]
+        public void CanDecodeJustOneFrame<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : unmanaged, IPixel<TPixel>
+        {
+            using (Image<TPixel> image = provider.GetImage(new TiffDecoder() { DecodingMode = FrameDecodingMode.First }))
+            {
+                Assert.Equal(1, image.Frames.Count);
+            }
+        }
+
         [Theory]
         [WithFile(RgbJpegCompressed, PixelTypes.Rgba32)]
         [WithFile(RgbWithStripsJpegCompressed, PixelTypes.Rgba32)]

tests/ImageSharp.Tests/TestImages.cs

@@ -873,6 +873,7 @@ public static class Tiff
             public const string MultiframeDeflateWithPreview = "Tiff/multipage_deflate_withPreview.tiff";
             public const string MultiframeDifferentSize = "Tiff/multipage_differentSize.tiff";
             public const string MultiframeDifferentVariants = "Tiff/multipage_differentVariants.tiff";
+            public const string MultiFrameMipMap = "Tiff/SKC1H3.tiff";
 
             public const string LittleEndianByteOrder = "Tiff/little_endian.tiff";