Cancellable codec API, and overloads for loading/saving

src/ImageSharp/Advanced/AdvancedImageExtensions.cs

@@ -5,6 +5,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Text;
+using System.Threading;
 using System.Threading.Tasks;
 using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Memory;
@@ -73,9 +74,10 @@ public static void AcceptVisitor(this Image source, IImageVisitor visitor)
         /// </summary>
         /// <param name="source">The source image.</param>
         /// <param name="visitor">The image visitor.</param>
+        /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
         /// <returns>A  <see cref="Task"/> representing the asynchronous operation.</returns>
-        public static Task AcceptVisitorAsync(this Image source, IImageVisitorAsync visitor)
-            => source.AcceptAsync(visitor);
+        public static Task AcceptVisitorAsync(this Image source, IImageVisitorAsync visitor, CancellationToken cancellationToken = default)
+            => source.AcceptAsync(visitor, cancellationToken);
 
         /// <summary>
         /// Gets the configuration for the image.

src/ImageSharp/Advanced/IImageVisitor.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
+using System.Threading;
 using System.Threading.Tasks;
 using SixLabors.ImageSharp.PixelFormats;
 
@@ -31,9 +32,10 @@ public interface IImageVisitorAsync
         /// Provides a pixel-specific implementation for a given operation.
         /// </summary>
         /// <param name="image">The image.</param>
+        /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
         /// <typeparam name="TPixel">The pixel type.</typeparam>
         /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
-        Task VisitAsync<TPixel>(Image<TPixel> image)
+        Task VisitAsync<TPixel>(Image<TPixel> image, CancellationToken cancellationToken)
             where TPixel : unmanaged, IPixel<TPixel>;
     }
 }

src/ImageSharp/Common/Exceptions/InvalidImageContentException.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
+using SixLabors.ImageSharp.Memory;
 
 namespace SixLabors.ImageSharp
 {
@@ -32,5 +33,10 @@ public InvalidImageContentException(string errorMessage, Exception innerExceptio
             : base(errorMessage, innerException)
         {
         }
+
+        internal InvalidImageContentException(Size size, InvalidMemoryOperationException memoryException)
+            : this($"Cannot decode image. Failed to allocate buffers for possibly degenerate dimensions: {size.Width}x{size.Height}.", memoryException)
+        {
+        }
     }
 }

src/ImageSharp/Formats/Bmp/BmpDecoder.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System.IO;
+using System.Threading;
 using System.Threading.Tasks;
 using SixLabors.ImageSharp.IO;
 using SixLabors.ImageSharp.Memory;
@@ -36,65 +37,42 @@ public Image<TPixel> Decode<TPixel>(Configuration configuration, Stream stream)
             Guard.NotNull(stream, nameof(stream));
 
             var decoder = new BmpDecoderCore(configuration, this);
-
-            try
-            {
-                using var bufferedStream = new BufferedReadStream(configuration, stream);
-                return decoder.Decode<TPixel>(bufferedStream);
-            }
-            catch (InvalidMemoryOperationException ex)
-            {
-                Size dims = decoder.Dimensions;
-
-                throw new InvalidImageContentException($"Cannot decode image. Failed to allocate buffers for possibly degenerate dimensions: {dims.Width}x{dims.Height}. This error can happen for very large RLE bitmaps, which are not supported.", ex);
-            }
+            return decoder.Decode<TPixel>(configuration, stream);
         }
 
         /// <inheritdoc />
         public Image Decode(Configuration configuration, Stream stream)
             => this.Decode<Rgba32>(configuration, stream);
 
         /// <inheritdoc/>
-        public async Task<Image<TPixel>> DecodeAsync<TPixel>(Configuration configuration, Stream stream)
+        public Task<Image<TPixel>> DecodeAsync<TPixel>(Configuration configuration, Stream stream, CancellationToken cancellationToken)
            where TPixel : unmanaged, IPixel<TPixel>
         {
             Guard.NotNull(stream, nameof(stream));
 
             var decoder = new BmpDecoderCore(configuration, this);
-
-            try
-            {
-                using var bufferedStream = new BufferedReadStream(configuration, stream);
-                return await decoder.DecodeAsync<TPixel>(bufferedStream).ConfigureAwait(false);
-            }
-            catch (InvalidMemoryOperationException ex)
-            {
-                Size dims = decoder.Dimensions;
-
-                throw new InvalidImageContentException($"Cannot decode image. Failed to allocate buffers for possibly degenerate dimensions: {dims.Width}x{dims.Height}. This error can happen for very large RLE bitmaps, which are not supported.", ex);
-            }
+            return decoder.DecodeAsync<TPixel>(configuration, stream, cancellationToken);
         }
 
         /// <inheritdoc />
-        public async Task<Image> DecodeAsync(Configuration configuration, Stream stream)
-            => await this.DecodeAsync<Rgba32>(configuration, stream).ConfigureAwait(false);
+        public async Task<Image> DecodeAsync(Configuration configuration, Stream stream, CancellationToken cancellationToken)
+            => await this.DecodeAsync<Rgba32>(configuration, stream, cancellationToken)
+            .ConfigureAwait(false);
 
         /// <inheritdoc/>
         public IImageInfo Identify(Configuration configuration, Stream stream)
         {
             Guard.NotNull(stream, nameof(stream));
 
-            using var bufferedStream = new BufferedReadStream(configuration, stream);
-            return new BmpDecoderCore(configuration, this).Identify(bufferedStream);
+            return new BmpDecoderCore(configuration, this).Identify(configuration, stream);
         }
 
         /// <inheritdoc/>
-        public Task<IImageInfo> IdentifyAsync(Configuration configuration, Stream stream)
+        public Task<IImageInfo> IdentifyAsync(Configuration configuration, Stream stream, CancellationToken cancellationToken)
         {
             Guard.NotNull(stream, nameof(stream));
 
-            using var bufferedStream = new BufferedReadStream(configuration, stream);
-            return new BmpDecoderCore(configuration, this).IdentifyAsync(bufferedStream);
+            return new BmpDecoderCore(configuration, this).IdentifyAsync(configuration, stream, cancellationToken);
         }
     }
 }

src/ImageSharp/Formats/Bmp/BmpDecoderCore.cs

@@ -6,6 +6,7 @@
 using System.Buffers.Binary;
 using System.Numerics;
 using System.Runtime.CompilerServices;
+using System.Threading;
 using SixLabors.ImageSharp.Common.Helpers;
 using SixLabors.ImageSharp.IO;
 using SixLabors.ImageSharp.Memory;
@@ -118,7 +119,7 @@ public BmpDecoderCore(Configuration configuration, IBmpDecoderOptions options)
         public Size Dimensions => new Size(this.infoHeader.Width, this.infoHeader.Height);
 
         /// <inheritdoc />
-        public Image<TPixel> Decode<TPixel>(BufferedReadStream stream)
+        public Image<TPixel> Decode<TPixel>(BufferedReadStream stream, CancellationToken cancellationToken)
             where TPixel : unmanaged, IPixel<TPixel>
         {
             try
@@ -197,7 +198,7 @@ public Image<TPixel> Decode<TPixel>(BufferedReadStream stream)
         }
 
         /// <inheritdoc />
-        public IImageInfo Identify(BufferedReadStream stream)
+        public IImageInfo Identify(BufferedReadStream stream, CancellationToken cancellationToken)
         {
             this.ReadImageHeaders(stream, out _, out _);
             return new ImageInfo(new PixelTypeInfo(this.infoHeader.BitsPerPixel), this.infoHeader.Width, this.infoHeader.Height, this.metadata);

src/ImageSharp/Formats/Bmp/BmpEncoder.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System.IO;
+using System.Threading;
 using System.Threading.Tasks;
 using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.PixelFormats;
@@ -42,11 +43,11 @@ public void Encode<TPixel>(Image<TPixel> image, Stream stream)
         }
 
         /// <inheritdoc/>
-        public Task EncodeAsync<TPixel>(Image<TPixel> image, Stream stream)
+        public Task EncodeAsync<TPixel>(Image<TPixel> image, Stream stream, CancellationToken cancellationToken)
             where TPixel : unmanaged, IPixel<TPixel>
         {
             var encoder = new BmpEncoderCore(this, image.GetMemoryAllocator());
-            return encoder.EncodeAsync(image, stream);
+            return encoder.EncodeAsync(image, stream, cancellationToken);
         }
     }
 }

src/ImageSharp/Formats/Bmp/BmpEncoderCore.cs

@@ -5,6 +5,7 @@
 using System.Buffers;
 using System.IO;
 using System.Runtime.InteropServices;
+using System.Threading;
 using System.Threading.Tasks;
 using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.Common.Helpers;
@@ -19,7 +20,7 @@ namespace SixLabors.ImageSharp.Formats.Bmp
     /// <summary>
     /// Image encoder for writing an image to a stream as a Windows bitmap.
     /// </summary>
-    internal sealed class BmpEncoderCore
+    internal sealed class BmpEncoderCore : IImageEncoderInternals
     {
         /// <summary>
         /// The amount to pad each row by.
@@ -97,32 +98,9 @@ public BmpEncoderCore(IBmpEncoderOptions options, MemoryAllocator memoryAllocato
         /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <param name="image">The <see cref="ImageFrame{TPixel}"/> to encode from.</param>
         /// <param name="stream">The <see cref="Stream"/> to encode the image data to.</param>
-        public async Task EncodeAsync<TPixel>(Image<TPixel> image, Stream stream)
+        /// <param name="cancellationToken">The token to request cancellation.</param>
+        public void Encode<TPixel>(Image<TPixel> image, Stream stream, CancellationToken cancellationToken)
             where TPixel : unmanaged, IPixel<TPixel>
-        {
-            if (stream.CanSeek)
-            {
-                this.Encode(image, stream);
-            }
-            else
-            {
-                using (var ms = new MemoryStream())
-                {
-                    this.Encode(image, ms);
-                    ms.Position = 0;
-                    await ms.CopyToAsync(stream).ConfigureAwait(false);
-                }
-            }
-        }
-
-        /// <summary>
-        /// Encodes the image to the specified stream from the <see cref="ImageFrame{TPixel}"/>.
-        /// </summary>
-        /// <typeparam name="TPixel">The pixel format.</typeparam>
-        /// <param name="image">The <see cref="ImageFrame{TPixel}"/> to encode from.</param>
-        /// <param name="stream">The <see cref="Stream"/> to encode the image data to.</param>
-        public void Encode<TPixel>(Image<TPixel> image, Stream stream)
-        where TPixel : unmanaged, IPixel<TPixel>
         {
             Guard.NotNull(image, nameof(image));
             Guard.NotNull(stream, nameof(stream));

src/ImageSharp/Formats/Gif/GifDecoder.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System.IO;
+using System.Threading;
 using System.Threading.Tasks;
 using SixLabors.ImageSharp.IO;
 using SixLabors.ImageSharp.Memory;
@@ -30,52 +31,25 @@ public Image<TPixel> Decode<TPixel>(Configuration configuration, Stream stream)
             where TPixel : unmanaged, IPixel<TPixel>
         {
             var decoder = new GifDecoderCore(configuration, this);
-
-            try
-            {
-                using var bufferedStream = new BufferedReadStream(configuration, stream);
-                return decoder.Decode<TPixel>(bufferedStream);
-            }
-            catch (InvalidMemoryOperationException ex)
-            {
-                Size dims = decoder.Dimensions;
-
-                GifThrowHelper.ThrowInvalidImageContentException($"Cannot decode image. Failed to allocate buffers for possibly degenerate dimensions: {dims.Width}x{dims.Height}.", ex);
-
-                // Not reachable, as the previous statement will throw a exception.
-                return null;
-            }
+            return decoder.Decode<TPixel>(configuration, stream);
         }
 
         /// <inheritdoc />
         public Image Decode(Configuration configuration, Stream stream)
             => this.Decode<Rgba32>(configuration, stream);
 
         /// <inheritdoc/>
-        public async Task<Image<TPixel>> DecodeAsync<TPixel>(Configuration configuration, Stream stream)
+        public Task<Image<TPixel>> DecodeAsync<TPixel>(Configuration configuration, Stream stream, CancellationToken cancellationToken)
             where TPixel : unmanaged, IPixel<TPixel>
         {
             var decoder = new GifDecoderCore(configuration, this);
-
-            try
-            {
-                using var bufferedStream = new BufferedReadStream(configuration, stream);
-                return await decoder.DecodeAsync<TPixel>(bufferedStream).ConfigureAwait(false);
-            }
-            catch (InvalidMemoryOperationException ex)
-            {
-                Size dims = decoder.Dimensions;
-
-                GifThrowHelper.ThrowInvalidImageContentException($"Cannot decode image. Failed to allocate buffers for possibly degenerate dimensions: {dims.Width}x{dims.Height}.", ex);
-
-                // Not reachable, as the previous statement will throw a exception.
-                return null;
-            }
+            return decoder.DecodeAsync<TPixel>(configuration, stream, cancellationToken);
         }
 
         /// <inheritdoc />
-        public async Task<Image> DecodeAsync(Configuration configuration, Stream stream)
-            => await this.DecodeAsync<Rgba32>(configuration, stream).ConfigureAwait(false);
+        public async Task<Image> DecodeAsync(Configuration configuration, Stream stream, CancellationToken cancellationToken)
+            => await this.DecodeAsync<Rgba32>(configuration, stream, cancellationToken)
+            .ConfigureAwait(false);
 
         /// <inheritdoc/>
         public IImageInfo Identify(Configuration configuration, Stream stream)
@@ -85,18 +59,16 @@ public IImageInfo Identify(Configuration configuration, Stream stream)
             var decoder = new GifDecoderCore(configuration, this);
 
             using var bufferedStream = new BufferedReadStream(configuration, stream);
-            return decoder.Identify(bufferedStream);
+            return decoder.Identify(bufferedStream, default);
         }
 
         /// <inheritdoc/>
-        public Task<IImageInfo> IdentifyAsync(Configuration configuration, Stream stream)
+        public Task<IImageInfo> IdentifyAsync(Configuration configuration, Stream stream, CancellationToken cancellationToken)
         {
             Guard.NotNull(stream, nameof(stream));
 
             var decoder = new GifDecoderCore(configuration, this);
-
-            using var bufferedStream = new BufferedReadStream(configuration, stream);
-            return decoder.IdentifyAsync(bufferedStream);
+            return decoder.IdentifyAsync(configuration, stream, cancellationToken);
         }
     }
 }

src/ImageSharp/Formats/Gif/GifDecoderCore.cs

@@ -6,6 +6,7 @@
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.Text;
+using System.Threading;
 using System.Threading.Tasks;
 using SixLabors.ImageSharp.IO;
 using SixLabors.ImageSharp.Memory;
@@ -97,7 +98,7 @@ public GifDecoderCore(Configuration configuration, IGifDecoderOptions options)
         private MemoryAllocator MemoryAllocator => this.Configuration.MemoryAllocator;
 
         /// <inheritdoc />
-        public Image<TPixel> Decode<TPixel>(BufferedReadStream stream)
+        public Image<TPixel> Decode<TPixel>(BufferedReadStream stream, CancellationToken cancellationToken)
             where TPixel : unmanaged, IPixel<TPixel>
         {
             Image<TPixel> image = null;
@@ -158,7 +159,7 @@ public Image<TPixel> Decode<TPixel>(BufferedReadStream stream)
         }
 
         /// <inheritdoc />
-        public IImageInfo Identify(BufferedReadStream stream)
+        public IImageInfo Identify(BufferedReadStream stream, CancellationToken cancellationToken)
         {
             try
             {

src/ImageSharp/Formats/Gif/GifEncoder.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System.IO;
+using System.Threading;
 using System.Threading.Tasks;
 using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.PixelFormats;
@@ -41,11 +42,11 @@ public void Encode<TPixel>(Image<TPixel> image, Stream stream)
         }
 
         /// <inheritdoc/>
-        public Task EncodeAsync<TPixel>(Image<TPixel> image, Stream stream)
+        public Task EncodeAsync<TPixel>(Image<TPixel> image, Stream stream, CancellationToken cancellationToken)
             where TPixel : unmanaged, IPixel<TPixel>
         {
             var encoder = new GifEncoderCore(image.GetConfiguration(), this);
-            return encoder.EncodeAsync(image, stream);
+            return encoder.EncodeAsync(image, stream, cancellationToken);
         }
     }
 }