Add missing SaveAsync method

Author: JimBobSquarePants

src/ImageSharp/Advanced/AdvancedImageExtensions.cs

@@ -23,7 +23,9 @@ public static class AdvancedImageExtensions
         /// </summary>
         /// <param name="source">The source image.</param>
         /// <param name="filePath">The target file path to save the image to.</param>
-        /// <returns>The matching encoder.</returns>
+        /// <exception cref="ArgumentNullException">The file path is null.</exception>
+        /// <exception cref="NotSupportedException">No encoder available for provided path.</exception>
+        /// <returns>The matching <see cref="IImageEncoder"/>.</returns>
         public static IImageEncoder DetectEncoder(this Image source, string filePath)
         {
             Guard.NotNull(filePath, nameof(filePath));

src/ImageSharp/ImageExtensions.cs

@@ -18,27 +18,29 @@ namespace SixLabors.ImageSharp
     public static partial class ImageExtensions
     {
         /// <summary>
-        /// Writes the image to the given stream using the currently loaded image format.
+        /// Writes the image to the given file path using an encoder detected from the path.
         /// </summary>
         /// <param name="source">The source image.</param>
         /// <param name="path">The file path to save the image to.</param>
         /// <exception cref="ArgumentNullException">The path is null.</exception>
+        /// <exception cref="NotSupportedException">No encoder available for provided path.</exception>
         public static void Save(this Image source, string path)
             => source.Save(path, source.DetectEncoder(path));
 
         /// <summary>
-        /// Writes the image to the given stream using the currently loaded image format.
+        /// Writes the image to the given file path using an encoder detected from the path.
         /// </summary>
         /// <param name="source">The source image.</param>
         /// <param name="path">The file path to save the image to.</param>
         /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
         /// <exception cref="ArgumentNullException">The path is null.</exception>
+        /// <exception cref="NotSupportedException">No encoder available for provided path.</exception>
         /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
         public static Task SaveAsync(this Image source, string path, CancellationToken cancellationToken = default)
             => source.SaveAsync(path, source.DetectEncoder(path), cancellationToken);
 
         /// <summary>
-        /// Writes the image to the given stream using the currently loaded image format.
+        /// Writes the image to the given file path using the given image encoder.
         /// </summary>
         /// <param name="source">The source image.</param>
         /// <param name="path">The file path to save the image to.</param>
@@ -56,7 +58,7 @@ public static void Save(this Image source, string path, IImageEncoder encoder)
         }
 
         /// <summary>
-        /// Writes the image to the given stream using the currently loaded image format.
+        /// Writes the image to the given file path using the given image encoder.
         /// </summary>
         /// <param name="source">The source image.</param>
         /// <param name="path">The file path to save the image to.</param>
@@ -73,12 +75,15 @@ public static async Task SaveAsync(
         {
             Guard.NotNull(path, nameof(path));
             Guard.NotNull(encoder, nameof(encoder));
-            using Stream fs = source.GetConfiguration().FileSystem.Create(path);
-            await source.SaveAsync(fs, encoder, cancellationToken).ConfigureAwait(false);
+
+            using (Stream fs = source.GetConfiguration().FileSystem.Create(path))
+            {
+                await source.SaveAsync(fs, encoder, cancellationToken).ConfigureAwait(false);
+            }
         }
 
         /// <summary>
-        /// Writes the image to the given stream using the currently loaded image format.
+        /// Writes the image to the given stream using the given image format.
         /// </summary>
         /// <param name="source">The source image.</param>
         /// <param name="stream">The stream to save the image to.</param>
@@ -115,6 +120,50 @@ public static void Save(this Image source, Stream stream, IImageFormat format)
             source.Save(stream, encoder);
         }
 
+        /// <summary>
+        /// Writes the image to the given stream using the given image format.
+        /// </summary>
+        /// <param name="source">The source image.</param>
+        /// <param name="stream">The stream to save the image to.</param>
+        /// <param name="format">The format to save the image in.</param>
+        /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
+        /// <exception cref="ArgumentNullException">The stream is null.</exception>
+        /// <exception cref="ArgumentNullException">The format is null.</exception>
+        /// <exception cref="NotSupportedException">The stream is not writable.</exception>
+        /// <exception cref="NotSupportedException">No encoder available for provided format.</exception>
+        /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
+        public static Task SaveAsync(
+            this Image source,
+            Stream stream,
+            IImageFormat format,
+            CancellationToken cancellationToken = default)
+        {
+            Guard.NotNull(stream, nameof(stream));
+            Guard.NotNull(format, nameof(format));
+
+            if (!stream.CanWrite)
+            {
+                throw new NotSupportedException("Cannot write to the stream.");
+            }
+
+            IImageEncoder encoder = source.GetConfiguration().ImageFormatsManager.FindEncoder(format);
+
+            if (encoder is null)
+            {
+                var sb = new StringBuilder();
+                sb.AppendLine("No encoder was found for the provided mime type. Registered encoders include:");
+
+                foreach (KeyValuePair<IImageFormat, IImageEncoder> val in source.GetConfiguration().ImageFormatsManager.ImageEncoders)
+                {
+                    sb.AppendFormat(" - {0} : {1}{2}", val.Key.Name, val.Value.GetType().Name, Environment.NewLine);
+                }
+
+                throw new NotSupportedException(sb.ToString());
+            }
+
+            return source.SaveAsync(stream, encoder, cancellationToken);
+        }
+
         /// <summary>
         /// Returns a Base64 encoded string from the given image.
         /// The result is prepended with a Data URI <see href="https://en.wikipedia.org/wiki/Data_URI_scheme"/>

tests/ImageSharp.Tests/Image/ImageTests.SaveAsync.cs

@@ -72,6 +72,37 @@ public async Task SetEncoding()
                 }
             }
 
+            [Theory]
+            [InlineData("test.png", "image/png")]
+            [InlineData("test.tga", "image/tga")]
+            [InlineData("test.bmp", "image/bmp")]
+            [InlineData("test.jpg", "image/jpeg")]
+            [InlineData("test.gif", "image/gif")]
+            public async Task SaveStreamWithMime(string filename, string mimeType)
+            {
+                using (var image = new Image<Rgba32>(5, 5))
+                {
+                    string ext = Path.GetExtension(filename);
+                    IImageFormat format = image.GetConfiguration().ImageFormatsManager.FindFormatByFileExtension(ext);
+                    Assert.Equal(mimeType, format.DefaultMimeType);
+
+                    using (var stream = new MemoryStream())
+                    {
+                        var asyncStream = new AsyncStreamWrapper(stream, () => false);
+                        await image.SaveAsync(asyncStream, format);
+
+                        stream.Position = 0;
+
+                        (Image Image, IImageFormat Format) imf = await Image.LoadWithFormatAsync(stream);
+
+                        Assert.Equal(format, imf.Format);
+                        Assert.Equal(mimeType, imf.Format.DefaultMimeType);
+
+                        imf.Image.Dispose();
+                    }
+                }
+            }
+
             [Fact]
             public async Task ThrowsWhenDisposed()
             {