Adding extensions was easier than I though

src/ImageSharp/Formats/ImageExtensions.Save.cs

@@ -9,6 +9,7 @@ using SixLabors.ImageSharp.Formats.Gif;
 using SixLabors.ImageSharp.Formats.Jpeg;
 using SixLabors.ImageSharp.Formats.Pbm;
 using SixLabors.ImageSharp.Formats.Png;
+using SixLabors.ImageSharp.Formats.Qoi;
 using SixLabors.ImageSharp.Formats.Tga;
 using SixLabors.ImageSharp.Formats.Webp;
 using SixLabors.ImageSharp.Formats.Tiff;
@@ -836,4 +837,105 @@ public static partial class ImageExtensions
               encoder ?? source.GetConfiguration().ImageFormatsManager.GetEncoder(TiffFormat.Instance),
               cancellationToken);
 
+    /// <summary>
+    /// Saves the image to the given stream with the Qoi format.
+    /// </summary>
+    /// <param name="source">The image this method extends.</param>
+    /// <param name="path">The file path to save the image to.</param>
+    /// <exception cref="System.ArgumentNullException">Thrown if the path is null.</exception>
+    public static void SaveAsQoi(this Image source, string path) => SaveAsQoi(source, path, default);
+
+    /// <summary>
+    /// Saves the image to the given stream with the Qoi format.
+    /// </summary>
+    /// <param name="source">The image this method extends.</param>
+    /// <param name="path">The file path to save the image to.</param>
+    /// <exception cref="System.ArgumentNullException">Thrown if the path is null.</exception>
+    /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
+    public static Task SaveAsQoiAsync(this Image source, string path) => SaveAsQoiAsync(source, path, default);
+
+    /// <summary>
+    /// Saves the image to the given stream with the Qoi format.
+    /// </summary>
+    /// <param name="source">The image this method extends.</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="System.ArgumentNullException">Thrown if the path is null.</exception>
+    /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
+    public static Task SaveAsQoiAsync(this Image source, string path, CancellationToken cancellationToken)
+        => SaveAsQoiAsync(source, path, default, cancellationToken);
+
+    /// <summary>
+    /// Saves the image to the given stream with the Qoi format.
+    /// </summary>
+    /// <param name="source">The image this method extends.</param>
+    /// <param name="path">The file path to save the image to.</param>
+    /// <param name="encoder">The encoder to save the image with.</param>
+    /// <exception cref="System.ArgumentNullException">Thrown if the path is null.</exception>
+    public static void SaveAsQoi(this Image source, string path, QoiEncoder encoder) =>
+        source.Save(
+            path,
+            encoder ?? source.GetConfiguration().ImageFormatsManager.GetEncoder(QoiFormat.Instance));
+
+    /// <summary>
+    /// Saves the image to the given stream with the Qoi format.
+    /// </summary>
+    /// <param name="source">The image this method extends.</param>
+    /// <param name="path">The file path to save the image to.</param>
+    /// <param name="encoder">The encoder to save the image with.</param>
+    /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
+    /// <exception cref="System.ArgumentNullException">Thrown if the path is null.</exception>
+    /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
+    public static Task SaveAsQoiAsync(this Image source, string path, QoiEncoder encoder, CancellationToken cancellationToken = default)
+        => source.SaveAsync(
+              path,
+              encoder ?? source.GetConfiguration().ImageFormatsManager.GetEncoder(QoiFormat.Instance),
+              cancellationToken);
+
+    /// <summary>
+    /// Saves the image to the given stream with the Qoi format.
+    /// </summary>
+    /// <param name="source">The image this method extends.</param>
+    /// <param name="stream">The stream to save the image to.</param>
+    /// <exception cref="System.ArgumentNullException">Thrown if the stream is null.</exception>
+    public static void SaveAsQoi(this Image source, Stream stream)
+        => SaveAsQoi(source, stream, default);
+
+    /// <summary>
+    /// Saves the image to the given stream with the Qoi format.
+    /// </summary>
+    /// <param name="source">The image this method extends.</param>
+    /// <param name="stream">The stream to save the image to.</param>
+    /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
+    /// <exception cref="System.ArgumentNullException">Thrown if the stream is null.</exception>
+    /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
+    public static Task SaveAsQoiAsync(this Image source, Stream stream, CancellationToken cancellationToken = default)
+        => SaveAsQoiAsync(source, stream, default, cancellationToken);
+
+    /// <summary>
+    /// Saves the image to the given stream with the Qoi format.
+    /// </summary>
+    /// <param name="source">The image this method extends.</param>
+    /// <param name="stream">The stream to save the image to.</param>
+    /// <param name="encoder">The encoder to save the image with.</param>
+    /// <exception cref="System.ArgumentNullException">Thrown if the stream is null.</exception>
+    public static void SaveAsQoi(this Image source, Stream stream, QoiEncoder encoder)
+        => source.Save(
+              stream,
+              encoder ?? source.GetConfiguration().ImageFormatsManager.GetEncoder(QoiFormat.Instance));
+
+    /// <summary>
+    /// Saves the image to the given stream with the Qoi format.
+    /// </summary>
+    /// <param name="source">The image this method extends.</param>
+    /// <param name="stream">The stream to save the image to.</param>
+    /// <param name="encoder">The encoder to save the image with.</param>
+    /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
+    /// <exception cref="System.ArgumentNullException">Thrown if the stream is null.</exception>
+    /// <returns>A <see cref="Task"/> representing the asynchronous operation.</returns>
+    public static Task SaveAsQoiAsync(this Image source, Stream stream, QoiEncoder encoder, CancellationToken cancellationToken = default)
+        => source.SaveAsync(
+              stream,
+              encoder ?? source.GetConfiguration().ImageFormatsManager.GetEncoder(QoiFormat.Instance),
+              cancellationToken);
 }

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

@@ -0,0 +1,135 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using SixLabors.ImageSharp.Formats.Qoi;
+using SixLabors.ImageSharp.Formats;
+using SixLabors.ImageSharp.PixelFormats;
+
+namespace SixLabors.ImageSharp.Tests.Formats.Qoi;
+
+public class ImageExtensionsTest
+{
+    [Fact]
+    public void SaveAsQoi_Path()
+    {
+        string dir = TestEnvironment.CreateOutputDirectory(nameof(ImageExtensionsTest));
+        string file = Path.Combine(dir, "SaveAsQoi_Path.qoi");
+
+        using (Image<L8> image = new(10, 10))
+        {
+            image.SaveAsQoi(file);
+        }
+
+        IImageFormat format = Image.DetectFormat(file);
+        Assert.True(format is QoiFormat);
+    }
+
+    [Fact]
+    public async Task SaveAsQoiAsync_Path()
+    {
+        string dir = TestEnvironment.CreateOutputDirectory(nameof(ImageExtensionsTest));
+        string file = Path.Combine(dir, "SaveAsQoiAsync_Path.qoi");
+
+        using (Image<L8> image = new(10, 10))
+        {
+            await image.SaveAsQoiAsync(file);
+        }
+
+        IImageFormat format = Image.DetectFormat(file);
+        Assert.True(format is QoiFormat);
+    }
+
+    [Fact]
+    public void SaveAsQoi_Path_Encoder()
+    {
+        string dir = TestEnvironment.CreateOutputDirectory(nameof(ImageExtensions));
+        string file = Path.Combine(dir, "SaveAsQoi_Path_Encoder.qoi");
+
+        using (Image<L8> image = new(10, 10))
+        {
+            image.SaveAsQoi(file, new QoiEncoder());
+        }
+
+        IImageFormat format = Image.DetectFormat(file);
+        Assert.True(format is QoiFormat);
+    }
+
+    [Fact]
+    public async Task SaveAsQoiAsync_Path_Encoder()
+    {
+        string dir = TestEnvironment.CreateOutputDirectory(nameof(ImageExtensions));
+        string file = Path.Combine(dir, "SaveAsQoiAsync_Path_Encoder.qoi");
+
+        using (Image<L8> image = new(10, 10))
+        {
+            await image.SaveAsQoiAsync(file, new QoiEncoder());
+        }
+
+        IImageFormat format = Image.DetectFormat(file);
+        Assert.True(format is QoiFormat);
+    }
+
+    [Fact]
+    public void SaveAsQoi_Stream()
+    {
+        using MemoryStream memoryStream = new();
+
+        using (Image<L8> image = new(10, 10))
+        {
+            image.SaveAsQoi(memoryStream);
+        }
+
+        memoryStream.Position = 0;
+
+        IImageFormat format = Image.DetectFormat(memoryStream);
+        Assert.True(format is QoiFormat);
+    }
+
+    [Fact]
+    public async Task SaveAsQoiAsync_StreamAsync()
+    {
+        using MemoryStream memoryStream = new();
+
+        using (Image<L8> image = new(10, 10))
+        {
+            await image.SaveAsQoiAsync(memoryStream);
+        }
+
+        memoryStream.Position = 0;
+
+        IImageFormat format = Image.DetectFormat(memoryStream);
+        Assert.True(format is QoiFormat);
+    }
+
+    [Fact]
+    public void SaveAsQoi_Stream_Encoder()
+    {
+        using MemoryStream memoryStream = new();
+
+        using (Image<L8> image = new(10, 10))
+        {
+            image.SaveAsQoi(memoryStream, new QoiEncoder());
+        }
+
+        memoryStream.Position = 0;
+
+        IImageFormat format = Image.DetectFormat(memoryStream);
+        Assert.True(format is QoiFormat);
+    }
+
+    [Fact]
+    public async Task SaveAsQoiAsync_Stream_Encoder()
+    {
+        using MemoryStream memoryStream = new();
+
+        using (Image<L8> image = new(10, 10))
+        {
+            await image.SaveAsQoiAsync(memoryStream, new QoiEncoder());
+        }
+
+        memoryStream.Position = 0;
+
+        IImageFormat format = Image.DetectFormat(memoryStream);
+        Assert.True(format is QoiFormat);
+    }
+}