Revert non-generic decode to use RGba32 and add comments

src/ImageSharp/Formats/IImageDecoder.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Six Labors and contributors.
+// Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
 using System.IO;
@@ -17,17 +17,16 @@ public interface IImageDecoder
         /// <typeparam name="TPixel">The pixel format.</typeparam>
         /// <param name="configuration">The configuration for the image.</param>
         /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
-        /// <returns>The decoded image of a given pixel type.</returns>
+        /// <returns>The <see cref="Image{TPixel}"/>.</returns>
         Image<TPixel> Decode<TPixel>(Configuration configuration, Stream stream)
             where TPixel : struct, IPixel<TPixel>;
 
         /// <summary>
         /// Decodes the image from the specified stream to an <see cref="Image"/>.
-        /// The decoder is free to choose the pixel type.
         /// </summary>
         /// <param name="configuration">The configuration for the image.</param>
         /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
-        /// <returns>The decoded image of a pixel type chosen by the decoder.</returns>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         Image Decode(Configuration configuration, Stream stream);
     }
 }

src/ImageSharp/Formats/Jpeg/JpegDecoder.cs

@@ -30,14 +30,7 @@ public Image<TPixel> Decode<TPixel>(Configuration configuration, Stream stream)
 
         /// <inheritdoc />
         public Image Decode(Configuration configuration, Stream stream)
-        {
-            Guard.NotNull(stream, nameof(stream));
-
-            using (var decoder = new JpegDecoderCore(configuration, this))
-            {
-                return decoder.Decode(stream);
-            }
-        }
+            => this.Decode<Rgba32>(configuration, stream);
 
         /// <inheritdoc/>
         public IImageInfo Identify(Configuration configuration, Stream stream)

src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs

@@ -204,22 +204,6 @@ public static JpegFileMarker FindNextFileMarker(byte[] marker, DoubleBufferedStr
             return new JpegFileMarker(marker[1], stream.Position - 2, true);
         }
 
-        /// <summary>
-        /// Decodes the image from the specified <see cref="Stream"/>  and sets the data to image.
-        /// </summary>
-        /// <param name="stream">The stream, where the image should be.</param>
-        /// <returns>The decoded image.</returns>
-        public Image Decode(Stream stream)
-        {
-            this.ParseStream(stream);
-            this.InitExifProfile();
-            this.InitIccProfile();
-            this.InitDerivedMetadataProperties();
-            return this.ColorSpace == JpegColorSpace.Grayscale
-                ? (Image)this.PostProcessIntoImage<L8>()
-                : this.PostProcessIntoImage<Rgb24>();
-        }
-
         /// <summary>
         /// Decodes the image from the specified <see cref="Stream"/>  and sets the data to image.
         /// </summary>

src/ImageSharp/Image.FromBytes.cs

@@ -270,7 +270,7 @@ public static unsafe Image<TPixel> Load<TPixel>(
         /// </summary>
         /// <param name="data">The byte array containing image data.</param>
         /// <param name="format">The detected format.</param>
-        /// <returns>A new <see cref="Image"/>.</returns>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static Image Load(byte[] data, out IImageFormat format) =>
             Load(Configuration.Default, data, out format);
 
@@ -279,24 +279,24 @@ public static Image Load(byte[] data, out IImageFormat format) =>
         /// </summary>
         /// <param name="data">The byte array containing encoded image data.</param>
         /// <param name="decoder">The decoder.</param>
-        /// <returns>A new <see cref="Image"/>.</returns>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static Image Load(byte[] data, IImageDecoder decoder) => Load(Configuration.Default, data, decoder);
 
         /// <summary>
-        /// Load a new instance of <see cref="Image{Rgba32}"/> from the given encoded byte array.
+        /// Load a new instance of <see cref="Image"/> from the given encoded byte array.
         /// </summary>
         /// <param name="config">The config for the decoder.</param>
         /// <param name="data">The byte array containing encoded image data.</param>
-        /// <returns>A new <see cref="Image{Rgba32}"/>.</returns>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static Image Load(Configuration config, byte[] data) => Load(config, data, out _);
 
         /// <summary>
-        /// Load a new instance of <see cref="Image{Rgba32}"/> from the given encoded byte array.
+        /// Load a new instance of <see cref="Image"/> from the given encoded byte array.
         /// </summary>
         /// <param name="config">The config for the decoder.</param>
         /// <param name="data">The byte array containing image data.</param>
         /// <param name="decoder">The decoder.</param>
-        /// <returns>A new <see cref="Image{Rgba32}"/>.</returns>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static Image Load(Configuration config, byte[] data, IImageDecoder decoder)
         {
             using (var stream = new MemoryStream(data))
@@ -306,12 +306,12 @@ public static Image Load(Configuration config, byte[] data, IImageDecoder decode
         }
 
         /// <summary>
-        /// Load a new instance of <see cref="Image{Rgba32}"/> from the given encoded byte array.
+        /// Load a new instance of <see cref="Image"/> from the given encoded byte array.
         /// </summary>
         /// <param name="config">The config for the decoder.</param>
         /// <param name="data">The byte array containing image data.</param>
         /// <param name="format">The mime type of the decoded image.</param>
-        /// <returns>A new <see cref="Image{Rgba32}"/>.</returns>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static Image Load(Configuration config, byte[] data, out IImageFormat format)
         {
             using (var stream = new MemoryStream(data))
@@ -321,18 +321,18 @@ public static Image Load(Configuration config, byte[] data, out IImageFormat for
         }
 
         /// <summary>
-        /// Load a new instance of <see cref="Image{Rgba32}"/> from the given encoded byte span.
+        /// Load a new instance of <see cref="Image"/> from the given encoded byte span.
         /// </summary>
         /// <param name="data">The byte span containing image data.</param>
-        /// <returns>A new <see cref="Image{Rgba32}"/>.</returns>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static Image Load(ReadOnlySpan<byte> data) => Load(Configuration.Default, data);
 
         /// <summary>
         /// Load a new instance of <see cref="Image"/> from the given encoded byte span.
         /// </summary>
         /// <param name="data">The byte span containing image data.</param>
         /// <param name="decoder">The decoder.</param>
-        /// <returns>A new <see cref="Image"/>.</returns>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static Image Load(ReadOnlySpan<byte> data, IImageDecoder decoder) =>
             Load(Configuration.Default, data, decoder);
 
@@ -341,7 +341,7 @@ public static Image Load(ReadOnlySpan<byte> data, IImageDecoder decoder) =>
         /// </summary>
         /// <param name="data">The byte span containing image data.</param>
         /// <param name="format">The detected format.</param>
-        /// <returns>A new <see cref="Image"/>.</returns>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static Image Load(ReadOnlySpan<byte> data, out IImageFormat format) =>
             Load(Configuration.Default, data, out format);
 
@@ -350,7 +350,7 @@ public static Image Load(ReadOnlySpan<byte> data, out IImageFormat format) =>
         /// </summary>
         /// <param name="config">The configuration options.</param>
         /// <param name="data">The byte span containing image data.</param>
-        /// <returns>A new <see cref="Image"/>.</returns>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static Image Load(Configuration config, ReadOnlySpan<byte> data) => Load(config, data, out _);
 
         /// <summary>
@@ -359,7 +359,7 @@ public static Image Load(ReadOnlySpan<byte> data, out IImageFormat format) =>
         /// <param name="config">The Configuration.</param>
         /// <param name="data">The byte span containing image data.</param>
         /// <param name="decoder">The decoder.</param>
-        /// <returns>A new <see cref="Image"/>.</returns>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static unsafe Image Load(
             Configuration config,
             ReadOnlySpan<byte> data,
@@ -380,7 +380,7 @@ public static unsafe Image Load(
         /// <param name="config">The configuration options.</param>
         /// <param name="data">The byte span containing image data.</param>
         /// <param name="format">The <see cref="IImageFormat"/> of the decoded image.</param>>
-        /// <returns>A new <see cref="Image"/>.</returns>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static unsafe Image Load(
             Configuration config,
             ReadOnlySpan<byte> data,

src/ImageSharp/Image.FromFile.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Six Labors and contributors.
+// Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
 using System;
@@ -39,17 +39,17 @@ public static IImageFormat DetectFormat(Configuration config, string filePath)
         }
 
         /// <summary>
-        /// Create a new instance of the <see cref="Image{Rgba32}"/> class from the given file.
+        /// Create a new instance of the <see cref="Image"/> class from the given file.
         /// </summary>
         /// <param name="path">The file path to the image.</param>
         /// <exception cref="NotSupportedException">
         /// Thrown if the stream is not readable nor seekable.
         /// </exception>
-        /// <returns>A new <see cref="Image{Rgba32}"/>.</returns>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static Image Load(string path) => Load(Configuration.Default, path);
 
         /// <summary>
-        /// Create a new instance of the <see cref="Image{Rgba32}"/> class from the given file.
+        /// Create a new instance of the <see cref="Image"/> class from the given file.
         /// </summary>
         /// <param name="path">The file path to the image.</param>
         /// <param name="format">The mime type of the decoded image.</param>
@@ -60,26 +60,26 @@ public static IImageFormat DetectFormat(Configuration config, string filePath)
         public static Image Load(string path, out IImageFormat format) => Load(Configuration.Default, path, out format);
 
         /// <summary>
-        /// Create a new instance of the <see cref="Image{Rgba32}"/> class from the given file.
+        /// Create a new instance of the <see cref="Image"/> class from the given file.
         /// </summary>
         /// <param name="config">The config for the decoder.</param>
         /// <param name="path">The file path to the image.</param>
         /// <exception cref="NotSupportedException">
         /// Thrown if the stream is not readable nor seekable.
         /// </exception>
-        /// <returns>A new <see cref="Image{Rgba32}"/>.</returns>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static Image Load(Configuration config, string path) => Load(config, path, out _);
 
         /// <summary>
-        /// Create a new instance of the <see cref="Image{Rgba32}"/> class from the given file.
+        /// Create a new instance of the <see cref="Image"/> class from the given file.
         /// </summary>
         /// <param name="config">The Configuration.</param>
         /// <param name="path">The file path to the image.</param>
         /// <param name="decoder">The decoder.</param>
         /// <exception cref="NotSupportedException">
         /// Thrown if the stream is not readable nor seekable.
         /// </exception>
-        /// <returns>A new <see cref="Image{Rgba32}"/>.</returns>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static Image Load(Configuration config, string path, IImageDecoder decoder)
         {
             using (Stream stream = config.FileSystem.OpenRead(path))
@@ -89,14 +89,14 @@ public static Image Load(Configuration config, string path, IImageDecoder decode
         }
 
         /// <summary>
-        /// Create a new instance of the <see cref="Image{Rgba32}"/> class from the given file.
+        /// Create a new instance of the <see cref="Image"/> class from the given file.
         /// </summary>
         /// <param name="path">The file path to the image.</param>
         /// <param name="decoder">The decoder.</param>
         /// <exception cref="NotSupportedException">
         /// Thrown if the stream is not readable nor seekable.
         /// </exception>
-        /// <returns>A new <see cref="Image{Rgba32}"/>.</returns>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static Image Load(string path, IImageDecoder decoder) => Load(Configuration.Default, path, decoder);
 
         /// <summary>
@@ -224,4 +224,4 @@ public static Image<TPixel> Load<TPixel>(Configuration config, string path, IIma
             }
         }
     }
-}
+}

src/ImageSharp/Image.FromStream.cs

@@ -80,7 +80,7 @@ public static IImageInfo Identify(Configuration config, Stream stream, out IImag
         /// <param name="format">The format type of the decoded image.</param>
         /// <exception cref="NotSupportedException">Thrown if the stream is not readable.</exception>
         /// <exception cref="UnknownImageFormatException">Image cannot be loaded.</exception>
-        /// <returns>A new <see cref="Image"/>.</returns>>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static Image Load(Stream stream, out IImageFormat format) => Load(Configuration.Default, stream, out format);
 
         /// <summary>
@@ -90,7 +90,7 @@ public static IImageInfo Identify(Configuration config, Stream stream, out IImag
         /// <param name="stream">The stream containing image information.</param>
         /// <exception cref="NotSupportedException">Thrown if the stream is not readable.</exception>
         /// <exception cref="UnknownImageFormatException">Image cannot be loaded.</exception>
-        /// <returns>A new <see cref="Image"/>.</returns>>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static Image Load(Stream stream) => Load(Configuration.Default, stream);
 
         /// <summary>
@@ -101,7 +101,7 @@ public static IImageInfo Identify(Configuration config, Stream stream, out IImag
         /// <param name="decoder">The decoder.</param>
         /// <exception cref="NotSupportedException">Thrown if the stream is not readable.</exception>
         /// <exception cref="UnknownImageFormatException">Image cannot be loaded.</exception>
-        /// <returns>A new <see cref="Image"/>.</returns>>
+        /// <returns>The <see cref="Image"/> in <see cref="Rgba32"/> pixel format.</returns>
         public static Image Load(Stream stream, IImageDecoder decoder) => Load(Configuration.Default, stream, decoder);
 
         /// <summary>