Added docs

src/ImageSharp/Formats/Jpeg/Components/Decoder/SpectralConverter.cs

@@ -3,10 +3,32 @@
 
 namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
 {
+    /// <summary>
+    /// Converter used to convert jpeg spectral data.
+    /// </summary>
+    /// <remarks>
+    /// This is tightly coupled with <see cref="HuffmanScanDecoder"/> and <see cref="JpegDecoderCore"/>.
+    /// </remarks>
     internal abstract class SpectralConverter
     {
+        /// <summary>
+        /// Injects jpeg image decoding metadata.
+        /// </summary>
+        /// <remarks>
+        /// This is guaranteed to be called only once at SOF marker by <see cref="HuffmanScanDecoder"/>.
+        /// </remarks>
+        /// <param name="frame"><see cref="JpegFrame"/> instance containing decoder-specific parameters.</param>
+        /// <param name="jpegData"><see cref="IRawJpegData"/> instance containing decoder-specific parameters.</param>
         public abstract void InjectFrameData(JpegFrame frame, IRawJpegData jpegData);
 
+        /// <summary>
+        /// Called once per spectral stride for each component in <see cref="HuffmanScanDecoder"/>.
+        /// This is called only for baseline interleaved jpegs.
+        /// </summary>
+        /// <remarks>
+        /// Spectral 'stride' doesn't particularly mean 'single stride'.
+        /// Actual stride height depends on the subsampling factor of the given component.
+        /// </remarks>
         public abstract void ConvertStrideBaseline();
     }
 }