fix remaining single-buffer specific code

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

@@ -38,7 +38,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
                 this.blockAreaSize.Height);
 
             this.BlockRowsPerStep = JpegImagePostProcessor.BlockRowsPerStep / this.Component.SubSamplingDivisors.Height;
-
         }
 
         /// <summary>

src/ImageSharp/Image.LoadPixelData.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Runtime.InteropServices;
 using SixLabors.ImageSharp.Advanced;
+using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp
@@ -118,10 +119,10 @@ namespace SixLabors.ImageSharp
             Guard.MustBeGreaterThanOrEqualTo(data.Length, count, nameof(data));
 
             var image = new Image<TPixel>(config, width, height);
-
-            data.Slice(0, count).CopyTo(image.Frames.RootFrame.GetPixelSpan());
+            data = data.Slice(0, count);
+            data.CopyTo(image.Frames.RootFrame.PixelBuffer.MemoryGroup);
 
             return image;
         }
     }
-}
+}

src/ImageSharp/ImageFrame.LoadPixelData.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Runtime.InteropServices;
 using SixLabors.ImageSharp.Advanced;
+using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp
@@ -43,7 +44,8 @@ namespace SixLabors.ImageSharp
 
             var image = new ImageFrame<TPixel>(configuration, width, height);
 
-            data.Slice(0, count).CopyTo(image.GetPixelSpan());
+            data = data.Slice(0, count);
+            data.CopyTo(image.PixelBuffer.MemoryGroup);
 
             return image;
         }

src/ImageSharp/ImageFrame.cs

@@ -3,6 +3,7 @@
 
 using System;
 using SixLabors.ImageSharp.Advanced;
+using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.Metadata;
 using SixLabors.ImageSharp.PixelFormats;
 
@@ -78,7 +79,7 @@ namespace SixLabors.ImageSharp
         /// <param name="disposing">Whether to dispose of managed and unmanaged objects.</param>
         protected abstract void Dispose(bool disposing);
 
-        internal abstract void CopyPixelsTo<TDestinationPixel>(Span<TDestinationPixel> destination)
+        internal abstract void CopyPixelsTo<TDestinationPixel>(MemoryGroup<TDestinationPixel> destination)
             where TDestinationPixel : struct, IPixel<TDestinationPixel>;
 
         /// <summary>

src/ImageSharp/ImageFrameCollection{TPixel}.cs

@@ -351,7 +351,7 @@ namespace SixLabors.ImageSharp
                 this.parent.GetConfiguration(),
                 source.Size(),
                 source.Metadata.DeepClone());
-            source.CopyPixelsTo(result.PixelBuffer.GetSingleSpan());
+            source.CopyPixelsTo(result.PixelBuffer.MemoryGroup);
             return result;
         }
     }

src/ImageSharp/ImageFrame{TPixel}.cs

@@ -218,15 +218,22 @@ namespace SixLabors.ImageSharp
             this.isDisposed = true;
         }
 
-        internal override void CopyPixelsTo<TDestinationPixel>(Span<TDestinationPixel> destination)
+        internal override void CopyPixelsTo<TDestinationPixel>(MemoryGroup<TDestinationPixel> destination)
         {
             if (typeof(TPixel) == typeof(TDestinationPixel))
             {
-                Span<TPixel> dest1 = MemoryMarshal.Cast<TDestinationPixel, TPixel>(destination);
-                this.PixelBuffer.GetSingleSpan().CopyTo(dest1);
+                this.PixelBuffer.MemoryGroup.TransformTo(destination, (s, d) =>
+                {
+                    Span<TPixel> d1 = MemoryMarshal.Cast<TDestinationPixel, TPixel>(d);
+                    s.CopyTo(d1);
+                });
+                return;
             }
 
-            PixelOperations<TPixel>.Instance.To(this.GetConfiguration(), this.PixelBuffer.GetSingleSpan(), destination);
+            this.PixelBuffer.MemoryGroup.TransformTo(destination, (s, d) =>
+            {
+                PixelOperations<TPixel>.Instance.To(this.GetConfiguration(), s, d);
+            });
         }
 
         /// <inheritdoc/>

src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroupExtensions.cs

@@ -126,11 +126,12 @@ namespace SixLabors.ImageSharp.Memory
             }
         }
 
-        internal static void TransformTo<T>(
-            this IMemoryGroup<T> source,
-            IMemoryGroup<T> target,
-            TransformItemsDelegate<T> transform)
-            where T : struct
+        internal static void TransformTo<TSource, TTarget>(
+            this IMemoryGroup<TSource> source,
+            IMemoryGroup<TTarget> target,
+            TransformItemsDelegate<TSource, TTarget> transform)
+            where TSource : struct
+            where TTarget : struct
         {
             Guard.NotNull(source, nameof(source));
             Guard.NotNull(target, nameof(target));
@@ -145,14 +146,14 @@ namespace SixLabors.ImageSharp.Memory
             }
 
             long position = 0;
-            var srcCur = new MemoryGroupCursor<T>(source);
-            var trgCur = new MemoryGroupCursor<T>(target);
+            var srcCur = new MemoryGroupCursor<TSource>(source);
+            var trgCur = new MemoryGroupCursor<TTarget>(target);
 
             while (position < source.TotalLength)
             {
                 int fwd = Math.Min(srcCur.LookAhead(), trgCur.LookAhead());
-                Span<T> srcSpan = srcCur.GetSpan(fwd);
-                Span<T> trgSpan = trgCur.GetSpan(fwd);
+                Span<TSource> srcSpan = srcCur.GetSpan(fwd);
+                Span<TTarget> trgSpan = trgCur.GetSpan(fwd);
                 transform(srcSpan, trgSpan);
 
                 srcCur.Forward(fwd);

src/ImageSharp/Memory/TransformItemsDelegate{T}.cs

@@ -5,5 +5,5 @@ using System;
 
 namespace SixLabors.ImageSharp.Memory
 {
-    internal delegate void TransformItemsDelegate<T>(ReadOnlySpan<T> source, Span<T> target);
+    internal delegate void TransformItemsDelegate<TSource, TTarget>(ReadOnlySpan<TSource> source, Span<TTarget> target);
 }