Removed using statements, added detailed comment

src/ImageSharp/Processing/Processors/Effects/OilPaintingProcessor{TPixel}.cs

@@ -68,21 +68,26 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
                 this.Configuration,
                 (rows) =>
                 {
-                    // Allocate the reusable source row buffer, to enable vectorized bulk conversions
+                    /* Allocate the two temporary Vector4 buffers, one for the source row and one for the target row.
-                    using IMemoryOwner<Vector4> sourceRowBuffer = configuration.MemoryAllocator.Allocate<Vector4>(rowWidth);
+                     * The ParallelHelper.IterateRowsWithTempBuffers overload is not used in this case because
-
+                     * the two allocated buffers have a length equal to the width of the source image,
+                     * and not just equal to the width of the target rectangle to process.
+                     * Furthermore, there are two buffers being allocated in this case, so using that overload would
+                     * have still required the explicit allocation of the secondary buffer.
+                     * Similarly, one temporary float buffer is also allocated from the pool, and that is used
+                     * to create the target bins for all the color channels being processed.
+                     * This buffer is only rented once outside of the main processing loop, and its contents
+                     * are cleared for each loop iteration, to avoid the repeated allocation for each processed pixel. */
+                    using (IMemoryOwner<Vector4> sourceRowBuffer = configuration.MemoryAllocator.Allocate<Vector4>(rowWidth))
+                    using (IMemoryOwner<Vector4> targetRowBuffer = configuration.MemoryAllocator.Allocate<Vector4>(rowWidth))
+                    using (IMemoryOwner<float> bins = configuration.MemoryAllocator.Allocate<float>(levels * 4))
+                    {
                         Span<Vector4> sourceRowVector4Span = sourceRowBuffer.Memory.Span;
                         Span<Vector4> sourceRowAreaVector4Span = sourceRowVector4Span.Slice(startX, rectangleWidth);
 
-                    // Allocate the reusable target row buffer
-                    using IMemoryOwner<Vector4> targetRowBuffer = configuration.MemoryAllocator.Allocate<Vector4>(rowWidth);
-
                         Span<Vector4> targetRowVector4Span = targetRowBuffer.Memory.Span;
                         Span<Vector4> targetRowAreaVector4Span = targetRowVector4Span.Slice(startX, rectangleWidth);
 
-                    // Rent the shared buffer only once per parallel item.
-                    using IMemoryOwner<float> bins = configuration.MemoryAllocator.Allocate<float>(levels * 4);
-
                         ref float binsRef = ref bins.GetReference();
                         ref int intensityBinRef = ref Unsafe.As<float, int>(ref binsRef);
                         ref float redBinRef = ref Unsafe.Add(ref binsRef, levels);
@@ -152,6 +157,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
 
                             PixelOperations<TPixel>.Instance.FromVector4Destructive(configuration, targetRowAreaVector4Span, targetRowAreaPixelSpan);
                         }
+                    }
                 });
 
             Buffer2D<TPixel>.SwapOrCopyContent(source.PixelBuffer, targetPixels);