Optimize Flip

src/ImageSharp/Processing/Processors/Transforms/FlipProcessor.cs

@@ -8,6 +8,7 @@ namespace ImageSharp.Processing.Processors
     using System;
     using System.Threading.Tasks;
 
+    using ImageSharp.Memory;
     using ImageSharp.PixelFormats;
 
     /// <summary>
@@ -57,24 +58,23 @@ namespace ImageSharp.Processing.Processors
             int height = source.Height;
             int halfHeight = (int)Math.Ceiling(source.Height * .5F);
 
-            using (PixelAccessor<TPixel> targetPixels = new PixelAccessor<TPixel>(width, height))
+            using (var targetPixels = new PixelAccessor<TPixel>(width, height))
-            {
-                using (PixelAccessor<TPixel> sourcePixels = source.Lock())
             {
                 Parallel.For(
                     0,
                     halfHeight,
                     this.ParallelOptions,
                     y =>
-                            {
-                                for (int x = 0; x < width; x++)
                         {
                             int newY = height - y - 1;
-                                    targetPixels[x, y] = sourcePixels[x, newY];
+                            Span<TPixel> sourceRow = source.GetRowSpan(y);
-                                    targetPixels[x, newY] = sourcePixels[x, y];
+                            Span<TPixel> altSourceRow = source.GetRowSpan(newY);
-                                }
+                            Span<TPixel> targetRow = targetPixels.GetRowSpan(y);
+                            Span<TPixel> altTargetRow = targetPixels.GetRowSpan(newY);
+
+                            sourceRow.CopyTo(altTargetRow);
+                            altSourceRow.CopyTo(targetRow);
                         });
-                }
 
                 source.SwapPixelsBuffers(targetPixels);
             }
@@ -91,9 +91,7 @@ namespace ImageSharp.Processing.Processors
             int height = source.Height;
             int halfWidth = (int)Math.Ceiling(width * .5F);
 
-            using (PixelAccessor<TPixel> targetPixels = new PixelAccessor<TPixel>(width, height))
+            using (var targetPixels = new PixelAccessor<TPixel>(width, height))
-            {
-                using (PixelAccessor<TPixel> sourcePixels = source.Lock())
             {
                 Parallel.For(
                     0,
@@ -101,14 +99,16 @@ namespace ImageSharp.Processing.Processors
                     this.ParallelOptions,
                     y =>
                         {
+                            Span<TPixel> sourceRow = source.GetRowSpan(y);
+                            Span<TPixel> targetRow = targetPixels.GetRowSpan(y);
+
                             for (int x = 0; x < halfWidth; x++)
                             {
                                 int newX = width - x - 1;
-                                    targetPixels[x, y] = sourcePixels[newX, y];
+                                targetRow[x] = sourceRow[newX];
-                                    targetPixels[newX, y] = sourcePixels[x, y];
+                                targetRow[newX] = sourceRow[x];
                             }
                         });
-                }
 
                 source.SwapPixelsBuffers(targetPixels);
             }