Optimize Pixellate

src/ImageSharp/Processing/Processors/Effects/PixelateProcessor.cs

@@ -66,47 +66,45 @@ namespace ImageSharp.Processing.Processors
             // Get the range on the y-plane to choose from.
             IEnumerable<int> range = EnumerableExtensions.SteppedRange(minY, i => i < maxY, size);
 
-            using (PixelAccessor<TPixel> sourcePixels = source.Lock())
-            {
-                Parallel.ForEach(
-                    range,
-                    this.ParallelOptions,
-                    y =>
+            Parallel.ForEach(
+                range,
+                this.ParallelOptions,
+                y =>
+                    {
+                        int offsetY = y - startY;
+                        int offsetPy = offset;
+
+                        // Make sure that the offset is within the boundary of the image.
+                        while (offsetY + offsetPy >= maxY)
                         {
-                            int offsetY = y - startY;
-                            int offsetPy = offset;
+                            offsetPy--;
+                        }
 
-                            for (int x = minX; x < maxX; x += size)
-                            {
-                                int offsetX = x - startX;
-                                int offsetPx = offset;
+                        Span<TPixel> row = source.GetRowSpan(offsetY + offsetPy);
 
-                                // Make sure that the offset is within the boundary of the image.
-                                while (offsetY + offsetPy >= maxY)
-                                {
-                                    offsetPy--;
-                                }
+                        for (int x = minX; x < maxX; x += size)
+                        {
+                            int offsetX = x - startX;
+                            int offsetPx = offset;
 
-                                while (x + offsetPx >= maxX)
-                                {
-                                    offsetPx--;
-                                }
+                            while (x + offsetPx >= maxX)
+                            {
+                                offsetPx--;
+                            }
 
-                                // Get the pixel color in the centre of the soon to be pixelated area.
-                                // ReSharper disable AccessToDisposedClosure
-                                TPixel pixel = sourcePixels[offsetX + offsetPx, offsetY + offsetPy];
+                            // Get the pixel color in the centre of the soon to be pixelated area.
+                            TPixel pixel = row[offsetX + offsetPx];
 
-                                // For each pixel in the pixelate size, set it to the centre color.
-                                for (int l = offsetY; l < offsetY + size && l < maxY; l++)
+                            // For each pixel in the pixelate size, set it to the centre color.
+                            for (int l = offsetY; l < offsetY + size && l < maxY; l++)
+                            {
+                                for (int k = offsetX; k < offsetX + size && k < maxX; k++)
                                 {
-                                    for (int k = offsetX; k < offsetX + size && k < maxX; k++)
-                                    {
-                                        sourcePixels[k, l] = pixel;
-                                    }
+                                    source[k, l] = pixel;
                                 }
                             }
-                        });
-            }
+                        }
+                    });
         }
     }
 }