Fix Oil Painting processor

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

@@ -70,9 +70,10 @@ namespace ImageSharp.Processing.Processors
             }
 
             using (PixelAccessor<TPixel> targetPixels = new PixelAccessor<TPixel>(source.Width, source.Height))
-            {
             using (PixelAccessor<TPixel> sourcePixels = source.Lock())
             {
+                sourcePixels.CopyTo(targetPixels);
+
                 Parallel.For(
                     minY,
                     maxY,
@@ -151,7 +152,6 @@ namespace ImageSharp.Processing.Processors
                             }
                         }
                     });
-                }
 
                 source.SwapPixelsBuffers(targetPixels);
             }