Reduced number of memory allocations

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

@@ -72,6 +72,15 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
                             int length = vectorSpan.Length;
                             ref Vector4 vectorSpanRef = ref MemoryMarshal.GetReference(vectorSpan);
 
+                            // Rent the shared buffer only once per parallel item
+                            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);
+                            ref float blueBinRef = ref Unsafe.Add(ref redBinRef, levels);
+                            ref float greenBinRef = ref Unsafe.Add(ref blueBinRef, levels);
+
                             for (int y = rows.Min; y < rows.Max; y++)
                             {
                                 Span<TPixel> sourceRow = source.GetPixelRowSpan(y);
@@ -83,13 +92,8 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
                                     int maxIntensity = 0;
                                     int maxIndex = 0;
 
-                                    using (IMemoryOwner<float> bins = configuration.MemoryAllocator.Allocate<float>(levels * 4, AllocationOptions.Clean))
+                                    // Clear the current shared buffer before processing each target pixel
-                                    {
+                                    bins.Memory.Span.Clear();
-                                        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);
-                                        ref float blueBinRef = ref Unsafe.Add(ref redBinRef, levels);
-                                        ref float greenBinRef = ref Unsafe.Add(ref blueBinRef, levels);
 
                                     for (int fy = 0; fy <= radius; fy++)
                                     {
@@ -134,7 +138,6 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
                                         Unsafe.Add(ref vectorSpanRef, x) = new Vector4(red, green, blue, alpha);
                                     }
                                 }
-                                }
 
                                 PixelOperations<TPixel>.Instance.FromVector4Destructive(configuration, vectorSpan, targetRowSpan);
                             }