Optimize RestoreToBackground

src/ImageSharp/Formats/Webp/WebpAnimationDecoder.cs

@@ -356,15 +356,8 @@ namespace SixLabors.ImageSharp.Formats.Webp
 
             var interest = Rectangle.Intersect(imageFrame.Bounds(), this.restoreArea.Value);
             Buffer2DRegion<TPixel> pixelRegion = imageFrame.PixelBuffer.GetRegion(interest);
-            for (int y = 0; y < pixelRegion.Height; y++)
-            {
-                Span<TPixel> pixelRow = pixelRegion.DangerousGetRowSpan(y);
-                for (int x = 0; x < pixelRow.Length; x++)
-                {
-                    ref TPixel pixel = ref pixelRow[x];
-                    pixel.FromRgba32(backgroundColor);
-                }
-            }
+            TPixel backgroundPixel = backgroundColor.ToPixel<TPixel>();
+            pixelRegion.Fill(backgroundPixel);
         }
 
         /// <summary>

src/ImageSharp/Memory/Buffer2DRegion{T}.cs

@@ -141,6 +141,9 @@ namespace SixLabors.ImageSharp.Memory
             return ref this.Buffer.DangerousGetRowSpan(y)[x];
         }
 
+        /// <summary>
+        /// Clears the contents of this <see cref="Buffer2DRegion{T}"/>.
+        /// </summary>
         internal void Clear()
         {
             // Optimization for when the size of the area is the same as the buffer size.
@@ -156,5 +159,25 @@ namespace SixLabors.ImageSharp.Memory
                 row.Clear();
             }
         }
+
+        /// <summary>
+        /// Fills the elements of this <see cref="Buffer2DRegion{T}"/> with the specified value.
+        /// </summary>
+        /// <param name="value">The value to assign to each element of the region.</param>
+        internal void Fill(T value)
+        {
+            // Optimization for when the size of the area is the same as the buffer size.
+            if (this.IsFullBufferArea)
+            {
+                this.Buffer.FastMemoryGroup.Fill(value);
+                return;
+            }
+
+            for (int y = 0; y < this.Rectangle.Height; y++)
+            {
+                Span<T> row = this.DangerousGetRowSpan(y);
+                row.Fill(value);
+            }
+        }
     }
 }

src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroupExtensions.cs

@@ -7,6 +7,12 @@ namespace SixLabors.ImageSharp.Memory
 {
     internal static class MemoryGroupExtensions
     {
+        /// <summary>
+        /// Fills the elements of this <see cref="IMemoryGroup{T}"/> with the specified value.
+        /// </summary>
+        /// <typeparam name="T">The type of element.</typeparam>
+        /// <param name="group">The group to fill.</param>
+        /// <param name="value">The value to assign to each element of the group.</param>
         internal static void Fill<T>(this IMemoryGroup<T> group, T value)
             where T : struct
         {
@@ -16,6 +22,11 @@ namespace SixLabors.ImageSharp.Memory
             }
         }
 
+        /// <summary>
+        /// Clears the contents of this <see cref="IMemoryGroup{T}"/>.
+        /// </summary>
+        /// <typeparam name="T">The type of element.</typeparam>
+        /// <param name="group">The group to clear.</param>
         internal static void Clear<T>(this IMemoryGroup<T> group)
             where T : struct
         {