Issue 551 solidbrush blend performance

src/ImageSharp.Drawing/Processing/Drawing/Brushes/SolidBrush{TPixel}.cs

@@ -90,16 +90,23 @@ internal override void Apply(Span<float> scanline, int x, int y)
 
                 MemoryManager memoryManager = this.Target.MemoryManager;
 
-                using (IBuffer<float> amountBuffer = memoryManager.Allocate<float>(scanline.Length))
+                if (this.Options.BlendPercentage == 1f)
                 {
-                    Span<float> amountSpan = amountBuffer.Span;
-
-                    for (int i = 0; i < scanline.Length; i++)
+                    this.Blender.Blend(memoryManager, destinationRow, destinationRow, this.Colors.Span, scanline);
+                }
+                else
+                {
+                    using (IBuffer<float> amountBuffer = memoryManager.Allocate<float>(scanline.Length))
                     {
-                        amountSpan[i] = scanline[i] * this.Options.BlendPercentage;
-                    }
+                        Span<float> amountSpan = amountBuffer.Span;
+
+                        for (int i = 0; i < scanline.Length; i++)
+                        {
+                            amountSpan[i] = scanline[i] * this.Options.BlendPercentage;
+                        }
 
-                    this.Blender.Blend(memoryManager, destinationRow, destinationRow, this.Colors.Span, amountSpan);
+                        this.Blender.Blend(memoryManager, destinationRow, destinationRow, this.Colors.Span, amountSpan);
+                    }
                 }
             }
         }

src/ImageSharp.Drawing/Processing/Drawing/Processors/FillProcessor.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Threading.Tasks;
+using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Processing.Drawing.Brushes;
@@ -49,39 +50,66 @@ protected override void OnFrameApply(ImageFrame<TPixel> source, Rectangle source
             int minY = Math.Max(0, startY);
             int maxY = Math.Min(source.Height, endY);
 
-            // Reset offset if necessary.
-            if (minX > 0)
-            {
-                startX = 0;
-            }
-
-            if (minY > 0)
-            {
-                startY = 0;
-            }
-
             int width = maxX - minX;
 
-            using (IBuffer<float> amount = source.MemoryManager.Allocate<float>(width))
-            using (BrushApplicator<TPixel> applicator = this.brush.CreateApplicator(
-                source,
-                sourceRectangle,
-                this.options))
+            // If there's no reason for blending, then avoid it.
+            if (this.IsSolidBrushWithoutBlending(out SolidBrush<TPixel> solidBrush))
             {
-                amount.Span.Fill(1f);
-
                 Parallel.For(
                     minY,
                     maxY,
                     configuration.ParallelOptions,
                     y =>
-                        {
-                            int offsetY = y - startY;
-                            int offsetX = minX - startX;
+                    {
+                        source.GetPixelRowSpan(y).Slice(minX, width).Fill(solidBrush.Color);
+                    });
+            }
+            else
+            {
+                // Reset offset if necessary.
+                if (minX > 0)
+                {
+                    startX = 0;
+                }
+
+                if (minY > 0)
+                {
+                    startY = 0;
+                }
+
+                using (IBuffer<float> amount = source.MemoryManager.Allocate<float>(width))
+                using (BrushApplicator<TPixel> applicator = this.brush.CreateApplicator(
+                    source,
+                    sourceRectangle,
+                    this.options))
+                {
+                    amount.Span.Fill(1f);
+
+                    Parallel.For(
+                        minY,
+                        maxY,
+                        configuration.ParallelOptions,
+                        y =>
+                            {
+                                int offsetY = y - startY;
+                                int offsetX = minX - startX;
 
-                            applicator.Apply(amount.Span, offsetX, offsetY);
-                        });
+                                applicator.Apply(amount.Span, offsetX, offsetY);
+                            });
+                }
             }
         }
+
+        private bool IsSolidBrushWithoutBlending(out SolidBrush<TPixel> solidBrush)
+        {
+            solidBrush = this.brush as SolidBrush<TPixel>;
+
+            return solidBrush != null
+                   && ((this.options.BlenderMode == PixelBlenderMode.Normal && this.options.BlendPercentage == 1f
+                                                                            && solidBrush.Color.ToVector4().W == 1f)
+                       || (this.options.BlenderMode == PixelBlenderMode.Over && this.options.BlendPercentage == 1f
+                                                                             && solidBrush.Color.ToVector4().W == 1f)
+                       || (this.options.BlenderMode == PixelBlenderMode.Src));
+        }
     }
 }