adapt ParallelHelper in: FliterProcessor, GlowProcessor, VignetteProcessor

src/ImageSharp/Common/ParallelUtils/ParallelHelper.cs

@@ -127,6 +127,15 @@ namespace SixLabors.ImageSharp.ParallelUtils
                     });
         }
 
+        public static void IterateRowsWithTempBuffer<T>(
+            Rectangle rectangle,
+            Configuration configuration,
+            Action<RowInterval, Memory<T>> body)
+            where T : struct
+        {
+            IterateRowsWithTempBuffer(rectangle, configuration.GetParallelSettings(), body);
+        }
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private static int DivideCeil(int dividend, int divisor)
         {

src/ImageSharp/Processing/Processors/Filters/FilterProcessor.cs

@@ -5,6 +5,7 @@ using System;
 using System.Numerics;
 using System.Threading.Tasks;
 using SixLabors.ImageSharp.Advanced;
+using SixLabors.ImageSharp.ParallelUtils;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.Primitives;
 
@@ -35,25 +36,24 @@ namespace SixLabors.ImageSharp.Processing.Processors.Filters
         protected override void OnFrameApply(ImageFrame<TPixel> source, Rectangle sourceRectangle, Configuration configuration)
         {
             var interest = Rectangle.Intersect(sourceRectangle, source.Bounds());
-            int startY = interest.Y;
-            int endY = interest.Bottom;
-            int startX = interest.X;
-            int endX = interest.Right;
+
             Matrix4x4 matrix = this.Matrix;
 
-            ParallelFor.WithConfiguration(
-                startY,
-                endY,
+            ParallelHelper.IterateRows(
+                interest,
                 configuration,
-                y =>
+                rows =>
                     {
-                        Span<TPixel> row = source.GetPixelRowSpan(y);
-
-                        for (int x = startX; x < endX; x++)
+                        for (int y = rows.Min; y < rows.Max; y++)
                         {
-                            ref TPixel pixel = ref row[x];
-                            var vector = Vector4.Transform(pixel.ToVector4(), matrix);
-                            pixel.PackFromVector4(vector);
+                            Span<TPixel> row = source.GetPixelRowSpan(y);
+
+                            for (int x = interest.X; x < interest.Right; x++)
+                            {
+                                ref TPixel pixel = ref row[x];
+                                var vector = Vector4.Transform(pixel.ToVector4(), matrix);
+                                pixel.PackFromVector4(vector);
+                            }
                         }
                     });
         }

src/ImageSharp/Processing/Processors/Overlays/GlowProcessor.cs

@@ -7,6 +7,7 @@ using System.Numerics;
 using System.Threading.Tasks;
 using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.Memory;
+using SixLabors.ImageSharp.ParallelUtils;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Primitives;
 using SixLabors.Memory;
@@ -84,6 +85,8 @@ namespace SixLabors.ImageSharp.Processing.Processors.Overlays
         /// <inheritdoc/>
         protected override void OnFrameApply(ImageFrame<TPixel> source, Rectangle sourceRectangle, Configuration configuration)
         {
+            // TODO: can we simplify the rectangle calculation?
+
             int startY = sourceRectangle.Y;
             int endY = sourceRectangle.Bottom;
             int startX = sourceRectangle.X;
@@ -113,36 +116,43 @@ namespace SixLabors.ImageSharp.Processing.Processors.Overlays
             }
 
             int width = maxX - minX;
+            int offsetX = minX - startX;
+
+            var workingRect = Rectangle.FromLTRB(minX, minY, maxX, maxY);
+
             using (IMemoryOwner<TPixel> rowColors = source.MemoryAllocator.Allocate<TPixel>(width))
             {
-                // Be careful! Do not capture rowColorsSpan in the lambda below!
-                Span<TPixel> rowColorsSpan = rowColors.GetSpan();
+                rowColors.GetSpan().Fill(glowColor);
 
-                for (int i = 0; i < width; i++)
-                {
-                    rowColorsSpan[i] = glowColor;
-                }
-
-                ParallelFor.WithTemporaryBuffer<float>(
-                    minY,
-                    maxY,
+                ParallelHelper.IterateRowsWithTempBuffer<float>(
+                    workingRect,
                     configuration,
-                    width,
-                    (y, amounts) =>
-                    {
-                        Span<float> amountsSpan = amounts.GetSpan();
-                        int offsetY = y - startY;
-                        int offsetX = minX - startX;
-                        for (int i = 0; i < width; i++)
+                    (rows, amounts) =>
                         {
-                            float distance = Vector2.Distance(center, new Vector2(i + offsetX, offsetY));
-                            amountsSpan[i] = (this.GraphicsOptions.BlendPercentage * (1 - (.95F * (distance / maxDistance)))).Clamp(0, 1);
-                        }
-
-                        Span<TPixel> destination = source.GetPixelRowSpan(offsetY).Slice(offsetX, width);
-
-                        this.blender.Blend(source.MemoryAllocator, destination, destination, rowColors.GetSpan(), amountsSpan);
-                    });
+                            Span<float> amountsSpan = amounts.Span;
+
+                            for (int y = rows.Min; y < rows.Max; y++)
+                            {
+                                int offsetY = y - startY;
+
+                                for (int i = 0; i < width; i++)
+                                {
+                                    float distance = Vector2.Distance(center, new Vector2(i + offsetX, offsetY));
+                                    amountsSpan[i] =
+                                        (this.GraphicsOptions.BlendPercentage * (1 - (.95F * (distance / maxDistance))))
+                                        .Clamp(0, 1);
+                                }
+
+                                Span<TPixel> destination = source.GetPixelRowSpan(offsetY).Slice(offsetX, width);
+
+                                this.blender.Blend(
+                                    source.MemoryAllocator,
+                                    destination,
+                                    destination,
+                                    rowColors.GetSpan(),
+                                    amountsSpan);
+                            }
+                        });
             }
         }
     }

src/ImageSharp/Processing/Processors/Overlays/VignetteProcessor.cs

@@ -7,6 +7,7 @@ using System.Numerics;
 using System.Threading.Tasks;
 using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.Memory;
+using SixLabors.ImageSharp.ParallelUtils;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Primitives;
 using SixLabors.Memory;
@@ -115,43 +116,43 @@ namespace SixLabors.ImageSharp.Processing.Processors.Overlays
             }
 
             int width = maxX - minX;
+            int offsetX = minX - startX;
+
+            var workingRect = Rectangle.FromLTRB(minX, minY, maxX, maxY);
+
             using (IMemoryOwner<TPixel> rowColors = source.MemoryAllocator.Allocate<TPixel>(width))
             {
-                // Be careful! Do not capture rowColorsSpan in the lambda below!
-                Span<TPixel> rowColorsSpan = rowColors.GetSpan();
-
-                for (int i = 0; i < width; i++)
-                {
-                    rowColorsSpan[i] = vignetteColor;
-                }
+                rowColors.GetSpan().Fill(vignetteColor);
 
-                ParallelFor.WithTemporaryBuffer<float>(
-                    minY,
-                    maxY,
+                ParallelHelper.IterateRowsWithTempBuffer<float>(
+                    workingRect,
                     configuration,
-                    width,
-                    (y, amounts) =>
+                    (rows, amounts) =>
                         {
-                            Span<float> amountsSpan = amounts.GetSpan();
-                            int offsetY = y - startY;
-                            int offsetX = minX - startX;
-                            for (int i = 0; i < width; i++)
+                            Span<float> amountsSpan = amounts.Span;
+
+                            for (int y = rows.Min; y < rows.Max; y++)
                             {
-                                float distance = Vector2.Distance(centre, new Vector2(i + offsetX, offsetY));
-                                amountsSpan[i] =
-                                    (this.GraphicsOptions.BlendPercentage * (.9F * (distance / maxDistance))).Clamp(
-                                        0,
-                                        1);
+                                int offsetY = y - startY;
+
+                                for (int i = 0; i < width; i++)
+                                {
+                                    float distance = Vector2.Distance(centre, new Vector2(i + offsetX, offsetY));
+                                    amountsSpan[i] =
+                                        (this.GraphicsOptions.BlendPercentage * (.9F * (distance / maxDistance))).Clamp(
+                                            0,
+                                            1);
+                                }
+
+                                Span<TPixel> destination = source.GetPixelRowSpan(offsetY).Slice(offsetX, width);
+
+                                this.blender.Blend(
+                                    source.MemoryAllocator,
+                                    destination,
+                                    destination,
+                                    rowColors.GetSpan(),
+                                    amountsSpan);
                             }
-
-                            Span<TPixel> destination = source.GetPixelRowSpan(offsetY).Slice(offsetX, width);
-
-                            this.blender.Blend(
-                                source.MemoryAllocator,
-                                destination,
-                                destination,
-                                rowColors.GetSpan(),
-                                amountsSpan);
                         });
             }
         }