Remove PixelAccessor and cleanup

src/ImageSharp.Drawing/Processors/DrawImageProcessor.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
-using System.Numerics;
 using System.Threading.Tasks;
 using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.Helpers;
@@ -42,7 +41,7 @@ namespace SixLabors.ImageSharp.Drawing.Processors
         /// <summary>
         /// Gets the image to blend.
         /// </summary>
-        public Image<TPixel> Image { get; private set; }
+        public Image<TPixel> Image { get; }
 
         /// <summary>
         /// Gets the alpha percentage value.
@@ -84,9 +83,7 @@ namespace SixLabors.ImageSharp.Drawing.Processors
                 maxY = Math.Min(this.Location.Y + this.Size.Height, maxY);
 
                 int width = maxX - minX;
-                using (Buffer<float> amount = new Buffer<float>(width))
-                using (PixelAccessor<TPixel> toBlendPixels = targetImage.Lock())
-                using (PixelAccessor<TPixel> sourcePixels = source.Lock())
+                using (var amount = new Buffer<float>(width))
                 {
                     for (int i = 0; i < width; i++)
                     {
@@ -99,8 +96,8 @@ namespace SixLabors.ImageSharp.Drawing.Processors
                         configuration.ParallelOptions,
                         y =>
                             {
-                                Span<TPixel> background = sourcePixels.GetRowSpan(y).Slice(minX, width);
-                                Span<TPixel> foreground = toBlendPixels.GetRowSpan(y - this.Location.Y).Slice(0, width);
+                                Span<TPixel> background = source.GetPixelRowSpan(y).Slice(minX, width);
+                                Span<TPixel> foreground = targetImage.GetPixelRowSpan(y - this.Location.Y).Slice(0, width);
                                 this.blender.Blend(background, background, foreground, amount);
                             });
                 }