No need to store the firstpass image as a variable.

Former-commit-id: a1f0b1c9a76b4bf24a704cfd95a922b11ded8189
Former-commit-id: df58b4f394a68e48fd3755ce250ec4ec062cc62f
Former-commit-id: 9234222f848afbdf9461e16ea76974fe56da37a6

src/ImageProcessorCore/Samplers/Processors/ResizeProcessor.cs

@@ -13,11 +13,6 @@ namespace ImageProcessorCore.Processors
     /// </summary>
     public class ResizeProcessor : ImageSampler
     {
-        /// <summary>
-        /// The image used for storing the first pass pixels.
-        /// </summary>
-        private Image firstPass;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="ResizeProcessor"/> class.
         /// </summary>
@@ -54,8 +49,6 @@ namespace ImageProcessorCore.Processors
                 this.HorizontalWeights = this.PrecomputeWeights(targetRectangle.Width, sourceRectangle.Width);
                 this.VerticalWeights = this.PrecomputeWeights(targetRectangle.Height, sourceRectangle.Height);
             }
-
-            this.firstPass = new Image(target.Width, source.Height);
         }
 
         /// <inheritdoc/>
@@ -121,8 +114,9 @@ namespace ImageProcessorCore.Processors
             // A 2-pass 1D algorithm appears to be faster than splitting a 1-pass 2D algorithm 
             // First process the columns. Since we are not using multiple threads startY and endY
             // are the upper and lower bounds of the source rectangle.
+            Image firstPass = new Image(target.Width, source.Height);
             using (PixelAccessor sourcePixels = source.Lock())
-            using (PixelAccessor firstPassPixels = this.firstPass.Lock())
+            using (PixelAccessor firstPassPixels = firstPass.Lock())
             using (PixelAccessor targetPixels = target.Lock())
             {
                 Parallel.For(

tests/ImageProcessorCore.Benchmarks/Samplers/Resize.cs

@@ -12,9 +12,9 @@
         [Benchmark(Baseline = true, Description = "System.Drawing Resize")]
         public Size ResizeSystemDrawing()
         {
-            using (Bitmap source = new Bitmap(400, 400))
+            using (Bitmap source = new Bitmap(2000, 2000))
             {
-                using (Bitmap destination = new Bitmap(100, 100))
+                using (Bitmap destination = new Bitmap(400, 400))
                 {
                     using (Graphics graphics = Graphics.FromImage(destination))
                     {
@@ -32,8 +32,8 @@
         [Benchmark(Description = "ImageProcessorCore Resize")]
         public CoreSize ResizeCore()
         {
-            CoreImage image = new CoreImage(400, 400);
+            CoreImage image = new CoreImage(2000, 2000);
-            image.Resize(100, 100);
+            image.Resize(400, 400);
             return new CoreSize(image.Width, image.Height);
         }
     }