Cleanup + update tests

src/ImageSharp/Processing/Processors/Transforms/AffineProcessor.cs

@@ -175,10 +175,6 @@ namespace SixLabors.ImageSharp.Processing.Processors
                                 // Precalulating transformed weights would require prior knowledge of every transformed pixel location
                                 // since they can be at sub-pixel positions on both axis.
                                 // I've optimized where I can but am always open to suggestions.
-                                //
-                                // TODO: If we can somehow improve edge pixel handling that would be most beneficial.
-                                // Currently the interpolated edge non-alpha components are altered which causes slight darkening of edges.
-                                // Ideally the edge pixels should represent the nearest sample with altered alpha component only.
                                 if (yScale > 1 && xScale > 1)
                                 {
                                     CalculateWeightsDown(top, bottom, minY, maxY, point.Y, sampler, yScale, ySpan);
@@ -200,12 +196,16 @@ namespace SixLabors.ImageSharp.Processing.Processors
                                     {
                                         float xWeight = xSpan[xx];
                                         var vector = source[i, j].ToVector4();
+
+                                        // Values are first premultiplied to prevent darkening of edge pixels
                                         var mupltiplied = new Vector4(new Vector3(vector.X, vector.Y, vector.Z) * vector.W, vector.W);
                                         sum += mupltiplied * xWeight * yWeight;
                                     }
                                 }
 
                                 ref TPixel dest = ref destRow[x];
+
+                                // Reverse the premultiplication
                                 dest.PackFromVector4(new Vector4(new Vector3(sum.X, sum.Y, sum.Z) / sum.W, sum.W));
                             }
                         });

src/ImageSharp/Processing/Processors/Transforms/ResizeProcessor.cs

@@ -8,6 +8,7 @@ using System.Numerics;
 using System.Threading.Tasks;
 using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.Memory;
+using SixLabors.ImageSharp.MetaData.Profiles.Exif;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.Primitives;
 
@@ -62,7 +63,7 @@ namespace SixLabors.ImageSharp.Processing.Processors
         }
 
         /// <inheritdoc/>
-        protected override unsafe void OnApply(ImageFrame<TPixel> source, ImageFrame<TPixel> cloned, Rectangle sourceRectangle, Configuration configuration)
+        protected override void OnApply(ImageFrame<TPixel> source, ImageFrame<TPixel> cloned, Rectangle sourceRectangle, Configuration configuration)
         {
             // Jump out, we'll deal with that later.
             if (source.Width == cloned.Width && source.Height == cloned.Height && sourceRectangle == this.ResizeRectangle)
@@ -190,5 +191,25 @@ namespace SixLabors.ImageSharp.Processing.Processors
                     });
             }
         }
+
+        /// <inheritdoc/>
+        protected override void AfterImageApply(Image<TPixel> source, Image<TPixel> destination, Rectangle sourceRectangle)
+        {
+            ExifProfile profile = destination.MetaData.ExifProfile;
+            if (profile == null)
+            {
+                return;
+            }
+
+            if (profile.GetValue(ExifTag.PixelXDimension) != null)
+            {
+                profile.SetValue(ExifTag.PixelXDimension, destination.Width);
+            }
+
+            if (profile.GetValue(ExifTag.PixelYDimension) != null)
+            {
+                profile.SetValue(ExifTag.PixelYDimension, destination.Height);
+            }
+        }
     }
 }

tests/ImageSharp.Tests/Processing/Transforms/TransformTests.cs

@@ -63,10 +63,10 @@ namespace SixLabors.ImageSharp.Tests.Processing.Transforms
             IResampler resampler = GetResampler(resamplerName);
             using (Image<TPixel> image = provider.GetImage())
             {
-                // TODO: Modify this matrix if we change our origin-concept 
-                var rotate = Matrix3x2.CreateRotation((float)Math.PI / 4f);
+                var rotate = Matrix3x2.CreateRotation((float)Math.PI / 4F, new Vector2(5 / 2F, 5 / 2F));
+                var translate = Matrix3x2.CreateTranslation((7 - 5) / 2F, (7 - 5) / 2F);
 
-                image.Mutate(c => c.Transform(rotate, resampler));
+                image.Mutate(c => c.Transform(rotate * translate, resampler));
                 image.DebugSave(provider, resamplerName);
 
                 VerifyAllPixelsAreWhiteOrTransparent(image);