Add benchmark file for average filter with 4bpp

tests/ImageSharp.Benchmarks/Codecs/Png/DecodeFilteredPng.cs

@@ -16,7 +16,8 @@ namespace SixLabors.ImageSharp.Benchmarks.Codecs
         private byte[] filter1;
         private byte[] filter2;
         private byte[] filter3;
-        private byte[] filter4;
+        private byte[] averageFilter3bpp;
+        private byte[] averageFilter4bpp;
 
         [GlobalSetup]
         public void ReadImages()
@@ -24,8 +25,9 @@ namespace SixLabors.ImageSharp.Benchmarks.Codecs
             this.filter0 = File.ReadAllBytes(TestImageFullPath(TestImages.Png.Filter0));
             this.filter1 = File.ReadAllBytes(TestImageFullPath(TestImages.Png.Filter1));
             this.filter2 = File.ReadAllBytes(TestImageFullPath(TestImages.Png.Filter2));
-            this.filter3 = File.ReadAllBytes(TestImageFullPath(TestImages.Png.Filter3));
-            this.filter4 = File.ReadAllBytes(TestImageFullPath(TestImages.Png.Filter4));
+            this.filter3 = File.ReadAllBytes(TestImageFullPath(TestImages.Png.Filter4));
+            this.averageFilter3bpp = File.ReadAllBytes(TestImageFullPath(TestImages.Png.AverageFilter3bpp));
+            this.averageFilter4bpp = File.ReadAllBytes(TestImageFullPath(TestImages.Png.AverageFilter4bpp));
         }
 
         [Benchmark(Baseline = true, Description = "None-filtered PNG file")]
@@ -40,13 +42,17 @@ namespace SixLabors.ImageSharp.Benchmarks.Codecs
         public Size PngFilter2()
             => LoadPng(this.filter2);
 
-        [Benchmark(Description = "Average-filtered PNG file")]
-        public Size PngFilter3()
-            => LoadPng(this.filter3);
+        [Benchmark(Description = "Average-filtered PNG file (3bpp)")]
+        public Size PngAvgFilter1()
+            => LoadPng(this.averageFilter3bpp);
+
+        [Benchmark(Description = "Average-filtered PNG file (4bpp)")]
+        public Size PngAvgFilter2()
+            => LoadPng(this.averageFilter4bpp);
 
         [Benchmark(Description = "Paeth-filtered PNG file")]
         public Size PngFilter4()
-            => LoadPng(this.filter4);
+            => LoadPng(this.filter3);
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private static Size LoadPng(byte[] bytes)

tests/ImageSharp.Tests/TestImages.cs

@@ -68,9 +68,11 @@ namespace SixLabors.ImageSharp.Tests
             public const string Filter0 = "Png/filter0.png";
             public const string Filter1 = "Png/filter1.png";
             public const string Filter2 = "Png/filter2.png";
-            public const string Filter3 = "Png/filter3.png";
+            public const string AverageFilter3bpp = "Png/filter3.png";
             public const string Filter4 = "Png/filter4.png";
 
+            public const string AverageFilter4bpp = "Png/AverageFilter4Bpp.png";
+
             // Paletted images also from http://www.schaik.com/pngsuite/pngsuite_fil_png.html
             public const string PalettedTwoColor = "Png/basn3p01.png";
             public const string PalettedFourColor = "Png/basn3p02.png";
@@ -159,7 +161,7 @@ namespace SixLabors.ImageSharp.Tests
             {
                 P1, Pd, Blur, Splash, Cross,
                 Powerpoint, SplashInterlaced, Interlaced,
-                Filter0, Filter1, Filter2, Filter3, Filter4,
+                Filter0, Filter1, Filter2, AverageFilter3bpp, Filter4,
                 FilterVar, VimImage1, VimImage2, VersioningImage1,
                 VersioningImage2, Ratio4x1, Ratio1x4
             };

tests/Images/Input/Png/AverageFilter4Bpp.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:7add6fba794bc76ccea2ee3a311b4050cf17f4f78b69a50785f7739b8b35919e
+size 181108