Additional png decoder tests for average filter

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

@@ -26,8 +26,8 @@ namespace SixLabors.ImageSharp.Benchmarks.Codecs
             this.filter1 = File.ReadAllBytes(TestImageFullPath(TestImages.Png.Filter1));
             this.filter2 = File.ReadAllBytes(TestImageFullPath(TestImages.Png.Filter2));
             this.filter3 = File.ReadAllBytes(TestImageFullPath(TestImages.Png.Filter4));
-            this.averageFilter3bpp = File.ReadAllBytes(TestImageFullPath(TestImages.Png.AverageFilter3bpp));
-            this.averageFilter4bpp = File.ReadAllBytes(TestImageFullPath(TestImages.Png.AverageFilter4bpp));
+            this.averageFilter3bpp = File.ReadAllBytes(TestImageFullPath(TestImages.Png.AverageFilter3BytesPerPixel));
+            this.averageFilter4bpp = File.ReadAllBytes(TestImageFullPath(TestImages.Png.AverageFilter4BytesPerPixel));
         }
 
         [Benchmark(Baseline = true, Description = "None-filtered PNG file")]

tests/ImageSharp.Tests/Formats/Png/PngDecoderTests.cs

@@ -111,6 +111,17 @@ namespace SixLabors.ImageSharp.Tests.Formats.Png
             image.CompareToOriginal(provider, ImageComparer.Exact);
         }
 
+        [Theory]
+        [WithFile(TestImages.Png.AverageFilter3BytesPerPixel, PixelTypes.Rgba64)]
+        [WithFile(TestImages.Png.AverageFilter4BytesPerPixel, PixelTypes.Rgba64)]
+        public void Decode_WithAverageFilter<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : unmanaged, IPixel<TPixel>
+        {
+            using Image<TPixel> image = provider.GetImage(PngDecoder);
+            image.DebugSave(provider);
+            image.CompareToOriginal(provider, ImageComparer.Exact);
+        }
+
         [Theory]
         [WithFile(TestImages.Png.GrayA8Bit, PixelTypes.Rgba32)]
         [WithFile(TestImages.Png.Gray1BitTrans, PixelTypes.Rgba32)]

tests/ImageSharp.Tests/TestImages.cs

@@ -68,10 +68,10 @@ 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 AverageFilter3bpp = "Png/filter3.png";
+            public const string AverageFilter3BytesPerPixel = "Png/filter3.png";
             public const string Filter4 = "Png/filter4.png";
 
-            public const string AverageFilter4bpp = "Png/AverageFilter4Bpp.png";
+            public const string AverageFilter4BytesPerPixel = "Png/AverageFilter4Bpp.png";
 
             // Paletted images also from http://www.schaik.com/pngsuite/pngsuite_fil_png.html
             public const string PalettedTwoColor = "Png/basn3p01.png";
@@ -161,7 +161,7 @@ namespace SixLabors.ImageSharp.Tests
             {
                 P1, Pd, Blur, Splash, Cross,
                 Powerpoint, SplashInterlaced, Interlaced,
-                Filter0, Filter1, Filter2, AverageFilter3bpp, Filter4,
+                Filter0, Filter1, Filter2, AverageFilter3BytesPerPixel, Filter4,
                 FilterVar, VimImage1, VimImage2, VersioningImage1,
                 VersioningImage2, Ratio4x1, Ratio1x4
             };