Improved jpeg encoding benchmark, updated benchmark 'baseline' for current encoding implementation

tests/ImageSharp.Benchmarks/Codecs/Jpeg/EncodeJpeg.cs

@@ -4,6 +4,7 @@
 using System.Drawing.Imaging;
 using System.IO;
 using BenchmarkDotNet.Attributes;
+using SixLabors.ImageSharp.Formats.Jpeg;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Tests;
 using SDImage = System.Drawing.Image;
@@ -12,10 +13,23 @@ namespace SixLabors.ImageSharp.Benchmarks.Codecs.Jpeg
 {
     public class EncodeJpeg
     {
-        // System.Drawing needs this.
+        private const string TestImage = TestImages.Jpeg.BenchmarkSuite.Jpeg420Exif_MidSizeYCbCr;
-        private Stream bmpStream;
+        private const int EncodingQuality = 100;
+
+        // GDI+ uses 4:1:1 subsampling - https://stackoverflow.com/questions/745610/how-to-disable-subsampling-with-net-gdi
+        // ImageSharp lowest subsampling is 4:2:0 which is an okay approximation
+        private const JpegSubsample EncodingSubsampling = JpegSubsample.Ratio420;
+
+        // System.Drawing
         private SDImage bmpDrawing;
+        private Stream bmpStream;
+        private ImageCodecInfo jpegCodec;
+        private EncoderParameters encoderParameters;
+
+        // ImageSharp
         private Image<Rgba32> bmpCore;
+        private JpegEncoder encoder;
+
         private MemoryStream destinationStream;
 
         [GlobalSetup]
@@ -23,12 +37,19 @@ namespace SixLabors.ImageSharp.Benchmarks.Codecs.Jpeg
         {
             if (this.bmpStream == null)
             {
-                const string TestImage = TestImages.Jpeg.BenchmarkSuite.Jpeg420Exif_MidSizeYCbCr;
                 this.bmpStream = File.OpenRead(Path.Combine(TestEnvironment.InputImagesDirectoryFullPath, TestImage));
+
                 this.bmpCore = Image.Load<Rgba32>(this.bmpStream);
                 this.bmpCore.Metadata.ExifProfile = null;
+                this.encoder = new JpegEncoder { Quality = EncodingQuality, Subsample = EncodingSubsampling };
+
                 this.bmpStream.Position = 0;
                 this.bmpDrawing = SDImage.FromStream(this.bmpStream);
+                this.jpegCodec = GetEncoder(ImageFormat.Jpeg);
+                this.encoderParameters = new EncoderParameters(1);
+                // Quality cast to long is necessary
+                this.encoderParameters.Param[0] = new EncoderParameter(Encoder.Quality, (long)EncodingQuality);
+
                 this.destinationStream = new MemoryStream();
             }
         }
@@ -45,29 +66,43 @@ namespace SixLabors.ImageSharp.Benchmarks.Codecs.Jpeg
         [Benchmark(Baseline = true, Description = "System.Drawing Jpeg")]
         public void JpegSystemDrawing()
         {
-            this.bmpDrawing.Save(this.destinationStream, ImageFormat.Jpeg);
+            this.bmpDrawing.Save(this.destinationStream, this.jpegCodec, this.encoderParameters);
             this.destinationStream.Seek(0, SeekOrigin.Begin);
         }
 
         [Benchmark(Description = "ImageSharp Jpeg")]
         public void JpegCore()
         {
-            this.bmpCore.SaveAsJpeg(this.destinationStream);
+            this.bmpCore.SaveAsJpeg(this.destinationStream, this.encoder);
             this.destinationStream.Seek(0, SeekOrigin.Begin);
         }
+
+        // https://docs.microsoft.com/en-us/dotnet/api/system.drawing.imaging.encoderparameter?redirectedfrom=MSDN&view=net-5.0
+        private static ImageCodecInfo GetEncoder(ImageFormat format)
+        {
+            ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders();
+            foreach (ImageCodecInfo codec in codecs)
+            {
+                if (codec.FormatID == format.Guid)
+                {
+                    return codec;
+                }
+            }
+            return null;
+        }
     }
 }
 
 /*
-BenchmarkDotNet=v0.12.1, OS=Windows 10.0.18363.959 (1909/November2018Update/19H2)
+BenchmarkDotNet=v0.12.1, OS=Windows 10.0.19042
-Intel Core i7-8650U CPU 1.90GHz (Kaby Lake R), 1 CPU, 8 logical and 4 physical cores
+Intel Core i7-6700K CPU 4.00GHz (Skylake), 1 CPU, 8 logical and 4 physical cores
-.NET Core SDK=3.1.302
+.NET Core SDK=6.0.100-preview.3.21202.5
-  [Host]     : .NET Core 3.1.6 (CoreCLR 4.700.20.26901, CoreFX 4.700.20.31603), X64 RyuJIT
+  [Host]     : .NET Core 3.1.13 (CoreCLR 4.700.21.11102, CoreFX 4.700.21.11602), X64 RyuJIT
-  DefaultJob : .NET Core 3.1.6 (CoreCLR 4.700.20.26901, CoreFX 4.700.20.31603), X64 RyuJIT
+  DefaultJob : .NET Core 3.1.13 (CoreCLR 4.700.21.11102, CoreFX 4.700.21.11602), X64 RyuJIT
 
 
-|                Method |     Mean |     Error |    StdDev | Ratio | RatioSD |
+|                Method |     Mean |    Error |   StdDev | Ratio | RatioSD |
-|---------------------- |---------:|----------:|----------:|------:|--------:|
+|---------------------- |---------:|---------:|---------:|------:|--------:|
-| 'System.Drawing Jpeg' | 4.297 ms | 0.0244 ms | 0.0228 ms |  1.00 |    0.00 |
+| 'System.Drawing Jpeg' | 39.54 ms | 0.269 ms | 0.225 ms |  1.00 |    0.00 |
-|     'ImageSharp Jpeg' | 5.286 ms | 0.1034 ms | 0.0967 ms |  1.23 |    0.02 |
+|     'ImageSharp Jpeg' | 47.25 ms | 0.937 ms | 1.219 ms |  1.20 |    0.02 |
 */