Merge pull request #604 from carbon/netcore21

Cross target NETCOREAPP2.1

appveyor.yml

@@ -1,18 +1,16 @@
 version: 1.0.0.{build}
-image: Visual Studio 2017 Preview
+image: Visual Studio 2017
 
 # prevent the double build when a branch has an active PR
 skip_branch_with_pr: true
 
 environment:
   matrix:
-    ### TODO: Enable the netcoreapp2.1 target when RC2 has been released!
-
-    #- target_framework: netcoreapp2.1
-    #  is_32bit: False
+    - target_framework: netcoreapp2.1
+      is_32bit: False
 
-    #- target_framework: netcoreapp2.1
-    #  is_32bit: True
+    - target_framework: netcoreapp2.1
+      is_32bit: True
 
     - target_framework: netcoreapp2.0
       is_32bit: False

run-tests.ps1

@@ -75,6 +75,11 @@ else {
         $xunitArgs += " --fx-version 2.0.0"
     }
 
+    if ($targetFramework -eq "netcoreapp2.1") {
+        # There were issues matching the correct installed runtime if we do not specify it explicitly:
+        $xunitArgs += " --fx-version 2.1.0"
+    }
+
     if ($is32Bit -eq "True") {
         $xunitArgs += " -x86"
     }

src/ImageSharp/Common/Extensions/StreamExtensions.cs

@@ -1,7 +1,7 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
-using System.Buffers;
+using System;
 using System.IO;
 
 namespace SixLabors.ImageSharp
@@ -11,6 +11,33 @@ namespace SixLabors.ImageSharp
     /// </summary>
     internal static class StreamExtensions
     {
+#if NETCOREAPP2_1
+        /// <summary>
+        /// Writes data from a stream into the provided buffer.
+        /// </summary>
+        /// <param name="stream">The stream.</param>
+        /// <param name="buffer">The buffer.</param>
+        /// <param name="offset">The offset within the buffer to begin writing.</param>
+        /// <param name="count">The number of bytes to write to the stream.</param>
+        public static void Write(this Stream stream, Span<byte> buffer, int offset, int count)
+        {
+            stream.Write(buffer.Slice(offset, count));
+        }
+
+        /// <summary>
+        /// Reads data from a stream into the provided buffer.
+        /// </summary>
+        /// <param name="stream">The stream.</param>
+        /// <param name="buffer">The buffer..</param>
+        /// <param name="offset">The offset within the buffer where the bytes are read into.</param>
+        /// <param name="count">The number of bytes, if available, to read.</param>
+        /// <returns>The actual number of bytes read.</returns>
+        public static int Read(this Stream stream, Span<byte> buffer, int offset, int count)
+        {
+            return stream.Read(buffer.Slice(offset, count));
+        }
+#endif
+
         /// <summary>
         /// Skips the number of bytes in the given stream.
         /// </summary>

src/ImageSharp/Common/Helpers/TestHelpers.cs

@@ -0,0 +1,24 @@
+// Copyright(c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+namespace SixLabors.ImageSharp.Common.Helpers
+{
+    /// <summary>
+    /// Internal utilities intended to be only used in tests.
+    /// </summary>
+    internal static class TestHelpers
+    {
+        /// <summary>
+        /// This constant is useful to verify the target framework ImageSharp has been built against.
+        /// Only intended to be used in tests!
+        /// </summary>
+        internal const string ImageSharpBuiltAgainst =
+#if NETSTANDARD1_1
+            "netstandard1.1";
+#elif NETCOREAPP2_1
+            "netcoreapp2.1";
+#else
+            "netstandard2.0";
+#endif
+    }
+}

src/ImageSharp/Formats/Bmp/BmpDecoderCore.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
+using System.Buffers.Binary;
 using System.IO;
 using System.Runtime.CompilerServices;
 using SixLabors.ImageSharp.MetaData;
@@ -251,7 +252,11 @@ namespace SixLabors.ImageSharp.Formats.Bmp
         /// <param name="buffer">Buffer for uncompressed data.</param>
         private void UncompressRle8(int w, Span<byte> buffer)
         {
+#if NETCOREAPP2_1
+            Span<byte> cmd = stackalloc byte[2];
+#else
             byte[] cmd = new byte[2];
+#endif
             int count = 0;
 
             while (count < buffer.Length)
@@ -475,12 +480,14 @@ namespace SixLabors.ImageSharp.Formats.Bmp
         /// </summary>
         private void ReadInfoHeader()
         {
+#if NETCOREAPP2_1
+            Span<byte> buffer = stackalloc byte[BmpInfoHeader.MaxHeaderSize];
+#else
             byte[] buffer = new byte[BmpInfoHeader.MaxHeaderSize];
+#endif
+            this.stream.Read(buffer, 0, BmpInfoHeader.HeaderSizeSize); // read the header size
 
-            // read header size
-            this.stream.Read(buffer, 0, BmpInfoHeader.HeaderSizeSize);
-
-            int headerSize = BitConverter.ToInt32(buffer, 0);
+            int headerSize = BinaryPrimitives.ReadInt32LittleEndian(buffer);
             if (headerSize < BmpInfoHeader.CoreSize)
             {
                 throw new NotSupportedException($"ImageSharp does not support this BMP file. HeaderSize: {headerSize}.");
@@ -504,7 +511,7 @@ namespace SixLabors.ImageSharp.Formats.Bmp
             else if (headerSize >= BmpInfoHeader.Size)
             {
                 // >= 40 bytes
-                this.infoHeader = BmpInfoHeader.Parse(buffer.AsSpan(0, 40));
+                this.infoHeader = BmpInfoHeader.Parse(buffer);
             }
             else
             {
@@ -520,8 +527,11 @@ namespace SixLabors.ImageSharp.Formats.Bmp
         /// </summary>
         private void ReadFileHeader()
         {
+#if NETCOREAPP2_1
+            Span<byte> buffer = stackalloc byte[BmpFileHeader.Size];
+#else
             byte[] buffer = new byte[BmpFileHeader.Size];
-
+#endif
             this.stream.Read(buffer, 0, BmpFileHeader.Size);
 
             this.fileHeader = BmpFileHeader.Parse(buffer);

src/ImageSharp/Formats/Bmp/BmpEncoderCore.cs

@@ -66,8 +66,11 @@ namespace SixLabors.ImageSharp.Formats.Bmp
                 reserved: 0,
                 fileSize: 54 + infoHeader.ImageSize);
 
-            byte[] buffer = new byte[40]; // TODO: stackalloc
-
+#if NETCOREAPP2_1
+            Span<byte> buffer = stackalloc byte[40];
+#else
+            byte[] buffer = new byte[40];
+#endif
             fileHeader.WriteTo(buffer);
 
             stream.Write(buffer, 0, BmpFileHeader.Size);

src/ImageSharp/Formats/Bmp/BmpInfoHeader.cs

@@ -132,6 +132,11 @@ namespace SixLabors.ImageSharp.Formats.Bmp
         /// <seealso href="https://msdn.microsoft.com/en-us/library/windows/desktop/dd183376.aspx"/>
         public static BmpInfoHeader Parse(ReadOnlySpan<byte> data)
         {
+            if (data.Length != Size)
+            {
+                throw new ArgumentException(nameof(data), $"Must be {Size} bytes. Was {data.Length} bytes.");
+            }
+
             return MemoryMarshal.Cast<byte, BmpInfoHeader>(data)[0];
         }
 

src/ImageSharp/Formats/Gif/LzwDecoder.cs

@@ -112,7 +112,12 @@ namespace SixLabors.ImageSharp.Formats.Gif
                 Unsafe.Add(ref suffixRef, code) = (byte)code;
             }
 
+#if NETCOREAPP2_1
+            Span<byte> buffer = stackalloc byte[255];
+#else
             byte[] buffer = new byte[255];
+#endif
+
             while (xyz < length)
             {
                 if (top == 0)
@@ -221,15 +226,21 @@ namespace SixLabors.ImageSharp.Formats.Gif
         /// The <see cref="int"/>.
         /// </returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
+#if NETCOREAPP2_1
+        private int ReadBlock(Span<byte> buffer)
+#else
         private int ReadBlock(byte[] buffer)
+#endif
         {
             int bufferSize = this.stream.ReadByte();
+
             if (bufferSize < 1)
             {
                 return 0;
             }
 
             int count = this.stream.Read(buffer, 0, bufferSize);
+
             return count != bufferSize ? 0 : bufferSize;
         }
 

src/ImageSharp/Formats/Jpeg/JpegEncoderCore.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
 using System.IO;
 using System.Runtime.CompilerServices;
 
@@ -736,16 +737,16 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         private void WriteStartOfFrame(int width, int height, int componentCount)
         {
             // "default" to 4:2:0
-            byte[] subsamples = { 0x22, 0x11, 0x11 };
-            byte[] chroma = { 0x00, 0x01, 0x01 };
+            Span<byte> subsamples = stackalloc byte[] { 0x22, 0x11, 0x11 };
+            Span<byte> chroma = stackalloc byte[] { 0x00, 0x01, 0x01 };
 
             switch (this.subsample)
             {
                 case JpegSubsample.Ratio444:
-                    subsamples = new byte[] { 0x11, 0x11, 0x11 };
+                    subsamples = stackalloc byte[] { 0x11, 0x11, 0x11 };
                     break;
                 case JpegSubsample.Ratio420:
-                    subsamples = new byte[] { 0x22, 0x11, 0x11 };
+                    subsamples = stackalloc byte[] { 0x22, 0x11, 0x11 };
                     break;
             }
 

src/ImageSharp/ImageSharp.csproj

@@ -5,7 +5,7 @@
     <VersionPrefix Condition="$(packageversion) != ''">$(packageversion)</VersionPrefix>
     <VersionPrefix Condition="$(packageversion) == ''">0.0.1</VersionPrefix>
     <Authors>Six Labors and contributors</Authors>
-    <TargetFrameworks>netstandard1.1;netstandard1.3;netstandard2.0</TargetFrameworks>
+    <TargetFrameworks>netstandard1.1;netstandard1.3;netstandard2.0;netcoreapp2.1</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <AssemblyName>SixLabors.ImageSharp</AssemblyName>
@@ -29,7 +29,7 @@
     <DebugType Condition="$(codecov) == ''">portable</DebugType>
     <DebugSymbols>True</DebugSymbols>
     <Features>IOperation</Features>
-    <LangVersion>7.2</LangVersion>
+    <LangVersion>7.3</LangVersion>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="..\Shared\*.cs" Exclude="bin\**;obj\**;**\*.xproj;packages\**" />
@@ -40,13 +40,21 @@
     <PackageReference Include="StyleCop.Analyzers" Version="1.1.0-beta007">
       <PrivateAssets>All</PrivateAssets>
     </PackageReference>
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="System.Runtime.CompilerServices.Unsafe" Version="4.5.1" />
+  </ItemGroup>
+   
+  <ItemGroup Condition=" '$(TargetFramework)' != 'netcoreapp2.1'">
     <PackageReference Include="System.Buffers" Version="4.5.0" />
-    <PackageReference Include="System.Memory" Version="4.5.0" />
-    <PackageReference Include="System.Runtime.CompilerServices.Unsafe" Version="4.5.0" />
+    <PackageReference Include="System.Memory" Version="4.5.1" />
   </ItemGroup>
+  
   <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard1.3' ">
     <PackageReference Include="System.IO.UnmanagedMemoryStream" Version="4.3.0" />
   </ItemGroup>
+
   <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard1.1' OR '$(TargetFramework)' == 'netstandard1.3'">
     <PackageReference Include="System.IO.Compression" Version="4.3.0" />
     <PackageReference Include="System.Threading.Tasks.Parallel" Version="4.3.0" />

src/ImageSharp/MetaData/Profiles/Exif/ExifConstants.cs

@@ -0,0 +1,21 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+namespace SixLabors.ImageSharp.MetaData.Profiles.Exif
+{
+    internal static class ExifConstants
+    {
+        public static readonly byte[] Header = {
+            (byte)'E',
+            (byte)'x',
+            (byte)'i',
+            (byte)'f',
+            0x00,
+            0x00,
+            (byte)'I',
+            (byte)'I',
+            0x2A,
+            0x00,
+        };
+    }
+}

src/ImageSharp/MetaData/Profiles/Exif/ExifReader.cs

@@ -140,26 +140,25 @@ namespace SixLabors.ImageSharp.MetaData.Profiles.Exif
 
         private unsafe string ConvertToString(ReadOnlySpan<byte> buffer)
         {
-#if NETSTANDARD1_1
-            byte[] bytes = buffer.ToArray();
+            Span<byte> nullChar = stackalloc byte[1] { 0 };
 
-            string result = Encoding.UTF8.GetString(bytes, 0, buffer.Length);
+            int nullCharIndex = buffer.IndexOf(nullChar);
 
-#else
-            string result;
+            if (nullCharIndex > -1)
+            {
+                buffer = buffer.Slice(0, nullCharIndex);
+            }
 
+#if NETSTANDARD1_1
+            return Encoding.UTF8.GetString(buffer.ToArray(), 0, buffer.Length);
+#elif NETCOREAPP2_1
+            return Encoding.UTF8.GetString(buffer);
+#else
             fixed (byte* pointer = &MemoryMarshal.GetReference(buffer))
             {
-                result = Encoding.UTF8.GetString(pointer, buffer.Length);
+                return Encoding.UTF8.GetString(pointer, buffer.Length);
             }
 #endif
-            int nullCharIndex = result.IndexOf('\0');
-            if (nullCharIndex != -1)
-            {
-                result = result.Substring(0, nullCharIndex);
-            }
-
-            return result;
         }
 
         /// <summary>

src/ImageSharp/MetaData/Profiles/Exif/ExifWriter.cs

@@ -90,16 +90,7 @@ namespace SixLabors.ImageSharp.MetaData.Profiles.Exif
 
             byte[] result = new byte[length];
 
-            result[0] = (byte)'E';
-            result[1] = (byte)'x';
-            result[2] = (byte)'i';
-            result[3] = (byte)'f';
-            result[4] = 0x00;
-            result[5] = 0x00;
-            result[6] = (byte)'I';
-            result[7] = (byte)'I';
-            result[8] = 0x2A;
-            result[9] = 0x00;
+            ExifConstants.Header.AsSpan().CopyTo(result); // 0-9
 
             int i = 10;
             uint ifdOffset = ((uint)i - StartIndex) + 4;
@@ -250,7 +241,7 @@ namespace SixLabors.ImageSharp.MetaData.Profiles.Exif
             return length;
         }
 
-        private int WriteArray(ExifValue value, byte[] destination, int offset)
+        private int WriteArray(ExifValue value, Span<byte> destination, int offset)
         {
             if (value.DataType == ExifDataType.Ascii)
             {
@@ -266,7 +257,7 @@ namespace SixLabors.ImageSharp.MetaData.Profiles.Exif
             return newOffset;
         }
 
-        private int WriteData(List<int> indexes, byte[] destination, int offset)
+        private int WriteData(List<int> indexes, Span<byte> destination, int offset)
         {
             if (this.dataOffsets.Count == 0)
             {
@@ -289,7 +280,7 @@ namespace SixLabors.ImageSharp.MetaData.Profiles.Exif
             return newOffset;
         }
 
-        private int WriteHeaders(List<int> indexes, byte[] destination, int offset)
+        private int WriteHeaders(List<int> indexes, Span<byte> destination, int offset)
         {
             this.dataOffsets = new List<int>();
 
@@ -370,7 +361,7 @@ namespace SixLabors.ImageSharp.MetaData.Profiles.Exif
             }
         }
 
-        private int WriteValue(ExifValue value, byte[] destination, int offset)
+        private int WriteValue(ExifValue value, Span<byte> destination, int offset)
         {
             if (value.IsArray && value.DataType != ExifDataType.Ascii)
             {

src/ImageSharp/PixelFormats/Rgba1010102.cs

@@ -188,7 +188,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <inheritdoc />
         public override bool Equals(object obj)
         {
-            return (obj is Rgba1010102) && this.Equals((Rgba1010102)obj);
+            return obj is Rgba1010102 other && this.Equals(other);
         }
 
         /// <inheritdoc />

src/ImageSharp/PixelFormats/Rgba32.cs

@@ -387,7 +387,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <inheritdoc/>
         public override bool Equals(object obj)
         {
-            return (obj is Rgba32) && this.Equals((Rgba32)obj);
+            return obj is Rgba32 other && this.Equals(other);
         }
 
         /// <inheritdoc/>

src/ImageSharp/PixelFormats/Rgba64.cs

@@ -187,7 +187,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <inheritdoc />
         public override bool Equals(object obj)
         {
-            return (obj is Rgba64) && this.Equals((Rgba64)obj);
+            return obj is Rgba64 other && this.Equals(other);
         }
 
         /// <inheritdoc />

src/ImageSharp/Primitives/DenseMatrix{T}.cs

@@ -89,6 +89,11 @@ namespace SixLabors.ImageSharp.Primitives
             }
         }
 
+        /// <summary>
+        /// Gets a Span wrapping the Data.
+        /// </summary>
+        internal Span<T> Span => new Span<T>(this.Data);
+
         /// <summary>
         /// Gets or sets the item at the specified position.
         /// </summary>
@@ -146,19 +151,13 @@ namespace SixLabors.ImageSharp.Primitives
         /// </summary>
         /// <param name="value">The value to fill each item with</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public void Fill(T value)
-        {
-            for (int i = 0; i < this.Data.Length; i++)
-            {
-                this.Data[i] = value;
-            }
-        }
+        public void Fill(T value) => this.Span.Fill(value);
 
         /// <summary>
         /// Clears the matrix setting each value to the default value for the element type
         /// </summary>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public void Clear() => Array.Clear(this.Data, 0, this.Data.Length);
+        public void Clear() => this.Span.Clear();
 
         /// <summary>
         /// Checks the coordinates to ensure they are within bounds.
@@ -183,28 +182,10 @@ namespace SixLabors.ImageSharp.Primitives
         }
 
         /// <inheritdoc/>
-        public bool Equals(DenseMatrix<T> other)
-        {
-            if (this.Columns != other.Columns)
-            {
-                return false;
-            }
-
-            if (this.Rows != other.Rows)
-            {
-                return false;
-            }
-
-            for (int i = 0; i < this.Data.Length; i++)
-            {
-                if (!this.Data[i].Equals(other.Data[i]))
-                {
-                    return false;
-                }
-            }
-
-            return true;
-        }
+        public bool Equals(DenseMatrix<T> other) =>
+            this.Columns == other.Columns &&
+            this.Rows == other.Rows &&
+            this.Span.SequenceEqual(other.Span);
 
         /// <inheritdoc/>
         public override bool Equals(object obj) => obj is DenseMatrix<T> other && this.Equals(other);

tests/ImageSharp.Tests/Drawing/Text/DrawTextOnImageTests.cs

@@ -1,29 +1,22 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
-using System.Numerics;
-
+using System;
+using System.Linq;
+using System.Text;
 using SixLabors.Fonts;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Processing;
-using SixLabors.ImageSharp.Processing.Drawing;
+using SixLabors.ImageSharp.Processing.Drawing.Pens;
 using SixLabors.ImageSharp.Processing.Text;
+using SixLabors.ImageSharp.Tests.TestUtilities.ImageComparison;
+using SixLabors.Primitives;
 
 using Xunit;
 // ReSharper disable InconsistentNaming
 
 namespace SixLabors.ImageSharp.Tests.Drawing.Text
 {
-    using System;
-    using System.Linq;
-    using System.Text;
-    using SixLabors.ImageSharp.Processing.Drawing.Brushes;
-    using SixLabors.ImageSharp.Processing.Drawing.Brushes.GradientBrushes;
-    using SixLabors.ImageSharp.Processing.Drawing.Pens;
-    using SixLabors.ImageSharp.Tests.TestUtilities.ImageComparison;
-    using SixLabors.Primitives;
-    using SixLabors.Shapes;
-
     [GroupOutput("Drawing/Text")]
     public class DrawTextOnImageTests
     {

tests/ImageSharp.Tests/ImageSharp.Tests.csproj

@@ -25,6 +25,7 @@
   <ItemGroup>
     <None Include="PixelFormats\PixelOperationsTests.Blender.cs" />
   </ItemGroup>
+  
   <ItemGroup>
     <PackageReference Include="Microsoft.CSharp" Version="4.5.0" />
     <PackageReference Include="System.Drawing.Common" Version="4.5.0" />

tests/ImageSharp.Tests/TestUtilities/TestEnvironment.cs

@@ -30,6 +30,13 @@ namespace SixLabors.ImageSharp.Tests
                     return Boolean.TryParse(Environment.GetEnvironmentVariable("CI"), out isCi) && isCi;
                 });
 
+        private static readonly Lazy<string> NetCoreVersionLazy = new Lazy<string>(GetNetCoreVersion);
+
+        /// <summary>
+        /// Gets the .NET Core version, if running on .NET Core, otherwise returns an empty string.
+        /// </summary>
+        internal static string NetCoreVersion => NetCoreVersionLazy.Value;
+
         // ReSharper disable once InconsistentNaming
         /// <summary>
         /// Gets a value indicating whether test execution runs on CI.
@@ -123,5 +130,19 @@ namespace SixLabors.ImageSharp.Tests
 
             return path;
         }
+
+        /// <summary>
+        /// Solution borrowed from:
+        /// https://github.com/dotnet/BenchmarkDotNet/issues/448#issuecomment-308424100
+        /// </summary>
+        private static string GetNetCoreVersion()
+        {
+            Assembly assembly = typeof(System.Runtime.GCSettings).GetTypeInfo().Assembly;
+            string[] assemblyPath = assembly.CodeBase.Split(new[] { '/', '\\' }, StringSplitOptions.RemoveEmptyEntries);
+            int netCoreAppIndex = Array.IndexOf(assemblyPath, "Microsoft.NETCore.App");
+            if (netCoreAppIndex > 0 && netCoreAppIndex < assemblyPath.Length - 2)
+                return assemblyPath[netCoreAppIndex + 1];
+            return "";
+        }
     }
 }

tests/ImageSharp.Tests/TestUtilities/Tests/TestEnvironmentTests.cs

@@ -4,6 +4,7 @@
 using System;
 using System.IO;
 
+using SixLabors.ImageSharp.Common.Helpers;
 using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Formats.Bmp;
 using SixLabors.ImageSharp.Formats.Gif;
@@ -13,9 +14,11 @@ using SixLabors.ImageSharp.Tests.TestUtilities.ReferenceCodecs;
 
 using Xunit;
 using Xunit.Abstractions;
+// ReSharper disable InconsistentNaming
 
 namespace SixLabors.ImageSharp.Tests
 {
+    
     public class TestEnvironmentTests
     {
         public TestEnvironmentTests(ITestOutputHelper output)
@@ -31,6 +34,29 @@ namespace SixLabors.ImageSharp.Tests
             Assert.True(Directory.Exists(path));
         }
 
+        /// <summary>
+        /// We need this test to make sure that the netcoreapp2.1 test execution actually covers the netcoreapp2.1 build configuration of ImageSharp.
+        /// </summary>
+        [Fact]
+        public void ImageSharpAssemblyUnderTest_MatchesExpectedTargetFramework()
+        {
+            this.Output.WriteLine("NetCoreVersion: " + TestEnvironment.NetCoreVersion);
+            this.Output.WriteLine("ImageSharpBuiltAgainst: " + TestHelpers.ImageSharpBuiltAgainst);
+
+            if (string.IsNullOrEmpty(TestEnvironment.NetCoreVersion))
+            {
+                this.Output.WriteLine("Not running under .NET Core!");
+            }
+            else if (TestEnvironment.NetCoreVersion.StartsWith("2.1"))
+            {
+                Assert.Equal("netcoreapp2.1", TestHelpers.ImageSharpBuiltAgainst);
+            }
+            else
+            {
+                Assert.Equal("netstandard2.0", TestHelpers.ImageSharpBuiltAgainst);
+            }
+        }
+
         [Fact]
         public void SolutionDirectoryFullPath()
         {