Merge branch 'main' into dp/jpeg-downscaling-decode

src/Directory.Build.props

@@ -27,6 +27,7 @@
     <InternalsVisibleTo Include="ImageSharp.Benchmarks" Key="$(SixLaborsPublicKey)" />
     <InternalsVisibleTo Include="ImageSharp.Tests.ProfilingSandbox" Key="$(SixLaborsPublicKey)" />
     <InternalsVisibleTo Include="SixLabors.ImageSharp.Tests" Key="$(SixLaborsPublicKey)" />
+    <InternalsVisibleTo Include="SixLabors.ImageSharp.Drawing.Tests" Key="$(SixLaborsPublicKey)" />
   </ItemGroup>
 
 </Project>

src/ImageSharp/Diagnostics/MemoryDiagnostics.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
 using System.Threading;
 
 namespace SixLabors.ImageSharp.Diagnostics
@@ -47,6 +48,16 @@ namespace SixLabors.ImageSharp.Diagnostics
             }
         }
 
+        /// <summary>
+        /// Fires when ImageSharp allocates memory from a MemoryAllocator
+        /// </summary>
+        internal static event Action MemoryAllocated;
+
+        /// <summary>
+        /// Fires when ImageSharp releases memory allocated from a MemoryAllocator
+        /// </summary>
+        internal static event Action MemoryReleased;
+
         /// <summary>
         /// Gets a value indicating the total number of memory resource objects leaked to the finalizer.
         /// </summary>
@@ -54,11 +65,17 @@ namespace SixLabors.ImageSharp.Diagnostics
 
         internal static bool UndisposedAllocationSubscribed => Volatile.Read(ref undisposedAllocationSubscriptionCounter) > 0;
 
-        internal static void IncrementTotalUndisposedAllocationCount() =>
+        internal static void IncrementTotalUndisposedAllocationCount()
+        {
             Interlocked.Increment(ref totalUndisposedAllocationCount);
+            MemoryAllocated?.Invoke();
+        }
 
-        internal static void DecrementTotalUndisposedAllocationCount() =>
+        internal static void DecrementTotalUndisposedAllocationCount()
+        {
             Interlocked.Decrement(ref totalUndisposedAllocationCount);
+            MemoryReleased?.Invoke();
+        }
 
         internal static void RaiseUndisposedMemoryResource(string allocationStackTrace)
         {

src/ImageSharp/Formats/Bmp/BmpDecoderCore.cs

@@ -122,11 +122,12 @@ namespace SixLabors.ImageSharp.Formats.Bmp
         public Image<TPixel> Decode<TPixel>(BufferedReadStream stream, CancellationToken cancellationToken)
             where TPixel : unmanaged, IPixel<TPixel>
         {
+            Image<TPixel> image = null;
             try
             {
                 int bytesPerColorMapEntry = this.ReadImageHeaders(stream, out bool inverted, out byte[] palette);
 
-                var image = new Image<TPixel>(this.Configuration, this.infoHeader.Width, this.infoHeader.Height, this.metadata);
+                image = new Image<TPixel>(this.Configuration, this.infoHeader.Width, this.infoHeader.Height, this.metadata);
 
                 Buffer2D<TPixel> pixels = image.GetRootFramePixelBuffer();
 
@@ -193,8 +194,14 @@ namespace SixLabors.ImageSharp.Formats.Bmp
             }
             catch (IndexOutOfRangeException e)
             {
+                image?.Dispose();
                 throw new ImageFormatException("Bitmap does not have a valid format.", e);
             }
+            catch
+            {
+                image?.Dispose();
+                throw;
+            }
         }
 
         /// <inheritdoc />

src/ImageSharp/Formats/Jpeg/Components/Decoder/SpectralConverter{TPixel}.cs

@@ -126,7 +126,9 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
                 }
             }
 
-            return this.pixelBuffer;
+            var buffer = this.pixelBuffer;
+            this.pixelBuffer = null;
+            return buffer;
         }
 
         /// <summary>
@@ -318,6 +320,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
 
             this.rgbBuffer?.Dispose();
             this.paddedProxyPixelRow?.Dispose();
+            this.pixelBuffer?.Dispose();
         }
     }
 }

src/ImageSharp/Formats/Png/PngDecoderCore.cs

@@ -227,10 +227,16 @@ namespace SixLabors.ImageSharp.Formats.Png
 
                 return image;
             }
+            catch
+            {
+                image?.Dispose();
+                throw;
+            }
             finally
             {
                 this.scanline?.Dispose();
                 this.previousScanline?.Dispose();
+                this.nextChunk?.Data?.Dispose();
             }
         }
 
@@ -472,6 +478,8 @@ namespace SixLabors.ImageSharp.Formats.Png
                 this.bytesPerSample = this.header.BitDepth / 8;
             }
 
+            this.previousScanline?.Dispose();
+            this.scanline?.Dispose();
             this.previousScanline = this.memoryAllocator.Allocate<byte>(this.bytesPerScanline, AllocationOptions.Clean);
             this.scanline = this.Configuration.MemoryAllocator.Allocate<byte>(this.bytesPerScanline, AllocationOptions.Clean);
         }
@@ -1359,6 +1367,7 @@ namespace SixLabors.ImageSharp.Formats.Png
             {
                 if (chunk.Type == PngChunkType.Data)
                 {
+                    chunk.Data?.Dispose();
                     return chunk.Length;
                 }
 
@@ -1453,6 +1462,9 @@ namespace SixLabors.ImageSharp.Formats.Png
                 if (validCrc != inputCrc)
                 {
                     string chunkTypeName = Encoding.ASCII.GetString(chunkType);
+
+                    // ensure when throwing we dispose the data back to the memory allocator
+                    chunk.Data?.Dispose();
                     PngThrowHelper.ThrowInvalidChunkCrc(chunkTypeName);
                 }
             }

src/ImageSharp/Formats/Tiff/Compression/Decompressors/JpegTiffCompression.cs

@@ -65,7 +65,8 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression.Decompressors
                         jpegDecoder.ParseStream(stream, scanDecoderGray, CancellationToken.None);
 
                         // TODO: Should we pass through the CancellationToken from the tiff decoder?
-                        CopyImageBytesToBuffer(buffer, spectralConverterGray.GetPixelBuffer(CancellationToken.None));
+                        using var decompressedBuffer = spectralConverterGray.GetPixelBuffer(CancellationToken.None);
+                        CopyImageBytesToBuffer(buffer, decompressedBuffer);
                         break;
                     }
 
@@ -81,7 +82,8 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Compression.Decompressors
                         jpegDecoder.ParseStream(stream, scanDecoder, CancellationToken.None);
 
                         // TODO: Should we pass through the CancellationToken from the tiff decoder?
-                        CopyImageBytesToBuffer(buffer, spectralConverter.GetPixelBuffer(CancellationToken.None));
+                        using var decompressedBuffer = spectralConverter.GetPixelBuffer(CancellationToken.None);
+                        CopyImageBytesToBuffer(buffer, decompressedBuffer);
                         break;
                     }
 

src/ImageSharp/Formats/Tiff/TiffDecoderCore.cs

@@ -157,40 +157,52 @@ namespace SixLabors.ImageSharp.Formats.Tiff
         public Image<TPixel> Decode<TPixel>(BufferedReadStream stream, CancellationToken cancellationToken)
             where TPixel : unmanaged, IPixel<TPixel>
         {
-            this.inputStream = stream;
-            var reader = new DirectoryReader(stream, this.Configuration.MemoryAllocator);
-
-            IEnumerable<ExifProfile> directories = reader.Read();
-            this.byteOrder = reader.ByteOrder;
-            this.isBigTiff = reader.IsBigTiff;
-
             var frames = new List<ImageFrame<TPixel>>();
-            foreach (ExifProfile ifd in directories)
+            try
             {
-                cancellationToken.ThrowIfCancellationRequested();
+                this.inputStream = stream;
-                ImageFrame<TPixel> frame = this.DecodeFrame<TPixel>(ifd, cancellationToken);
+                var reader = new DirectoryReader(stream, this.Configuration.MemoryAllocator);
-                frames.Add(frame);
+
+                IEnumerable<ExifProfile> directories = reader.Read();
+                this.byteOrder = reader.ByteOrder;
+                this.isBigTiff = reader.IsBigTiff;
 
-                if (this.decodingMode is FrameDecodingMode.First)
+                foreach (ExifProfile ifd in directories)
                 {
-                    break;
+                    cancellationToken.ThrowIfCancellationRequested();
+                    ImageFrame<TPixel> frame = this.DecodeFrame<TPixel>(ifd, cancellationToken);
+                    frames.Add(frame);
+
+                    if (this.decodingMode is FrameDecodingMode.First)
+                    {
+                        break;
+                    }
                 }
-            }
 
-            ImageMetadata metadata = TiffDecoderMetadataCreator.Create(frames, this.ignoreMetadata, reader.ByteOrder, reader.IsBigTiff);
+                ImageMetadata metadata = TiffDecoderMetadataCreator.Create(frames, this.ignoreMetadata, reader.ByteOrder, reader.IsBigTiff);
 
-            // TODO: Tiff frames can have different sizes.
+                // TODO: Tiff frames can have different sizes.
-            ImageFrame<TPixel> root = frames[0];
+                ImageFrame<TPixel> root = frames[0];
-            this.Dimensions = root.Size();
+                this.Dimensions = root.Size();
-            foreach (ImageFrame<TPixel> frame in frames)
+                foreach (ImageFrame<TPixel> frame in frames)
-            {
-                if (frame.Size() != root.Size())
                 {
-                    TiffThrowHelper.ThrowNotSupported("Images with different sizes are not supported");
+                    if (frame.Size() != root.Size())
+                    {
+                        TiffThrowHelper.ThrowNotSupported("Images with different sizes are not supported");
+                    }
                 }
+
+                return new Image<TPixel>(this.Configuration, metadata, frames);
             }
+            catch
+            {
+                foreach (ImageFrame<TPixel> f in frames)
+                {
+                    f.Dispose();
+                }
 
-            return new Image<TPixel>(this.Configuration, metadata, frames);
+                throw;
+            }
         }
 
         /// <inheritdoc/>
@@ -240,8 +252,8 @@ namespace SixLabors.ImageSharp.Formats.Tiff
             var stripOffsetsArray = (Array)tags.GetValueInternal(ExifTag.StripOffsets).GetValue();
             var stripByteCountsArray = (Array)tags.GetValueInternal(ExifTag.StripByteCounts).GetValue();
 
-            IMemoryOwner<ulong> stripOffsetsMemory = this.ConvertNumbers(stripOffsetsArray, out Span<ulong> stripOffsets);
+            using IMemoryOwner<ulong> stripOffsetsMemory = this.ConvertNumbers(stripOffsetsArray, out Span<ulong> stripOffsets);
-            IMemoryOwner<ulong> stripByteCountsMemory = this.ConvertNumbers(stripByteCountsArray, out Span<ulong> stripByteCounts);
+            using IMemoryOwner<ulong> stripByteCountsMemory = this.ConvertNumbers(stripByteCountsArray, out Span<ulong> stripByteCounts);
 
             if (this.PlanarConfiguration == TiffPlanarConfiguration.Planar)
             {
@@ -262,8 +274,6 @@ namespace SixLabors.ImageSharp.Formats.Tiff
                     cancellationToken);
             }
 
-            stripOffsetsMemory?.Dispose();
-            stripByteCountsMemory?.Dispose();
             return frame;
         }
 

src/ImageSharp/Formats/Webp/WebpDecoderCore.cs

@@ -82,38 +82,47 @@ namespace SixLabors.ImageSharp.Formats.Webp
         public Image<TPixel> Decode<TPixel>(BufferedReadStream stream, CancellationToken cancellationToken)
             where TPixel : unmanaged, IPixel<TPixel>
         {
-            this.Metadata = new ImageMetadata();
+            Image<TPixel> image = null;
-            this.currentStream = stream;
+            try
+            {
+                this.Metadata = new ImageMetadata();
+                this.currentStream = stream;
 
-            uint fileSize = this.ReadImageHeader();
+                uint fileSize = this.ReadImageHeader();
 
-            using (this.webImageInfo = this.ReadVp8Info())
+                using (this.webImageInfo = this.ReadVp8Info())
-            {
-                if (this.webImageInfo.Features is { Animation: true })
                 {
-                    WebpThrowHelper.ThrowNotSupportedException("Animations are not supported");
+                    if (this.webImageInfo.Features is { Animation: true })
-                }
+                    {
+                        WebpThrowHelper.ThrowNotSupportedException("Animations are not supported");
+                    }
 
-                var image = new Image<TPixel>(this.Configuration, (int)this.webImageInfo.Width, (int)this.webImageInfo.Height, this.Metadata);
+                    image = new Image<TPixel>(this.Configuration, (int)this.webImageInfo.Width, (int)this.webImageInfo.Height, this.Metadata);
-                Buffer2D<TPixel> pixels = image.GetRootFramePixelBuffer();
+                    Buffer2D<TPixel> pixels = image.GetRootFramePixelBuffer();
-                if (this.webImageInfo.IsLossless)
+                    if (this.webImageInfo.IsLossless)
-                {
+                    {
-                    var losslessDecoder = new WebpLosslessDecoder(this.webImageInfo.Vp8LBitReader, this.memoryAllocator, this.Configuration);
+                        var losslessDecoder = new WebpLosslessDecoder(this.webImageInfo.Vp8LBitReader, this.memoryAllocator, this.Configuration);
-                    losslessDecoder.Decode(pixels, image.Width, image.Height);
+                        losslessDecoder.Decode(pixels, image.Width, image.Height);
-                }
+                    }
-                else
+                    else
-                {
+                    {
-                    var lossyDecoder = new WebpLossyDecoder(this.webImageInfo.Vp8BitReader, this.memoryAllocator, this.Configuration);
+                        var lossyDecoder = new WebpLossyDecoder(this.webImageInfo.Vp8BitReader, this.memoryAllocator, this.Configuration);
-                    lossyDecoder.Decode(pixels, image.Width, image.Height, this.webImageInfo);
+                        lossyDecoder.Decode(pixels, image.Width, image.Height, this.webImageInfo);
-                }
+                    }
 
-                // There can be optional chunks after the image data, like EXIF and XMP.
+                    // There can be optional chunks after the image data, like EXIF and XMP.
-                if (this.webImageInfo.Features != null)
+                    if (this.webImageInfo.Features != null)
-                {
+                    {
-                    this.ParseOptionalChunks(this.webImageInfo.Features);
+                        this.ParseOptionalChunks(this.webImageInfo.Features);
-                }
+                    }
 
-                return image;
+                    return image;
+                }
+            }
+            catch
+            {
+                image?.Dispose();
+                throw;
             }
         }
 

tests/ImageSharp.Tests/Formats/Bmp/BmpDecoderTests.cs

@@ -20,6 +20,7 @@ using static SixLabors.ImageSharp.Tests.TestImages.Bmp;
 namespace SixLabors.ImageSharp.Tests.Formats.Bmp
 {
     [Trait("Format", "Bmp")]
+    [ValidateDisposedMemoryAllocations]
     public class BmpDecoderTests
     {
         public const PixelTypes CommonNonDefaultPixelTypes = PixelTypes.Rgba32 | PixelTypes.Bgra32 | PixelTypes.RgbaVector;

tests/ImageSharp.Tests/Formats/Gif/GifDecoderTests.cs

@@ -18,6 +18,7 @@ using Xunit;
 namespace SixLabors.ImageSharp.Tests.Formats.Gif
 {
     [Trait("Format", "Gif")]
+    [ValidateDisposedMemoryAllocations]
     public class GifDecoderTests
     {
         private const PixelTypes TestPixelTypes = PixelTypes.Rgba32 | PixelTypes.RgbaVector | PixelTypes.Argb32;

tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.Metadata.cs

@@ -179,11 +179,16 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
             var testFile = TestFile.Create(imagePath);
             using (var stream = new MemoryStream(testFile.Bytes, false))
             {
-                IImageInfo imageInfo = useIdentify
+                if (useIdentify)
-                ? ((IImageInfoDetector)decoder).Identify(Configuration.Default, stream, default)
+                {
-                : decoder.Decode<Rgba32>(Configuration.Default, stream, default);
+                    IImageInfo imageInfo = ((IImageInfoDetector)decoder).Identify(Configuration.Default, stream, default);
-
+                    test(imageInfo);
-                test(imageInfo);
+                }
+                else
+                {
+                    using var img = decoder.Decode<Rgba32>(Configuration.Default, stream, default);
+                    test(img);
+                }
             }
         }
 

tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.cs

@@ -22,6 +22,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
 {
     // TODO: Scatter test cases into multiple test classes
     [Trait("Format", "Jpg")]
+    [ValidateDisposedMemoryAllocations]
     public partial class JpegDecoderTests
     {
         public const PixelTypes CommonNonDefaultPixelTypes = PixelTypes.Rgba32 | PixelTypes.Argb32 | PixelTypes.Bgr24 | PixelTypes.RgbaVector;

tests/ImageSharp.Tests/Formats/Pbm/PbmDecoderTests.cs

@@ -11,6 +11,7 @@ using static SixLabors.ImageSharp.Tests.TestImages.Pbm;
 namespace SixLabors.ImageSharp.Tests.Formats.Pbm
 {
     [Trait("Format", "Pbm")]
+    [ValidateDisposedMemoryAllocations]
     public class PbmDecoderTests
     {
         [Theory]

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

@@ -19,6 +19,7 @@ using Xunit;
 namespace SixLabors.ImageSharp.Tests.Formats.Png
 {
     [Trait("Format", "Png")]
+    [ValidateDisposedMemoryAllocations]
     public partial class PngDecoderTests
     {
         private const PixelTypes TestPixelTypes = PixelTypes.Rgba32 | PixelTypes.RgbaVector | PixelTypes.Argb32;

tests/ImageSharp.Tests/Formats/Tga/TgaDecoderTests.cs

@@ -16,6 +16,7 @@ using static SixLabors.ImageSharp.Tests.TestImages.Tga;
 namespace SixLabors.ImageSharp.Tests.Formats.Tga
 {
     [Trait("Format", "Tga")]
+    [ValidateDisposedMemoryAllocations]
     public class TgaDecoderTests
     {
         private static TgaDecoder TgaDecoder => new();

tests/ImageSharp.Tests/Formats/Tiff/TiffDecoderTests.cs

@@ -14,6 +14,7 @@ using static SixLabors.ImageSharp.Tests.TestImages.Tiff;
 namespace SixLabors.ImageSharp.Tests.Formats.Tiff
 {
     [Trait("Format", "Tiff")]
+    [ValidateDisposedMemoryAllocations]
     public class TiffDecoderTests : TiffDecoderBaseTester
     {
         public static readonly string[] MultiframeTestImages = Multiframes;

tests/ImageSharp.Tests/Formats/WebP/WebpDecoderTests.cs

@@ -13,6 +13,7 @@ using static SixLabors.ImageSharp.Tests.TestImages.Webp;
 namespace SixLabors.ImageSharp.Tests.Formats.Webp
 {
     [Trait("Format", "Webp")]
+    [ValidateDisposedMemoryAllocations]
     public class WebpDecoderTests
     {
         private static WebpDecoder WebpDecoder => new();

tests/ImageSharp.Tests/Image/ImageTests.LoadPixelData.cs

@@ -14,6 +14,7 @@ namespace SixLabors.ImageSharp.Tests
             [Theory]
             [InlineData(false)]
             [InlineData(true)]
+            [ValidateDisposedMemoryAllocations]
             public void FromPixels(bool useSpan)
             {
                 Rgba32[] data = { Color.Black, Color.White, Color.White, Color.Black, };

tests/ImageSharp.Tests/Image/LargeImageIntegrationTests.cs

@@ -55,6 +55,8 @@ namespace SixLabors.ImageSharp.Tests
 
             static void RunTest(string formatInner)
             {
+                using IDisposable mem = MemoryAllocatorValidator.MonitorAllocations();
+
                 Configuration configuration = Configuration.Default.Clone();
                 configuration.PreferContiguousImageBuffers = true;
                 IImageEncoder encoder = configuration.ImageFormatsManager.FindEncoder(

tests/ImageSharp.Tests/MemoryAllocatorValidator.cs

@@ -0,0 +1,77 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+using System.Threading;
+using SixLabors.ImageSharp.Diagnostics;
+using Xunit;
+
+namespace SixLabors.ImageSharp.Tests
+{
+    public static class MemoryAllocatorValidator
+    {
+        private static readonly AsyncLocal<TestMemoryDiagnostics> LocalInstance = new();
+
+        public static bool MonitoringAllocations => LocalInstance.Value != null;
+
+        static MemoryAllocatorValidator()
+        {
+            MemoryDiagnostics.MemoryAllocated += MemoryDiagnostics_MemoryAllocated;
+            MemoryDiagnostics.MemoryReleased += MemoryDiagnostics_MemoryReleased;
+        }
+
+        private static void MemoryDiagnostics_MemoryReleased()
+        {
+            TestMemoryDiagnostics backing = LocalInstance.Value;
+            if (backing != null)
+            {
+                backing.TotalRemainingAllocated--;
+            }
+        }
+
+        private static void MemoryDiagnostics_MemoryAllocated()
+        {
+            TestMemoryDiagnostics backing = LocalInstance.Value;
+            if (backing != null)
+            {
+                backing.TotalAllocated++;
+                backing.TotalRemainingAllocated++;
+            }
+        }
+
+        public static TestMemoryDiagnostics MonitorAllocations()
+        {
+            var diag = new TestMemoryDiagnostics();
+            LocalInstance.Value = diag;
+            return diag;
+        }
+
+        public static void StopMonitoringAllocations() => LocalInstance.Value = null;
+
+        public static void ValidateAllocations(int expectedAllocationCount = 0)
+            => LocalInstance.Value?.Validate(expectedAllocationCount);
+
+        public class TestMemoryDiagnostics : IDisposable
+        {
+            public int TotalAllocated { get; set; }
+
+            public int TotalRemainingAllocated { get; set; }
+
+            public void Validate(int expectedAllocationCount)
+            {
+                var count = this.TotalRemainingAllocated;
+                var pass = expectedAllocationCount == count;
+                Assert.True(pass, $"Expected a {expectedAllocationCount} undisposed buffers but found {count}");
+            }
+
+            public void Dispose()
+            {
+                this.Validate(0);
+                if (LocalInstance.Value == this)
+                {
+                    StopMonitoringAllocations();
+                }
+            }
+        }
+    }
+}

tests/ImageSharp.Tests/TestUtilities/ImageComparison/ImageComparingUtils.cs

@@ -26,7 +26,7 @@ namespace SixLabors.ImageSharp.Tests.TestUtilities.ImageComparison
             }
 
             var testFile = TestFile.Create(path);
-            Image<Rgba32> magickImage = DecodeWithMagick<Rgba32>(new FileInfo(testFile.FullPath));
+            using Image<Rgba32> magickImage = DecodeWithMagick<Rgba32>(new FileInfo(testFile.FullPath));
             if (useExactComparer)
             {
                 ImageComparer.Exact.VerifySimilarity(magickImage, image);

tests/ImageSharp.Tests/TestUtilities/ImageProviders/FileProvider.cs

@@ -7,6 +7,7 @@ using System.Collections.Generic;
 using System.IO;
 using System.Reflection;
 using System.Threading.Tasks;
+using SixLabors.ImageSharp.Diagnostics;
 using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
@@ -158,8 +159,13 @@ namespace SixLabors.ImageSharp.Tests
                     return this.LoadImage(decoder);
                 }
 
-                var key = new Key(this.PixelType, this.FilePath, decoder);
+                // do not cache so we can track allocation correctly when validating memory
+                if (MemoryAllocatorValidator.MonitoringAllocations)
+                {
+                    return this.LoadImage(decoder);
+                }
 
+                var key = new Key(this.PixelType, this.FilePath, decoder);
                 Image<TPixel> cachedImage = Cache.GetOrAdd(key, _ => this.LoadImage(decoder));
 
                 return cachedImage.Clone(this.Configuration);

tests/ImageSharp.Tests/ValidateDisposedMemoryAllocationsAttribute.cs

@@ -0,0 +1,33 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+using System.Diagnostics;
+using System.Reflection;
+using Xunit.Sdk;
+
+namespace SixLabors.ImageSharp.Tests
+{
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
+    public class ValidateDisposedMemoryAllocationsAttribute : BeforeAfterTestAttribute
+    {
+        private readonly int expected = 0;
+
+        public ValidateDisposedMemoryAllocationsAttribute()
+            : this(0)
+        {
+        }
+
+        public ValidateDisposedMemoryAllocationsAttribute(int expected)
+            => this.expected = expected;
+
+        public override void Before(MethodInfo methodUnderTest)
+            => MemoryAllocatorValidator.MonitorAllocations();
+
+        public override void After(MethodInfo methodUnderTest)
+        {
+            MemoryAllocatorValidator.ValidateAllocations(this.expected);
+            MemoryAllocatorValidator.StopMonitoringAllocations();
+        }
+    }
+}