Apply ICC Profile / Color Conversion when decoding PNG

src/ImageSharp/Formats/Png/PngDecoderCore.cs

@@ -7,9 +7,12 @@
 using System.Globalization;
 using System.IO.Compression;
 using System.IO.Hashing;
+using System.Numerics;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using System.Text;
+using SixLabors.ImageSharp.ColorProfiles;
+using SixLabors.ImageSharp.ColorProfiles.Icc;
 using SixLabors.ImageSharp.Common.Helpers;
 using SixLabors.ImageSharp.Compression.Zlib;
 using SixLabors.ImageSharp.Formats.Png.Chunks;
@@ -23,6 +26,7 @@
 using SixLabors.ImageSharp.Metadata.Profiles.Icc;
 using SixLabors.ImageSharp.Metadata.Profiles.Xmp;
 using SixLabors.ImageSharp.PixelFormats;
+using SixLabors.ImageSharp.Processing;
 
 namespace SixLabors.ImageSharp.Formats.Png;
 
@@ -323,6 +327,11 @@ protected override Image<TPixel> Decode<TPixel>(BufferedReadStream stream, Cance
                 PngThrowHelper.ThrowNoData();
             }
 
+            if (this.Options.TryGetIccProfileForColorConversion(metadata.IccProfile, out IccProfile? iccProfile))
+            {
+                ApplyRgbaCompatibleIccProfile(image, iccProfile, CompactSrgbV4Profile.Profile);
+            }
+
             return image;
         }
         catch
@@ -2153,4 +2162,39 @@ private static bool IsXmpTextData(ReadOnlySpan<byte> keywordBytes)
 
     private void SwapScanlineBuffers()
         => (this.scanline, this.previousScanline) = (this.previousScanline, this.scanline);
+
+    private static void ApplyRgbaCompatibleIccProfile<TPixel>(Image<TPixel> image, IccProfile sourceProfile, IccProfile destinationProfile)
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        ColorConversionOptions options = new()
+        {
+            SourceIccProfile = sourceProfile,
+            TargetIccProfile = destinationProfile,
+        };
+
+        ColorProfileConverter converter = new(options);
+
+        image.Mutate(o => o.ProcessPixelRowsAsVector4((pixelsRow, _) =>
+                {
+                    using IMemoryOwner<Rgb> rgbBuffer = image.Configuration.MemoryAllocator.Allocate<Rgb>(pixelsRow.Length);
+                    Span<Rgb> rgbPacked = rgbBuffer.Memory.Span;
+                    ref Rgb rgbPackedRef = ref MemoryMarshal.GetReference(rgbPacked);
+
+                    for (int x = 0; x < pixelsRow.Length; x++)
+                    {
+                        Unsafe.Add(ref rgbPackedRef, x) = Rgb.FromScaledVector4(pixelsRow[x]);
+                    }
+
+                    converter.Convert<Rgb, Rgb>(rgbPacked, rgbPacked);
+
+                    Span<float> pixelsRowAsFloats = MemoryMarshal.Cast<Vector4, float>(pixelsRow);
+                    ref float pixelsRowAsFloatsRef = ref MemoryMarshal.GetReference(pixelsRowAsFloats);
+
+                    int cIdx = 0;
+                    for (int x = 0; x < pixelsRow.Length; x++, cIdx += 4)
+                    {
+                        Unsafe.As<float, Rgb>(ref Unsafe.Add(ref pixelsRowAsFloatsRef, cIdx)) = rgbPacked[x];
+                    }
+                }));
+    }
 }

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

@@ -206,6 +206,20 @@ public void Decode_WithAverageFilter<TPixel>(TestImageProvider<TPixel> provider)
         image.CompareToOriginal(provider, ImageComparer.Exact);
     }
 
+    [Theory]
+    [WithFile(TestImages.Png.Icc.Perceptual, PixelTypes.Rgba32)]
+    [WithFile(TestImages.Png.Icc.PerceptualcLUTOnly, PixelTypes.Rgba32)]
+    [WithFile(TestImages.Png.Icc.SRgbGray, PixelTypes.Rgba32)]
+    public void Decode_WhenColorProfileHandlingIsConvert_ApplyIccProfile<TPixel>(TestImageProvider<TPixel> provider)
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        using Image<TPixel> image = provider.GetImage(PngDecoder.Instance, new DecoderOptions { ColorProfileHandling = ColorProfileHandling.Convert });
+
+        image.DebugSave(provider);
+        image.CompareToReferenceOutput(provider);
+        Assert.Null(image.Metadata.IccProfile);
+    }
+
     [Theory]
     [WithFile(TestImages.Png.SubFilter3BytesPerPixel, PixelTypes.Rgba32)]
     [WithFile(TestImages.Png.SubFilter4BytesPerPixel, PixelTypes.Rgba32)]

tests/ImageSharp.Tests/MemoryAllocatorValidator.cs

@@ -22,7 +22,10 @@ private static void MemoryDiagnostics_MemoryReleased()
         TestMemoryDiagnostics backing = LocalInstance.Value;
         if (backing != null)
         {
-            backing.TotalRemainingAllocated--;
+            lock (backing)
+            {
+                backing.TotalRemainingAllocated--;
+            }
         }
     }
 
@@ -31,8 +34,11 @@ private static void MemoryDiagnostics_MemoryAllocated()
         TestMemoryDiagnostics backing = LocalInstance.Value;
         if (backing != null)
         {
-            backing.TotalAllocated++;
-            backing.TotalRemainingAllocated++;
+            lock (backing)
+            {
+                backing.TotalAllocated++;
+                backing.TotalRemainingAllocated++;
+            }
         }
     }
 

tests/ImageSharp.Tests/TestImages.cs

@@ -166,6 +166,13 @@ public static class Png
         // Issue 3000: https://github.com/SixLabors/ImageSharp/issues/3000
         public const string Issue3000 = "Png/issues/issue_3000.png";
 
+        public static class Icc
+        {
+            public const string SRgbGray = "Png/icc-profiles/sRGB_Gray.png";
+            public const string Perceptual = "Png/icc-profiles/Perceptual.png";
+            public const string PerceptualcLUTOnly = "Png/icc-profiles/Perceptual-cLUT-only.png";
+        }
+
         public static class Bad
         {
             public const string MissingDataChunk = "Png/xdtn0g01.png";