ImageSharp produces a corrupted image on .NET 6 Preview 6

[kerams]

Description

Originally reported in SixLabors/ImageSharp#1704.

Loading a PNG file and immediately saving it as Jpeg works as expected on .NET 5. However when I switch to net6.0 in the csproj, only the top part of the image appears in the output jpeg file, the rest is black.

Steps to Reproduce

Create s console C# application and reference ImageSharp 1.0.3. First run this with net5.0 in the csproj, then compare the result to net6.0.

using SixLabors.ImageSharp;
using System.IO;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            using var img = Image.Load("unknown.png");
            var fs = File.OpenWrite("unknown.jpeg");
            img.SaveAsJpeg(fs);
            fs.Flush();
            fs.Close();
        }
    }
}

Use this image
https://user-images.githubusercontent.com/5063478/126033585-4efb31ce-c231-4229-8412-68fb73950ffc.png

The result on 5.0.400-preview.21277.10 looks like the original image.

The result on 6.0.100-preview.6.21355.2 looks like this
https://user-images.githubusercontent.com/5063478/126033623-0f886133-bc0d-4449-8048-d5d29a0e377c.jpeg

Configuration

dotnet --info

.NET SDK (reflecting any global.json): Version: 6.0.100-preview.6.21355.2 Commit: 7f8e0d76c0

Runtime Environment:
OS Name: Windows
OS Version: 10.0.19043
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\6.0.100-preview.6.21355.2\

Host (useful for support):
Version: 6.0.0-preview.7.21318.2
Commit: 1401202

.NET SDKs installed:
5.0.400-preview.21277.10 [C:\Program Files\dotnet\sdk]
6.0.100-preview.6.21355.2 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.0-preview.6.21355.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.0-preview.6.21352.12 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.0-preview.6.21353.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Regression?

Yes, works on 5.0.400-preview.21277.10.

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[stephentoub]

cc: @tannergooding

[lewing]

We're looking into some mono image loading problems in ImageSharp that we bisected back to #53644

cc @danroth27 @vargaz

[stephentoub]

These look suspect:
https://github.com/SixLabors/ImageSharp/blob/e8d39b87e4d14fcf52cac387a82f067283e6670e/src/ImageSharp/Formats/Png/PngDecoderCore.cs#L509-L514
https://github.com/SixLabors/ImageSharp/blob/e8d39b87e4d14fcf52cac387a82f067283e6670e/src/ImageSharp/Formats/Png/PngDecoderCore.cs#L580-L585

Tagging subscribers to this area: @dotnet/area-system-io
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

Originally reported in SixLabors/ImageSharp#1704.

Loading a PNG file and immediately saving it as Jpeg works as expected on .NET 5. However when I switch to net6.0 in the csproj, only the top part of the image appears in the output jpeg file, the rest is black.

Steps to Reproduce

Create s console C# application and reference ImageSharp 1.0.3. First run this with net5.0 in the csproj, then compare the result to net6.0.

using SixLabors.ImageSharp;
using System.IO;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            using var img = Image.Load("unknown.png");
            var fs = File.OpenWrite("unknown.jpeg");
            img.SaveAsJpeg(fs);
            fs.Flush();
            fs.Close();
        }
    }
}

Use this image
https://user-images.githubusercontent.com/5063478/126033585-4efb31ce-c231-4229-8412-68fb73950ffc.png

The result on 5.0.400-preview.21277.10 looks like the original image.

The result on 6.0.100-preview.6.21355.2 looks like this
https://user-images.githubusercontent.com/5063478/126033623-0f886133-bc0d-4449-8048-d5d29a0e377c.jpeg

Configuration

dotnet --info

.NET SDK (reflecting any global.json): Version: 6.0.100-preview.6.21355.2 Commit: 7f8e0d76c0

Runtime Environment:
OS Name: Windows
OS Version: 10.0.19043
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\6.0.100-preview.6.21355.2\

Host (useful for support):
Version: 6.0.0-preview.7.21318.2
Commit: 1401202

.NET SDKs installed:
5.0.400-preview.21277.10 [C:\Program Files\dotnet\sdk]
6.0.100-preview.6.21355.2 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 6.0.0-preview.6.21355.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.0-preview.6.21352.12 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.0-preview.6.21353.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Regression?

Yes, works on 5.0.400-preview.21277.10.

Author:	kerams
Assignees:	-
Labels:	area-System.IO, untriaged
Milestone:	-

[stephentoub]

These look suspect

Indeed, if I make these changes:

D:\repos\ImageSharp\src\ImageSharp [master ≡]> git diff
diff --git a/src/ImageSharp/Formats/Png/PngDecoderCore.cs b/src/ImageSharp/Formats/Png/PngDecoderCore.cs
index de70a9dff..779341b1c 100644
--- a/src/ImageSharp/Formats/Png/PngDecoderCore.cs
+++ b/src/ImageSharp/Formats/Png/PngDecoderCore.cs
@@ -506,11 +506,15 @@ private void DecodePixelData<TPixel>(DeflateStream compressedStream, ImageFrame<
             while (this.currentRow < this.header.Height)
             {
                 Span<byte> scanlineSpan = this.scanline.GetSpan();
-                int bytesRead = compressedStream.Read(scanlineSpan, this.currentRowBytesRead, this.bytesPerScanline - this.currentRowBytesRead);
-                this.currentRowBytesRead += bytesRead;
-                if (this.currentRowBytesRead < this.bytesPerScanline)
+                while (this.currentRowBytesRead < this.bytesPerScanline)
                 {
-                    return;
+                    int bytesRead = compressedStream.Read(scanlineSpan, this.currentRowBytesRead, this.bytesPerScanline - this.currentRowBytesRead);
+                    if (bytesRead <= 0)
+                    {
+                        return;
+                    }
+
+                    this.currentRowBytesRead += bytesRead;
                 }

                 this.currentRowBytesRead = 0;
@@ -577,11 +581,15 @@ private void DecodeInterlacedPixelData<TPixel>(DeflateStream compressedStream, I

                 while (this.currentRow < this.header.Height)
                 {
-                    int bytesRead = compressedStream.Read(this.scanline.GetSpan(), this.currentRowBytesRead, bytesPerInterlaceScanline - this.currentRowBytesRead);
-                    this.currentRowBytesRead += bytesRead;
-                    if (this.currentRowBytesRead < bytesPerInterlaceScanline)
+                    while (this.currentRowBytesRead < bytesPerInterlaceScanline)
                     {
-                        return;
+                        int bytesRead = compressedStream.Read(this.scanline.GetSpan(), this.currentRowBytesRead, bytesPerInterlaceScanline - this.currentRowBytesRead);
+                        if (bytesRead <= 0)
+                        {
+                            return;
+                        }
+
+                        this.currentRowBytesRead += bytesRead;
                     }

                     this.currentRowBytesRead = 0;

Before this change, I could repro with the example in this issue. After this change, it appears to work correctly.

[adamsitnik]

Since this was caused by a breaking change that we have introduced on purpose (dotnet/docs#24649) and fixed by @stephentoub in SixLabors/ImageSharp#1707, I am closing the issue.