Imagesharp: System.NullReferenceException when attempt to Mutate.Draw on a new created Image<L8>

[sn4k3]

Description

What i'm trying to do: Resize white pixels but keep original image Width & Height

Error: newImage=error CS0103: The name 'newImage' does not exist in the current context

void Resize() is called under a Task
this[layerIndex].Image; // Creates a new Image that loads compressed bytes in
Parallel Loop is executed once, every image instance are new objects created inside the loop (Not shared with other iterations)
Only line "newImage.Mutate(o => o.DrawImage(image, location, 1f));" can trigger the error, Resize operation always pass.

Collection is from 500 to 1000 images but i also tried with just one, same behaviour
This error don't always happens, if i keep redoing same operation sometimes it finish ok without error, others dont.

If i turn Parallel for into a normal for loop problem seens to never happen but of course way slower than using parallel which is what make me use Parallel instead.

System Configuration

• ImageSharp version: 1.0.0-rc0002
• Environment (Operating system, version and so on): Windows 10 v1909
• .NET Framework version: .NET Standard 2.0 library, method called from .NET Framework 4.8 WinForm

[antonfirsov]

@sn4k3 how is the compilation error CS0103 related to the rest of the issue?

Any chance you can create a self-contained console app repro? A lot may depend on image sizes, position of x,y and other contextual factors.

[sn4k3]

Repo here: https://github.com/sn4k3/PrusaSL1Viewer
How to reproduce: Execute Main app -> Menu -> Open -> sl1 file from zip. Go to Menu -> Mutators -> Resize -> Pick any value diferent from 100 -> Click ok -> Error happen here
Note the error doesn't always trigger but most of the times will

Void Resize(): https://github.com/sn4k3/PrusaSL1Viewer/blob/master/PrusaSL1Reader/FileFormat.cs#L636
Called at: https://github.com/sn4k3/PrusaSL1Viewer/blob/master/PrusaSL1Viewer/FrmMain.cs#L1893

input_file.zip

[JimBobSquarePants]

I think this might be related to #1230 @sn4k3 if you can provide a stack trace that would be really useful.

[sn4k3]

System.NullReferenceException
HResult=0x80004003
Message=A referência de objecto não foi definida como uma instância de um objecto.
Source=mscorlib
StackTrace:
at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
at SixLabors.ImageSharp.GraphicOptionsDefaultsExtensions.GetGraphicsOptions(Configuration configuration)
at SixLabors.ImageSharp.GraphicOptionsDefaultsExtensions.GetGraphicsOptions(IImageProcessingContext context)
at SixLabors.ImageSharp.Processing.DrawImageExtensions.DrawImage(IImageProcessingContext source, Image image, Point location, Single opacity)
at UVtools.Parser.FileFormat.<>c__DisplayClass124_1.b__2(IImageProcessingContext o) in D:\Tiago\Dropbox\Programming\C#\UVtools\UVtools.Parser\FileFormat.cs:line 687

[JimBobSquarePants]

@sn4k3 Perfect. Yep, definitely the same issue. I've got #1234 waiting for review to fix this.