Fail to Load a Gif Image with v2.0.0 but works with v1.0.4 on the same machine.

ImageSharp version

2.0.0

Other ImageSharp packages and versions

1.0.4

Environment (Operating system, version and so on)

Windows 10

.NET Framework version

.NET 5

Description

I came across a gif image https://www.muhammadniaz.net/wp-content/uploads/2013/06/Stronghold-Crusader-Extreme-Cover.gif which loaded correctly with ImageSharp v1.0.4 but failed with v2.0.0 with an unmanaged exception which cannot be caught by the try-catch

Steps to Reproduce

try
{
    var client = new HttpClient();
    string url = "https://www.muhammadniaz.net/wp-content/uploads/2013/06/Stronghold-Crusader-Extreme-Cover.gif";
    var bytes = await client.GetByteArrayAsync(url);
    var image = SixLabors.ImageSharp.Image.Load(bytes, out var format);
    Console.WriteLine(format);
}
catch (Exception e)
{
    Console.WriteLine(e.Message);
    Console.WriteLine(e.StackTrace);
    Debugger.Break();
}

Images

Confirmed. Memory access violation in LzwDecoder. Will compare GifDecoderCore in 1.0.4 with the one from main to see what I can spot. It's likely got something to do with our new XMP functionality as I've already checked the missing colortable fix.

It's definitely the XMP application extension handling. I've fixed the reader so far but it looks like the writer does not match the specification also and is not writing the data in subblocks..

Handle empty XMP profiles. Fix #2012

Here is another gif file which even fails the v1.0.4 https://www.rxlist.com/images/rxlist/drona1.gif

Here is another gif file which even fails the v1.0.4

That image is actually corrupt. The minimum code specified is greater than the specification allows.

Windows Explorer can't open it, nor can Photos, Paint, or Paint.NET.

Edge can though, as can VS Code, returning it as a 276 x 49135 transparent gif which is actually incorrect according to the specification because there's no Graphic Control Extension present in the image and thus no transparency flag.

I can update the decoder to simply ignore frame indices data if it's corrupt. This will return a 276 x 49135 black gif.

From time to time, corrupted image would be encountered. The main problem is that an unmanaged exception would be thrown and the process would be terminated. Is it possible to catch the unmanaged exception and throw a managed one so that the situation could be handled in the C# code ?

Did you read the referenced PR?

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Fail to Load a Gif Image with v2.0.0 but works with v1.0.4 on the same machine. #2012

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Fail to Load a Gif Image with v2.0.0 but works with v1.0.4 on the same machine. #2012

Description

ImageSharp version

Other ImageSharp packages and versions

Environment (Operating system, version and so on)

.NET Framework version

Description

Steps to Reproduce

Images

Activity

JimBobSquarePants commented on Feb 18, 2022

JimBobSquarePants commented on Feb 18, 2022

paulyipkh commented on Feb 19, 2022

JimBobSquarePants commented on Feb 19, 2022

paulyipkh commented on Feb 19, 2022

JimBobSquarePants commented on Feb 19, 2022

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