SkiaSharp: [BUG] Xamarin : Broken Bitmap.Encode on real devices

@mattleibow i’m not sure what your involvement is in this but if you could take a look at this critical issue i’m sure we’d all appreciate it!

I experienced the exact same thing and had to roll back to a previous version (iOS and Android / MAUI).

With the release of .net-8.0, which is meant to be the saving graces for MAUI - and SkiaSharp is pretty closely linked. Maybe the .net-8 release is just taking major priority over everything else?

It is a little concerning…

I can contribute to the issue: we’re using 2.88.6

Original image:

Encode on windows (works):

Encode on android (same result on ios; broken):

Using https://www.guiffy.com/Binary-Diff-Tool.html I found a difference in a small amount of bytes:

To my analysis, the broken image is shifted to the right and having an artifact at the top left. Sometimes the image is darkened, brightened, pink, purple, cyan… just a broken calculation of the bits based on the bytes different.

That’s the code I used to resize the image:

  private static Stream resizeImage(Stream sourceImageStream, SKEncodedImageFormat imageFormat, int quality)
  {
    // make sure the image stream is readable from the start
    try { sourceImageStream.Position = 0; } catch (NotSupportedException) { }

    using var inputStream = new SKManagedStream(sourceImageStream);
    using var original = SKImage.FromEncodedData(inputStream);

    var imageWidth = original.Width;
    var imageHeight = original.Height;

    var useWidth = imageWidth;
    var useHeight = imageHeight;

    var info = new SKImageInfo(useWidth, useHeight, original.ColorType, original.AlphaType, original.ColorSpace);
    using var surface = SKSurface.Create(info);
    surface.Canvas.Clear();
	
    surface.Canvas.DrawImage(original,
      SKRect.Create(0, 0, useWidth, useHeight)
    );
    surface.Canvas.Flush();

    using var snapshot = surface.Snapshot();

    using var data = snapshot.Encode(imageFormat, quality);
    var resizedContent = data.ToArray();

    var resizedContentStream = new MemoryStream(resizedContent);

    return resizedContentStream;
  }

I’m sure the code could be shorter (as others posted) but I wanted to give you a way to reproduce the exact same bytes.

I really hope that helps!

From my observations:

• loading PNG image and saving as JPEG: ❌ broken
• loading JPEG image and saving as PNG: ✅ working
• generating image and saving as JPEG: ❌ broken
• generating image and saving as PNG: ✅ working

Tested on: MacBook Pro 16 M2 Max ARM64, Sonoma 14.1.1

It’s exactly the same for us, we did a downgrade to the previous version but since there’s a high-severity vulnerability (https://github.com/advisories/GHSA-j7hp-h8jx-5ppr), it would be really nice to have a patch for that…

Hello @IainS1986 , unfortunately the images uploaded to the test project are in JPG and RGBA format.

JPGs don’t support transparency, so they will be in RGB format.

Might confirm a bit more that it’s JPG/RGB images specifically…

Oh wow, I just spent the last hour pulling my hair out over this same issue trying to figure out if I was doing something wrong. Glad to know I’m not the only one. I only get this bug in iOS.

Thanks for stopping me from Googling endlessly searching for solutions. 👍

Anyone who can, please fix.

Echoing what everyone else has said, we are experiencing a similar issue on our Xamarin.iOS project, except rather than just being “darker,” the images seem to either be completely black or look really corrupt. Just a couple examples of what some photos look like:

Photos look normal when running on UWP and in the simulator, but when deployed to a physical iOS device they are corrupted like this. Downgrading our Xamarin.iOS project to SkiaSharp version 2.8.8.3 fixed this issue for us. We are going with this solution for now because this concerns a critical part of our application, but since there is a major vulnerability in this package, a fix is very much needed.