[QUESTION] SKBitmap.Decode(stream) will dispose this stream, feature or bug?

[xtuzy]

I use SKBitmap.Decode(stream) to create a Bitmap, when i need continue use this stream, i found it is dispose.

Skiasharp Version: 2.88.2

[LukePulverenti]

Are you saying this was different in earlier versions?

[xtuzy]

no difference compare with 2.88.0, i just feel it is not right, stream should be disposed by user like this

using(var stream = ***)
{
  var bitmap = SKBitmap.Decode(stream);
}

[dallonxu]

@xtuzy

Just use SKData to wrap the stream, the stream will not be closed after SKBitmap.Decode.

using(var stream = ***)
{
    var skData = SKData.Create(stream);
    var bitmap = SKBitmap.Decode(skData);
    //stream will not be closed here
}

[maxenko]

This is a really bad design choice if not a bug.

[mattleibow]

I'll need to confirm, but I am pretty sure this is expected. The decode usually reads all the way to the end, and the stream may not always be rewindable. So there was not much point in keeping it open... However, the Stream overloads could maybe get an additional parameter to indicate whether or not to close the stream.

[nifiz]

@mattleibow Managing a Stream should be left up to the user, not a completely different function they call.

[Ebola-Chan-bot]

I'll need to confirm, but I am pretty sure this is expected. The decode usually reads all the way to the end, and the stream may not always be rewindable. So there was not much point in keeping it open... However, the Stream overloads could maybe get an additional parameter to indicate whether or not to close the stream.

At least for me, this behavior is very unexpected. I usually keep a Stream instance for multiple purposes, rather than expecting it to be disposed by a seemingly "read-only" operation. And it cost me so much time to find that the bug in my app ultimately comes from this behavior.

[tigransard]

there is another workaround that I fond in the code

var skStream = new SKManagedStream(stream, disposeManagedStream: false);
using var bitmap = SKBitmap.Decode(skStream);

in this case your original Stream will not be closed;

[mattleibow]

I think we could ad some internal wrapper/proxy stream so you can disable this feature.

Skia will always dispose, but we can hide it if we want.

@tigransard has a good workaround that we could implement internally.