quality parameter is ignored in Bitmap.Save with .jpg

[lostmsu]

Describe the bug
The parameter does not appear to have any effect and no warning is reported.

To Reproduce
Steps to reproduce the behavior:

1. Create a new Bitmap (I used WriteableBitmap) of ~1920x1080
2. Fill it with non-trivial data
3. Call bitmap.Save("test.jpg", quality: 10) (I also tried 1)

Expected behavior
You get a low quality version of the bitmap weighting under 100KB

Actual behavior
You get a high quality file over 1MB in size.
It appears the resulting file is actually a PNG instead of JPEG.

Screenshots
N/A

Desktop (please complete the following information):

• OS: Windows
• Version 11.0.2

[maxkatz6]

Looks like quality parameter is not passed here
https://github.com/AvaloniaUI/Avalonia/blob/master/src/Skia/Avalonia.Skia/ImmutableBitmap.cs#L161-L171

[timunie]

@lostmsu as @maxkatz6 pointed out where the bug may be, are you willing to provide a PR for a fix? It would be very appreciated.

[TETYYS]

It appears the resulting file is actually a PNG instead of JPEG.

To be clear, check for file extension is not present here, it is always saved as PNG https://github.com/AvaloniaUI/Avalonia/blob/1896e8ad68dc0fdb6c1055d36a97b926e0a32f17/src/Skia/Avalonia.Skia/Helpers/ImageSavingHelper.cs#L57C51-L57C51

[kekekeks]

We kinda need to add some basic support for BitmapEncoder API

[lostmsu]

I started working on support for image formats at least for saving. PR should be out in an hour or so.

[dbriard]

Hi, this issue is closed but the PR do not seem to allow to save as Jpeg.

That would be really really really convinient if we can Save an Avalonia as Jpeg in addition to PNG, really.

My typical use case: I am doing image manipulation using my own buffer, and then I need to display it, and to save it as Jpeg. So I have to:

1. Convert my buffer to SKBitmap to Save it as Jpeg
2. Convert again to Avalonia Bitmap to display it
   I could avoid one unnecessary convertion if Avalonia allow me to save as Jpeg directly.

[workgroupengineering]

My typical use case: I am doing image manipulation using my own buffer, and then I need to display it, and to save it as Jpeg. So I have to:

1. Convert my buffer to SKBitmap to Save it as Jpeg

2. Convert again to Avalonia Bitmap to display it
   I could avoid one unnecessary convertion if Avalonia allow me to save as Jpeg directly.

You can use only SKBitmap. To display it, see this.

[dbriard]

My typical use case: I am doing image manipulation using my own buffer, and then I need to display it, and to save it as Jpeg. So I have to:

1. Convert my buffer to SKBitmap to Save it as Jpeg

2. Convert again to Avalonia Bitmap to display it
   I could avoid one unnecessary convertion if Avalonia allow me to save as Jpeg directly.

You can use only SKBitmap. To display it, see this.

Correct, there is this workaround, thanks for the remainder.

I am also investigating to see if I can create a SKImage pointing to an existing memory buffer for the save operation.