Autodetect bit depth on saving .png files fails on beta 4.216.7765.43041

[frio]

This can be reproduced as follows: make a transparent image and paint on it with < 256 colors without antialiasing, ensuring 1-bit transparency depth. If there is partial transparency or the number of colors is sufficiently high, this exception does not occur. 

 

Attached is an image that's been saved as 32-bit, trying to resave it as autodetect fails.

 

Exception:

System.ArgumentException: palette colors must be opaque (A=255), although 1 transparent color as the last entry is permitted
   at PaintDotNet.Imaging.PaletteMap..ctor(IEnumerable`1 colors) in D:\src\pdn\src\Framework\Imaging\PaletteMap.cs:line 27
   at PaintDotNet.Imaging.ProximityPaletteMap..ctor(IEnumerable`1 palette) in D:\src\pdn\src\Framework\Imaging\ProximityPaletteMap.cs:line 46
   at PaintDotNet.Data.WicFileTypeHelpers.Save(IBitmapSource`1 sourceBgra32, Vector2Double dpi, Metadata metadata, Stream output, ContainerFormat containerFormat, Nullable`1 preferredVendor, IMetadataTranscoder metadataTranscoder, IEnumerable`1 encoderOptions, SavableBitDepths bitDepth, IReadOnlyList`1 paletteForIndexed, Int32 ditherLevelForIndexed, ProgressEventHandler progressCallback, Object progressCallbackSender) in D:\src\pdn\src\PaintDotNet\Data\WicFileTypeHelpers.cs:line 290
   at PaintDotNet.Data.PngFileType.OnFinalSave(Document input, Stream output, Surface flattenedImage, SavableBitDepths bitDepth, IReadOnlyList`1 paletteColors, Int32 ditherLevel, PropertyBasedSaveConfigToken token, ProgressEventHandler progressCallback) in D:\src\pdn\src\PaintDotNet\Data\PngFileType.cs:line 263
   at PaintDotNet.Data.InternalFileType.FinalSave(Document input, Stream output, Surface scratchSurface, SavableBitDepths bitDepth, QuantizationAlgorithm quantizationAlgorithm, Int32 alphaThreshold, Int32 ditherLevel, ImageColorsAnalysis analysis, PropertyBasedSaveConfigToken token, ProgressEventHandler progressCallback, Double progressStart, Double progressEnd) in D:\src\pdn\src\PaintDotNet\Data\InternalFileType.cs:line 510
   at PaintDotNet.Data.InternalFileType.GetSavableBitDepthFileLength(SavableBitDepths bitDepth, Document input, Surface scratchSurface, QuantizationAlgorithm quantizationAlgorithm, Int32 ditherLevel, Int32 alphaThreshold, PropertyBasedSaveConfigToken token, ProgressEventHandler progressCallback, Double progressStart, Double progressEnd) in D:\src\pdn\src\PaintDotNet\Data\InternalFileType.cs:line 454
   at PaintDotNet.Data.InternalFileType.ChooseBitDepth(Document input, Surface scratchSurface, QuantizationAlgorithm quantizationAlgorithm, Int32 ditherLevel, Int32 alphaThreshold, PropertyBasedSaveConfigToken token, ProgressEventHandler progressCallback, Double progressStart, Double progressEnd, HashSet`1 allowedBitDepths, HashSet`1 losslessBitDepths, ImageColorsAnalysis analysis) in D:\src\pdn\src\PaintDotNet\Data\InternalFileType.cs:line 346
   at PaintDotNet.Data.InternalFileType.OnSaveT(Document input, Stream output, PropertyBasedSaveConfigToken token, Surface scratchSurface, ProgressEventHandler progressCallback) in D:\src\pdn\src\PaintDotNet\Data\InternalFileType.cs:line 167
   at PaintDotNet.FileType.Save(Document input, Stream output, SaveConfigToken token, Surface scratchSurface, ProgressEventHandler callback, Boolean rememberToken) in D:\src\pdn\src\Data\FileType.cs:line 261
   at PaintDotNet.Dialogs.SaveConfigDialog.<>c__DisplayClass49_0.<UpdatePreviewAsync>b__0() in D:\src\pdn\src\PaintDotNet\Dialogs\SaveConfigDialog.cs:line 613
   at System.Threading.Tasks.Task.Execute()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at PaintDotNet.Dialogs.SaveConfigDialog.<UpdatePreviewAsync>d__49.MoveNext() in D:\src\pdn\src\PaintDotNet\Dialogs\SaveConfigDialog.cs:line 632

 

Edited April 7, 2021 by frio
added image that reproduces the bug

[Rick Brewster]

Aha, this is easy for me to reproduce, thanks! I'll get it fixed asap.

 

Looks like the same issue reported by @HopperElec over here, https://forums.getpaint.net/topic/118070-paintnet-4216-beta-build-7765/?do=findComment&comment=582506, but their sample image didn't reproduce this for me.

 

[HopperElec]

Ah yes, I was also not using anti-aliasing and was not using transparency so this is likely the same issue

[HopperElec]

Is there any temporary solutions? Like, is there a way to edit the file having issues to remove what is causing the issue (like fix the bit depth), or is there a way to downgrade pdn temporarily to the version I didn't have this issue in?

[ardneh]

You can download v4.2.15 here:

https://www.getpaint.net/download.html
 

[HopperElec]

Surely that's the version I'm already using, which is the one with this bug I'm trying to avoid?

[toe_head2001]

@HopperElec, Do you not realize you've been using a beta release of v4.2.16?

[HopperElec]

Oh no I didn't sorry

[Rick Brewster]

Try the new 4.2.16 build that I just put out: 

 

[frio]

Tested, saves the files it used to previously stumble on with autodetect. Thanks!

 

(And I have to take this opportunity to add: thanks for all these ~15 years paint.net has been an indispensable tool for my purposes, over all kinds of Photoshops and what have you.)