But I found out what was wrong. It had something to do with HiDPI support.
ModernizePicture was:
[code] If input.hasAlphaChannel Then Return input
Dim result As New Picture( input.Width, input.Height )
result.HorizontalResolution = input.HorizontalResolution
result.VerticalResolution = input.VerticalResolution
result.Graphics.DrawPicture( input, 0, 0 )
Return result[/code]
I deleted the first line, now it ALWAYS makes a new copy of the image. Now it works. I totally don’t understand why an image would be immutable because of HiDPI, but apparently, it is.