I was doing a project and ran into this problem: When creating a big ARGB PNG (8192x8192 as an example), sometimes when viewing it in Windows Photo Viewer and other Microsoft programs, the background is shown as BLACK even though I use Color.Transparent or FromARGB(0, 255, 255, 255) or FromARGB(0, 0, 0, 0). After discovering this I created another file with Paint.NET (all transparent, 32bit) just for test And it did the same thing: Sometimes when opened, it indicated transparent, and some times the same file was showing plain black! I also had seen this behavior outputting to TIFF, but at the time I thought it was something I did (not closing a filled polygon or something...)
I also tried with... smaller files, like 1000x1000, and they never had the issue.
I confirmed the behavior at a friends setup (also a Win7, 64bit)... sooo Whats going on? Why cant my Windows 7 PS1 Pro, 64Bit (and most important: the customers setup) not interpret alpha on 'big' files?