Dear Rick Brewster,
I just want to clarify a thing. NET Framework 2.0 officially has support for 32-Bit Bitmap with Alphachannel although in MSDN documentation the alpha bit is stated as unused.
You can try this out by doing following:
Bitmap Bmp = new Bitmap(Width, Height, Format32bppArgb);
Then just draw a bit with colors with alpha < 255
Bmp.Save("test.bmp", Imaging.ImageFormat.Bmp)
You will see (just open the corresponding Bitmap file with a hex viewer) that alpha values are correctly saved. So it means, it is supported. Image.FromFile() does currently not support this alpha channel of Bitmaps afaik. But loading a 32 bit bitmap isn't that difficult by direct reading bit values into buffer. Just take a look at http://www.codeproject.com/cs/miscctrl/ ... etDemo.asp
So if you want I will provide you with the corresponding 32-Bitmap Loader code which could be added to Paint.Net.
Btw. Photoshop does officially support alphachannel in bitmaps ... even though there seems to be a bug in theire code.
Another way storing alpha information in bitmaps would be the possibility to use Bitfields (Compression = BI_BITFIELDS insteadt of BI_RGB). Since there is a BitmapHeader.RedMask ... AlphaMask, the Bitmap may be saved as 32 Bit Bitmap with BI_BITFIELDS by setting corresponding masks.
However this isn't mentioned officially in MSDN documentation, but nothing speaks against it
regards
bkausbk