Export Snapshot question

[Dave]

Hi,

I need to export a snapshot in a non-compressed format, from looking  
at the documentation I can export in the following formats:

JPEG
GIF
PNG
PBM
PGM
PPM

JPEG is no good for what I want since it is lossy. GIF is no good  
because it only supports 8 bit color and I need 24 bit (if not 32 bit  
with Alpha Channel) I'm not sure what PBM, PGM or PPM are? Which  
leaves PNG which uses lossless compression, however what are the  
defaults for the image? (Pixel Size, Component Size etc.). Also, is  
there a way to specify the settings?

Thanks a lot
All the Best
Dave