Image resource question

FROM : Edward J. Stembler
DATE : Wed Jan 23 21:38:39 2008

Hello,

Which image format is the best to use for my Cocoa apps?  What is the 
generally preferred format, and are there any limitations I should 
know about?

For example, when perusing the resources of various apps, I noticed 
that some developers use TIFFs, some use PNGs, and some even use PDFs 
for images.  Personally I'm a big fan of PNG since it supports alpha-
transparencies.  I'm just wondering why anyone would use TIFF if you 
could use PNG instead?  I'm guessing that some use PDFs if they have 
their artwork in vector format originally (EPS or AI) and want to 
eventually support resolution independence.