Why not draw everything in Quartz 2D or import only PNGs? In what situation would someone use both Quartz 2D and PNGs in an application?
closed as off topic by Philip Regan Apr 15 '11 at 20:29
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You are very confused about what these two things are. It is not a situation of choosing one or the other. Your question is not unlike saying "should you use pens or ink to write with?"
Quartz 2D is the Mac framework for displaying 2D graphics: http://en.wikipedia.org/wiki/Quartz_2D
PNG is a raster file format: http://en.wikipedia.org/wiki/Portable_Network_Graphics
The key terms to look for in those description are "raster" and "bitmap." Note that Quartz is used to display bitmap images on Macs, and PNG is a kind of bitmap image.