iPhone/iPad draw pdf like iBooks?

Question

Does anyone know how to use core graphics to draw a pdf like in iBooks. I can already draw a pdf page using core graphics but was curious how iBooks shows a lower quality view of each page so it loads fast and then when you stay on a page longer it renders it a full quality. This makes it able to open the pdf without having to make the user wait like most magazine apps you see on ipad. Any ideas would help!

Answer 1

Apple have some "ZoomingPDFViewer" sample code:

http://developer.apple.com/library/ios/#samplecode/ZoomingPDFViewer/Introduction/Intro.html#//apple_ref/doc/uid/DTS40010281

I suspect that might give you some good ideas :-)

Answer 2

I assume they use multiple layers, the first layer loads the pdf in low resolution and the better resolution is prepared in the background. When ready these layers are swapped.

Have a look at CGPDFDocumentRef and CATiledLayer in the documentation.