PDF or image loading on iPhone

Where I have to start if I want to load only a part of an image or pdf. So I would like to render only a part from a pdf file. How can this be do开发者_StackOverflowne?

I would imagine that you will need to work with images rather than PDF (or convert any PDF to an image first)

Some options:

1) You could build a viewer that sends the screen size coordinates and a point on the image that requires viewing to return only the part of the image required.

2) Have a look the iPhone seadragon app (free). This uses Microsoft seadragon and Deepzoom technology that you could look at to service large images for zooming. more info on seadragon here: http://www.seadragon.com/