background image size iphone

Normal background image is 320x480 pixels. and for 开发者_开发知识库retina is 640x960 pixels.

Now i have to put my background image and i have status bar(20) and navigation bar (44).

So i have to reduce 64(20+44) from 480(normal) or from 960(retina)?

1. if i reduce 64 from normal then normal image will be 320x416 pixels and retina will be 640x832 pixels.
2. if i reduce 64 from retina then normal will be 320x448 and retina will be 640x896 .

It is confusing me.. this 64(20+44) i reduce from which image type because other one will be exactly half or double of it.

Reduce from the normal size.

64px = height to remove from normal display.

128px = height to remove from the retina.

Don't forget that in the retina display the status bar and nav bar will also be 2x the height :)

You do everything based upon the 320x480 size, then retina scales everything up. Using images suffixed @2x will allow you to replace the assets (mainly UIImage) for the retina version, this doesnt work for direct resource file references or video/audio files though so just be careful.

So measure for 320 for all your assets then your retina ones will simply be twice the size