I have a graphic designer who is doing some graphics for my iPhone app. Most recently she made me a background pattern and posed me two questions that I’m unsure of how to answer:
1) What should the size of the background pattern be?
-For this I know that when I’m programming my app,the screen is in terms of 320 by 480 (when in portrait mode), however is this the appropriate unit that I should give her (I’m only worried about iPhone 4 and below for now)? Like for instance, I know there is a retina display and I’ve seen the phone resolution of my phone also be listed as 640 x 960. I’m just confused of what the best thing to tell her regarding this is, she does not have any iPhone experience and will be using the traditional graphic programs like illustrator, photo shop etc to do the graphic design.
2) What file type should it be?
-I’ve read the iPhone supports mostly all of the most popular graphic file types, but is there anyone particular that would work best on an iPhone app?
The standard for iPhone resource images is PNG. If you want to target iPhone 4+ with retina display, have the designer provide two versions of the PNG: A standard version and a double-sized version which should have @2x appended after the filename, but before the extension.
So
for regular resolution and
for retina resolution. iOS will automatically pick the best one to use based on the screen available.