Making wallpaper for the iPhone 4 is very easy. Just like making wallpaper for any other device or computer screen, you just need to get the right dimensions and make an image of that size.
The iPhone 4 features a “Retina Screen”, which is Apple’s fancy name for a high resolution mobile display. This display is 960 pixels high, 640 pixels wide and 326 pixels per inch. This means that your iPhone 4 wallpaper should be a 960 × 640 326 DPI image.
Everyone probably has their own method for making wallpaper. Mine’s not the only one and probably not the best, but it’s quick and it works. Here are the steps I use to make iPhone 4 wallpaper:
You now have an image perfectly cropped and sized for the iPhone 4 Retina Display. Save it as a jpg and put it on your phone!
I also have a Photoshop action that can be used to make iPhone 4 Retina Display wallpaper. It works on a duplicate of whatever active image you have open, so it is non-destructive. Its process is as follows:
If the area you want at the center of your wallpaper is not at the center of your image, just make a quick square crop with the correct central focal point before running the action.