I have a bunch of small icons that I use in my apps and for all of them, I just doubled the size of the image and added @2x to the name. For most of the icons that was all I needed to do because the frame I created for the images was a fixed number of points. iOS scaled the images appropriately. For some images I determined the frame size by looking at the size of the image. For those images I had to divide by the scale factor or the images would be twice as big as I wanted. e.g.
CGFloat deviceScale = [UIScreen mainScreen].scale;
cButton.frame = CGRectMake(0, 0, cImage.size.width/deviceScale, cImage.size.height/deviceScale);
All of my games rely heavily on graphics and they are large—too large to include both a normal size and @2x version. I can get the device to display the images as if they were labeled @2x by a simple conversion.
if ([[Utilities deviceType] isEqual:@"iPhone Retina4"] || [[Utilities deviceType] isEqual:@"iPhone Retina35"] ) {
pictLeft = [UIImage imageWithCGImage:pictLeft.CGImage scale:2 orientation:pictLeft.imageOrientation];
pictRight = [UIImage imageWithCGImage:pictRight.CGImage scale:2 orientation:pictRight.imageOrientation];
}
This works on the iPhone because the images are way bigger than they need to be. On the iPad they aren’t more than twice the number of pixels that are displayed, so it doesn’t work.