I am designing UI for an application which is going to be available for both Android and iPhone. While for android, slicing/chopping up the UI elements is pretty much simple and straight forward, we have to resize the UI elements for ldpi, mdpi, hdpi and xhdpi. i.e., 36X36, 42X42, 72X72 and 96X96 respectively. However, am not sure about resizing the UI elements for iPhone. I read somewhere that we have to resize the UI elements in @x and @2x sizes and also I've read we need to change the ppi of the UI elements as well, like 163ppi and 326ppi.
So, I am confused between: 1) By resizing image.png @x and @2x 2) By changing the image.png's 163ppi and 326ppi versions.
Which one is the appropriate way?