PSD file dimensions and resolution for Android app design
I heard and read different things regarding what should be the PSD file's dimensions and resolution for designing Android apps. Unfortunately, I came across different approaches for configuring PSD files, which I found confusing.
This page in Android Developer site says a lot about supporting screen sizes, but does not show how to configure the PSD files: http://developer.android.com/guide/practices/screens_support.html
So, in order to clarify this issue I will present the approach I take, and I would love to hear comments about it.
How I set the PSD:
I set the PSD's dimensions to 480x800 px (for portrait), and I set the resolution according to the current screen density I want to support, meaning:
- 320 Pixel/Inch for xhdpi
- 240 Pixel/Inch for hdpi
- 160 Pixel/Inch for mdpi
- 120 Pixel/Inch for ldpi
- 213 Pixel/Inch for tvdpi
(see the link above regarding screen support to understand why to use these numbers)
So what I do is design for the highest density I want for my app (say for example hdpi) and export, then I change the resolution the the next lower density (mdpi) and export and so on...
As for launcher icons, it is specified how to build the icons at: http://developer.android.com/guide/practices/ui_guidelines/icon_design_launcher.html#size
All of the templates I found for icons used a 72 Pixel/Inch resolution in the PSD.
Edit:
So to make my question clear - is this approach correct? is it recommended?
Answer
Never assume a pixel size for your screen (e.g. 480x800 is a no go), you never know what your size or aspect ratio is going to be, and assuming these things is going to make your life very difficult in the future.
You should start at the highest resolution you can (it's not going to be long before XXHDPI is going to be more common), and work down from there. Determine what size the graphic needs to be. If you want it to be about an inch wide, multiply it by the density (e.g. 1 * 320 for XHDPI, 1 * 160 for MDPI, 1 * 240 for HDPI) to get the pixel size.
The DPI setting in Photoshop does not matter. People get confused and think it does, but for designing graphics for screens, it's irrelevant unless you want to check the physical size (e.g. if you set the document density to 320 dpi, and then check the image size, it should show you what the physical size -- such as inches -- is for a screen of that density). When creating a new document, you could create a new document at say 1 inch by 0.5 inch, at 320 dpi, and it will create it at the correct pixel size. I'd advise against it. Stick to pixel sizes that are multiples of 4 for the best quality when resizing.
Basically, take a more generic approach -- design the graphics you need at the highest resolution you plan to support, find areas where the size is flexible, and if necessary make stretchable 9-patch images for those areas. Then create versions for the lower densities once you've finished that.