1. Break up your screens into UI elements
It’s a good idea to provide mock-up screens as a reference – but these are not the files a developer wants to work with. You need to break the design apart into its different UI elements. Any button, frame, indicator, switch, arrow, toggle that you designed needs to be provided in a separate file. If you leave this task to the developer your design might suffer inferior Photoshop skills and you’re wasting his time.
2. USE LAYERS, align them, provide all states
In each element file you need to provide all the states and color variations as separate layers. Take a custom button as an example. It comes in three colors and has two states (normal and pressed). That means you have to provide a button.psd with six layers: “black_normal”, “black_pressed”, “blue_normal” … you get the idea. Make sure to provide complete sets here. If you leave out layers, you’ve left the completion of your design to the programmer. When you have complex set of layers where it is not obvious how they interact, make it simple for people by creating Layer comps in Photoshop. Also, make sure you’ve aligned the content of the different layers to their correct positions. The programmer should be able to simply save each layer in a separate .PNG without any extra work.
3. Use a sensible naming convention
If you pick a sensible naming convention for your files the programmer can adopt them and carry them on into the code with their original names. This makes it easier for both parties when designs needs to be updated, changed or expanded. Sensible file names from a programmers perspective means:
- follow a consistent naming pattern. Example: header_button.psd, header_gradient.psd, header_logo.psd or similar.
- use safe characters: lowercase a-z, 0-9 and _
4. Align to pixels
This really shouldn’t need telling, but apparently still does: Align your shapes to pixels. This means, almost without exception, any shape you add to your design must have a top-left and width-height that is in full-pixel values. This can be done easily in Illustrator, and moderately easily in Photoshop (“Snap to pixels” in the Shapes dialog). Coming back to the programmer with miss-aligned half pixels is literally like flipping him the bird.
5. Summarize your color, font and margin choices
A lot of what the programmer ends up doing is condensing your design into reusable components and variables, hopefully without compromising its look. You can help in this by providing a list of your design guidelines. Ideally this list would contain your choices of:
- Colors: text colors, button colors, list colors, effect colors
- Gradients: backgrounds, effects etc.
- Fonts: list of faces used, list of sizes used, shadow effect settings
- Margins/Paddings: numbers for guides or grids used
6. Make your graphics scalable
It is no longer realistic to believe you are designing for one resolution or platform. More likely your design will be used for developing apps on both tablets and mobile phones across multiple platforms. Your design needs to be scaleable. You should always use vector shapes, your gradients and effects should be scaleable, you should never use pixmaps, your fonts should be readily available or embedded in the file. Basically, your image should look good rasterized to any size.
7. Tips for the elite designer
If you’re already following the above guidelines you’re making most app developer happy. But if you want to go the extra mile, here are some tips to make your programmer even happier:
- create scripts the programmer can run to render all assets to an arbitrary resolution
- put your designs into any sort of version control system (git / svn / rcs / perforce) - we honestly don’t care. Anything is better than zip files over mail, dropbox or whatever.
- pre-render the assets to our current target resolutions – we’d love you for it.
Icons by http://dryicons.com
Yesterday I was presenting (covered here by 
Sveinung had a really interesting talk about the different apps that apps.no had launched and how they had fared in the market. He was very frank and open about everything and I really enjoyed the talk. Our business idea is basically same as them, make own apps + consult and make apps for others, so it was really good to hear from someone that was already doing this, and succeeding. Here are the numbers:
Peter from Rovio talked about their insane success with the Angry Birds game. It’s been the top selling game for the iPhone for over 5 months, thats more than anyone else – ever. They have sold, at least, 7 million copies of it on the Apple App Store for the iPhone only, more if you add iPad. They launched in December 2009, and since then have had a crazy ride.
Rovio is aiming for 100 million downloads of Angry Birds – they call it the “Tetris strategy”. And they might succeed – when they released the Android version a few days ago, they had 2-3 million downloads in as many days. Wow.
The last talk I attended was about HTML5 apps. Nikolai had a very enthusiastic talk about HTML5 apps, and how that was not a utopian dream, but actually a reality already. I think his talk clearly showed it is not quite there yet. The fact that for the iPhone, to use bluetooth support in an HTML5 app, you have to jailbrake it and write a platform spesific extension for PhoneGap speaks for itself.
