The biggest thing of all, I believe, is actually testing your design on a device. Text you think looks good when you're in Photoshop has a tendency to be too small or too large, or too gray or not enough saturation on a device. So, if you're designing - and can't get a build to your phone to actually play with - email yourself an exported PNG of correct resolution and open it up on your phone. You should be able to see and "play" with it as best as you can for absolutely no money.
It seems like this was written for the designer, not developer, so I would also like to add one more thing. If you're a designer and tasked on working with a developer to make an app happen (or vice versa really), then work side by side as much as you can with that person and have regular discussions. You'll both drive each other toward a better project than just piecewise doing things in a more waterfall-esque approach.
This is a very good guide. The only part I found odd was the advice to design at 1x rather than 2x. My strategy, is design in 2x, but everything must have even dimensions. For the iPhone I just downsample the assets and don't even bother to check if they look good. For iPad, I will touchup 1x assets if needed.
I've found that the best reason to design at 1x is because the coordinates match the coordinates for the developer and also because sometimes the 2x size won't split nice and evenly if you don't keep it in mind. For instance 15px for a gutter.
If you can keep things like that in mind, then designing at 2x means way less work later on (doing a batch /2 on size in Photoshop over all assets is stupid simple).
That is what I actually meant by even dimensions. I meant divisible by 2, not balanced.
It just seems impossible to take something with texture at 1x, and then scale it up. I often pick subtle textures for 2x, and then just drop or re-zoom the texture in the 1x version. How many people really have non-retina devices these days?
If you use Sketch to draw your interface, you get @2x exporting and slicing is built in. It hurts my head to think about what I would have to do if I was using Photoshop.
Question for designers: how do you share your designs with clients/team, in order to explore both design & workflows? (this would be at Photoshop stage, no coding started yet. An example: the series of Instanote mockups from the article)
Do you do this as a series of images in any order, or do you use some tool such as Invision, to build interactive prototypes?
> A point can be represented by many pixels (normally one or four).
This is a distance vs. area mistake, right? I thought that a point is used as a one-dimensional (distance) unit, and is generally one or two physical pixels.
It seems like this was written for the designer, not developer, so I would also like to add one more thing. If you're a designer and tasked on working with a developer to make an app happen (or vice versa really), then work side by side as much as you can with that person and have regular discussions. You'll both drive each other toward a better project than just piecewise doing things in a more waterfall-esque approach.