Jul 3, 2012

Minimal marketable app - Instant Mustache #2

This article is part of a series of articles about the development process of Instant Mustache, a fun camera app that adds mustaches to all faces using face detection. Click here to get a chronological list of all published articles about Instant Mustache.

In the last article I described roughly the idea behind Instant Mustache. Now it's time to get more concrete. While doing so we try to follow the principle of the minimal marketable feature (MMF).

Minimal marketable feature
The idea behind the minimal marketable feature is to strip all aspects of a feature that are not necessarily needed to end up with a useful (or marketable) feature. After that you'll end up with smaller features that are easier and faster to develop. This is only a very rough explanation of MMF. You can find a way better Introduction to Minimum marketable feature at the upstart blog.

Minimal marketable app
In this case we are slightly modifying this idea to end up with something like a minimal marketable app. This means we are going one level higher and strip all features that are not essentially required for a first releasable app. This does not mean that we won't develop these features at all but our first version will be without them enabling us to ship the app as early as possible.
Let's continue with an example. When you think about the app (see first article) you will very fast come up with an idea like: The user should be able to select between a bunch of mustaches - more mustaches = more fun. But do we really need this feature when we launch the app? No, we don't. Our fun app will still be fun with one single mustache. Of course this is one of the first features we should have in the next release after the initial one.

Another feature that's easy to come up with is switching between the cameras of a device. In most cases this means switching between back and front camera. Again for our basic app it's totally acceptable to strip this feature in the first release. The users of our app won't be able to take pictures of themselves easily and therefore they won't have much fun when there's no mustache-less friend to photograph around. Therefore we should rank this feature high as well to implement it right after the first release.

In our case the minimal marketable feature set is an app that has two screens: A camera screen - with a camera preview and a button to take a picture - and a second screen that shows the picture you took and has an option to share this picture. The camera preview will show a live preview. Every detected face on the live preview will automatically have a mustache overlayed. If you take a picture the second screen will show the composed picture including the added mustaches. The user will be able to share the picture via the Android intent system.

Roadmap and Milestones
Nothing is more motivating than playing around with what you have created. In contrast nothing is more killing motivation than programming for ages without coming up with something that runs at all. This leads us to the goal to always have a running prototype that step by step gets features added until it's ready to ship. So let's break the functionality into parts that can be implemented in order and always leave us with a working prototype that we can deploy on our phone and use at the next party.
  • Milestone #1: A camera screen that shows the camera preview and has a button to take a photo. The photos will be saved on the SD card. After that we will end up with a basic camera app that we can use to take photos on the go. Goodbye native camera app!
  • Milestone #2: We add the second screen. After taking a photo we’ll switch to this second screen which shows the taken photo and has an option to share the photo.
  • Milestone #3: It’s time to add the face tracking. We’ll use the face tracking and display mustaches for every face on top of the camera preview.
  • Milestone #4: When taking a photo we’ll compose the final photo using the information of the face tracking. The composed photo will contain mustaches like the preview screen before. The composed photo will be saved on the SD card and shown in the second screen. We are ready to release!