Software engineering is full of trade-offs: speed/memory usage, features/bugs, etc. The list goes on and on. The Android team here at Instructure found an interesting trade-off: developer-time versus application size. As we get new icons/images from our UI/UX team, we have two choices: bundle all of them into the application or add them as they’re needed in our project. The trade-off becomes relatively straight-forward: either we spend time constantly adding images to our project or the user has to deal with their size when they install our application.

At a high-level, the solution is simple: find all the unused drawables in the project and remove them when you build for release. Historically that’s been a tedious and error-prone process, but not anymore. I’m proud to announce a new open-source script from Instructure: ImageSweep. It will run through every file in your project and check for references to drawable resources using regular expressions to check for instances of R.drawable. and @drawable/. The script will then iterate through the resource folder and delete ALL unused drawable resources.

It’s extremely easy to use. Simply run:

    python ImageSweep.py project_src_directory

where project_src_directory is the relative or absolute file-path where your source code lives. Make sure the chosen directory contains all of your source code and AndroidManifest.xml, but none of the libraries you’ve included. The script auto-determines where the project’s resource folder is and libraries can potentially break this detection.

We recently added this script to our release process for Canvas for Android. In that project, we were able to delete 2,593 files for a total of 72.37 Mbs freed on disk. This correlated to a 46% size decrease on the apk itself and 26% size decrease on the installed application.

To get started, visit the project homepage. Take note of the warnings in the README prior to using the script.