How and why I built PerspectiveTransform cocoapod
About me
I am an iOS developer with 10 years of experience, have built and released over 80 apps to the AppStore.
The problem I wanted to solve
Many apps have an onboarding flow to show how the app is used. Our designer wanted to show live screenshots of the app as it looks in a hands of users. This requires transforming a screenshot into the perspective of a user shown on a picture.
By calculating Core Animation transformation CATransform3D matrix we can tranform an image to place it exactly within the boundaries.
What is PerspectiveTransform cocoapod?
PerspectiveTransform is a Cocoapod library that allows 3D transformation of a view into a perspective defined by 4 corners.
https://cocoapods.org/pods/PerspectiveTransform
Tech stack
I've used multiple approaches:
- OpenCV - open-source computer vision framework on Mac and iOS.
- Accelerate.framework by Apple
- SIMD framework by Apple
The process of building PerspectiveTransform cocoapod
There was one solution I found online but it was using an inefficient method of linear equations to solve the problem
Challenges I faced
Computer vision framework is quite large, takes a long time to install and slow as it does multiple iterations to approximate the solution.
Key learnings
SIMD - "Single Instruction Multiple Data" builtin iOS framework provided the most efficient and elegant solution to the problem.
Tips and advice
TDD or Test Driven Development is a very helpful way to discover new more efficient and elegant solutions.
Final thoughts and next steps
Github repository:
https://github.com/paulz/PerspectiveTransform
100% test coverage report:
https://codecov.io/gh/paulz/PerspectiveTransform
Continuous Integration on Circle CI and Travis:
https://circleci.com/gh/paulz/PerspectiveTransform
https://travis-ci.org/paulz/PerspectiveTransform
