Core Image: Performance, Prototyping, and Python

WWDC 2018

Core Image Performance APIs

• Inserting intermediates
• Kernel language features

Inserting Intermediates

Caching of Intermediates

• Intermediates are cached by default
• Can turn off for all renders on a CIContext
  let context = CIContext(options: [.cacheIntermediates : false] );
• Or turn on for specific intermediates
  image.insertingIntermediate(cache: true);

2 Ways to Write CIKernels

New Features for Better Performance

• Half float support
  - Faster operations (on A11 devices)
  - Smaller registers increase utilization
• Group reads
  - 4 single-channel pixels per read
• Group writes
  - 4 pixels written per kernel execution

Step 1: Convert to Metal

Step2: Use half-float

Step 3: Use Group reads and Write

• 2x Faster kernel execution time
• https://developer.apple.com/documentation/coreimage/writing_custom_kernels

PyCoreImage

PyObjC

• Since Mac OS X 10.5 Leopard
• Python and ObjC bridge
• Colon → underscore

Python Bindings

PyCoreImage

Core Image for Python

Cheat Sheet

Demo1

• Sample Link

Demo 2