how to implement tilt shift blur(like circle selective blur in instagram) in ios using coreimage framework

Question

I know that, this can be done using GPUImageFramework. But I want it done using CoreImageFramework. Any tutorial?

Answer 1

Apple covers tilt-shift in the CoreImage Programming Guide: Tilt-Shift Filter Recipe.

To adapt this method to a circle, you'd want to use a CIRadialGradient instead of two CILinearGradients