Sale has ended but you can still get this app.
Download Blurate Now
Blurate

Official Description

With Blurate you can create highly customized image filtering techniques.

OpenCL 1.2 graphics device required:
https://support.apple.com/en-us/HT202823

Provide the description of a filter in Blurate's graphical user interface by opening the KernelDesigner tool. It will craft OpenCL (TM) compute kernels to implement the filter description. You can apply the filter on your images.

Hold Alt key to enable wand functionality.

The filter descriptions can be saved, exported and reproduced on other OpenCL compatible devices.