Tutorial: A Colored Lens On A Black And White Background With Core Graphics

You have likely noticed the effect in many different applications where the area showing what the user has currently selected is in color, and the unselected area is black and white. It may be a small detail, but it could give your app or game an extra amount of polish.

I’ve come across tutorial demonstrating how to implement this effect using Core Graphics. The tutorial demonstrates how to render the image with separate black and white, and color sections, and how to draw a polished looking lens over the colored area. The tutorial also covers some performance optimizations that you may need to perform.

The tutorial is from Yuchen of ClingMarks, and here’s a video demonstrating the end result:

You can find the tutorial here:
Implement “Focus Area” Special Effect in iPhone Apps

A simple concept, but it can definitely add a touch of class to an interface.