MHRotaryKnob

This is a UIControl that acts like a rotary knob. In operation it is similar to 
a UISlider but its shape is square rather than long and narrow.

HOW TO USE:

Copy MHRotaryKnob.h and MHRotaryKnob.m into your project. Add QuartzCore to your
target's frameworks.

You have to provide the images for the knob and the background. The demo project
includes a few basic images but you probably want to use graphics that suit your
app's look-and-feel better. 

(The demo project also includes Knob.xcf, which is the source GIMP file that I
used to draw the knob image.)

If you want to do more fancy drawing, then you can easily modify the class. Its
-valueDidChangeFrom:to:animated: method is invoked whenever the value changes. 
In the default implementation it simply rotates the knob image. You can change 
or override this method to do custom drawing.

SYSTEM REQUIREMENTS:

iOS 3.0 or higher