IPhone / iPad brightness control controller (image included)

Question

I found this interesting interface (starts in 33 seconds http://vimeo.com/22946428 ) and would like to create something similar for my own applications. I am particularly interested in the circular intensity indicator / pen, as in the attached image. It has a very futuristic feeling for it and should be fairly easy to use using touchsMoved: gesture recognizer callback.

But in order not to reinvent the wheel, are there any open source libraries that offer advanced user interface features, such as those in the picture / video?

Update: Hubert's answer demonstrates how to use the movement of one finger to rotate a disc. The second part of the puzzle: how to fill in a color control?

I’m thinking about turning the background color image, but part of it needs to be cropped or covered with something else to vary from an empty background to a full one. Perhaps the cut out element (about 1 radian) can hide the set of fan-shaped segments following the finger and create the illusion of a continuously increasing or decreasing filling of the sensor. 6 segments x, y will be continuously animated, positioning them in such a way as to cover only the necessary share of the control.

Answer 1

, , iOS:

http://www.raywenderlich.com/9864/how-to-create-a-rotating-wheel-control-with-uikit

http://maniacdev.com/2012/02/tutorial-creating-a-one-figure-rotation-gesture-recognizer-for-a-rotary-knob-control-on-ios/

http://maniacdev.com/2011/12/open-source-libraries-for-easily-adding-rotary-knob-controls-in-your-ios-apps/

Answer 2

: GaugeKit

, , - !

Answer 3

Here is an example of a circular review of progress. In combination with one rotary control with one finger, it creates a similar pressure gauge for the requested one (by simply superimposing 2 controls on top of each other)

Then link the two controls to the rotation callback:

  - (void) rotation: (CGFloat) angle
{
    // calculate rotation angle
    imageAngle += angle;
    if (imageAngle > 360)
        imageAngle -= 360;
    else if (imageAngle < -360)
        imageAngle += 360;

 progress = imageAngle/360.0;
}

DACircularProgress view + OneFingerRotationGestrureRecognizer