# maskCircle

## PURPOSE

Creates an image of a 'pie slice' of a circle.

## SYNOPSIS

function mask = maskCircle( angleStart, angleSiz, r, nSamples )

## DESCRIPTION

     Creates an image of a 'pie slice' of a circle.

     Creates a 2D array of size (2rx2r) with values between 0 and 1.
     Specifically, mask has values 1 inside the pie slice of the circle
     defined by angleStart and angleSiz.  For example, using
     angleStart=-pi/4 and angleSiz=pi/2 would give a quarter circle facing
     right.  nsample conrols the accuracty of the circle at its boundaries.
     That is if nSamples>1, pixels at the boundary which will have fractions
     values (when a pixel should be say half inside the circle and half
     outside of the circle).  Note that running time is
     O(nSamples^2*radius^2), so don't use a value that is too high for either.
     A series of masks whose angles together go from 0-2pi will sum exactly to
     form a radius r circle. r may be either an integer, or an integer + .5. A
     pixel is considered to belong to the circle iff it is within the given
     angle and has a value strictly smaller then r.

     USAGE
      mask = maskCircle( angleStart, angleSiz, r, [nSamples] )

     INPUTS
      angleStart   - start position of circle
      angleSiz     - number of radians to continue circle for
      r            - mask radius (integer or integer+.5)
      nSamples     - [1] controls sampling accuracy

     OUTPUTS
      mask         - the created image, size 2r by 2r

     EXAMPLE
      mask1 = maskCircle( -pi/8, pi/4, 20, 20 ); figure(1); im(mask1);
      mask2 = maskCircle( pi/8, pi/8, 20, 20 );  figure(2); im(mask2);
      figure(3); im(mask1+mask2);

     See also MASKELLIPSE, MASKSPHERE

     Piotr's Image&Video Toolbox      Version 2.0
     Copyright 2008 Piotr Dollar.  [pdollar-at-caltech.edu]
     Please email me if you find bugs, or have suggestions or questions!
     Licensed under the Lesser GPL [see external/lgpl.txt]

## CROSS-REFERENCE INFORMATION

This function calls:

- localSum Fast routine for box filtering.

This function is called by: