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 angle_start and angle_size. For example, using angle_start=-pi/4 and angle_size=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. INPUTS angle_start - start position of circle angle_size - number of radians to continue circle for r - mask radius (integer or integer+.5) nsamples - [optional] controls sampling accuracy [1 by default] OUTPUTS mask - the created image, size 2r by 2r EXAMPLE mask1 = mask_circle( -pi/8, pi/4, 20, 20 ); figure(1); im(mask1); mask2 = mask_circle( pi/8, pi/8, 20, 20 ); figure(2); im(mask2); figure(3); im(mask1+mask2); DATESTAMP 29-Sep-2005 2:00pm See also MASK_ELLIPSE