;+
; NAME:
;      makerho
;
; PURPOSE:
;      Creates an array whose values are the distances
;      from the center of each pixel in the array.
;
; CATEGORY:
;      Geometry, computed holography
;
; CALLING SEQUENCE:
;      rho = makerho()
;
; INPUTS:
;      none
;
; KEYWORD PARAMETERS:
;         cal: [xc,yc,xfac] coordinates of optical axis on SLM face
;                 and scale factor for x-coordinate.
;                 Setting this parameter overrides global
;                 calibrations.
;         nocal : if set, ignore CAL and do not use global
;                 calibration constants.
;         dim : one- or two-component specification of the phase-mask's
;               dimensions.  If set, overrides and **overwrites**
;               global calibrations.
;               
; OUTPUTS:
;         theta: array of angles around center, in radians
;
; COMMON BLOCKS:
;         HOLO_COMMON:
;         Contains global calibration constants.
;         
; PROCEDURE:
;         straightforward.
;
; EXAMPLE:
;         rho = makerho()
;
; MODIFICATION HISTORY:
; 10/8/2004 David G. Grier, New York Universty, created.
; 06/05/2006: DGG. Use calibration constants from HOLO_COMMON.
;    Added NOCAL keyword.
;
; Copyright (c) 2006 David G. Grier
; 
; LICENSE
;
;    This program is free software; you can redistribute it and/or
;    modify it under the terms of the GNU General Public License as
;    published by the Free Software Foundation; either version 2 of the
;    License, or (at your option) any later version.
;
;    This program is distributed in the hope that it will be useful,
;    but WITHOUT ANY WARRANTY; without even the implied warranty of
;    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
;    General Public License for more details.
;
;    You should have received a copy of the GNU General Public License
;    along with this program; if not, write to the Free Software
;    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
;    02111-1307 USA
;
;    If the Internet and WWW are still functional when you are using
;    this, you shold be able to access the GPL here: 
;    http://www.gnu.org/copyleft/gpl.html
;-

function makerho, dim = dim, cal = cal, nocal = nocal

common holo_common, c

w = c.doe_w
h = c.doe_h
if n_elements(dim) ge 1 then begin
    w = dim[0]
    if n_elements(dim) eq 2 then $
      h = dim[1] $
    else $
      h = w
    c.doe_w = w
    c.doe_h = h
endif

if keyword_set(nocal) then begin
    xc = 0.
    yc = 0.
    xfac = 1.
endif else if n_elements(cal) ge 2 then begin
    xc = double(cal[0])
    yc = double(cal[1])
    if n_elements(cal) ge 3 then $
      xfac = double(cal[2])
endif else begin
    xc = c.xc
    yc = c.yc
    xfac = c.xscale
endelse

x = (findgen(w, h) mod w) - (w - 1.)/2.
y = floor(findgen(w, h) / w) - (h - 1)/2.
rho = sqrt((y - yc)^2 + (xfac*x - xc)^2)

return, rho
end