;+
; NAME: 
; 	register_demo
; PURPOSE:
; Demonstrate how to use subreg.pro and mosf.pro to register and mosaic images
;
; NOTES:
;	Note that this just shows off the basics of how to use this code. 
;	subreg and mosf both have many, many options. You should take a look
;	at the documentation for each of those to find out more.  ;	Frankly, they've grown
;	a little crufty over time. None of this code is very clean! But it
;	works well enough in practice...
;
; 
; INPUTS:
; 	imgs			an array of images.
; OUTPUTS:
; 	mosaic			the final mosaic of the images
; 	mosaic_exp		an array showing how many original images (exposures) 
; 					contributed to each pixel of the output mosaic.
; KEYWORDS:
;
; HISTORY:
; 	Began 2003-07-30 21:44:38 by Marshall Perrin 
;-
;###########################################################################
;
; LICENSE
;
; This software is OSI Certified Open Source Software.
; OSI Certified is a certification mark of the Open Source Initiative.
;
; Copyright © 2003 by Marshall Perrin
;   
; This software is provided "as-is", without any express or
; implied warranty. In no event will the authors be held liable
; for any damages arising from the use of this software.
;   
; Permission is granted to anyone to use this software for any
; purpose, including commercial applications, and to alter it and
; redistribute it freely, subject to the following restrictions:
;   
; 1. The origin of this software must not be misrepresented; you must
;    not claim you wrote the original software. If you use this software
;    in a product, an acknowledgment in the product documentation
;    would be appreciated, but is not required.
;   
; 2. Altered source versions must be plainly marked as such, and must
;    not be misrepresented as being the original software.
;   
; 3. This notice may not be removed or altered from any source distribution.
;   
; For more information on Open Source Software, visit the Open Source
; web site: http://www.opensource.org.
;   
;###########################################################################


pro register_demo,imgs,mosaic,mosaic_exp

; use cross-correlations to register all images against
; the first one. There are different methods for computing
; the subpixel positioning; see the help for subreg.
; They all work about the same but sometimes one algorithm
; works a bit better than another.
subreg,imgs[*,*,0],imgs,shifts

; due to historical reasons, the mosaic-making code takes as
; input, not the shifts between images, but the coordinates
; in each image which map to the same point. But it's easy 
; enough to computer this from the shifts vector. This could 
; probably all be rewritten to be much cleaner, but it hasn't been 
; a priority yet...

sz = size(imgs)
xo = sz[1]/2 & yo = sz[2]/2  						; arbitrarily choose middle of first iamge.
dx=xo-transpose(shifts[0,*]) 						; calculate where this is in the other images
dy=yo-transpose(shifts[1,*]) 						; using the shifts relative to the first one

xstar = max(dx)
ystar = max(dy)

    for j = 0, sz[3]-1 do begin
		; make sure that we're within the right ranges. This is necessary 
		; since the FFT shift finding 'wraps', so it can return a shift of -N/2
		; instead of N/2 and so on. I should rewrite this to use where() rather
		; than a for loop...
		if dx[j] lt 0 then dx[j]=dx[j]+sz[1]
		if dx[j] gt sz[1] then dx[j]=dx[j]-sz[1]
		if dy[j] lt 0 then dy[j]=dy[j]+sz[2]
		if dy[j] gt sz[2] then dy[j]=dy[j]-sz[2]
	endfor


   ;make mosaic
   mosf, imgs, dx, dy, mosaic, mosaic_exp,/subpixel,interp_type="F"

end