Re: iterating POLY_2D

[David Williams <d.williams(at)qub.ac.uk>]

Just as a postscript...

Christophe Morisset helpfully suggested that I also post the routine
that's giving me bother. It's included below. I'd really appreciate any
help anyone can give.


Dave Williams.

-- 
;+
;NAME:
;   	frames_move.pro
;PURPOSE:
;   	To remove the shaking from a sequence of digital
;   	images in the form of a 50x40x200 floating point
;   	array.
;INPUTS:
;   	DATA - the input array
;OUTPUTS:
;   	DATAOUT - the stabilised sequence
;   	DISPARR - the 2x200 array containing the
;   	    displacement co-ordinates relative to
;   	    DATA(*,*,0).
;-
PRO frames_move,data,dataout,disparr

sizD=SIZE(data)
disparr=fltarr(2,sizD(3))
dataout=fltarr(sizD(1),sizD(2),sizD(3))
dataout(*,*,0)=data(*,*,0)
;the original image will be the same in the output
;as it's the reference point from which
;the displacement in the rest of the images
;is measured.

;make the temporary gradient array to
;define the edges of the main feature:
gradex=fltarr(sizD(1),sizD(2),sizD(3))
FOR g=0,sizD(3)-1 DO BEGIN
    gradex(*,*,g)=grad(data(*,*,g))
    ;(I've included this GRAD function
    ;below in a commented section. It
    ;comes from the IDL User's Guide.)
ENDFOR

;set up the comparison array BIGJUMP and the
;contents of the first image equal to
;the original image in the sequence passed.
bigjump=fltarr(sizD(1)-1,sizD(2)-1,2)
bigjump(*,*,0)=gradex(1:sizD(1)-1,1:sizD(2)-1,0)

FOR k=1,sizD(3)-1 DO BEGIN
    bigjump(*,*,1)=gradex(1:sizD(1)-1,1:sizD(2)-1,k)
    ;set the second image equal to the image
    ;that is to be compared to the original image,
    ;removing the first X and Y lines which get
    ;wrapped around by the GRAD routine.
    
    dxy=tr_get_disp(bigjump)
    ;dxy is created by a specialised routine
    ;written for the TRACE SolarSoft IDL distribution
    disparr(0,k)=-dxy(0,1)
    disparr(1,k)=-dxy(1,1)
    ;get the cross-correlation displacement
    
    ;this is the bit I'm having trouble iterating successfully:
    dataout(*,*,1)=POLY_2D(data(*,*,1),$
    [disparr(0,k),0.,1.,0.],$
    [disparr(1,k),1.,0.,0.],cubic=-0.5)
    PRINT,'polynomial interpolation completed for iteration
'+ARR2STR(k,/trim)
    
ENDFOR

END

;the GRAD.PRO function is as follows, and is used in FRAMES_MOVE.PRO
;to enhance the accuracy of the routine by detectin the edges of the
;slightly fuzzy main feature:
;
;FUNCTION GRAD, IMAGE
;
;RETURN, ABS(IMAGE - SHIFT(IMAGE,1,0)) + $
;    ABS(IMAGE-SHIFT(IMAGE,0,1))
;   
;END
;

=============================================================
David R. Williams,		Tel.: (+44 1232) 273509
APS Division,
Pure & Applied Physics Dept.,
Queen's University,
Belfast,
BT7 1NN.		http://star.pst.qub.ac.uk/~drw/
=============================================================