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;+ |
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; NAME: TRK |
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; PURPOSE: |
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; This function, given an 2 images, will return the shifts in |
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; x and y direction that will align the second |
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; image b with respect to a. |
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; CATEGORY: |
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; image processing |
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; CALLING SEQUENCE: |
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; shift = trk(img,ref,mask=mask) |
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; INPUTS: |
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; |
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; img - The image that you want to track with |
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; respect to a. |
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; type: array,any type,arr(nx,ny) |
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; ref - The reference image. |
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; type: array,any type,arr(nx,ny) |
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; |
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; OUTPUTS: |
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; |
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; shifts = vector containing shifts |
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; TYPE: float(2) |
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; |
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; KEYWORDS |
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; mask = fourier filter is applied to image and reference |
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; currently available, |
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; mask = 1 -> highpass |
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; mask = 2 -> butterwoth highpass |
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; |
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; SIDE EFFECTS: None. |
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; RESTRICTIONS: None. |
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; PROCEDURE: |
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; MODIFICATION HISTORY: |
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; Dec. 91 TR |
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; Feb. 07 RW (avoids sticking to flat field) |
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;- |
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; |
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|
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function trk,img,ref,mask=mask,sub=sub,sf=sf, ccf=ccf, flatfield=flatfield |
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|
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;print,'track is running' |
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|
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;Compute sizes of a and b and nx and ny |
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sza=size(img) & szb=size(ref) |
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nx=sza(1) & ny=sza(2) |
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shifts = fltarr(2) |
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ma = 1 |
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|
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;Array size : ERROR CHECK. |
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if (sza(0) ne szb(0))or(sza(1) ne szb(1))or(sza(2) ne szb(2)) then begin |
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print,'Array sizes not equal' |
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return,0 |
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endif |
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|
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if keyword_set(sub) then begin |
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subz = sub |
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if keyword_set(mask) then begin |
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case mask of |
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1: ma = hipass(subz,subz) |
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2: ma = bwth(subz,subz) |
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endcase |
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endif |
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lox = nx/2-subz/2 |
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hix = lox+subz-1 |
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loy = ny/2-subz/2 |
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hiy = loy+subz-1 |
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|
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endif else begin |
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lox=0 |
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hix=nx-1 |
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loy=0 |
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hiy=ny-1 |
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if keyword_set(mask) then begin |
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case mask of |
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1: ma = hipass(nx,ny) |
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2: ma = bwth(nx,ny) |
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endcase |
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endif |
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endelse |
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|
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sref=ref(lox:hix,loy:hiy) |
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simg=img(lox:hix,loy:hiy) |
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if keyword_set(sf) then begin |
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sref=sref-sfit(sref,1) |
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simg=simg-sfit(simg,1) |
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endif |
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|
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;Compute fft's |
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fref=fft(sref,-1) & fimg=fft(simg,-1) |
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|
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;Compute the correlation between the two images (ccf) |
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ccf=fft(fimg*conj(fref)*ma,1) |
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|
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|
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;Compute nx/2 and ny/2 |
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sz = size(sref) |
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sx=sz(1)/2 & sy=sz(2)/2 |
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|
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;Convert ccf to float and shift. |
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ccf=float(ccf) & ccf=shift(ccf,sx,sy) |
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|
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;interpolate ccf at center point to avoid sticking to the flat field |
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|
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|
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if keyword_set(flatfield) then begin |
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c4x=(spline([findgen(7), 8+findgen(7)], [ccf[sx-7:sx-1, sy], ccf[sx+1:sx+7, sy]], findgen(15)))[7] |
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c4y=(spline([findgen(7), 8+findgen(7)], [reform(ccf[sx, sy-7:sy-1]), reform(ccf[sx, sy+1:sy+7])], findgen(15)))[7] |
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ccf[sx,sy]=0.5*(c4x+c4y) |
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endif |
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|
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;Find position of max of ccf. |
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ps=max_pos(ccf) |
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|
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;Determine shift and shift function. |
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sx=ps(0)-sx |
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sy=ps(1)-sy |
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shifts(0)=-sx |
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shifts(1)=-sy |
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|
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;print,'Shifts in x and y',-sx,-sy |
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|
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return, shifts |
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|
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end |
