Ron,
I wrote this a while back, allows edge values to be extrapolated or inserts
a value for missing. Definitely handy for image processing.
regards
Martin
; %M_FILE: h:\martin\idl\ra\math\mrd_shift.pro %
; %M_CREATED: 18/09/2001 10:39:26 %
; %M_MODIFIED: 18/09/2001 13:16:42 %
; %M_AUTHOR: MRD %
function mrd_shift, a, sa, MISSING=MISSING, EXTRAPOLATE=EXTRAPOLATE
;+
; MRD_SHIFT
; enhanced SHIFT function
;
; a - the array (upto 4 dim)
; sa - shift array [sx,sy,..]
; This enhanced function deals with data wrapping
; i.e. the data shifted in from array edges, in three possible ways:
; (default): data WRAPs (this is SHIFT's behaviour)
; MISSING: use this value in cells shift in from outside the dataset
; EXTRAPOLATE: ie use nearest data value (replicates original edge)
;
; restictions: none known
; Author: MR Downing 17/9/2001
;-
a1 = shift(a,sa)
s = size(a)
if s(0) gt 4 then message, "not implemented above 4 dimentions
if keyword_set(EXTRAPOLATE) then begin
dim = 1
if s[0] ge dim and n_elements(sa) ge dim then begin
sh = sa[dim-1] mod s(dim)
for i = 0, (abs(sa[dim-1]) < s(dim) ) -1 do begin
if sh ge 0 then begin
a1[i,*,*,*] = a1[sh,*,*,*]
endif else begin
a1[s(dim)-1-i,*,*,*] = a1[s(dim)+sh-1,*,*,*]
endelse
endfor
endif
dim = 2
if s[0] ge dim and n_elements(sa) ge dim then begin
sh = sa[dim-1] mod s(dim)
for i = 0, (abs(sa[dim-1]) < s(dim) ) -1 do begin
if sh ge 0 then begin
a1[*,i,*,*,*] = a1[*,sh,*,*,*]
endif else begin
a1[*,s(dim)-1-i,*,*,*] = a1[*,s(dim)+sh-1,*,*,*]
endelse
endfor
endif
dim = 3
if s[0] ge dim and n_elements(sa) ge dim then begin
sh = sa[dim-1] mod s(dim)
for i = 0, (abs(sa[dim-1]) < s(dim) ) -1 do begin
if sh ge 0 then begin
a1[*,*,i,*,*,*] = a1[*,*,sh,*,*,*]
endif else begin
a1[*,*,s(dim)-1-i,*,*,*] = a1[*,*,s(dim)+sh-1,*,*,*]
endelse
endfor
endif
dim = 4
if s[0] ge dim and n_elements(sa) ge dim then begin
sh = sa[dim-1] mod s(dim)
for i = 0, (abs(sa[dim-1]) < s(dim) ) -1 do begin
if sh ge 0 then begin
a1[*,*,*,i,*,*,*] = a1[*,*,*,sh,*,*,*]
endif else begin
a1[*,*,*,s(dim)-1-i,*,*,*] = a1[*,*,*,s(dim)+sh-1,*,*,*]
endelse
endfor
endif
endif else if defined(MISSING) then begin
dim = 1
if s[0] ge dim and n_elements(sa) ge dim then begin
sh = -s(dim) > sa[dim-1] < s(dim)
if sh gt 0 then begin
a1[0:sh-1,*,*,*]=MISSING
endif else if sh lt 0 then begin
a1[s(dim)+sh:s(dim)-1,*,*,*]=MISSING
endif
endif
dim = 2
if s[0] ge dim and n_elements(sa) ge dim then begin
sh = -s(dim) > sa[dim-1] < s(dim)
if sh gt 0 then begin
a1[*,0:sh-1,*,*]=MISSING
endif else if sh lt 0 then begin
a1[*,s(dim)+sh:s(dim)-1,*,*]=MISSING
endif
endif
dim = 3
if s[0] ge dim and n_elements(sa) ge dim then begin
sh = -s(dim) > sa[dim-1] < s(dim)
if sh gt 0 then begin
a1[*,*,0:sh-1,*]=MISSING
endif else if sh lt 0 then begin
a1[*,*,s(dim)+sh:s(dim)-1,*]=MISSING
endif
endif
dim = 4
if s[0] ge dim and n_elements(sa) ge dim then begin
sh = -s(dim) > sa[dim-1] < s(dim)
if sh gt 0 then begin
a1[*,*,*,0:sh-1]=MISSING
endif else if sh lt 0 then begin
a1[*,*,*,s(dim)+sh:s(dim)-1]=MISSING
endif
endif
endif
return , a1
end
pro test, vol, s1=s,shift_arr=sh_arr, byte=byte
if undefined(sh_arr) then sh_arr = [20,10,45]
if undefined(vol) then begin
vol = dist(s,s)
if keyword_set(byte) then vol = bytscl(vol)
if keyword_set(double) then vol = double(vol)
vol = rebin(vol,s,s,s, /sample)
endif
help, vol
t0= systime(1)
vol1 = shift(vol, sh_arr)
t1= systime(1)
print, "shift: done in ", t1-t0, " sec"
t0= systime(1)
vol1 = mrd_shift(vol, sh_arr, /ext)
t1= systime(1)
print, "mrd_shift /ext: done in ", t1-t0, " sec"
t0= systime(1)
vol1 = mrd_shift(vol, sh_arr, missing=-1)
t1= systime(1)
print, "mrd_shift mis: done in ", t1-t0, " sec"
t0= systime(1)
vol1 = mrd_shift(vol, sh_arr)
t1= systime(1)
print, "mrd_shift: done in ", t1-t0, " sec"
end
--
----------------------------------------
Martin Downing,
Clinical Research Physicist,
Grampian Orthopaedic RSA Research Centre,
Woodend Hospital, Aberdeen, AB15 6LS.
"ronn kling" <ronn@rlkling.com> wrote in message
news:B9F5202A.78C0%ronn@rlkling.com...
> Hello All,
>
> I was wondering if anyone has a routine out there that allows you to shift
> an array without wrapping? The shift routine works great but anything
that
> gets pushed off on one edge gets wrapped around to the other. I just want
to
> throw this wrapped part away. A simple 1D example is
>
> in = [1,2,3,4,5]
> print, shift(in,2)
> IDL> 4,5,1,2,3
>
> what I want is
>
> print, shiftNoWrap(in,2)
> IDL> 0,0,1,2,3
>
> Of couse, it really needs to work on a 2D image....
>
> Thanks,
> Ronn
>
>
> --
> Ronn Kling
> KRS, inc.
> email: ronn@rlkling.com
> "Application Development with IDL" programming book updated for IDL5.5!
> "Calling C from IDL, Using DLM's to extend your IDL code"!
> "Power Graphics with IDL, A Beginner's Guide to Object Graphics", NEW
BOOK!
> http://www.rlkling.com/
>
>
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