>>>> > "Pryhoda" == PRYHODA <bjp8350@osfmail.isc.rit.edu> writes:
In article <1995May10.175428.15046@ultb.isc.rit.edu> bjp8350@osfmail.isc.rit.edu (PRYHODA) writes:
Pryhoda> How can I seperate the LONGWORD VECTOR into its X and Y
Pryhoda> components? so I can use the distance formula. Or is there an
Pryhoda> easier way to find the distance between each pixel?
I have a function the changes a one-dimensional index for an array
into its multi-dimensional version. It more generally performs
decoding for arbitrary dimensions/radix/bases.
It is not necessarily the best solution for your particular problem,
but I find it useful in a large variety of instances.
I have included the function below. See the EXAMPLE section in the
header.
I hope this is useful. If you have improvements, please let me know.
Thanks,
Chris
--- Begin included file ------
FUNCTION Decode, scl, dim, help=help, quiet=quiet
;+
; $Id: decode.pro,v 1.4 1995/05/10 16:20:27 chase Exp $
;
; NAME:
;
; DECODE
;
; PURPOSE:
;
; Decode a vector of scalars into the dimensions d1,...,dn in order
; of increasing significance. Useful for conversions between
; different base/radix, time conversions, etc. See EXAMPLE below.
;
; CATEGORY:
;
; Mathematical Functions
;
; CALLING SEQUENCE:
;
; Result = DECODE(Scl, Dim)
;
; INPUTS:
;
; Scl - Vector of scalars to be decoded.
;
; Dim - If a scalar, then it is used as a repeated base for the
; decoding, i.e., D1,...,DN=Dim.
; If a 1 dimensional vector, then it is taken as the
; dimensions D1,...,DN.
; If > 1 dimensional array, then the dimensions of the array
; are used for D1,...,DN.
; The dimensions increase in significance, i.e., the first
; dimension is the least significant and the last dimension is
; the most significant.
;
; Dim need not be integral.
;
; D1*D2*...*DN must be representable to the precision of a double
; for the results to be accurate.
;
; KEYWORD PARAMETERS:
;
; HELP - Provide help (this information). No other action is performed.
;
; QUIET - Do not print warning when Scl is outside total dimensions.
;
; OUTPUTS:
;
; Result - Array of size NxM where M is dimension of Scl. Array has
; the same type as Scl. Result(*,i) is the decoding of the
; scalar Scl(i). If Scl(i) is larger then the dimensioned
; size, i.e. D1*D2*...*DN, then the modulus, Scl(i) mod
; D1*D2*...*DN, is decoded. Result(j-1,i) corresponds to
; dimension Dj with Result(N-1,i) the most significant
; digit of the decoding.
;
; PROCEDURE:
;
; Let b0,...,bN be the decoding. Then Scl can be represented as:
;
; Scl = D1*D2*...*D[N-1]*bN + ... + D1*D2*b3 + D1*b2 + b1
;
; = D1(D2(...(D[N-1]*bN + b[N-1])...+ b2 ) + b2) + b1
;
;
; with 0 <= bi < Di, and b2,...,bN integral.
; If Scl is floating point then b1 may not be integral.
;
; The representation is unique for Scl, i.e., there are not two
; distinct decodings resulting in the same Scl.
;
; EXAMPLE:
;
; scl = [20,63]
; ; Conversion to base 16
; print,decode(scl,16)
;
; ; Convert times in seconds to second, minute, hour, day
; t = [1.,60.,3600.d0,24.*3600d0] # [[32,55,10,2],[59,0,23,364]]
; print,t
; print,decode(t,[60,60,24,365])
;
; ; Conversion to binary (base 2)
; print,decode(scl,2)
; ; Invert the decoding
; print,2^indgen(5)#decode(scl,2)
;
; ; Arbitrary decoding. Generates a warning for decoding 63 in
; ; which case (63 mod 3*4*5) = 3 is decoded.
; print,decode(scl,[3,4,5])
; print,[1,3,3*4]#decode(scl,[3,4,5])
; print,[1,3,3*4,3*4*5]#decode(scl,[3,4,5,6])
;
; ; Convert 1D index into a multi-dimensional index
; w=dist(20,20)
; a=max(w,i)
; ; Get 2D index for max
; print,decode(i,w)
;
; MODIFICATION HISTORY:
;
; Mon Feb 27 16:13:20 1995, Chris Chase S1A
; <chase@retro.jhuapl.edu>
;
; Handles non-integral dimensions and inputs.
;
; Mon Jul 18 15:58:18 1994, Chris Chase S1A <chase@jackson>
; Fixed/cleaned up.
;
; Mon Jul 26 12:17:56 1993, Chris Chase <chase@aphill>
; Created. Named for similar APL function.
;
;-
if keyword_set(help) then begin
doc_library, 'decode'
return, ''
endif
s = size(dim)
if (s(0) eq 0) then begin
d = replicate(dim, ceil(alog(max(scl))/alog(dim)))
endif else begin
if (s(0) gt 1) then d = s(1:s(0)) $
else d = dim
endelse
nd = n_elements(d)
;; Use double to make sure it is big enough
dd = double(d)
for i=1, nd-1 do dd(i) = dd(i)*dd(i-1)
v = scl
if max(v/dd(nd-1)) gt 1 then begin
if not keyword_set(quiet) then begin
print, "Warning - function DECODE: scalar outside dimension " + $
"bounds, decode of modulus returned."
endif
v(*) = v(*) mod dd(nd-1)
endif
index = replicate(v(0), nd, n_elements(v))
for i = nd-1, 1, -1 do begin
f = long(v/dd(i-1))
index(i, *) = f
v = v-f*dd(i-1)
endfor
index(0, *) = v
return, index
end
--
===============================
Bldg 24-E188
The Applied Physics Laboratory
The Johns Hopkins University
Laurel, MD 20723-6099
(301)953-6000 x8529
chris.chase@jhuapl.edu
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