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Re: Thinning algorithm without for loops [message #55285 is a reply to message #55193]

Wed, 08 August 2007 00:33

Paolo Grigis
Messages: 171
Registered: December 2003

Senior Member

[...]
>
> This code implements the first iteration of Zhang-Suen thinning
> without a single for loop!
>

You are shifting "img" too many times... you only need to compute
your neighbors values p1... p8 first, and then you can have the
next statements use that values instead, for instance

tot=p1+p2+...+p8

and so on for the other conditions.

Ciao,
Paolo

> PRO zsthin,img,thinimg
>
> siz=size(img)
>
> ;Array to hold the sums we're looking for
> tot=lonarr(siz[1],siz[2])
>
> tot+=shift(img,1,0)
> tot+=shift(img,1,1)
> tot+=shift(img,1,-1)
> tot+=shift(img,0,1)
> tot+=shift(img,0,-1)
> tot+=shift(img,-1,0)
> tot+=shift(img,-1,1)
> tot+=shift(img,-1,-1)
>
> cond3=intarr(siz[1],siz[2])
>
> cond3[*,*]=1
>
> cond3*=shift(img,1,0)
> cond3*=shift(img,-1,0)
> cond3*=shift(img,0,-1)
>
> ;4. If P[1]*P[3]*P[5]=0
>
> cond4=intarr(siz[1],siz[2])
> cond4[*,*]=1
>
> cond4*=shift(img,0,1)
> cond4*=shift(img,1,0)
> cond4*=shift(img,0,-1)
>
> ;2. The number of 0-1 transitions in the ordered sequence
> ;P[1],P[2],...,P[8],P[1] Is exactly 1
>
>
> p1=shift(img,0,1)
> p2=shift(img,1,1)
> p3=shift(img,1,0)
> p4=shift(img,1,-1)
> p5=shift(img,0,-1)
> p6=shift(img,-1,-1)
> p7=shift(img,-1,0)
> p8=shift(img,-1,1)
>
> cond2=intarr(siz[1],siz[2])
>
> p=[[[p1]],[[p2]],[[p3]],[[p4]],[[p5]],[[p6]],[[p7]],[[p8]],[ [p1]]]
>
> FOR i=0,7 DO BEGIN
> wh=where(p[*,*,i] eq 0 AND p[*,*,i+1] eq 1)
> cond2[wh]+=1
> ENDFOR
>
> tvscl,cond2
>
> wh=where(cond2 eq 1)
>
> cond2[*,*]=0
>
> cond2[wh]=1
>
> wh=where(tot GE 2 AND tot LE 6 AND cond3 eq 0 AND cond4 eq 0 AND cond2
> eq 1)
>
> wh11=intarr(siz[1],siz[2])
>
> wh11[wh]=1
>
> newimg=img-wh11
>
> newimg>=0
>
>
> END
>
>
> I'll do the second subiteration in a bit, should be too hard.
>

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[Message index]

		Re: Thinning algorithm without for loops By: nathan12343 on Tue, 07 August 2007 14:57
		Re: Thinning algorithm without for loops By: nathan12343 on Tue, 07 August 2007 11:45
		Re: Thinning algorithm without for loops By: Conor on Tue, 07 August 2007 06:28
		Re: Thinning algorithm without for loops By: Jeff N. on Mon, 06 August 2007 12:55
		Re: Thinning algorithm without for loops By: JD Smith on Wed, 08 August 2007 14:33
		Re: Thinning algorithm without for loops By: Paolo Grigis on Wed, 08 August 2007 00:33

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