comp.lang.idl-pvwave archive: archive » Re: Avoiding FOR loops (version googleplex.infinity)

Home » Public Forums » archive » Re: Avoiding FOR loops (version googleplex.infinity)

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: Avoiding FOR loops (version googleplex.infinity) [message #59808 is a reply to message #59727]

Wed, 09 April 2008 23:13

Gaurav
Messages: 50
Registered: January 2007

Member

Dear All,
Over the past two days I was able to think of an algorithm and it
solved my problem. And now, looking at Tom's solution above, it
appears that it is almost the same thing that I came up with.

What I did was to pad up my image with kernelSize/2 pixels all around
and then compare it with temporary arrays shifted all around the
kernel by turn. Wherever the shifted array was equal to the padded
array, I added one in the final, output array. Run this loop for the
kernel size and you are done. Now it is up to you guys to decide if it
is exactly the same as Tom's or there is some difference and as to
which would be faster. Here follows my code:

################### Code begin ################################
dims = size(img,/dimensions) ; getting the dimensions of input image
output_img = bytarr(dims(0), dims(1))

kernelSize = 5 ;define the kernel size (here, 5)
padSize = FLOOR(kernelSize /2.0) ;calculate the padding to generate
around the original image
paddedImg = bytarr(dims(0)+2*padSize, dims(1)+2*padSize) ;initialize
the padded image
paddedImg(padSize, padSize) = img ;define the padded image
tempImg = bytarr(dims(0)+2*padSize, dims(1)+2*padSize) ;will contain
the padded, final output

for x = -padSize, padSize do begin
for y = -padSize, padSize do begin
if x eq 0 and y eq 0 then continue ;we do not want to compare with
the element itself
;the x, y loops shift the whole image array around the kernel and
compares the shifted image with the original
indices = WHERE(paddedImg eq SHIFT(paddedImg, x, y)) ;
tempImg(indices) = finalImg(indices) + 1 ;increment '1' wherever an
eqality is found
endfor
endfor
output_img = EXTRAC(tempImg, padSize, padSize, dims(0),
dims(1)) ;extract the output image from the padded output image.
################# end of code/algorithm ####################

In my case it works wonderfully well and speeds things up by a factor
of a few hundred times. Any further optimization would be highly
appreciated.

I guess, I ought to go for a manicure for my gnawed nails now.

Cheers,
Gaurav

Report message to a moderator

[Message index]

		Re: Avoiding FOR loops (version googleplex.infinity) By: Gaurav on Tue, 08 April 2008 02:41
		Re: Avoiding FOR loops (version googleplex.infinity) By: Gaurav on Mon, 07 April 2008 22:31
		Re: Avoiding FOR loops (version googleplex.infinity) By: MichaelT on Mon, 07 April 2008 09:27
		Re: Avoiding FOR loops (version googleplex.infinity) By: MichaelT on Mon, 07 April 2008 09:25
		Re: Avoiding FOR loops (version googleplex.infinity) By: MichaelT on Mon, 07 April 2008 09:19
		Re: Avoiding FOR loops (version googleplex.infinity) By: Tom McGlynn on Wed, 09 April 2008 08:18
		Re: Avoiding FOR loops (version googleplex.infinity) By: Gaurav on Wed, 09 April 2008 23:13
		Re: Avoiding FOR loops (version googleplex.infinity) By: nathan12343 on Tue, 08 April 2008 14:33

Previous Topic:	Re: fastest way to find the first non-zero value in an array
Next Topic:	delvar, all

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Sun Oct 12 16:32:31 PDT 2025

Total time taken to generate the page: 0.01266 seconds