| Re: quick matrix algebra question [message #46858 is a reply to message #46855] |
Mon, 09 January 2006 13:17  |
Dick Jackson
Messages: 347
Registered: August 1998
|
Senior Member |
|
|
Hi Brad,
<b_gom@hotmail.com> wrote in message
news:1136835388.675373.55640@z14g2000cwz.googlegroups.com...
> I'm sure someone must have a quick solution for this problem. I have a
> color transformation that I want to apply to an RGB pixel as follows:
>
> M=fltarr(3,3)
> RGB=bytarr(3)
> ;fill RGB and M with some values
> result = transpose(M ## RGB) ;apply the transform.
To do this with consistency when there's more than one pixel, you might want
to flip things around:
IDL> m=FIndGen(3,3)
IDL> RGB=BIndGen(3)
IDL> Print,Transpose(M ## RGB)
5.00000 14.0000 23.0000
IDL> Print,RGB ## Transpose(M)
5.00000 14.0000 23.0000
Same result, but now this is extensible to a (3, n) array...
> Now, result contains the new values in the same format as RGB.
> The question is: how do I do this efficiently on an RGB image (ie a
> (3,col,row) array)? Quick, before I use a for loop!
col=40
row=50
RGB=BIndGen(3, col, row)
;; Reform RGB to (3, n)
RGB = Reform(rgb, 3, Long(col)*row, /Overwrite) ; this is fast
result = RGB ## Transpose(M) ;apply the transform.
;; Reform the arrays back to (3, col, row)
RGB = Reform(RGB, 3, col, row, /Overwrite)
result = Reform(result, 3, col, row, /Overwrite)
There you go!
Cheers,
--
-Dick
Dick Jackson / dick@d-jackson.com
D-Jackson Software Consulting / http://www.d-jackson.com
Calgary, Alberta, Canada / +1-403-242-7398 / Fax: 241-7392
|
|
|
|
comp.lang.idl-pvwave archive
Members
Search
Help
Login
Home
