Newsgroups: comp.archives
Path: utzoo!utgpu!news-server.csri.toronto.edu!ox.com!emv
From: raja@bombay.cps.msu.edu (Narayan S. Raja)
Subject: [graphics] Re: How do I separate color images into RGB channels.
Message-ID: <1991Jan10.213252.23290@ox.com>
Followup-To: comp.graphics
Keywords: color, RGB
Sender: emv@ox.com (Edward Vielmetti)
Reply-To: raja@cpswh.cps.msu.edu
Organization: PRIP Lab, Comp. Sci. Dept., MSU
References: <651@ub.d.umn.edu> <1991Jan10.111006.11356@msuinfo.cl.msu.edu>
Date: Thu, 10 Jan 1991 21:32:52 GMT
Approved: emv@ox.com (Edward Vielmetti)
X-Original-Newsgroups: comp.graphics

Archive-name: graphics/pixutils/fbm/1991-01-10
Archive: nl.cs.cmu.edu:/usr/mlm/ftp/fbm.tar.Z [128.2.222.56]
Original-posting-by: raja@bombay.cps.msu.edu (Narayan S. Raja)
Original-subject: Re: How do I separate color images into RGB channels.
Reposted-by: emv@ox.com (Edward Vielmetti)


In article <651@ub.d.umn.edu>, (Haseen I. Alam) writes:

<  I need to get hold of some programs that will run in SunTools, and will
<  allow me to separate a color image into its RGB channels and display them
<  separately.  It will be nice if it will recombine them again.


Get Michael Mauldin's "FBM" set of utilities:
  available by anonymous ftp from the "/usr/mlm/ftp" 
  subdirectory on nl.cs.cmu.edu (128.2.222.56).
  (You can only cd straight to that directory).

The FBM utilities are independent of your windowing
environment.  I assume you want to work with 8-bit 
colour Sunraster files.

------------------------------------------------------
Going from 8-bit colour to the 3 colour planes is
easy:

   cat image.ras | clr2gray -S -r1 > image.red.ras
   cat image.ras | clr2gray -S -g1 > image.grn.ras
   cat image.ras | clr2gray -S -b1 > image.blu.ras

(The 3 colour planes are themselves extracted as
 Sun grayscale rasterfiles).

Going from 3 colour planes back to an 8-bit colour
image is somewhat painful (anyone know a better way?):

 1. remember the number of rows and columns
 2. strip off the header by some means, leaving
      3 "raw" images (just the bytes, no header)
 3. concatenate these raw files in the order r,g,b:

      cat image.red.raw image.grn.raw image.blu.raw > image.raw

 4. convert to fbm format:

      raw2fbm -d3 -hrows -wcols < image.raw > image.fbm

    where rows=no. of rows, cols=no. of columns

 5. quantize to 8 bits:

      fbquant -S < image.fbm > image.8-bit-ras
------------------------------------------------------

Narayan Sriranga Raja.