Date: Wed, 8 Oct 2003 11:16:02 +0100
To: lablgtk at kaba.or.jp
Subject: Reading RGB values of a colour index from a colormap
Message-ID: <20031008101602.GA4920 at redhat.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
From: Richard Jones <rich at annexia.org>


I'm trying to write a PseudoColor image to a file. Reading pixels
from this image gives me colour indexes. I want to map these indexes
to (r,g,b) values, but there doesn't seem to be a way.

This is my working code so far (see 'XXX'):

----------------------------------------------------------------------

  let img = Gdk.Image.get pm ~x:0 ~y:0 ~width ~height in
  let vis = Gdk.Image.get_visual img in

  let depth = Gdk.Visual.depth vis in
  eprintf "visual depth = %d\n" depth;

  let colparser =
    match Gdk.Visual.get_type vis with
	`TRUE_COLOR | `DIRECT_COLOR ->
	  Gdk.Truecolor.color_parser vis
      | `PSEUDO_COLOR ->
	  (fun i ->
	     XXX)
      | _ ->
	  failwith "visual type not supported (greyscale monitor?)"
  in
	
  let chan = open_out_bin "print.ppm" in
  output_string chan (Printf.sprintf "P6 %d %d 255\n" width height);
  for y = 0 to height-1 do
    for x = 0 to width-1 do
      let pix = Gdk.Image.get_pixel img ~x ~y in
      let r, g, b = colparser pix in
      output_char chan (char_of_int r);
      output_char chan (char_of_int g);
      output_char chan (char_of_int b)
    done;
  done;
  close_out chan;

----------------------------------------------------------------------

Rich.

-- 
Richard Jones. http://www.annexia.org/ http://freshmeat.net/users/rwmj
Merjis Ltd. http://www.merjis.com/ - all your business data are belong to you.
NET::FTPSERVER is a full-featured, secure, configurable, database-backed
FTP server written in Perl: http://www.annexia.org/freeware/netftpserver/