Re: getting color from gdk::pixbuf

[muppet <scott asofyet org>]

On Tue, 2004-03-02 at 06:56, Domsodi Gergely wrote:
> Hi!
>
> I have a Gdk::Pixbuf (got it from a .png file) in a Gtk2::Image.
>
> I want to get colors of specific pixels of this image, and give it to a
> Gtk2::Gdk::Color so that I can draw with that color to a
> Gtk2::Gdk::Pixmap.
>
> How can I do this?

use $pixbuf->get_pixels to fetch the rgb image data as a packed scalar,
and then use unpack() or substr() to extract the pixels you want.  not
very efficient for large pixbufs, but perl isn't meant for bit-banging.

  #
  # warning, untested code, watch for falling bullshit
  #
  $pixels = $pixbuf->get_pixels;

  # n_channels should be 3 for rgb data, and 4 if there is alpha data.
  $depth = $pixbuf->get_n_channels;
  $offset = $row * $pixbuf->get_rowstride + $col * $depth;

  ($r, $g, $b, $a) = unpack "C*", 
                            substr $pixels, $offset, $depth;
  # $a will be undefined if $depth is 3.
  # $[rgb] will be on the range [0-255] --- bitshift them left by 8
  # for use with a Gtk2::Gdk::Color (to put them in the range
  # [0-65535]).


-- 
muppet <scott at asofyet dot org>