Re: getting color from gdk::pixbuf (probably a bug in Gdk::Pixbuf)

[doome <doome uhulinux hu>]

Is it possible that the get_pixels function doesn't work?
The get_pixels function returns nothing, however the png image shows up
in the Gtk2::Image.

$pixbuf = Gtk2::Gdk::Pixbuf->new_from_file(foobar.png);
$image = Gtk2::Image->new_from_pixbuf($pixbuf);
$pixels = $pixbuf->get_pixels;

The $image shows up in the window, but the $pixels string is empty.

Using the latest stable releases: Glib2 1.022   Gtk2 1.023



On 02 Mar 2004 15:02:23 -0500
muppet <scott asofyet org> wrote:

> 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>
> 
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> 


-- 
Domsodi Gergely / UHU-Linux