Gtk2 Simple Image Fade

Category:	GUI Programming
Author/Contact Info	zentara of perlmonks
Description:	A very simple demo of fading between images. The one thing to note, is that composite on a pixbuf will be cumulative, so notice I reset the base pixbuf to it's original on every timer call. There may be better ways around the problem. Also I chose an alpha increment and timer speed to be effective, yet not too cpu intensive. Additionally note that I read in the images to be the same scale. In a more complex "slideshow", you will have to deal with the effects of compositing files of different sizes.
#!/usr/bin/perl use strict; use warnings; use Gtk2 '-init'; use LWP::Simple; # cheap webget, no error reporting if( ! -e 'earth.jpg' and ! -e 'moon.jpg'){ print "downloading test images, please wait\n"; foreach my $localfile('earth.jpg','moon.jpg'){ mirror( "http://zentara.net/$localfile", $localfile ); } } my $mw = Gtk2::Window->new; $mw->signal_connect('destroy', sub { Gtk2->main_quit }); my $vp = Gtk2::Viewport->new(undef, undef); $mw->add($vp); my $pixbuf = Gtk2::Gdk::Pixbuf->new_from_file_at_scale ('earth.jpg', 6 +00,600,0); my $pixbufa = $pixbuf->copy(); #my ($x, $y) = ($pixbufa->get_width, $pixbufa->get_height); #print "$x $y\n"; my $pixbuf1 = Gtk2::Gdk::Pixbuf->new_from_file_at_scale ('moon.jpg', 6 +00,600,0); my $pixbufb = $pixbuf1->copy(); #my ($x1, $y1) = ($pixbufb->get_width, $pixbufb->get_height); #print "$x1 $y1\n"; #$pixbuf1->composite ($pixbuf, $dest_x, $dest_y, $dest_width, $dest_he +ight, # $offset_x, $offset_y, $scale_x, $scale_y, $interp_type, $overa +ll_alpha) # start with base image my $toggle = 5; my $alpha = 0; $pixbufb->composite ($pixbufa, 0, 0, 600, 600, 0, 0, 1, 1, 'nearest', $alpha); # 0 <= alpha <= 255 my $image = Gtk2::Image->new_from_pixbuf ($pixbufa); $vp->add($image); $mw->set_title("fade demo"); $mw->show_all(); my $id = Glib::Timeout->add (100, \&sequence); Gtk2->main; sub sequence{ $alpha += $toggle; print "$alpha\n"; if ($alpha == 255){ $toggle = -5 } if ($alpha == 0){ $toggle = 5 } $pixbufb->composite ($pixbufa, 0, 0, 600, 600, 0, 0, 1, 1, 'nearest', $alpha); # 0 <= alpha <= 255 $image->set_from_pixbuf ($pixbufa); Gtk2->main_iteration while Gtk2->events_pending; # prevents accumulation of pixbuf changes $pixbufa = $pixbuf->copy(); return 1; }

Comment on Gtk2 Simple Image Fade Download Code

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Re: Gtk2 Simple Image Fade
by zentara (Archbishop) on Jan 21, 2009 at 18:07 UTC

#!/usr/bin/perl
use strict;
use warnings;
use Gtk2 '-init';

# a list to get most of the standard graphic formats into a glob
my @exts = qw(wbmp wmf jpeg jpg bmp gif pcx png pnm pbm 
               pgm ppm tga targa xbm tiff tif xpm );
 
@exts = map { $_ = "*.$_" } @exts;   #map to setup the glob below
my @files = <@exts>; #non recursive
if(scalar @files == 0){ die "No photo files found\n" }
print "@files\n";


my $mw = Gtk2::Window->new;
$mw->signal_connect('destroy', sub { Gtk2->main_quit });

my $vp = Gtk2::Viewport->new(undef, undef);
$mw->add($vp);

# start with base image
my $alpha =  0;
my $next = 0;
my $pb_base = Gtk2::Gdk::Pixbuf->new_from_file_at_scale ($files[0], 60
+0,600,0);
my $pb_base_orig = $pb_base->copy();
#get next pixbuf
push (@files,shift(@files));  
my $pb_next = Gtk2::Gdk::Pixbuf->new_from_file_at_scale ($files[0], 60
+0,600,0);

my $image = Gtk2::Image->new_from_pixbuf ($pb_base);
$vp->add($image);
$mw->set_title("fade demo");
$mw->show_all();

my $id = Glib::Timeout->add (100, \&sequence);

Gtk2->main;

sub sequence{

   if( $next ){
      # set base to be the previous next
      $pb_base = $pb_next;
      $pb_base_orig = $pb_base->copy();
      $image->set_from_pixbuf ($pb_base);
      Gtk2->main_iteration while Gtk2->events_pending;
      
      #get next pixbuf
      push (@files,shift(@files));  
      $pb_next = Gtk2::Gdk::Pixbuf->new_from_file_at_scale ($files[0],
+ 600,600,0);
      $next = 0;
      $alpha = 0;

    }else{
    
    $alpha += 5;
    print "$alpha\n"; 
    if ($alpha == 255){ $next = 1; }  
    
   #$pixbuf1->composite ($pixbuf, $dest_x, $dest_y, $dest_width, $dest
+_height,
    #       $offset_x, $offset_y, $scale_x, $scale_y, $interp_type, $o
+verall_alpha)

    $pb_next->composite ($pb_base, 0, 0, 600, 600,
           0, 0, 1, 1, 'nearest', $alpha);  # 0 <= alpha <= 255
    
    $image->set_from_pixbuf ($pb_base);
}

    Gtk2->main_iteration while Gtk2->events_pending;
    # prevents accumulation of pixbuf changes
    $pb_base = $pb_base_orig->copy();
 return 1;
}
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