Mastering Perl/Tk

Simple Photo Rotations

Using standard Photo methods, it’s possible to rotate an image 90 degrees clockwise, 90 degrees counter-clockwise, or flip it 180 degrees.^[6]

Once encapsulated in a module—call it Tk::PhotoRotateSimple—we can showcase its capabilities with this code, the result of which is shown in Figure 17-22.

use Tk;
use Tk::PhotoRotateSimple;
use subs qw/rotate/;
use strict;

my $mw = MainWindow->new;
my $p = $mw->Photo(-file => Tk->findINC('Xcamel.gif'));

rotate 'Original';
rotate 'flip';
rotate 'l90';
rotate 'r90';

MainLoop;

sub rotate {

    my $direction = shift;

    my $f = $mw->Frame(qw/-width 100 -height 100/)->pack(qw/-side left/);
    $f->packPropagate(0);
    $f->Label(-text => $direction)->pack;
    my $i = $f->Label(-image => $p)->pack(qw/-expand 1 -fill both -anchor c/);

    return if $direction eq 'Original';

    my $tmp = $mw->Photo;
    $tmp->copy($p);
    $tmp->rotate_simple($direction);
    $i->configure(-image => $tmp);
    
}

$p is our friendly camel Photo object. Using it as the original, we call rotate to rotate the image three times: 180 degrees, left 90 degrees, and right 90 degrees. The first call to rotate does no rotation, it just displays the original Photo and returns. The rotate_simple method rotates the actual Photo, so we make a temporary copy in order to preserve the original. Then call rotate_simple with flip, l90, or r90.

So much for the user’s point of view; let’s see the actual module.

Figure 17-22. Rotate window

The first thing to note is that we are extending the class Tk::Photo ...