Tk::JPEG

[Amoe]

I'm a pretty total newbie to Tk, and I wanted to play with JPEG support. I searched CPAN and checked out Tk::JPEG, which seemed suited for my purposes. So I installed it, read the Tk documentation and tried to write a small script which will display the file 'test.jpg'. However, when I tried to run this:

use strict;
use warnings;
use Tk;
use Tk::JPEG;

my($main_window);

$main_window = MainWindow->new();
$main_window->Photo(-format => 'jpeg', -file => 'test.jpg')->pack;
MainLoop;

I was greeted with the fateful words:

'wrong # args: should be "pack option arg ?arg ...?" at tk.pl line 9.'

Not to be put off, I tried specifying more arguments to the pack function., specifically '-side => 'bottom'' and '-expand => 1'. Rather annoyingly, this caused the following incomprehensible error message:

'bad option "image1": must be configure, forget, info, propagate or sl
+aves at tk.pl line 9'

Removing either of the arguments furnished no solution. The most helpful thing someone could do here would just be to post a very basic chunk of Tk::JPEG using code, that I could learn from. I expect it's something really simple I'm missing here, but hey, better to ask and be a fool for five minutes...

[ichimunki]

You can't attach a Photo to a MainWindow (Correction: Yes, you can, see Jouke's great example "below"). It needs to belong to a Label or a Button or a Text widget (and probably others).

my $mw = MainWindow->new;
my $button = $mw->Button()->pack();
my $photo = $button->Photo( -format => 'jpeg', -file => 'test.jpg' );
$button->configure( -image => $photo );
MainLoop;

See also the perldoc for Tk::Photo, it's infinitely more useful than the docs for Tk::JPEG.

Update: now tested, added configure method, without which Tk never realizes it's supposed to be the -image for $button.

[Amoe]

Aha. I thought it was something obvious, and I had probably read the wrong docs...*hits self* Thanks a lot.

[Jouke]

And of course you can define all of this at once:

  my $mw = MainWindow->new;
  my $photo = $button->Photo( -format => 'jpeg', 
                              -file   => 'test.jpg' );
  my $button = $mw->Button(-image => $photo)->pack();
  MainLoop;



Jouke Visser, Perl 'Adept'
Using Perl to help the disabled: pVoice and pStory

[ichimunki]

I think it's a little strange to call a method on $button before you have declared $button with my $button. Maybe you patched your parser with a lookahead feature, "hey, do I declare this later, if so I can use it now, right?" :)