nikwasi has asked for the wisdom of the Perl Monks concerning the following question:

Hi,

I am creating a screen capture gui using perl/TK. The script will capture a screen using imageMagick. I then display the captured image in my main window. I would like to delete the image and remove it from the display. I tried using destroy(), however I get the following error when I attempt to delete: 

 Tk::Error: Can't call method "destroy" without a package or object re
+ference at ./Capture4.pl line 80.
 Tk callback for .frame.pane.frame.frame.button
 Tk::__ANON__ at /usr/lib/perl5/Tk.pm line 250
 Tk::Button::butUp at /usr/lib/perl5/Tk/Button.pm line 175
 <ButtonRelease-1>
 (command bound to event)

[download]

I would like the window to redraw without the image. Perhaps there is a better way to do this? Any help would be appreciated. Oh! here is the code to the script 

#!/usr/bin/perl -w

use strict;
use Tk;
use Tk::WinPhoto;
use Tk::JPEG;
use Tk::Pane;

my $mw = MainWindow->new();
$mw->minsize(qw(670 510));
$mw->configure(-background=>'gray');
$mw->title("Screen Capture GUI"); 

my $img_count = 0;

my $but_capture = $mw->Button( -text => "Capture Screen", -command => 
+sub { \&Grab() } );
$but_capture -> place(-x=>10,-y=>5, -width=>650);

my $exit = $mw->Button( -text => "Exit", -command => sub { exit } );
$exit -> place(-x=>560,-y=>460, -width=>100);

my $frame2_1 = $mw->Scrolled(qw/Pane -scrollbars ose/);
$frame2_1 -> place(-x=>10,-y=>50, -width=>650, -height=>400 );



MainLoop();


sub Grab(){

######################################################################
+####
#Creating file handle and taking picture
my $tim = time();
my $fname = "/tmp/".$tim.".jpg";
print "$fname\n";
system("import -frame $fname");

#resize to display in window
my $fname2=$fname."sm.jpg";
system("convert -size 350X350 $fname -resize 350x350 $fname2");

######################################################################
+####
$img_count++;
my $mini;

#Frame packed in scrolling Pane
$mini = $frame2_1->Frame(-background=>'#3300ff')->pack(-anchor => 'w',
+ -fill =>"x");


#create new frame to hold new image contents

my $img_label = $mini->Label(-text=>"Image $img_count");
$img_label ->pack();

my $pic_location = $mini->Label(-text=>"Pathname:");
$pic_location ->pack(); 

my $pic_fname = $mini->Entry(-width=>50,-textvariable=>"$fname");
$pic_fname ->pack(); 

my $pic = $mini->Photo( -file =>"$fname2");
my $f =$mini->Label(-image => $pic);
$f ->pack();

my $but_delete = $mini ->Button( -text => "Delete Image", -command => 
+sub { \&Delete($mini) } );
$but_delete -> pack();

my $blank1 = $frame2_1->Label(-text=>"");
$blank1 ->pack();
}

sub Delete(){
my $fn =@_;
$fn ->destroy;
}

[download]

Replies are listed 'Best First'.
Re: Issue destroying image using perl/TK
by lamprecht (Friar) on Mar 22, 2011 at 22:22 UTC
    my $fn =@_;

    does not do what you think it does


    Cheers, Christoph
[reply]
[d/l]

      Specifically,
          my $fn = @_;
      initializes  $fn with the number of elements in the  @_ array (array evaluated in scalar context). What is almost certainly wanted is
          my ($fn) = @_;
      or better yet
          my $fn = shift;
      to initialize  $fn with the first element (index 0) of the array, Update: which, in this case, is an object reference by which an object method is called.

[reply]
[d/l]
[select]

        This did the trick. Thanks

        @_ is the list of incoming parameters to a subroutine. What is the significants of () around the scaler pv?

[reply]
Re: Issue destroying image using perl/TK
by Khen1950fx (Canon) on Mar 23, 2011 at 10:25 UTC
    Your screen capture doesn't work. Based on this, here's a sub that does a full capture. 
    #!/usr/bin/perl

use strict;
use warnings;
use Tk;
use Tk::WinPhoto;

my $mw = MainWindow->new();
full_capture();

MainLoop;

sub full_capture {
    my @id = grep { $_ =~ 'Window id' } split( "\n", `xwininfo -root` 
+);
    my @ids = split( ' ', $id[0] );
    ( my $id ) = grep { $_ =~ /0x/ } @ids;

    my $image = $mw->Photo(
        -format => 'Window',
        -data   => oct( $mw->id ),
        -data   => oct('0x00022'),
        -data   => oct($id)
    );

    my $pathname = './rootwindow.' . time . '.png';
    $image->write( $pathname, -format => 'BMP | PPM | XPM' );
}

    [download]
[reply]
[d/l]
      I have seen code similar to this, however it does not do everything I needed.

      I am using imagemagick to perform the screen grab. It has features for grabbing the window under the cursor and rubber-banding regions with the mouse. I particularly like the -frame option that allows the image to capture the window manager frame. Being a separate application, it must be installed on the linux platform for it to work. It can be downloaded from:

      http://www.imagemagick.org/script/index.php

      PS. The command line invocation for imagemagick is a bit misleading. The command to make a screen grab is 

      import -frame some_pic_name.jpg

      [download]
      Cheers, Tim
[reply]
[d/l]

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