Perl Imager::Screenshot not doing screenshot with default parameters -

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i have following code:

use imager::screenshot 'screenshot'; $img = screenshot(hwnd => 'active',      left => 450,      right => 200,      top => 50,      bottom => 50 ); $img->write(file => 'screenshot.png', type => 'png' ) ||      print "failed: ", $img->{errstr} , "\n";

it prints:

"can't call method "write" on undefined value @ line 3"

but when do:

use imager::screenshot 'screenshot'; $img = screenshot(hwnd => 'active',      left => 100,       right => 300,       top => 100,       bottom => 300 );  $img->write(file => 'screenshot.png', type => 'png' ) ||       print "failed: ", $img->{errstr} , "\n";

it take screenshot. why left, right, top , bottom values matter here?

edit: after research found out left param must smaller right param , top must smaller bottom.

have tried checking error? e.g.

my $img = screenshot(...) or die imager->errstr;

edit: try code:

use imager::screenshot 'screenshot'; $img = screenshot(hwnd => 'active',     left => 450,      right => 200,      top => 50,      bottom => 50 ) or die imager->errstr; $img->write(file => 'screenshot.png', type => 'png' ) ||      print "failed: ", $img->errstr, "\n";

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