I've just had a look at the source code for version 0.73 or PDF::API2, and it looks like the paragraph() method is hard-coded to work downwards from the height that you specify. It works through the provided text from start to end, fitting as much as possible on each line, then repeating with the remaining text.

However, it does tell you how much of the height it used, when called in a list context:

($text_remaining, $height_remaining) = $txt->paragraph('long paragraph
+ here ...', $width, $height, -align => 'center');
[download]

$height -= $height_remaining/2; # untested!
[download]

It worked!!!


Instead of dummy text, I wrote the original text in white color. The background is white. So the white text is not viewable in the pdf. Is it a bad idea?? Is there any other way instead of putting the original text?

$text->fillcolor('#ffffff');
$text->translate($x, $y);
($overflow_text, $height_remaining) = $text->paragraph(qq{text here}, 
+$width, $height);
[download]

$y is re-calculated with respect to $height_remaining.


$y -= $height_remaining / 2;
[download]

Now I wrote the text again in black font. So now the text is vertically aligned in the given height.

$text->fillcolor('#000000');
$text->translate($x, $y);
$text->paragraph(qq{text here}, $width, $height);
[download]

Thanks again!!!

Another angle of attack is to try to solve the problem by subclassing/overriding.

For example here's the code from PDF::API2::Content for outputting centered text.

sub text_center
{
  my ($self,$text,@opts)=@_;
  my $width=$self->advancewidth($text);
  return $self->text($text,-indent=>-($width/2),@opts);
}
[download]

The following overrides the text method, giving us the ability to disable text output at will, allowing to precompute the height of the paragraph:

#!/usr/bin/perl
package PreflightText;
use common::sense;

use base 'PDF::API2::Content::Text';

our $PREFLIGHT;

sub text {
    my $self = shift;
    my $text = shift;

    return $PREFLIGHT
        ? $self->advancewidth($text)
        : $self->SUPER::text($text, @_)
}

######################################################################
package main;
use common::sense;
use PDF::API2;

my $para = "Lorem ipsum dolor sit amet, consectetur adipisicing elit, 
+sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut
+ enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi
+ ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehe
+nderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur
+. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui o
+fficia deserunt mollit anim id est laborum.";

my $pdf = PDF::API2->new();
my $page = $pdf->page(0);

my $txt = $page->text;

bless $txt, 'PreflightText';

$txt->font($pdf->corefont('Times-Roman') => 10);
$txt->transform(-translate=>[0, 0]);
$txt->lead(12);

my $actual_height =  do {
    #
    # compute, but don't output
    #
    local(${PreflightText::PREFLIGHT}) = 1;

    my (undef, $height_remaining) = $txt->paragraph($para,'500', '1000
+', -align => 'center');
    1000 - $height_remaining;
};

#
# now do actual output of the vertically centered text
#
$txt->transform(-translate=>[300, 500 + $actual_height/2]);
my ($text_remaining) = $txt->paragraph($para,'500', '1000', -align => 
+'center');

my $saveas = "/tmp/center.pdf";
warn "saving as: $saveas\n";
$pdf->saveas($saveas);
[download]