Re: PDF::API2 and opacity

Once upon a time I had the same problem, which I then put away for 'later', but your request made me look it up.

The method for it is actually quite simple, however due to the level of documentation for PDF::API2, nobody knows how :)

Let's start by creating the document, add an A4-page, create text and gfxhandlers and add a font:

my $pdf = PDF::API2->new( -file => "Test.pdf" );
my $page1 = $pdf->page;
$page1->mediabox (210/mm, 297/mm);
my $gfx = $page1->gfx;
my $text = $page1->text;
my %fonts = (
  Helvetica => {
    Roman  => $pdf->corefont( 'Helvetica', -encoding => 'latin1' ),
  }
);
[download]

Then we'll make some Extended Graphics states...One for everything we want transparent, and one for the non-transparent states.

my $EGTransparent = $pdf->egstate();
my $EGNormal = $pdf->egstate();
$EGTransparent->transparency(0.5);
$EGNormal->transparency(0);
[download]

Suppose we now want to write some transparent text:

$text->egstate($EGTransparent);
$text->font($fonts{Helvetica}{Roman}, 16/pt);
$text->translate(31/mm,250/mm);
$text->text("This is a Test, just so you know", undef);
$text->egstate($EGNormal);
[download]

And add a transparent image to write transparent text over:

$gfx->egstate($EGTransparent);
$gfx->image($pdf->image_tiff("Image.tif"), 1/mm, 148/mm, 137/mm, 137/m
+m);
$gfx->egstate($EGNormal);
[download]

And then add some non-transparent text, to show the difference:

$text->translate(31/mm,200/mm);
$text->text("This is a Test, just so you know", undef);
[download]

And save our result...of course :)

$pdf->save;
[download]

All done.

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Re^2: PDF::API2 and opacity by rainboxx (Initiate) on Aug 02, 2010 at 12:31 UTC
Neighbour, thanks for your code! It's close to what I'm searching and maybe this will help me to get to what I want to accomplish! But maybe you can help me directly, too: I'm trying to import an existing PDF page from file into a new PDF that is just beeing created with PDF::API2. I need to set the attribute "overprint" so the text above is printed over the background (without this attribute/option, the background is not printed behind the text so some printers leave white lines when printing the black ink). The module ExtGState, Extended Graphics states, seems to have methods for this attribute, but I don't know how to say they have to be applied to the background image. Any suggestions?	[reply]
Re^3: PDF::API2 and opacity by Neighbour (Friar) on Aug 03, 2010 at 14:14 UTC
I'm not entirely sure I understand what your problem is, but here is some code I use to make a "Test"-copy of a given PDF: sub PrintTextAngle { my ($texthandler, $x, $y, $rot, $text, $options) = @_; $texthandler->transform('-translate'=> [6/mm+$x/mm,10/mm+$y/mm], ' +-rotate'=>$rot); $texthandler->text($text, $options); } my $pdf_input = PDF::API2->open("$Filename"); foreach my $pagenr (1..$pdf_input->pages) { my $page = $pdf_input->openpage($pagenr); my $texthandler = $page->text; my $font = $pdf_input->corefont( 'Helvetica-Bold', -encode => ' +latin1' ); $texthandler->fillcolor('grey'); $texthandler->font($font, 256/pt); PrintTextAngle($texthandler, 50, 60, 45, "TEST"); $texthandler->font($font, 56/pt); PrintTextAngle($texthandler, 20, 10, 0, "Do not throw away!"); } $pdf_input->saveas("$Filename-TEST.pdf"); [download] This leaves the background (the imported PDF contents) intact and prints the text over this background (Though not semi-transparent, which you might want). If you still insist on toying with the overprint setting, use this: `my $EGOverprint = $pdf->egstate(); my $EGNormal = $pdf->egstate(); $EGOverprint->strokeoverprint(1); $EGNormal->strokeoverprint(0);` [download] Before calling PrintTextAngle, set the Extended Graphics State using: `$text->egstate($EGOverprint);` [download] Then print, and afterwards (if you want to print some more without using overprint) restore the Extended Graphics State with: `$text->egstate($EGNormal);` [download]	[reply] [d/l] [select]