Text visibility problem in the official PDF Reference PDF file.

Hello PDFtron Team and others users,
Text visibility problem. The only thing we need to kwnow is when a
page have text hidden. That is all.

In the forum we read: "In general, there is no a 'perfect solution'
the text visibility problem. " (

The PDF is the official PDF reference. By the way the link in
http://www.pdftron.com/pdfnet/faq.html , SDF section is not working.

The real link I guess is: http://partners.adobe.com/public/developer/en/pdf/PDFReference.pdf

The last Page have call "overprint and blending" have hidden text that
we detect using Adobe Acrobat Reader and other tools. All we need is
to know when page have hidden text like this one. We try
textextractor, text element gstate... nothing. Please help. We use

Last page PDF: http://www.cibeles.net/PDFReferenceFinalPage.pdf
Screen capture: http://www.cibeles.net/texthidden.png

Please help us.

Thank you in advance.

Hi Carlos,

In this file, text is covered by a small white rectangle:

/T1_0 1 Tf
-0.0001 Tc 9 0 0 9 131.4657 379.6077 Tm
1 0 0 1 -9.482254 -0.6773071 cm
1 1 1 sc
/GS1 gs
137.167 389.667 64 -13.333 re

How did you use TextExtractor? Did you use e_remove_hidden_text +
e_no_invisible_text flag in TextExtractor.Begin().

To detect obscured/hidden text maybe you could compare the string
returned by TextExtractor.GetAsText()
with and without these flags.

Hello Support,
Here our code in PHP. If you can try please do that and give us the
code; with that PDF page.

$txt2 = new TextExtractor();
$media_box = new Rect($page->GetMediaBox());

$iConteoPalabrasSinRemoverOcultas = $txt2->GetWordCount();

$txt2->Begin($page, $media_box, TextExtractor::e_remove_hidden_text |
$iConteoPalabrasRemoviendoOcultas = $txt2->GetWordCount();

if($iConteoPalabrasSinRemoverOcultas <>
   $bHaveHiddenText = true; //<<<<< here if the word count are diff