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From Jeremias Maerki <...@jeremias-maerki.ch>
Subject Re: Transparent Text
Date Mon, 02 Mar 2009 15:30:27 GMT
Good point. I missed that.

On 02.03.2009 16:03:47 Jay Berkenbilt wrote:
> Duncan McGregor <duncan@oneeyedmen.com> wrote:
> 
> > Hi
> >
> > I'm trying to work out how to write transparent text to overlay OCR
> > data on top of its source image.
> >
> > I've seen it done in PDFs, but cannot find how to represent
> > transparency in xsl:fo
> >
> > Thanks in anticipation
> >
> > Duncan McGregor
> 
> To fill in a bit of missing information here, transparent text in PDFs
> is not done by tweaking aspects of how the text is displayed, like
> transparent text or white on white.  It is a specific feature
> supported by the PDF specification.  Specifically, there is an
> argument to the Tr (text rendering) operator.  If you place
> 
> 3 Tr
> 
> after your BT to begin a text stream, the resulting text will be
> invisible.  This is the correct way of putting "hidden text" in a PDF
> for overlaying OCR data on top of an image.
> 
> I suppose the PDF output system in fop would have to specifically
> support this.
> 
> Hope that helps...
> 
> -- 
> Jay Berkenbilt <ejb@ql.org>
> 



Jeremias Maerki


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