It's all in the font, really. If an OT substitution results in a
character from the font's PUA being inserted in the character stream
(except for a few standard ligatures), then the result will be broken
searches. Because of this, modern fonts (including those from Adobe) are
avoiding the PUA and placing the targets of OT substitutions in
unencoded slots with names that enable searches (like "Q.alt", "Q_u").
My advice is to seek out fonts that avoid the PUA as much as possible
(at least for standard features like entries in the "liga" table), and
lobby the makers of fonts such as Libertine to start avoiding it as
well. In the Libertine "liga" table, the pair "Qu" produces a ligature
named "Q_u" that is at location U+E048 in the PUA. I see a number of
other ligatures in that section of the PUA as well: fb, ffb, ffh, ffj,
ffk, fft, fh, fj, fk, ft and so on. The result is a great many very nice
looking PDFs that can't be searched reliably.
Peter
On 10/14/2012 06:04 PM, Andrew Cunningham wrote:
This is the nature of the PDF format. It is a preprint format the
focuses on glyphs rather than characters
It partly depends on the font, and the OT features being used.
In theory you can have ActualText in the PDF, but once you move to
complex scripts all bets are off. Without a complete rewrite of the
PDF standard .... fidelity to the text is not really possible. PDF
format wasn't designed to do it.
The way we used PDFs is well outside the design parameters of the format.
It is possible to extract text, but even at its optimal,
post-processing would be needed to reorder characters in some complex
scripts.
Andrew
On Oct 15, 2012 7:57 AM, "Peter Dyballa" <[email protected]
<mailto:[email protected]>> wrote:
Am 14.10.2012 um 16:30 schrieb Joe Corneli:
> However, if I extend the MWE there slightly, I can find
"prefix", but
> not "quantitative". (My PDF reader is Evince on Ubuntu 12.04.)
The capital Q is not what you see... GNU Emacs tells me:
character: ? (displayed as ?) (codepoint
57416, #o160110, #xe048)
preferred charset: unicode (Unicode (ISO10646))
code point in charset: 0xE048
The code point is in the PUA, Private Use Area. I used pdftotext
version 0.20.4 to extract the text.
When I use pdftohtml version 0.20.4 to extract the text and create
HTML files, I see in OmniWeb the word: î ^antitative...
--
Greetings
Pete
Got Mole problems?
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