Re: interpreting gray-scale text as black

I attached a file that redefines the color operators.
Then you can run
pdftops -level1 grey-scale.pdf 
gs toblack.ps grey-scale.ps
I used pdftops from poppler.  -level1 and -level1sep make the color operators easier to catch.
There is probably a better way.
William


Date: Thu, 26 Mar 2015 09:31:59 -0700
From: [email protected]
To: [email protected]
Subject: [gs-devel] interpreting gray-scale text as black

I use Ghostscript in HylaFAX to produce faxable TIFF image data.  A 
simplified example of what HylaFAX does with Ghostscript is this...
 
gs -q -sDEVICE=tiffg4 -dNOPAUSE -dSAFER=true -dBATCH -r204x196 
-sOutputFile=output.tif input.pdf
 
Occasionally users send faxes which originate as PDFs with color or 
gray-scale text in them.  Naturally, Ghostscript has to produce a 
dithered image result since ITU G4 data is monochrome.
 
Often the user who sends faxes from PDFs with color or gray-scale text 
will complain that the text is either not readable (dark-enough) or that 
the document takes too long to transmit (due to the increased data 
size).  Ghostscript does an excellent job of rendering blue as a shade 
of gray, but many users seem to prefer if the blue text is translated to 
black.
 
I would like to implement a way to help those users that does not 
require them to reproduce their source document with black-only text 
(which is what I currently have to do).
 
I've attached a sample PDF with text in black and then various shades of 
gray.
 
Using Ghostscript, how would you "shift" the interpretation of the 
gray-scale text such that the output image text would be noticeably 
darker for the gray-scale text or all simply made to be black?
 
Thanks,
 
Lee.
 
 

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