PDF Quality (was RE: barline problem)

[Kress, Stephen]

I've recently been doing a lot of work with creating PDF files (I'm working on a Java library to create PDFs using Java's standard Graphics object style).  If you have the ability, I have a simple experiment for you to try to see if it improves your line rendering quality.

You will need an editor like EMACS that you can use to manually change your PDF file without disturbing the embedded binary data and that can handle UNIX style line ends.  Now for the experiment.

Edit your PDF file and search for the string "/Type/ExtGState".  It should be preceeded by a double angle bracket, << (probably on the same line).  It probably has a single line like, "/OPM 1" followed by a closing double angle bracket, >> and the word "endobj".  (The double angle brackets mark the boundaries of a PDF dictionary object.)  After the "/OPM 1" but befor the angle brackets, add the text, "/SA true".  So the line should end up looking like, "/OPM 1/SA true>>endobj" (or something like that).

Be sure to follow the above for every instance of "/Type/ExtGState" in your file (though I believe you'll only find one).

The ExtGState dictionary type is used by a PDF document as a properties dictionary for setting graphic state properties for a page.  The "/SA" property (essentially) turns on antialiasing (i.e., "best rendering") for line art in the PDF document (which is *not* on by default).

If this experiment works out, perhaps there's a way to have GhostScript (or whatever is creating the PDF file for lily) include this property by defult, or a sed script or something.

2006-06-17, 19:43:39
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