[cairo-bugs] [Bug 13679] New: Error-prone eexec stream in PDF

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Sat Dec 15 15:14:59 PST 2007


           Summary: Error-prone eexec stream in PDF
           Product: cairo
           Version: 1.4.9
          Platform: Other
        OS/Version: All
            Status: NEW
          Severity: minor
          Priority: medium
         Component: pdf backend
        AssignedTo: krh at bitplanet.net
        ReportedBy: alexcher at quadnet.net
         QAContact: cairo-bugs at cairographics.org

I have a PDF file generated by cairo 1.4.10 that contains a Type 1 font
with eexec stream that is likely to cause problems for PDF consumers.
The file works on Acrobat, prompted a fix in Ghostscript, doesn't work
on Adobe level 3 printers with build-in PDF interpreter.

The cause of the problem is the differences between handling space
characters '\t', '\r', '\n', ' ' after eexec operator.
Adobe PostScript interpreters always skips them and bug-compatible clones
do the same. Adobe Acrobat doesn't skip space characters.

The sample PDF file contains '\r' character in the stream "5 0" that must be
interpreted. When PDF is converted to PS without complete re-writing of the
font stream, this character is skipped resulting in an invalid font.

To generate robust PDF one has to modify the original stream (for instance,
prepend spaces) to avoid any of the skipped space characters in the 1st
position of the eexec-encoded stream. See seexec.c in current Ghostscript
sources for details.

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