Bug 202735 - bbox device doesn't allow min coords < 0
Summary: bbox device doesn't allow min coords < 0
Alias: None
Product: Ghostscript
Classification: Unclassified
Component: Other Driver (show other bugs)
Version: master
Hardware: All All
: P1 normal
Assignee: Ray Johnston
Depends on:
Reported: 2000-03-09 07:17 UTC by L. Peter Deutsch
Modified: 2013-11-18 07:50 UTC (History)
1 user (show)

See Also:
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Description L. Peter Deutsch 2000-03-09 07:17:33 UTC
Originally reported by: lpd@users.sourceforge.net
I have found small bug in bbox device.  Adobe eps specification doesn't say anything about bbox values must be positive, and, for example Adobe Illustrator, simply can create epses with negative bboxes.  In such case, ghostscipt returns zero instead of proper negative number.
Comment 1 L. Peter Deutsch 2000-03-09 07:22:03 UTC
Comment originally by lpd@users.sourceforge.net
(Ghostscript version: 6.0)

This is an architectural restriction in Ghostscript: all devices impose an implicit clipping region of [0 0 infinity infinity] in device space, in addition to the region set by setclip. We might be able to work around it by making the default/initial CTM for the bbox device include a large positive translation, and then biasing the bounding box that the device reports, but it\'s unlikely that we will get to this soon.
Comment 2 Ray Johnston 2000-03-10 15:56:06 UTC
Comment originally by rayjj@users.sourceforge.net
I don\'t know how \"kosher\" it is, but I\'ve noticed that if the bbox device has negative
 coordinates for the ImagingBBox[0] and [1] values, then negative values ARE handled.

For example:

% gs -q -sDEVICE=bbox -dNOPAUSE
GS><< /ImagingBBox [ -4000. -4000. 4000. 4000. ] >> setpagedevice
GS>-100 -200 moveto 300 400 lineto stroke
%%BoundingBox: -101 -201 301 401
%%HiResBoundingBox: -100.416020 -200.277345 300.416018 400.277348

L. Peter Deutsch replied:
> I\'m pretty sure you can\'t rely on this -- I think there are several places
> in the graphics library that assume that a device\'s coordinate space is all
> in the first quadrant.  But it\'s a reasonable shot at a workaround.
Comment 3 Jack Moffitt 2000-05-09 14:27:19 UTC
Comment originally by jch@users.sourceforge.net
I had a similar problem, and solved it by removing the
implicit clipping in my private version of GS (I'm relying
on the driver to do clipping for me). Mostly, this consisted
in replacing all the clipping macros with dummies, defining my own initial clippath function, and fixing a few modulus
operations that assumed positive device coordinates.

The changes are not quite complete, and I still sometimes
have incorrect rendering with halftones which I suspect
to be due clipping.  For what it's worth, the changes
are available, albeit lost in the mass of the DPS patches.


Comment 4 Ray Johnston 2001-04-02 16:09:22 UTC
Comment originally by rayjj@users.sourceforge.net
Logged In: YES 

We acknowledge that this is a valid issue, but we do not have
resources available to address this at this time.

This problem report has been moved to doc/Issues.htm where it
may remain open for some time. Relevant comments are
captured there along with the ID# of this report.

By moving this issue to the widely distributed Ghostscript
documentation, we wish to make this issue well known and
solicit help in improving Ghostscript in this area.

Thanks for your input!
Comment 5 Ray Johnston 2008-09-01 12:00:27 UTC
Re-opening so we can close this with a different resolution.
Comment 6 Ray Johnston 2008-09-01 12:03:04 UTC
The architectural changes mentioned by 'jch' never materialized, and this
hasn't surfaced as an issue for anyone else in the past 8 years, so I am
closing this as WONTFIX.

Note that the 'work around' mentioned in Comment #2 is probably the best:

   << /ImagingBBox [ -4000. -4000. 4000. 4000. ] >> setpagedevice

Comment 7 Terry Burton 2013-11-18 07:50:30 UTC
The published workaround no longer appears to work:

$ gs --version

$ gs -q -sDEVICE=bbox -dNOPAUSE
GS><< /ImagingBBox [ -4000. -4000. 4000. 4000. ] >> setpagedevice
GS>-100 -200 moveto 300 400 lineto stroke
%%BoundingBox: 32 0 301 401
%%HiResBoundingBox: 32.723999 0.000000 300.419991 400.283988
GS> quit