Hi,
Another proposal:
I'm using the following code when I need a precise Bounding Box -
letting ghostscript do the job:
def GetBB(c, filename="-", resolution=100,
gscommand="grep -v -E '^%%(HiRes)?BoundingBox' | gs", gsoptions="",
textalphabits=4, graphicsalphabits=4,
ciecolor=False, **kwargs):
gscommand += " -dEPSCrop -dNOPAUSE -dQUIET -dBATCH -r%i -q -sDEVICE=bbox
-sOutputFile=%s" % (resolution, filename)
if gsoptions:
gscommand += " %s" % gsoptions
if textalphabits is not None:
gscommand += " -dTextAlphaBits=%i" % textalphabits
if graphicsalphabits is not None:
gscommand += " -dGraphicsAlphaBits=%i" % graphicsalphabits
if ciecolor:
gscommand += " -dUseCIEColor"
gscommand += " -"
pipe_in, pipe_out, pipe_err = os.popen3(gscommand)
c.writeEPSfile(pipe_in, **kwargs)
pipe_in.close()
for line in pipe_err.readlines():
m=re.match(r"^%%HiResBoundingBox: ([-0-9\.]*) ([-0-9\.]*) ([0-9\.]*)
([0-9\.]*)$",line)
if m != None:
b = map(lambda x: unit.length(float(x),unit="pt"), m.groups())
return bbox.bbox(b[0],b[1],b[2],b[3])
raise IOError("Can't determine BoundingBox")
It's more or less a copy of "canvas.pipeGS", however:
- as ghostscript writes the bbox onto the standard error-stream, I need
"os.popen3" to get the result from within python.
- I use a trivial regexp to get the boundingboxes-Data
- I use "grep" to guarantee that pyx is not passing its
BoundingBox-Date to ghostscript.
With that code, I can pass an arbitrary canvas to "GetBB", and it will
return the precise boundingBox - including linewidth.
However, the huge problem is: my ghostscript gives wrong results for
negative coordinates - maybe it's just a question of the parameters?
Axel
On Sun, Oct 18, 2009 at 01:56:12PM +0200, Joerg Lehmann wrote:
> Hi,
>
> On 17.10.09, Alan G Isaac wrote:
> > On 10/17/2009 9:26 AM, Michael SCHINDLER wrote:
> > > The problem is that
> > > the true bounding box of a picture does depend on both the paths and
> > > the respective linewidth. It is simple to calculate bounding boxes for
> > > lines; for curves it is more difficult. PyX calculates these two.
> > > Including also the linewidth and stroke effects coming from the
> > > different linejoin parameters is really difficult. We decided not to
> > > do this, as it would lead to a reimplementation of ghostscript.
> >
> > Did you consider using Bless's bbox code (comes with ps2eps, GPL license)?
>
> I guess, you mean this code:
>
> http://www.tex.ac.uk/tex-archive/support/ps2eps/src/C/bbox.c
>
> Unfortunately, it requires having a rasterized version of the graphics
> output.
>
> > It would be really nice to get a better bounding box.
>
> From a perfectionists point of view, I would agree. Practically,
> however, it only very seldomnly happened that the bounding box produced
> by PyX was not good enough.
>
> Best,
>
> Jörg
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