about contibuting to octave

[xianghang liu]

On Wed, Mar 4, 2009 at 2:48 PM, Shai Ayal <shaiay at gmail.com> wrote:

> 2009/3/4 xianghang liu <xianghangliu at gmail.com>:
> >
> >
> > On Wed, Mar 4, 2009 at 10:00 AM, Ben Abbott <bpabbott at mac.com> wrote:
> >>
> >> On Mar 3, 2009, at 2:52 PM, Michael Goffioul wrote:
> >>
> >>> On Tue, Mar 3, 2009 at 6:51 PM, Shai Ayal <shaiay at gmail.com> wrote:
> >>>>
> >>>> I think this is a good idea -- this will decouple the text object from
> >>>> the backend.
> >>>>
> >>>> We will need to know what fonts gnuplot uses to get freetype to get us
> >>>> gnuplot's font metrics?
> >>>> I think we can get the standard postscript font metrics from similar
> >>>> type1 fonts which freetype can use (I distributed a set of ps-similar
> >>>> fonts with octplot)
> >>>
> >>> I guess gnuplot backend would use the back-up implementation.
> >>> Or we could still use freetype, hoping that gnuplot will use the same
> >>> metrics...
> >>>
> >>> Michael.
> >>
> >> Gnuplot uses the GD library.
> >>
> >>        http://en.wikipedia.org/wiki/GD_Graphics_Library
> >>
> >>        http://www.libgd.org/Main_Page
> >>
> >> After reading some hits via Google, it appears that this library can
> >> calculate the bounding rectangle text without rendering it, and that
> gdlib
> >> handles freetype, PS type 1 fonts, and truetype.
> >>
> >>        http://my.php.net/gd
> >>
> >>        imageftbbox — Give the bounding box of a text using fonts via
> >> freetype2
> >>
> >>        imagepsbbox — Give the bounding box of a text rectangle using
> >> PostScript Type1 fonts
> >>
> >>        imagettfbbox — Give the bounding box of a text using TrueType
> fonts
> >>
> >> Ben
> >>
> >>
> > So there are already 3 methods to get the extent property without
> dependency
> > on backends:
>
> Well none of them are implemented in octave yet ...
>
> > use GD library
> > use freetype
> > back-up method if these libraries is absent or the font is non-standard
> >
>
> Since it seems that GD uses freetype also, I would go for freetype +
> very simple backup.
>
> Shai
>

In freetype, I found two functions

   - FT_Outline_Get_BBox* *Compute the exact bounding box of an outline.
   - FT_Outline_Get_CBox Return an outline's ‘control box’.

After a rough glance at ftgl's bounding box computation, I think it
use FT_Outline_Get_CBox
to compute the box of each glyph and add them together to get the extent of
the string. Shall we just follow the same method?



 Xianghang
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