Re: about contibuting to octave

[xianghang liu]

On Wed, Mar 4, 2009 at 10:00 AM, Ben Abbott <address@hidden> wrote:

On Mar 3, 2009, at 2:52 PM, Michael Goffioul wrote:

On Tue, Mar 3, 2009 at 6:51 PM, Shai Ayal <address@hidden> 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:

• use GD library
• use freetype
• back-up method if these libraries is absent or the font is non-standard
  

Any mistakes?

-- 
Xianghang Liu