Re: [GD-DEVEL] GD2-File-Format Documentation

Hi Dieter,

On Nov 13, 2007 5:49 PM, Dieter Guthmann <[email protected]> wrote:
> Hello there,
>
> is there a documentation of the GD2 file-format? Is the GD2 file-format
> stable or changing with every release of libgd?

It is stable and I don't think we will change something anytime soon.

> The documentation at <http://www.libgd.org/%22OldGdFileFormats%22> is
> veeeery small *ggg*.

I can only agree :)

> Originally I thought that libgd can write all the file-formats which it
> can read, but I was wrong :-(.
> There is only read-support for XPM which I considered first, but
> XPM-writing is not possible...

Adding write support for XPM should not be that hard. One question, is it
only about speed or do you also have a limitation about the dependencies?
like libpng.

> I need a fileformat with low
> compression-overhead (slow machine) but with acceptable file-size (at
> least <7MB better <5MB for a ~7Mpixel-File in color)... so I'm currently
> thinking about a GD2-support in my application...
> Which compression is used in gd2?

The same used in GIF, see the compress function in gd_gif_out.c, it is used
by gd_gd2.c.

By the way, we are working on adding new image formats for the gd
2.1.x serie. TGA,
BMP and tiff are in cvs. If it is useful, I can think about a write
mode for the TGA format.
It is a relatively simple format and uses RLE as compression (fast to
read and write but not
as good as the other compression method).

Gruß,
--Pierre