[pygtk] Help with pygtk save_to_callback

[Tim Evans]

Michael Urban wrote:
> Hi all,
> 
> I need some help using the pixbuf safe_to_callback method. Basically,
> what I need to do is take a pixbuf, and save it to an in memory
> buffer in jpg format that I can dump to a db. I'm running into two
> main problems:
> 
> 1: The callback seems to get called multiple times. So calling
> pixbuf.save_to_callback apparently doesn't pass all of the buffer in
> one call, but make several calls to the callback.

The callback replaces fwrite to a file, it may be called many times in 
the course of saving a file.

> 2: Simply trying to append onto the end of a buffer that you build
> incrementally does not work. It causes a gobject.GError write
> function failed.

I would need to see your code to understand why this isn't working.

> Can anyone give me a simple example of how I would write a callback
> function for pixbuf.save_to_callback that would build an in memory
> buffer that stores the image in the given file type?

Untested, but maybe something like this, where 'p' is a pixbuf:

   import cStringIO as StringIO

   io = StringIO.StringIO()
   p.save_to_callback(io.write, 'png')
   buffer = io.getvalue()

-- 
Tim Evans
Applied Research Associates NZ
http://www.aranz.co.nz/