class Pic(static.Data):
    """Runs a db query for id, and either 1) retrieves the file name,
    resizes, and provides image/jpeg, or 2) provides an error as
    text/plain.  This class really shouldn't derive from static.Data,
    but instead delegate to it, because it's dynamic."""
    
    def __init__ (self, id):
        def fail (err):
            self.data = str (err)
            self.type = 'text/plain'
        def succeed (res):
            if len (res) == 0:
                fail ('No pic for %s' % id)
                return
            fn = res[0][0]
            im = Image.open (itis_if.prefix + fn) # XXX
            new_width = 600
            new_sz = (new_width, (new_width * im.size [1]) / im.size [0])
            im = im.resize (new_sz)
            fil = StringIO()
            im.save (fil, "JPEG")
            del im
            self.data = fil.getvalue ()
            self.type = 'image/jpeg'

        query = 'SELECT filename FROM pics WHERE id = %s' % (id,)
        self.deferred = (
            itis_if.dbpool.runQuery (query).addCallbacks (succeed, fail))
    def renderHTTP (self, request):
        if self.deferred.called:
            return static.Data.renderHTTP (self, request)
        else:
            finished = defer.Deferred ()
            finished.addBoth (lambda s: self.renderHTTP (request))
            self.deferred.chainDeferred (finished)
            return finished