PS_open_mem -- Creates a PostScript document in memory
int PS_open_mem(PSDoc *psdoc, size_t (*writeproc)(PSDoc *p, void *data, size_t size))
Creates a PostScript document in memory. It actually does it by
using the given output function instead of using the internal file output
function. It is up to the application calling this function, what to do
with the data passed to the writeproc. The writeproc must return the
number of written bytes. writeproc is usually called at least once
within any other function.
Returns -1 in case of an error and 0 otherwise.