NAME
im_iterate - PIO input from image
SYNOPSIS
#include <vips/vips.h>
int im_iterate( im, start_fn, scan_fn, stop_fn, a, b )
IMAGE *im;
void *(*start_fn)();
int (*scan_fn)();
int (*stop_fn)();
void *a, *b;
where, typically,
void *start_fn( im, a, b )
IMAGE *im;
void *a, *b;
int scan_fn( or, seq, a, b )
REGION *or;
void *seq;
void *a, *b;
int stop_fn( seq, a, b )
void *seq;
void *a, *b;
DESCRIPTION
im_iterate(3) is used for PIO image input. See ‘VIPS Library
Programmers’ guide,’ in the accompanying documentation, for an
introduction to this function.
im_iterate(3) makes one or more regions on im, and starts one or more
sequences running over the image. im_iterate(3) guarantees that
- scan_fn() will see each of the pels in im exactly once
- start_fn() and stop_fn() are both exclusive
See the guide, the man page for im_generate(3), and the source to
im_deviate(3) for examples.
On machines with SVR4 threads and several CPUs, im_generate(3) and
im_iterate(3) automatically parallelise programs. You can set the
desired concurrency level with the environment variable IM_CONCURRENCY,
for example
example% setenv IM_CONCURRENCY 2
example% stats fred.v
will run stats with enough concurrency to keep 2 CPUs fully occupied.
If IM_CONCURRENCY is not set, then it defaults to 1.
RETURN VALUE
All functions return 0 on success and non-zero on error.
SEE ALSO
im_generate(3).
COPYRIGHT
National Gallery, 1993
AUTHOR
J. Cupitt - 23/7/93
30 October 1992