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IM_ITERATE

IM_ITERATE

Section: C Library Functions (3) Updated: 30 October 1992
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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


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
SEE ALSO
COPYRIGHT
AUTHOR

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Time: 21:48:21 GMT, April 16, 2011