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