58 lines
1.9 KiB
Groff
58 lines
1.9 KiB
Groff
.TH IM_HEADER 3 "7 May 2002"
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.SH NAME
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im_header_int, im_header_double, im_header_string, im_header_get,
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im_header_get_type, im_header_map \- read fields from the image header
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.SH SYNOPSIS
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#include <vips/vips.h>
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int im_header_int( IMAGE *image, const char *field, int *out )
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.br
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int im_header_double( IMAGE *image, const char *field, double *out )
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.br
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int im_header_string( IMAGE *image, const char *field, char **out )
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.br
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GType im_header_get_type( IMAGE *im, const char *field );
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.br
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int im_header_get( IMAGE *im, const char *field, GValue *value_copy );
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.br
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typedef void *(*im_header_map_fn)( IMAGE *,
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const char *, GValue *, void *, void * );
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.br
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void *im_header_map( IMAGE *im,
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im_header_map_fn fn, void *a, void *b );
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.SH DESCRIPTION
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.B im_header_int(3)
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reads the value of an integer header field. These are
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"Xsize", "Ysize", "Bands", "Bbits", "BandFmt", "Coding", and "Type", or any
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integer meta field.
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.B im_header_double(3)
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reads the value of the integer header fields. These are
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"Xres", and "Yres", or any double meta field.
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.B im_header_string(3)
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reads the value of the integer header fields. These are
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"Hist", and "filename" or any string meta field.
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.B im_header_get_type(3)
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returns the GType (eg. G_TYPE_INT) for a field. It returns zero if the field
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does not exist. It does not set
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.B im_error(3),
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so it's useful for test for a field's existence.
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.B im_header_get(3)
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fills the GValue with a copy of the field value, if the field exists. The
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value should be zeroed but otherwise uninitialised. The value should be unset
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once the user has finished with it.
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.B im_header_map(3)
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maps a function over all header fields, presenting the value of each field as
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a GValue. Return non-NULL from the map function to stop iteration early. It
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maps over the builtin fields first, then any meta fields.
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.SH RETURN VALUE
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All functions returns 0 on success and -1 on error.
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.SH SEE ALSO
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im_close(3), im_open(3).
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