libtiff/man/TIFFGetField.3tiff

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.\" Copyright (c) 1988-1997 Sam Leffler
.\" Copyright (c) 1991-1997 Silicon Graphics, Inc.
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.if n .po 0
.TH TIFFGetField 3TIFF "March 18, 2005" "libtiff"
.SH NAME
TIFFGetField, TIFFVGetField \- get the value(s) of a tag in an open
.SM TIFF
file
.SH SYNOPSIS
.B "#include <tiffio.h>"
.sp
.BI "int TIFFGetField(TIFF *" tif ", ttag_t " tag ", " ... ")"
.sp
.B "#include <stdarg.h>"
.sp
.BI "int TIFFVGetField(TIFF *" tif ", ttag_t " tag ", va_list " ap ")"
.br
.BI "int TIFFGetFieldDefaulted(TIFF *" tif ", ttag_t " tag ", " ... ")"
.br
.BI "int TIFFVGetFieldDefaulted(TIFF *" tif ", ttag_t " tag ", va_list " ap ")"
.SH DESCRIPTION
.IR TIFFGetField
returns the value of a tag or pseudo-tag associated with the the current
directory of the opened
.SM TIFF
file
.IR tif .
(A
.I pseudo-tag 
is a parameter that is used to control the operation of the
.SM TIFF
library but whose value is not read or written to the underlying file.) The
file must have been previously opened with
.IR TIFFOpen (3TIFF).
The tag is identified by
.IR tag ,
one of the values defined in the include file
.B tiff.h
(see also the table below). The type and number of values returned is
dependent on the tag being requested. The programming interface uses a
variable argument list as prescribed by the
.IR stdarg (3)
interface. The returned values should only be interpreted if
.IR TIFFGetField
returns 1.
.PP
.IR TIFFVGetField
is functionally equivalent to
.IR TIFFGetField
except that it takes a pointer to a variable argument list.
.I TIFFVGetField
is useful for layering interfaces on top of the functionality provided by
.IR TIFFGetField .
.PP
.IR TIFFGetFieldDefaulted
and
.IR TIFFVGetFieldDefaulted
are identical to 
.IR TIFFGetField
and
.IR TIFFVGetField ,
except that if a tag is not defined in the current directory and it has a
default value, then the default value is returned.
.PP
The tags understood by
.IR libtiff(3TIFF),
the number of parameter values, and the types for the returned values are
shown below. The data types are specified as in C and correspond to the types
used to specify tag values to
.IR TIFFSetField (3TIFF).
Remember that
.IR TIFFGetField
returns parameter values, so all the listed data types are pointers to storage
where values should be returned.
Consult the
.SM TIFF
specification (or relevant industry specification) for information on the
meaning of each tag and their possible values.
.PP
.nf
.ta \w'TIFFTAG_CONSECUTIVEBADFAXLINES'u+2n +\w'Count'u+2n +\w'TIFFFaxFillFunc*'u+2n
\fITag Name\fP	\fICount\fP	\fITypes\fP	\fINotes\fP
.sp 5p
TIFFTAG_ARTIST	1	const char**
TIFFTAG_BADFAXLINES	1	uint32*
TIFFTAG_BITSPERSAMPLE	1	uint16*
TIFFTAG_CLEANFAXDATA	1	uint16*
TIFFTAG_COLORMAP	3	const uint16**	1<<BitsPerSample arrays
TIFFTAG_COMPRESSION	1	uint16*
TIFFTAG_CONSECUTIVEBADFAXLINES	1	uint32*
TIFFTAG_COPYRIGHT	1	const char**
TIFFTAG_DATATYPE	1	uint16*
TIFFTAG_DATETIME	1	const char**
TIFFTAG_DOCUMENTNAME	1	const char**
TIFFTAG_DOTRANGE	2	uint16*
TIFFTAG_EXTRASAMPLES	2	uint16*,const uint16**	count & types array
TIFFTAG_FAXFILLFUNC	1	TIFFFaxFillFunc*	G3/G4 compression pseudo-tag
TIFFTAG_FAXMODE	1	int*	G3/G4 compression pseudo-tag
TIFFTAG_FILLORDER	1	uint16*
TIFFTAG_GROUP3OPTIONS	1	uint32*
TIFFTAG_GROUP4OPTIONS	1	uint32*
TIFFTAG_HALFTONEHINTS	2	uint16*
TIFFTAG_HOSTCOMPUTER	1	const char**
TIFFTAG_ICCPROFILE	2	const uint32*,const void**	count, profile data
TIFFTAG_IMAGEDEPTH	1	uint32*
TIFFTAG_IMAGEDESCRIPTION	1	const char**
TIFFTAG_IMAGELENGTH	1	uint32*
TIFFTAG_IMAGEWIDTH	1	uint32*
TIFFTAG_INKNAMES	1	const char**
TIFFTAG_INKSET	1	uint16*
TIFFTAG_JPEGCOLORMODE	1	int*	JPEG pseudo-tag
TIFFTAG_JPEGQUALITY	1	int*	JPEG pseudo-tag
TIFFTAG_JPEGTABLES	2	uint32*,const void**	count & tables
TIFFTAG_JPEGTABLESMODE	1	int*	JPEG pseudo-tag
TIFFTAG_MAKE	1	const char**
TIFFTAG_MATTEING	1	uint16*
TIFFTAG_MAXSAMPLEVALUE	1	uint16*
TIFFTAG_MINSAMPLEVALUE	1	uint16*
TIFFTAG_MODEL	1	const char**
TIFFTAG_ORIENTATION	1	uint16*
TIFFTAG_PAGENAME	1	const char**
TIFFTAG_PAGENUMBER	2	uint16*
TIFFTAG_PHOTOMETRIC	1	uint16*
TIFFTAG_PHOTOSHOP	2	uint32*,const void**	count, data
TIFFTAG_PLANARCONFIG	1	uint16*
TIFFTAG_PREDICTOR	1	uint16*
TIFFTAG_PRIMARYCHROMATICITIES	1	const float**	6-entry array
TIFFTAG_REFERENCEBLACKWHITE	1	const float**	6-entry array
TIFFTAG_RESOLUTIONUNIT	1	uint16*
TIFFTAG_RICHTIFFIPTC	2	uint32*,const void**	count, data
TIFFTAG_ROWSPERSTRIP	1	uint32*
TIFFTAG_SAMPLEFORMAT	1	uint16*
TIFFTAG_SAMPLESPERPIXEL	1	uint16*
TIFFTAG_SMAXSAMPLEVALUE	1	double*
TIFFTAG_SMINSAMPLEVALUE	1	double*
TIFFTAG_SOFTWARE	1	const char**
TIFFTAG_STONITS	1	const double**
TIFFTAG_STRIPBYTECOUNTS	1	const uint32**
TIFFTAG_STRIPOFFSETS	1	const uint32**
TIFFTAG_SUBFILETYPE	1	uint32*
TIFFTAG_SUBIFD	2	uint16*,const uint64**	count & offsets array
TIFFTAG_TARGETPRINTER	1	const char**
TIFFTAG_THRESHHOLDING	1	uint16*
TIFFTAG_TILEBYTECOUNTS	1	const uint32**
TIFFTAG_TILEDEPTH	1	uint32*
TIFFTAG_TILELENGTH	1	uint32*
TIFFTAG_TILEOFFSETS	1	const uint32**
TIFFTAG_TILEWIDTH	1	uint32*
TIFFTAG_TRANSFERFUNCTION	1 or 3\(dg	const uint16**1<<BitsPerSample entry arrays
TIFFTAG_WHITEPOINT	1	const float**	2-entry array
TIFFTAG_XMLPACKET	2	uint32*,const void**	count, data
TIFFTAG_XPOSITION	1	float*
TIFFTAG_XRESOLUTION	1	float*
TIFFTAG_YCBCRCOEFFICIENTS	1	const float**	3-entry array
TIFFTAG_YCBCRPOSITIONING	1	uint16*
TIFFTAG_YCBCRSUBSAMPLING	2	uint16*
TIFFTAG_YPOSITION	1	float*
TIFFTAG_YRESOLUTION	1	float*\(dd
.fi
\(dg If
.I SamplesPerPixel
is one, then a single array is returned; otherwise three arrays are returned.
.fi
\(dd The contents of this field are quite complex.  See 
.IR "The ICC Profile Format Specification" ,
Annex B.3 "Embedding ICC Profiles in TIFF Files" (available at
http://www.color.org) for an explanation.
.SH AUTOREGISTERED TAGS
If you can't find the tag in the table above that means this is an unsupported
tag and is not directly supported by
.BR libtiff(3TIFF)
library. You will still be able to read it's value if you know the data type of
that tag. For example, if you want to read the LONG value from the tag 33424
and ASCII string from the tag 36867 you can use the following code:
.PP
.RS
.nf
uint32  count;
void    *data;

TIFFGetField(tiff, 33424, &count, &data);
printf("Tag %d: %d, count %d\n", 33424, *(uint32 *)data, count);
TIFFGetField(tiff, 36867, &count, &data);
printf("Tag %d: %s, count %d\n", 36867, (char *)data, count);
.fi
.RE
.PP
.SH RETURN VALUES
1 is returned if the tag is defined in the current directory; otherwise a 0 is
returned.
.SH DIAGNOSTICS
All error messages are directed to the
.BR TIFFError (3TIFF)
routine.
.PP
.BR "Unknown field, tag 0x%x" .
An unknown tag was supplied.
.SH "SEE ALSO"
.BR TIFFOpen (3TIFF),
.BR TIFFSetField (3TIFF),
.BR TIFFSetDirectory (3TIFF),
.BR TIFFReadDirectory (3TIFF),
.BR TIFFWriteDirectory (3TIFF)
.BR libtiff (3TIFF),
.PP
Libtiff library home page:
.BR http://www.simplesystems.org/libtiff/