tiffgetfield.3t

tiff文件开发库

.\" $Header: /cvsroot/osrs/libtiff/man/TIFFGetField.3t,v 1.3 2002/03/01 04:09:03 warmerda Exp $
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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 3T "August 22, 1997"
.SH NAME
TIFFGetField, TIFFVGetField \- get the value(s) of a tag in an open
.SM TIFF
file
.SH SYNOPSIS
.B "#include <tiffio.h>"
.br
.B "int TIFFGetField(TIFF* tif, ttag_t tag, ...)"
.sp 5p
.B "#include <stdarg.h>"
.br
.B "int TIFFVGetField(TIFF* tif, ttag_t tag, va_list ap)"
.sp 5p
.B "int TIFFGetFieldDefaulted(TIFF* tif, ttag_t tag, ...)"
.br
.B "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 open
.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 (3T).
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 ,
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 (3T).
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 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	char**
TIFFTAG_BADFAXLINES	1	uint32*
TIFFTAG_BITSPERSAMPLE	1	uint16*
TIFFTAG_CLEANFAXDATA	1	uint16*
TIFFTAG_COLORMAP	3	uint16**	1<<BitsPerSample arrays
TIFFTAG_COMPRESSION	1	uint16*
TIFFTAG_CONSECUTIVEBADFAXLINES	1	uint32*
TIFFTAG_COPYRIGHT	1	char**
TIFFTAG_DATATYPE	1	uint16*
TIFFTAG_DATETIME	1	char**
TIFFTAG_DOCUMENTNAME	1	char**
TIFFTAG_DOTRANGE	2	uint16*
TIFFTAG_EXTRASAMPLES	2	uint16*,uint16**	count & types array
TIFFTAG_FAXMODE	1	int*	G3/G4 compression pseudo-tag
TIFFTAG_FAXFILLFUNC	1	TIFFFaxFillFunc*	G3/G4 compression pseudo-tag
TIFFTAG_FILLORDER	1	uint16*
TIFFTAG_GROUP3OPTIONS	1	uint32*
TIFFTAG_GROUP4OPTIONS	1	uint32*
TIFFTAG_HALFTONEHINTS	2	uint16*
TIFFTAG_HOSTCOMPUTER	1	char**
TIFFTAG_IMAGEDEPTH	1	uint32*
TIFFTAG_IMAGEDESCRIPTION	1	char**
TIFFTAG_IMAGELENGTH	1	uint32*
TIFFTAG_IMAGEWIDTH	1	uint32*
TIFFTAG_INKNAMES	1	char**
TIFFTAG_INKSET	1	uint16*
TIFFTAG_JPEGTABLES	2	u_short*,void**	count & tables
TIFFTAG_JPEGQUALITY	1	int*	JPEG pseudo-tag
TIFFTAG_JPEGCOLORMODE	1	int*	JPEG pseudo-tag
TIFFTAG_JPEGTABLESMODE	1	int*	JPEG pseudo-tag
TIFFTAG_MAKE	1	char**
TIFFTAG_MATTEING	1	uint16*
TIFFTAG_MAXSAMPLEVALUE	1	uint16*
TIFFTAG_MINSAMPLEVALUE	1	uint16*
TIFFTAG_MODEL	1	char**
TIFFTAG_ORIENTATION	1	uint16*
TIFFTAG_PAGENAME	1	char**
TIFFTAG_PAGENUMBER	2	uint16*
TIFFTAG_PHOTOMETRIC	1	uint16*
TIFFTAG_PLANARCONFIG	1	uint16*
TIFFTAG_PREDICTOR	1	uint16*
TIFFTAG_PRIMARYCHROMATICITIES	1	float**	6-entry array
TIFFTAG_REFERENCEBLACKWHITE	1	float**	2*SamplesPerPixel array
TIFFTAG_RESOLUTIONUNIT	1	uint16*
TIFFTAG_ROWSPERSTRIP	1	uint32*
TIFFTAG_SAMPLEFORMAT	1	uint16*
TIFFTAG_SAMPLESPERPIXEL	1	uint16*
TIFFTAG_SMAXSAMPLEVALUE	1	double*
TIFFTAG_SMINSAMPLEVALUE	1	double*
TIFFTAG_SOFTWARE	1	char**
TIFFTAG_STONITS	1	double**
TIFFTAG_STRIPBYTECOUNTS	1	uint32**
TIFFTAG_STRIPOFFSETS	1	uint32**
TIFFTAG_SUBFILETYPE	1	uint32*
TIFFTAG_SUBIFD	2	uint16*,uint32**	count & offsets array
TIFFTAG_TARGETPRINTER	1	char**
TIFFTAG_THRESHHOLDING	1	uint16*
TIFFTAG_TILEBYTECOUNTS	1	uint32**
TIFFTAG_TILEDEPTH	1	uint32*
TIFFTAG_TILELENGTH	1	uint32*
TIFFTAG_TILEOFFSETS	1	uint32**
TIFFTAG_TILEWIDTH	1	uint32*
TIFFTAG_TRANSFERFUNCTION	1 or 3\(dg	uint16**	1<<BitsPerSample entry arrays
TIFFTAG_WHITEPOINT	1	float**	2-entry array
TIFFTAG_XPOSITION	1	float*
TIFFTAG_XRESOLUTION	1	float*
TIFFTAG_YCBCRCOEFFICIENTS	1	float**	3-entry array
TIFFTAG_YCBCRPOSITIONING	1	uint16*
TIFFTAG_YCBCRSUBSAMPLING	2	uint16*
TIFFTAG_YPOSITION	1	float*
TIFFTAG_YRESOLUTION	1	float*
TIFFTAG_ICCPROFILE	2	uint32*,void**	count, profile data\(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 "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
.IR TIFFError (3T)
routine.
.PP
.BR "Unknown field, tag 0x%x" .
An unknown tag was supplied.
.SH "SEE ALSO"
.IR libtiff (3T),
.IR TIFFOpen (3T),
.IR TIFFSetField (3T),
.IR TIFFSetDirectory (3T),
.IR TIFFReadDirectory (3T),
.IR TIFFWriteDirectory (3T)