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NAME

TIFFGetField, TIFFVGetField - get the value(s) of a tag in an open TIFF file

SYNOPSIS

#include <tiffio.h>
int TIFFGetField(TIFF* tif, ttag_t tag, ...)

#include <stdarg.h>
int TIFFVGetField(TIFF* tif, ttag_t tag, va_list ap)

int TIFFGetFieldDefaulted(TIFF* tif, ttag_t tag, ...)
int TIFFVGetFieldDefaulted(TIFF* tif, ttag_t tag, va_list ap)

DESCRIPTION

TIFFGetField returns the value of a tag or pseudo-tag associated with the the current directory of the open TIFF file tif. (A pseudo-tag is a parameter that is used to control the operation of the TIFF library but whose value is not read or written to the underlying file.) The file must have been previously opened with TIFFOpen(3T). The tag is identified by tag, one of the values defined in the include file 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 stdarg(3) interface. The returned values should only be interpreted if TIFFGetField returns 1.

TIFFVGetField is functionally equivalent to TIFFGetField except that it takes a pointer to a variable argument list. TIFFVGetField is useful for layering interfaces on top of the functionality provided by TIFFGetField.

TIFFGetFieldDefaulted and TIFFVGetFieldDefaulted are identical to TIFFGetField and 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.

The tags understood by 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 TIFFSetField(3T). Remember that TIFFGetField returns parameter values, so all the listed data types are pointers to storage where values should be returned. Consult the TIFF specification for information on the meaning of each tag and their possible values.

Tag Name    Count    Types    Notes

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_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_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    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*
If SamplesPerPixel is one, then a single array is returned; otherwise three arrays are returned.

RETURN VALUES

1 is returned if the tag is defined in the current directory; otherwise a 0 is returned.

DIAGNOSTICS

All error messages are directed to the TIFFError(3T) routine.

Unknown field, tag 0x%x. An unknown tag was supplied.

SEE ALSO

libtiff(3T), TIFFOpen(3T), TIFFSetField(3T), TIFFSetDirectory(3T), TIFFReadDirectory(3T), TIFFWriteDirectory(3T)

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