TIFFSetField

NAME

TIFFSetField, TIFFVSetField − set the value(s) of a tag in a TIFF file open for writing

SYNOPSIS

#include <tiffio.h>

int TIFFSetField(TIFF *tif, ttag_t tag, ...)

#include <stdarg.h>

int TIFFVSetField(TIFF *tif, ttag_t tag, va_list ap)

DESCRIPTION

TIFFSetField sets the value of a field or pseudo-tag in the current directory associated with 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.) To set the value of a field the file must have been previously opened for writing with TIFFOpen(3TIFF); pseudo-tags can be set whether the file was opened for reading or writing. The field is identified by tag, one of the values defined in the include file tiff.h (see also the table below). The actual value is specified using a variable argument list, as prescribed by the stdarg(3) interface (or, on some machines, the varargs(3) interface.)

TIFFVSetField is functionally equivalent to TIFFSetField except that it takes a pointer to a variable argument list. TIFFVSetField is useful for writing routines that are layered on top of the functionality provided by TIFFSetField.

The tags understood by libtiff, the number of parameter values, and the expected types for the parameter values are shown below. The data types are: char* is null-terminated string and corresponds to the ASCII data type; uint16 is an unsigned 16-bit value; uint32 is an unsigned 32-bit value; uint16* is an array of unsigned 16-bit values. void* is an array of data values of unspecified type.

Consult the TIFF specification for information on the meaning of each tag.

† Tag may not have its values changed once data is written.
‡ If SamplesPerPixel is one, then a single array is passed; otherwise three arrays should be passed.
* The contents of this field are quite complex. See The ICC Profile Format Specification, Annex B.3 "Embedding ICC Profiles in TIFF Files" (available at http://www.color.org) for an explanation.

RETURN VALUES

1 is returned if the operation was successful. Otherwise, 0 is returned if an error was detected.

DIAGNOSTICS

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

%s: Cannot modify tag "%s" while writing. Data has already been written to the file, so the specified tag’s value can not be changed. This restriction is applied to all tags that affect the format of written data.

%d: Bad value for "%s". An invalid value was supplied for the named tag.

SEE ALSO

TIFFOpen(3TIFF), TIFFGetField(3TIFF), TIFFSetDirectory(3TIFF), TIFFWriteDirectory(3TIFF), TIFFReadDirectory(3TIFF), libtiff(3TIFF)

Libtiff library home page: http://www.simplesystems.org/libtiff/