63c666344f
According to http://bugzilla.maptools.org/show_bug.cgi?id=2125#c6 callers are not allowed to modify pointer or array values returned from TIFFGetField or the like. So, make this explicit in the documentation by specifying these things as const. Note that this is not an ABI change, since C does not encode const in libraries. Also, this is not really an API change, since the varargs call strips away all the types anyway. So it really is more of a documentation change. fixes #11
229 lines
7.8 KiB
Plaintext
229 lines
7.8 KiB
Plaintext
.\"
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.\" Copyright (c) 1988-1997 Sam Leffler
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.\" Copyright (c) 1991-1997 Silicon Graphics, Inc.
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.\"
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.\" Permission to use, copy, modify, distribute, and sell this software and
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.\" its documentation for any purpose is hereby granted without fee, provided
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.\" that (i) the above copyright notices and this permission notice appear in
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.\" all copies of the software and related documentation, and (ii) the names of
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.\" Sam Leffler and Silicon Graphics may not be used in any advertising or
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.\" publicity relating to the software without the specific, prior written
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.\" permission of Sam Leffler and Silicon Graphics.
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.\"
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.\" THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND,
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.\" EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
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.\" WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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.\"
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.\" IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR
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.\" ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
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.\" OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
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.\" WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
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.\" LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
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.\" OF THIS SOFTWARE.
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.\"
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.if n .po 0
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.TH TIFFGetField 3TIFF "March 18, 2005" "libtiff"
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.SH NAME
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TIFFGetField, TIFFVGetField \- get the value(s) of a tag in an open
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.SM TIFF
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file
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.SH SYNOPSIS
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.B "#include <tiffio.h>"
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.sp
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.BI "int TIFFGetField(TIFF *" tif ", ttag_t " tag ", " ... ")"
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.sp
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.B "#include <stdarg.h>"
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.sp
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.BI "int TIFFVGetField(TIFF *" tif ", ttag_t " tag ", va_list " ap ")"
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.br
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.BI "int TIFFGetFieldDefaulted(TIFF *" tif ", ttag_t " tag ", " ... ")"
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.br
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.BI "int TIFFVGetFieldDefaulted(TIFF *" tif ", ttag_t " tag ", va_list " ap ")"
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.SH DESCRIPTION
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.IR TIFFGetField
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returns the value of a tag or pseudo-tag associated with the the current
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directory of the opened
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.SM TIFF
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file
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.IR tif .
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(A
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.I pseudo-tag
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is a parameter that is used to control the operation of the
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.SM TIFF
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library but whose value is not read or written to the underlying file.) The
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file must have been previously opened with
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.IR TIFFOpen (3TIFF).
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The tag is identified by
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.IR tag ,
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one of the values defined in the include file
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.B tiff.h
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(see also the table below). The type and number of values returned is
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dependent on the tag being requested. The programming interface uses a
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variable argument list as prescribed by the
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.IR stdarg (3)
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interface. The returned values should only be interpreted if
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.IR TIFFGetField
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returns 1.
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.PP
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.IR TIFFVGetField
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is functionally equivalent to
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.IR TIFFGetField
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except that it takes a pointer to a variable argument list.
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.I TIFFVGetField
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is useful for layering interfaces on top of the functionality provided by
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.IR TIFFGetField .
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.PP
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.IR TIFFGetFieldDefaulted
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and
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.IR TIFFVGetFieldDefaulted
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are identical to
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.IR TIFFGetField
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and
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.IR TIFFVGetField ,
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except that if a tag is not defined in the current directory and it has a
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default value, then the default value is returned.
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.PP
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The tags understood by
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.IR libtiff(3TIFF),
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the number of parameter values, and the types for the returned values are
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shown below. The data types are specified as in C and correspond to the types
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used to specify tag values to
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.IR TIFFSetField (3TIFF).
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Remember that
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.IR TIFFGetField
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returns parameter values, so all the listed data types are pointers to storage
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where values should be returned.
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Consult the
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.SM TIFF
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specification (or relevant industry specification) for information on the
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meaning of each tag and their possible values.
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.PP
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.nf
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.ta \w'TIFFTAG_CONSECUTIVEBADFAXLINES'u+2n +\w'Count'u+2n +\w'TIFFFaxFillFunc*'u+2n
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\fITag Name\fP \fICount\fP \fITypes\fP \fINotes\fP
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.sp 5p
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TIFFTAG_ARTIST 1 const char**
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TIFFTAG_BADFAXLINES 1 uint32*
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TIFFTAG_BITSPERSAMPLE 1 uint16*
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TIFFTAG_CLEANFAXDATA 1 uint16*
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TIFFTAG_COLORMAP 3 const uint16** 1<<BitsPerSample arrays
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TIFFTAG_COMPRESSION 1 uint16*
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TIFFTAG_CONSECUTIVEBADFAXLINES 1 uint32*
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TIFFTAG_COPYRIGHT 1 const char**
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TIFFTAG_DATATYPE 1 uint16*
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TIFFTAG_DATETIME 1 const char**
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TIFFTAG_DOCUMENTNAME 1 const char**
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TIFFTAG_DOTRANGE 2 uint16*
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TIFFTAG_EXTRASAMPLES 2 uint16*,const uint16** count & types array
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TIFFTAG_FAXFILLFUNC 1 TIFFFaxFillFunc* G3/G4 compression pseudo-tag
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TIFFTAG_FAXMODE 1 int* G3/G4 compression pseudo-tag
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TIFFTAG_FILLORDER 1 uint16*
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TIFFTAG_GROUP3OPTIONS 1 uint32*
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TIFFTAG_GROUP4OPTIONS 1 uint32*
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TIFFTAG_HALFTONEHINTS 2 uint16*
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TIFFTAG_HOSTCOMPUTER 1 const char**
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TIFFTAG_ICCPROFILE 2 const uint32*,const void** count, profile data
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TIFFTAG_IMAGEDEPTH 1 uint32*
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TIFFTAG_IMAGEDESCRIPTION 1 const char**
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TIFFTAG_IMAGELENGTH 1 uint32*
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TIFFTAG_IMAGEWIDTH 1 uint32*
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TIFFTAG_INKNAMES 1 const char**
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TIFFTAG_INKSET 1 uint16*
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TIFFTAG_JPEGCOLORMODE 1 int* JPEG pseudo-tag
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TIFFTAG_JPEGQUALITY 1 int* JPEG pseudo-tag
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TIFFTAG_JPEGTABLES 2 uint32*,const void** count & tables
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TIFFTAG_JPEGTABLESMODE 1 int* JPEG pseudo-tag
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TIFFTAG_MAKE 1 const char**
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TIFFTAG_MATTEING 1 uint16*
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TIFFTAG_MAXSAMPLEVALUE 1 uint16*
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TIFFTAG_MINSAMPLEVALUE 1 uint16*
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TIFFTAG_MODEL 1 const char**
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TIFFTAG_ORIENTATION 1 uint16*
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TIFFTAG_PAGENAME 1 const char**
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TIFFTAG_PAGENUMBER 2 uint16*
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TIFFTAG_PHOTOMETRIC 1 uint16*
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TIFFTAG_PHOTOSHOP 2 uint32*,const void** count, data
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TIFFTAG_PLANARCONFIG 1 uint16*
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TIFFTAG_PREDICTOR 1 uint16*
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TIFFTAG_PRIMARYCHROMATICITIES 1 const float** 6-entry array
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TIFFTAG_REFERENCEBLACKWHITE 1 const float** 6-entry array
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TIFFTAG_RESOLUTIONUNIT 1 uint16*
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TIFFTAG_RICHTIFFIPTC 2 uint32*,const void** count, data
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TIFFTAG_ROWSPERSTRIP 1 uint32*
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TIFFTAG_SAMPLEFORMAT 1 uint16*
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TIFFTAG_SAMPLESPERPIXEL 1 uint16*
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TIFFTAG_SMAXSAMPLEVALUE 1 double*
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TIFFTAG_SMINSAMPLEVALUE 1 double*
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TIFFTAG_SOFTWARE 1 const char**
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TIFFTAG_STONITS 1 const double**
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TIFFTAG_STRIPBYTECOUNTS 1 const uint32**
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TIFFTAG_STRIPOFFSETS 1 const uint32**
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TIFFTAG_SUBFILETYPE 1 uint32*
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TIFFTAG_SUBIFD 2 uint16*,const uint64** count & offsets array
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TIFFTAG_TARGETPRINTER 1 const char**
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TIFFTAG_THRESHHOLDING 1 uint16*
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TIFFTAG_TILEBYTECOUNTS 1 const uint32**
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TIFFTAG_TILEDEPTH 1 uint32*
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TIFFTAG_TILELENGTH 1 uint32*
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TIFFTAG_TILEOFFSETS 1 const uint32**
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TIFFTAG_TILEWIDTH 1 uint32*
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TIFFTAG_TRANSFERFUNCTION 1 or 3\(dg const uint16**1<<BitsPerSample entry arrays
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TIFFTAG_WHITEPOINT 1 const float** 2-entry array
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TIFFTAG_XMLPACKET 2 uint32*,const void** count, data
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TIFFTAG_XPOSITION 1 float*
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TIFFTAG_XRESOLUTION 1 float*
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TIFFTAG_YCBCRCOEFFICIENTS 1 const float** 3-entry array
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TIFFTAG_YCBCRPOSITIONING 1 uint16*
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TIFFTAG_YCBCRSUBSAMPLING 2 uint16*
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TIFFTAG_YPOSITION 1 float*
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TIFFTAG_YRESOLUTION 1 float*\(dd
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.fi
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\(dg If
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.I SamplesPerPixel
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is one, then a single array is returned; otherwise three arrays are returned.
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.fi
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\(dd The contents of this field are quite complex. See
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.IR "The ICC Profile Format Specification" ,
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Annex B.3 "Embedding ICC Profiles in TIFF Files" (available at
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http://www.color.org) for an explanation.
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.SH AUTOREGISTERED TAGS
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If you can't find the tag in the table above that means this is an unsupported
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tag and is not directly supported by
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.BR libtiff(3TIFF)
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library. You will still be able to read it's value if you know the data type of
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that tag. For example, if you want to read the LONG value from the tag 33424
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and ASCII string from the tag 36867 you can use the following code:
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.PP
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.RS
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.nf
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uint32 count;
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void *data;
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TIFFGetField(tiff, 33424, &count, &data);
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printf("Tag %d: %d, count %d\n", 33424, *(uint32 *)data, count);
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TIFFGetField(tiff, 36867, &count, &data);
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printf("Tag %d: %s, count %d\n", 36867, (char *)data, count);
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.fi
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.RE
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.PP
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.SH RETURN VALUES
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1 is returned if the tag is defined in the current directory; otherwise a 0 is
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returned.
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.SH DIAGNOSTICS
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All error messages are directed to the
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.BR TIFFError (3TIFF)
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routine.
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.PP
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.BR "Unknown field, tag 0x%x" .
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An unknown tag was supplied.
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.SH "SEE ALSO"
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.BR TIFFOpen (3TIFF),
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.BR TIFFSetField (3TIFF),
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.BR TIFFSetDirectory (3TIFF),
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.BR TIFFReadDirectory (3TIFF),
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.BR TIFFWriteDirectory (3TIFF)
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.BR libtiff (3TIFF),
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.PP
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Libtiff library home page:
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.BR http://www.simplesystems.org/libtiff/
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