.\" $Id: TIFFReadDirectory.3tiff,v 1.3 2010-12-12 01:45:35 faxguy Exp $

.\"

.\" Copyright (c) 1988-1997 Sam Leffler

.\" Copyright (c) 1991-1997 Silicon Graphics, Inc.

.\"

.\" Permission to use, copy, modify, distribute, and sell this software and 

.\" its documentation for any purpose is hereby granted without fee, provided

.\" that (i) the above copyright notices and this permission notice appear in

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.\" Sam Leffler and Silicon Graphics may not be used in any advertising or

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.\" THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND, 

.\" EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY 

.\" WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.  

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.\" IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR

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.\" WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF 

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.\" OF THIS SOFTWARE.

.\"

.if n .po 0

.TH TIFFReadDirectory 3TIFF "October 15, 1995" "libtiff"

.SH NAME

TIFFReadDirectory \- get the contents of the next directory in an open

.SM TIFF

file

.SH SYNOPSIS

.B "#include <tiffio.h>"</tiffio.h>

.sp

.BI "int TIFFReadDirectory(TIFF *" tif ")"

.SH DESCRIPTION

Read the next directory in the specified file and make it the current

directory. Applications only need to call

.I TIFFReadDirectory

to read multiple subfiles in a single

.SM TIFF

file\(em

the first directory in a file is automatically read when

.IR TIFFOpen

is called.

.SH NOTES

If the library is compiled with 

.SM STRIPCHOP_SUPPORT

enabled, then images that have a single uncompressed strip or tile of data are

automatically treated as if they were made up of multiple strips or tiles of

approximately 8 kilobytes each. This operation is done only in-memory; it does

not alter the contents of the file. However, the construction of the ``chopped

strips'' is visible to the application through the number of strips [tiles]

returned by 

.I TIFFNumberOfStrips

[\c

.IR TIFFNumberOfTiles ].

.SH "RETURN VALUES"

If the next directory was successfully read, 1 is returned. Otherwise, 0 is

returned if an error was encountered, or if there are no more directories to

be read.

.SH DIAGNOSTICS

All error messages are directed to the

.IR TIFFError (3TIFF)

routine.

All warning messages are directed to the

.IR TIFFWarning (3TIFF)

routine.

.PP

\fBSeek error accessing TIFF directory\fP.

An error occurred while positioning to the location of the

directory.

.PP

\fBWrong data type %d for field "%s"\fP.

The tag entry in the directory had an incorrect data type.

For example, an

.I ImageDescription

tag with a

.SM SHORT

data type.

.PP

\fBTIFF directory is missing required "%s" field\fP.

The specified tag is required to be present by the

.SM TIFF

5.0 specification, but is missing.

The directory is (usually) unusable.

.PP

\fB%s: Rational with zero denominator\fP.

A directory tag has a

.SM RATIONAL

value whose denominator is zero.

.PP

\fBIncorrect count %d for field "%s" (%lu, expecting %lu); tag ignored\fP.

The specified tag's count field is bad.

For example, a count other than 1 for a

.I SubFileType

tag.

.PP

\fBCannot handle different per-sample values for field "%s"\fP.

The tag has

.I SamplesPerPixel

values and they are not all the same; e.g.

.IR BitsPerSample .

The library is unable to handle images of this sort.

.PP

\fBCount mismatch for field "%s"; expecting %d, got %d\fP.

The count field in a

tag does not agree with the number expected by the library.

This should never happen, so if it does, the library refuses to

read the directory.

.PP

\fBInvalid TIFF directory; tags are not sorted in ascending order\fP.

The directory tags are not properly sorted as specified

in the

.SM TIFF

5.0 specification.

This error is not fatal.

.PP

\fBIgnoring unknown field with tag %d (0x%x)\fP.

An unknown tag was encountered in the directory;

the library ignores all such tags.

.PP

\fBTIFF directory is missing required "ImageLength" field\fP.

The image violates the specification by not having a necessary field.

There is no way for the library to recover from this error.

.PP

\fBTIFF directory is missing required "PlanarConfig" field\fP.

The image violates the specification by not having a necessary field.

There is no way for the library to recover from this error.

.PP

\fBTIFF directory is missing required "StripOffsets" field\fP.

The image has multiple strips, but is missing the tag that

specifies the file offset to each strip of data.

There is no way for the library to recover from this error.

.PP

\fBTIFF directory is missing required "TileOffsets" field\fP.

The image has multiple tiles, but is missing the tag that

specifies the file offset to each tile of data.

There is no way for the library to recover from this error.

.PP

\fBTIFF directory is missing required "StripByteCounts" field\fP.

The image has multiple strips, but is missing the tag that

specifies the size of each strip of data.

There is no way for the library to recover from this error.

.PP

\fBTIFF directory is missing required "StripByteCounts" field, calculating from imagelength\fP.

The image violates the specification by not having a necessary field.

However, when the image is comprised of only one strip or tile, the

library will estimate the missing value based on the file size.

.PP

\fBBogus "StripByteCounts" field, ignoring and calculating from imagelength\fP.

Certain vendors violate the specification by writing zero for

the StripByteCounts tag when they want to leave the value

unspecified.

If the image has a single strip, the library will estimate

the missing value based on the file size.

.SH "SEE ALSO"

.BR TIFFOpen (3TIFF),

.BR TIFFWriteDirectory (3TIFF),

.BR TIFFSetDirectory (3TIFF),

.BR TIFFSetSubDirectory (3TIFF),

.BR libtiff (3TIFF)

.PP

Libtiff library home page:

.BR http://www.remotesensing.org/libtiff/