TIFFReadDirectory(3tiff)

NAME

       TIFFReadDirectory  -  get the contents of the next directory in an open
       TIFF file

SYNOPSIS

       #include <tiffio.h>

       int TIFFReadDirectory(TIFF *tif)

DESCRIPTION

       Read the next directory in the specified file and make it  the  current
       directory.  Applications  only  need  to call TIFFReadDirectory to read
       multiple subfiles in a single TIFF file-- the first directory in a file
       is automatically read when TIFFOpen is called.

NOTES

       If  the library is compiled with 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 approxi-
       mately 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 TIFFNumberOfStrips [TIFFNumberOfTiles].

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.

DIAGNOSTICS

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

       Seek error accessing TIFF directory.  An error occurred while position-
       ing to the location of the directory.

       Wrong  data type %d for field "%s".  The tag entry in the directory had
       an incorrect data type.  For example, an ImageDescription  tag  with  a
       SHORT data type.

       TIFF  directory  is  missing required "%s" field.  The specified tag is
       required to be present by the TIFF 5.0 specification, but  is  missing.
       The directory is (usually) unusable.

       %s:  Rational  with  zero  denominator.  A directory tag has a RATIONAL
       value whose denominator is zero.

       Incorrect count %d for field "%s" (%lu, expecting  %lu);  tag  ignored.
       The  specified  tag's  count  field is bad.  For example, a count other
       than 1 for a SubFileType tag.

       Cannot handle different per-sample values for field "%s".  The tag  has
       SamplesPerPixel values and they are not all the same; e.g.  BitsPerSam-
       ple.  The library is unable to handle images of this sort.

       Count mismatch for field "%s"; expecting %d, got %d.  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.

       Invalid  TIFF  directory;  tags are not sorted in ascending order.  The
       directory tags are not properly sorted as specified  in  the  TIFF  5.0
       specification.  This error is not fatal.

       Ignoring  unknown field with tag %d (0x%x).  An unknown tag was encoun-
       tered in the directory; the library ignores all such tags.

       TIFF directory is missing requred "ImageLength" field.  The image  vio-
       lates  the  specification by not having a necessary field.  There is no
       way for the library to recover from this error.

       TIFF directory is missing requred "PlanarConfig" field.  The image vio-
       lates  the  specification by not having a necessary field.  There is no
       way for the library to recover from this error.

       TIFF directory is missing requred "StripOffsets" field.  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.

       TIFF  directory  is missing requred "TileOffsets" field.  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.

       TIFF directory is missing required "StripByteCounts" field.  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.

       TIFF directory is missing required "StripByteCounts" field, calculating
       from imagelength.  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.

       Bogus  "StripByteCounts"  field,  ignoring  and calculating from image-
       length.  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.

SEE ALSO

       libtiff(3TIFF),  TIFFOpen(3TIFF), TIFFWriteDirectory(3TIFF), TIFFSetDi-
       rectory(3TIFF), TIFFSetSubDirectory(3TIFF)

libtiff                        October 15, 1995       TIFFReadDirectory(3TIFF)