TIFFReadScanline(3tiff)

TIFFReadScanline(3TIFFMISC. REFERENCE MANUAL PAGETIFFReadScanline(3TIFF)

NAME

     TIFFReadScanline - read and decode a scanline of  data  from
     an open TIFF file

SYNOPSIS

     #include <tiffio.h>

     int TIFFReadScanline(TIFF *tif, tdata_t buf, uint32 row

DESCRIPTION

     Read the data for the specified row into the (user supplied)
     data buffer buf.  The data are returned decompressed and, in
     the native byte- and bit-ordering, but are otherwise  packed
     (see further below). The buffer must be large enough to hold
     an entire scanline of data.  Applications  should  call  the
     routine  TIFFScanlineSize to find out the size (in bytes) of
     a scanline buffer.  The row parameter is always used by TIF-
     FReadScanline; the sample parameter is used only if data are
     organized in separate planes (PlanarConfiguration=2).

NOTES

     The library attempts to hide bit- and byte-ordering  differ-
     ences between the image and the native machine by converting
     data to the native machine order.  Bit reversal is  done  if
     the  FillOrder  tag  is  opposite  to the native machine bit
     order. 16- and 32-bit samples are automatically byte-swapped
     if  the  file  was written with a byte order opposite to the
     native machine byte order,

     In C++ the sample parameter defaults to 0.

RETURN VALUES

     TIFFReadScanline returns -1 if it detects an  error;  other-
     wise 1 is returned.

DIAGNOSTICS

     All error messages are directed to the TIFFError(3TIFF) rou-
     tine.

     Compression algorithm does not support random access.   Data
     was  requested  in  a  non-sequential order from a file that
     uses a  compression  algorithm  and  that  has  RowsPerStrip
     greater than one.  That is, data in the image is stored in a
     compressed form, and with multiple rows packed into a strip.
     In  this case, the library does not support random access to
     the data. The data should either be  accessed  sequentially,
     or  the  file should be converted so that each strip is made
     up of one row of data.

BUGS

     Reading  subsampled  YCbCR  data  does  not  work  correctly
     because, for PlanarConfiguration=2 the size of a scanline is

libtiff           Last change: October 15, 1995                 1

TIFFReadScanline(3TIFFMISC. REFERENCE MANUAL PAGETIFFReadScanline(3TIFF)

     not calculated on a per-sample basis, and  for  PlanarConfi-
     guration=1 the library does not unpack the block-interleaved
     samples; use the strip- and tile-based  interfaces  to  read
     these formats.

SEE ALSO

     libtiff(3TIFF),                             TIFFOpen(3TIFF),
     TIFFReadEncodedStrip(3TIFF), TIFFReadRawStrip(3TIFF)

libtiff           Last change: October 15, 1995                 2