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, tsample_t sample)

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 TIFFReadScanline; 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 differences 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; otherwise 1 is returned.

DIAGNOSTICS

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

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

SEE ALSO

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

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