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_t 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 TIFFErrorExtR() 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)

AUTHOR

       LibTIFF contributors

COPYRIGHT

       1988-2024, LibTIFF contributors