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

       1988-2022, LibTIFF contributors

4.7                                               Apr 30, 2025                           TIFFREADSCANLINE(3tiff)