TIFFReadScanline(3tiff) - phpMan

TIFFReadScanline(3TIFF)                                                   TIFFReadScanline(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, 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  (PlanarConfigura-
       tion=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-sequen-
       tial 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 PlanarConfigura-
       tion=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.remotesensing.org/libtiff/



libtiff                                  October 15, 1995                 TIFFReadScanline(3TIFF)

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