TIFFReadScanline - read and decode a scanline of data from an open TIFF file
#include <tiffio.h> int TIFFReadScanline(TIFF *tif, tdata_t buf, uint32 row, tsample_t sam- ple)
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 sam-
ple)
DESCRIPTION
Read the data for the specified row into the (user supplied) data buf-
fer 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. Appli-
cations 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 orga-
nized 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 automati-
cally 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 Pla-
narConfiguration=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/
libtiff October 15, 1995 TIFFReadScanline(3TIFF)