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.remotesensing.org/libtiff/
