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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 sample)
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).
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.
TIFFReadScanline
returns -1 if it detects an error; otherwise 1 is returned.
All
error messages are directed to the TIFFError(3)
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.
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.
libtiff(3)
, TIFFOpen(3)
, TIFFReadEncodedStrip(3)
,
TIFFReadRawStrip(3)
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