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TIFFReadScanline
TIFFReadScanline
NAME
SYNOPSIS
DESCRIPTION
NOTES
RETURN VALUES
DIAGNOSTICS
BUGS
SEE ALSO
NAME
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TIFFReadScanline − read and decode a scanline of
data from an open TIFF file
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SYNOPSIS
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#include <tiffio.h>
int TIFFReadScanline(TIFF *tif,
tdata_t buf, uint32 row,
tsample_t sample)
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DESCRIPTION
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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).
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NOTES
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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.
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RETURN VALUES
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TIFFReadScanline returns −1 if it detects an
error; otherwise 1 is returned.
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DIAGNOSTICS
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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.
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BUGS
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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.
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SEE ALSO
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TIFFOpen(3TIFF),
TIFFReadEncodedStrip(3TIFF),
TIFFReadRawStrip(3TIFF), libtiff(3TIFF)
Libtiff library home page:
http://www.simplesystems.org/libtiff/
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