TIFFREADSCANLINE(3tiff) LibTIFF 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_t row, tsample_t
sample)
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 ma-
chine 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 TIFFErrorExtR() 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 ac-
cessed 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 in-
terfaces to read these formats.
SEE ALSO
TIFFOpen (3tiff), TIFFReadEncodedStrip (3tiff), TIFFReadRawStrip
(3tiff), libtiff (3tiff)
AUTHOR
LibTIFF contributors
COPYRIGHT
1988-2023, LibTIFF contributors
4.5 Nov 23, 2023 TIFFREADSCANLINE(3tiff)
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