TIFFReadScanline - read and decode a scanline of data from an open TIFF file
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 (PlanarConfigura-
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(3T) routine.
Compression algorithm does not support random access. Data was requested in a non-sequen-
tial 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 PlanarConfigura-
tion=1 the library does not unpack the block-interleaved samples; use the strip- and tile-
based interfaces to read these formats.
libtiff(3T), TIFFOpen(3T), TIFFReadEncodedStrip(3T), TIFFReadRawStrip(3T)
October 15, 1995 TIFFReadScanline(3T)