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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 <small>TIFF</small> file

SYNOPSIS

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#include <tiffio.h>

int TIFFReadScanline(TIFF *tif,

tdata_t buf, uint32 row,

tsample_t sample)

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).

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.

RETURN VALUES

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TIFFReadScanline returns −1 if it detects an

error; otherwise 1 is returned.

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.

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.

SEE ALSO

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TIFFOpen(3TIFF),

TIFFReadEncodedStrip(3TIFF),

TIFFReadRawStrip(3TIFF), libtiff(3TIFF)

Libtiff library home page:

http://www.remotesensing.org/libtiff/