libtiff/man/TIFFWriteScanline.3t

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.if n .po 0
.TH TIFFWriteScanline 3T "December 16, 1991"
.SH NAME
TIFFWriteScanline \- write a scanline to an open
.SM TIFF
file
.SH SYNOPSIS
.B "#include <tiffio.h>"
.br
.B "int TIFFWriteScanline(TIFF* tif, tdata_t buf, uint32 row, tsample_t sample)"
.SH DESCRIPTION
Write data to a file at the specified row.
The
.I sample
parameter is used only if data are organized in separate planes (\c
.IR PlanarConfiguration =2).
The data are assumed to be uncompressed and in the native
bit- and byte-order of the host machine.
The data written to the file is
compressed according to the compression scheme
of the current
.SM TIFF
directory (see further below).
If the current scanline is past the end of the current subfile, the
.I ImageLength
field is automatically increased to include the scanline (except
for
.IR PlanarConfiguration =2,
where the
.I ImageLength
cannot be changed once the first data are written).
If the
.I ImageLength
is increased, the
.I StripOffsets
and
.I StripByteCounts
fields are similarly enlarged to reflect data written past the
previous end of image.
.SH NOTES
The library writes encoded data using the native machine byte order.
Correctly implemented
.SM TIFF
readers are expected to do any necessary byte-swapping to
correctly process image data with BitsPerSample greater than 8.
The library attempts to hide bit-ordering differences
between the image and the native machine by converting data
from the native machine order.
.PP
In C++ the
.I sample
parameter defaults to 0.
.PP
Once data are written to a file for the current directory,
the values of certain tags may not be altered; see
.IR TIFFSetField (3T)
for more information.
.PP
It is not possible to write scanlines to a file that
uses a tiled organization.  The routine
.IR TIFFIsTiled
can be used to determine if the file is organized
as tiles or strips.
.SH "RETURN VALUES"
.IR TIFFWriteScanline
returns \-1 if it immediately detects an error
and 1 for a successful write.
.SH DIAGNOSTICS
All error messages are directed to the
.IR TIFFError (3T)
routine.
.PP
.BR "%s: File not open for writing .
The file was opened for reading, not writing.
.PP
.BR "Can not write scanlines to a tiled image" .
An attempt was made to write a scanline to a tiled image.
The image is assumed to be organized in tiles because the
.I TileWidth
and
.I TileLength
tags have been set with
.IR TIFFSetField (3T).
.PP
.BR "Compression algorithm does not support random access" .
Data was written in a non-sequential order to a file that
uses a compression algorithm and that has
.I RowsPerStrip
greater than one.
That is, data in the image is to be 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 written as entire strips,
sequentially by rows, or the value of
.I RowsPerStrip
should be set to one.
.PP
\fB%s: Must set "ImageWidth" before writing data\fP.
The image's width has not be set before the first write.
See
.IR TIFFSetField (3T)
for information on how to do this.
.PP
\fB%s: Must set "PlanarConfiguration" before writing data\fP.
The organization of data has not be defined before the first write.
See
.IR TIFFSetField (3T)
for information on how to do this.
.PP
\fBCan not change "ImageLength" when using separate planes\fP.
Separate image planes are being used (\c
.IR PlanarConfiguration =2),
but the number of rows has not been specified before the first write.
The library supports the dynamic growth of an image only when data
are organized in a contiguous manner (\c
.IR PlanarConfiguration =1).
.PP
.BR "%d: Sample out of range, max %d" .
The
.I sample
parameter was greater than the value of the SamplesPerPixel tag.
.PP
.BR "%s: No space for strip arrays .
There was not enough space for the arrays that hold strip
offsets and byte counts.
.SH BUGS
Writing subsampled YCbCR data does not work correctly
because, for 
.IR PlanarConfiguration =2
the size of a scanline is not calculated on a per-sample basis,
and for
.IR PlanarConfiguration =1
the library does not pack the block-interleaved samples.
.SH "SEE ALSO"
.IR libtiff (3T),
.IR TIFFOpen (3T),
.IR TIFFWriteEncodedStrip (3T),
.IR TIFFWriteRawStrip (3T)