.\"
.\" Copyright (c) 1988-1997 Sam Leffler
.\" Copyright (c) 1991-1997 Silicon Graphics, Inc.
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.if n .po 0
.TH TIFFWriteScanline 3TIFF "December 16, 1991" "libtiff"
.SH NAME
TIFFWriteScanline \- write a scanline to an open
.SM TIFF
file
.SH SYNOPSIS
.B "#include <tiffio.h>"
.sp
.BI "int TIFFWriteScanline(TIFF *" tif ", tdata_t " buf ", uint32_t " 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 (3TIFF)
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 (3TIFF)
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 (3TIFF).
.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
.BR TIFFSetField (3TIFF)
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
.BR TIFFSetField (3TIFF)
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"
.BR TIFFOpen (3TIFF),
.BR TIFFWriteEncodedStrip (3TIFF),
.BR TIFFWriteRawStrip (3TIFF),
.BR libtiff (3TIFF)
.PP
Libtiff library home page:
.BR http://www.simplesystems.org/libtiff/