.\" $Id: TIFFReadScanline.3tiff,v 1.2 2005-11-02 11:07:18 dron Exp $

.\"

.\" Copyright (c) 1988-1997 Sam Leffler

.\" Copyright (c) 1991-1997 Silicon Graphics, Inc.

.\"

.\" Permission to use, copy, modify, distribute, and sell this software and 

.\" its documentation for any purpose is hereby granted without fee, provided

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.\" IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR

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.\"

.if n .po 0

.TH TIFFReadScanline 3TIFF "October 15, 1995" "libtiff"

.SH NAME

TIFFReadScanline \- read and decode a scanline of data from an open

.SM TIFF

file

.SH SYNOPSIS

.B "#include <tiffio.h>"</tiffio.h>

.sp

.BI "int TIFFReadScanline(TIFF *" tif ", tdata_t " buf ", uint32 " row ", tsample_t " sample ")"

.SH DESCRIPTION

Read the data for the specified row into the (user supplied) data buffer

.IR 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

.IR TIFFScanlineSize

to find out the size (in bytes) of a scanline buffer.

The

.I row

parameter is always used by

.IR TIFFReadScanline ;

the

.I sample

parameter is used only if data are organized in separate planes (\c

.IR PlanarConfiguration =2).

.SH NOTES

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

.I 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,

.PP

In C++ the

.I sample

parameter defaults to 0.

.SH "RETURN VALUES"

.IR TIFFReadScanline

returns \-1 if it detects an error; otherwise 1 is returned.

.SH DIAGNOSTICS

All error messages are directed to the

.IR TIFFError (3TIFF)

routine.

.PP

.BR "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

.I 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.

.SH BUGS

Reading 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 unpack the block-interleaved samples; use the strip- and

tile-based interfaces to read these formats.

.SH "SEE ALSO"

.BR TIFFOpen (3TIFF),

.BR TIFFReadEncodedStrip (3TIFF),

.BR TIFFReadRawStrip (3TIFF),

.BR libtiff (3TIFF)

.PP

Libtiff library home page:

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