tiffmedian.1

tiff文件开发库

.\"	$Header: /cvsroot/osrs/libtiff/man/tiffmedian.1,v 1.2 2003/05/05 10:41:17 dron Exp $
.\"
.\" Copyright (c) 1990-1997 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
.\" that (i) the above copyright notices and this permission notice appear in
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.\" WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.  
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.\" IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR
.\" ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
.\" OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
.\" WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF 
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.\" OF THIS SOFTWARE.
.\"
.if n .po 0
.TH TIFFMEDIAN 1 "October 15, 1995"
.SH NAME
tiffmedian \- apply the median cut algorithm to data in a
.SM TIFF
file
.SH SYNOPSIS
.B tiffmedian
[
.I options
]
.I input.tif
.I output.tif
.SH DESCRIPTION
.I tiffmedian
applies the median cut algorithm to an
.SM RGB
image in
.I input.tif
to generate a palette image that is written to
.IR output.tif .
The generated colormap has, by default, 256 entries.
The image data is quantized by mapping each
pixel to the closest color values in the colormap.
.SH OPTIONS
.TP
.B \-c
Specify the compression to use for data written to the output file:
.B none 
for no compression,
.B packbits
for PackBits compression,
.B lzw
for Lempel-Ziv & Welch compression,
and
.B zip
for Deflate compression.
By default
.I tiffmedian
will compress data according to the value of the
.I Compression
tag found in the source file.
.IP
.SM LZW
compression can be specified together with a 
.I predictor
value.
A predictor value of 2 causes
each scanline of the output image to undergo horizontal
differencing before it is encoded; a value
of 1 forces each scanline to be encoded without differencing.
LZW-specific options are specified by appending a ``:''-separated
list to the ``lzw'' option; e.g.
.B "\-c lzw:2"
for
.SM LZW
compression with horizontal differencing.
.TP
.B \-C
Specify the number of entries to use in the generated colormap.
By default all 256 entries/colors are used.
.TP
.B \-f
Apply Floyd-Steinberg dithering before selecting a colormap entry.
.TP
.B \-r
Specify the number of rows (scanlines) in each strip of data
written to the output file.
By default,
.I tiffmedian
attempts to set the rows/strip
that no more than 8 kilobytes of data appear in a strip.
.SH NOTES
This program is derived from Paul Heckbert's
.I median
program.
.SH "SEE ALSO"
.IR pal2rgb (1),
.IR tiffinfo (1),
.IR tiffcp (1),
.IR tiffcmp (1),
.IR libtiff (3)
.PP
"Color Image Quantization for Frame Buffer Display", Paul
Heckbert, SIGGRAPH proceedings, 1982, pp. 297-307.