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RLEQUANT(1)		    General Commands Manual		   RLEQUANT(1)

NAME
       rlequant	- variance based color quantization for	RLE images

SYNOPSIS
       rlequant	 [  -b bits ] [	-c ] [ -d ] [ -f ] [ -i	cubeside ] [ -m	] [ -n
	      colors ] [ -r mapfile ] [	-o outfile ] [ infile ]

DESCRIPTION
       This program quantizes the colors in an RLE  image  using  a  variance-
       based method.  See colorquant(3)	for more details on the	method.

       -b bits
	      The  colors  in  the  input image	will be	"prequantized" to this
	      many bits	before applying	the variance-based method.  Two	inter-
	      nal  tables  of size 2^(3*bits) are allocated, so	values of bits
	      greater than 6 are likely	to cause thrashing or may prevent  the
	      program  from  running  at all.  The default value of bits is 5.
	      It must be less than or equal to 8 and greater than 0.

       -c     Only the color map will be output; the image will	not  be	 digi-
	      tized.  The output file will be a	0x0 RLE	file with a color map,
	      suitable for input to rleldmap(1), rledither(1), or rlequant -r.

       -d     Floyd Steinberg dithering	is performed on	the output.   This  is
	      very  helpful  for  images  being	quantized to a small number of
	      colors.

       -f     If this option is	specified,  a  faster  approximation  will  be
	      used.  In	most cases, the	error so introduced will be barely no-
	      ticeable.

       -i cubeside
	      Initializes the output color map with a  "color  cube"  of  size
	      cubeside^3.   I.e., if -i	2 were specified, the 8	corners	of the
	      color cube (black, red,  green,  blue,  yellow,  cyan,  magenta,
	      white)  would be added to	the output colormap.  This reduces the
	      number of	colors available for  quantization.   The  color  cube
	      will  be	used to	quantize the output image, but will not	other-
	      wise affect the choice of	representative colors.

       -m     Computes a single	color map suitable for quantizing all the  in-
	      put  images.   This  is useful when the quantized	images will be
	      used as a	"movie"	(e.g., with the	-m flag	 of  getx11(1)).   The
	      input  may  not  come from a pipe	when this option is specified,
	      unless -c	is also	specified.

       -n colors
	      The output image will be quantized to at most colors colors.  It
	      might  have  fewer  if the input image has only a	few colors it-
	      self.  The default value of colors is 256	-  cubesize^3  -  map-
	      size.   It  must	be less	than or	equal to 256.  If a color cube
	      (-c) or an input map (-r)	is given, colors may be	 0;  otherwise
	      it must be greater than 0.

       -r mapfile
	      The  color  map  from  the RLE file mapfile will be added	to the
	      output color map.	 The number of colors in the input color  map,
	      mapsize  is calculated as	follows: If a color_map_length comment
	      is present in mapfile, its value is used.	 If not, the  size  of
	      the  color map (usually 256) is used (the	rlehdr(1) program will
	      display the color	map size and the comment,  if  present).   The
	      input  color  map	will be	used to	quantize the output image, but
	      will not otherwise affect	the choice of  representative  colors.
	      If  the  combination -n 0	-r mapfile is specified, then rlequant
	      will just	quantize (and dither, if requested) the	 input	images
	      to  the  given  colormap.	  This	is  usually  faster than using
	      rledither.

       -o outfile
	      The output will be written to the	file outfile.  If  not	speci-
	      fied,  or	 if  outfile is	"-", the output	will be	written	to the
	      standard output stream.

       infile This file	contains one or	more concatenated  RLE	images.	  Each
	      will  be processed in turn.  A separate quantization map will be
	      constructed for each image.  If not specified, or	if  infile  is
	      "-", the image(s)	will be	read from the standard input stream.

EXAMPLES
       rlequant	file.rle
	      Quantizes	file.rle to 256	colors using a 5-bit pre-quantization.
	      If file.rle has multiple images, each will get its own  (differ-
	      ent) colormap.

       rlequant	-m file.rle
	      Quantizes	file.rle to 256	colors using a 5-bit pre-quantization.
	      If file.rle has multiple images, they will all be	used to	choose
	      the color	map, and will all be quantized to the same color map.

       cat *.rle | rlequant -m -c >map.rle ;
		   cat *.rle | rlequant	-n 0 -r	map.rle
	      Computes	a single colormap based	on all the images in the files
	      *.rle, then quantizes each image to that color map.  The	output
	      is the stream of quantized images.

       rlequant	-i 4 -d	file.rle
	      Compute  192  representative  colors for each image in file.rle,
	      add a 4x4x4 color	cube to	the  resulting	color  map,  and  then
	      quantize	the  image to the resulting set	of colors with dither-
	      ing.

       rlequant	-b 6 file.rle
	      Quantize file.rle	to 256 colors using a  6-bit  prequantization.
	      This  provides  slightly	more  precision	in color matching than
	      does a 5-bit prequantization.  It	also runs significantly	slower
	      and requires approximately 8 times the memory for	its intermedi-
	      ate storage.

SEE ALSO
       mcut(1),	rledither(1), rlehdr(1), urt(1), colorquant(3),	RLE(5).

AUTHOR
       Spencer W. Thomas
       Craig Kolb (Yale	University) wrote the color quantization code.
       Rod Bogart wrote	the dithering code.

4th Berkeley Distribution	 June 12, 1990			   RLEQUANT(1)

NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | SEE ALSO | AUTHOR

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