ppmqvga(1) [redhat man page]
PPMQVGA(1) General Commands Manual PPMQVGA(1) NAME
ppmqvga - 8 plane quantization SYNOPSIS
ppmqvga [ options ] [ input file ] DESCRIPTION
ppmqvga quantizes PPM files to 8 planes, with optional Floyd-Steinberg dithering. Input is a PPM file from the file named, or standard input of no file is provided. Options -d dither. Apply Floyd-Steinberg dithering to the data -q quiet. Produces no progress reporting, and no terminal output unless and error occurs. -v verbose. Produces additional output describing the number of colors found, and some information on the resulting mapping. May be repeated to generate loads of internal table output, but generally only useful once. EXAMPLES
ppmqvga -d my_image.ppm | ppmtogif >my_image.gif tgatoppm zombie.tga | ppmqvga | ppmtotif > zombie.tif SEE ALSO
ppmquant DIAGNOSTICS
Error messages if problems, various levels of optional progress reporting. LIMITATIONS
none known. AUTHOR
Original by Lyle Rains (lrains@netcom.com) as ppmq256 and ppmq256fs combined, documented, and enhanced by Bill Davidsen (david- sen@crd.ge.com) Copyright Copyright 1991,1992 by Bill Davidsen, all rights reserved. The program and documentation may be freely distributed by anyone in source or binary format. Please clearly note any changes. local PPMQVGA(1)
Check Out this Related Man Page
ppmquant(1) General Commands Manual ppmquant(1) NAME
ppmquant - quantize the colors in a portable pixmap down to a specified number SYNOPSIS
ppmquant [-floyd|-fs] ncolors [ppmfile] ppmquant [-floyd|-fs] [-nofloyd|-nofs] -mapfile mapfile [ppmfile] All options can be abbreviated to their shortest unique prefix. You may use two hyphens instead of one to designate an option. You may use either white space or equals signs between an option name and its value. DESCRIPTION
pnmquant is a newer, more general program that is backward compatible with ppmquant. ppmquant may be faster, though. Reads a PPM image as input. Chooses ncolors colors to best represent the image, maps the existing colors to the new ones, and writes a PPM image as output. The quantization method is Heckbert's "median cut". Alternately, you can skip the color-choosing step by specifying your own set of colors with the -mapfile option. The mapfile is just a ppm file; it can be any shape, all that matters is the colors in it. For instance, to quantize down to the 8-color IBM TTL color set, you might use: P3 8 1 255 0 0 0 255 0 0 0 255 0 0 0 255 255 255 0 255 0 255 0 255 255 255 255 255 If you want to quantize one image to use the colors in another one, just use the second one as the mapfile. You don't have to reduce it down to only one pixel of each color, just use it as is. If you use a mapfile, the output image has the same maxval as the mapfile. Otherwise, the output maxval is the same as the input maxval, or less in some cases where the quantization process reduces the necessary resolution. The -floyd/-fs option enables a Floyd-Steinberg error diffusion step. Floyd-Steinberg gives vastly better results on images where the unmodified quantization has banding or other artifacts, especially when going to a small number of colors such as the above IBM set. How- ever, it does take substantially more CPU time, so the default is off. -nofloyd/-nofs means not to use the Floyd-Steinberg error diffusion. This is the default. REFERENCES
"Color Image Quantization for Frame Buffer Display" by Paul Heckbert, SIGGRAPH '82 Proceedings, page 297. SEE ALSO
pnmquant(1), ppmquantall(1), pnmdepth(1), ppmdither(1), ppm(5) AUTHOR
Copyright (C) 1989, 1991 by Jef Poskanzer. 12 January 1991 ppmquant(1)