tiffmedian



TIFFMEDIAN(1)                                                    TIFFMEDIAN(1)




NAME

       tiffmedian - apply the median cut algorithm to data in a TIFF file


SYNOPSIS

       tiffmedian [ options ] input.tif output.tif


DESCRIPTION

       tiffmedian  applies  the  median  cut  algorithm  to  an  RGB  image in
       input.tif to generate a palette image that is  written  to  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 col-
       ormap.


OPTIONS

       -c     Specify  the  compression  to use for data written to the output
              file: none for no compression, packbits  for  PackBits  compres-
              sion,  lzw  for  Lempel-Ziv  &  Welch  compression,  and zip for
              Deflate compression.  By default tiffmedian will  compress  data
              according  to  the  value  of  the  Compression tag found in the
              source file.

              LZW compression can  be  specified  together  with  a  predictor
              value.   A predictor value of 2 causes each scanline of the out-
              put 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.  -c lzw:2 for
              LZW compression with horizontal differencing.

       -C     Specify the number of entries to use in the generated  colormap.
              By default all 256 entries/colors are used.

       -f     Apply  Floyd-Steinberg  dithering  before  selecting  a colormap
              entry.

       -r     Specify the number of rows (scanlines) in  each  strip  of  data
              written  to the output file.  By default, tiffmedian attempts to
              set the rows/strip that no more than 8 kilobytes of data  appear
              in a strip.


NOTES

       This program is derived from Paul Heckbert’s median program.


SEE ALSO

       pal2rgb(1), tiffinfo(1), tiffcp(1), tiffcmp(1), libtiff(3)

       "Color  Image  Quantization  for  Frame Buffer Display", Paul Heckbert,
       SIGGRAPH proceedings, 1982, pp. 297-307.



                               October 15, 1995                  TIFFMEDIAN(1)

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