TIFFMEDIANSection: User Commands (1)
Updated: November 2, 2005
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NAMEtiffmedian - apply the median cut algorithm to data in a TIFF file
SYNOPSIStiffmedian [ options ] input.tif output.tif
DESCRIPTIONtiffmedian 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 colormap.
- Specify the compression to use for data written to the output file: none for no compression, packbits for PackBits compression, 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 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. -c lzw:2 for LZW compression with horizontal differencing.
- Specify the number of entries to use in the generated colormap. By default all 256 entries/colors are used.
- Apply Floyd-Steinberg dithering before selecting a colormap entry.
- 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.
NOTESThis program is derived from Paul Heckbert's median program.
SEE ALSOpal2rgb(1), tiffinfo(1), tiffcp(1), tiffcmp(1), libtiff(3TIFF)
Color Image Quantization for Frame Buffer Display, Paul Heckbert, SIGGRAPH proceedings, 1982, pp. 297-307.
Libtiff library home page: http://www.remotesensing.org/libtiff/