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    The following form allows you to view linux man pages.

    Command:

    pnmrotate

    
    
    

    SYNOPSIS

           pnmrotate [-noantialias] angle [pnmfile]
    
    
    

    DESCRIPTION

           Reads  a  portable  anymap as input.  Rotates it by the specified angle
           and produces a portable anymap as output.  If  the  input  file  is  in
           color,  the  output  will  be too, otherwise it will be grayscale.  The
           angle is in degrees (floating point), measured  counter-clockwise.   It
           can  be negative, but it should be between -90 and 90.  Also, for rota-
           tions greater than 45 degrees you may get better results if  you  first
           use  pnmflip to do a 90 degree rotation and then pnmrotate less than 45
           degrees back the other direction
    
           The rotation algorithm is Alan Paeth's three-shear method.  Each  shear
           is implemented by looping over the source pixels and distributing frac-
           tions to each of the destination pixels.  This has  an  "anti-aliasing"
           effect  -  it  avoids  jagged edges and similar artifacts.  However, it
           also means that the original colors or gray levels  in  the  image  are
           modified.   If  you  need to keep precisely the same set of colors, you
           can use the -noantialias flag.  This does the shearing by moving pixels
           without  changing  their  values.   If you want anti-aliasing and don't
           care about the precise colors, but still need  a  limited  *number*  of
           colors, you can run the result through ppmquant.
    
           All flags can be abbreviated to their shortest unique prefix.
    
    
    

    REFERENCES

           "A  Fast Algorithm for General Raster Rotation" by Alan Paeth, Graphics
           Interface '86, pp. 77-81.
    
    
    

    SEE ALSO

           pnmshear(1), pnmflip(1), pnm(5), ppmquant(1)
    
    
    

    AUTHOR

           Copyright (C) 1989, 1991 by Jef Poskanzer.
    
                                    12 January 1991                   pnmrotate(1)
    
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