phpman > man > pnmshear(1)

pnmshear(1)                            General Commands Manual                           pnmshear(1)



NAME
       pnmshear - shear a portable anymap by some angle

SYNOPSIS
       pnmshear [-noantialias] angle [pnmfile]

DESCRIPTION
       Reads  a  portable anymap as input.  Shears 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), and measures this:
           +-------+  +-------+
           |       |  |\       \
           |  OLD  |  | \  NEW  \
           |       |  |an\       \
           +-------+  |gle+-------+
       If the angle is negative, it shears the other way:
           +-------+  |-an+-------+
           |       |  |gl/       /
           |  OLD  |  |e/  NEW  /
           |       |  |/       /
           +-------+  +-------+
       The angle should not get too close to 90 or -90, or the resulting anymap will be unreasonably
       wide.

       The shearing is implemented by looping over the source pixels and distributing  fractions  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.

SEE ALSO
       pnmrotate(1), pnmflip(1), pnm(5), ppmquant(1)

AUTHOR
       Copyright (C) 1989, 1991 by Jef Poskanzer.



                                           12 January 1991                               pnmshear(1)