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)