ppmshear

Section: User Commands (1)
Updated: 08 February 1989
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NAME

ppmshear - shear a portable pixmap by some angle

SYNOPSIS

ppmshear angle [ppmfile]

DESCRIPTION

Reads a portable pixmap as input. Shears it by the specified angle and produces a portable pixmap as output. 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 pixmap will be unreasonably wide.

The shearing is implemented by looping over the source pixels and distributing fractions to each of the destination pixels.

AUTHOR

Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation. This software is provided "as is" without express or implied warranty.