Ppmshift User Manual(0)                                Ppmshift User Manual(0)



NAME
       ppmshift - shift lines of a PPM image left or right by a random amount


SYNOPSIS
       ppmshift shift [ppmfile]


DESCRIPTION
       This program is part of Netpbm(1)

       ppmshift reads a PPM image as input.  Shifts every row of image data to
       the left or right by a random amount, within a range of shift pixels.
       The random distribution is uniform, centered at zero movement.

       The randomness in the image is limited before Netpbm 10.37 (December
       2006) -- if you run the program twice in the same second, you may get
       identical output.

       This is another one of those effects I intended to use for MPEG tests.
       Unfortunately, this program will not help me here - it creates too
       random patterns to be used for animations.  Still, it might give
       interesting results on still images.


EXAMPLE
       Check this out: Save your favourite model's picture from something like
       alt.binaries.pictures.supermodels (ok, or from any other picture
       source), convert it to ppm, and process it e.g. like this, assuming the
       picture is 800x600 pixels:

            #take the upper half, and leave it like it is
            pamcut -top=0 -width=800 -height=300 cs.ppm >upper.ppm

            #take the lower half, flip it upside down, dim it and distort it a little
            pamcut -top=300 -width=800 -height=300 cs.ppm | \
                pamflip -topbottom | \
                ppmdim 0.7 | \
                ppmshift 10 >lower.ppm

            #and concatenate the two pieces
            pnmcat -topbottom upper.ppm lower.ppm >newpic.ppm


       The resulting picture looks like the image being reflected on a water
       surface with slight ripples.


SEE ALSO
       ppm(5) , pamcut(1) , pamflip(1) , ppmdim(1) , pnmcat(1)




AUTHOR
       Copyright (C) 1993 by Frank Neumann

netpbm documentation           20 November 2008        Ppmshift User Manual(0)