ppmshift

Updated: 16 November 1993
Table Of Contents

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.

ppmshift reads a PPM image as input. Shifts every row of image data to the left or right by a certain amount. The shift parameter determines by how many pixels a row is to be shifted at most.

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.