ppmshift - Man Page

• Shift the lines in the input image by a randomized amount not exceeding s to the left or to the right: ppmshift s path/to/input_file.ppm > path/to/output_file.ppm

tldr.sh

ppmshift shift [ppmfile]

This program is part of Netpbm(1).

ppmshift reads a PPM image as input.  It 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 an effect the author intended to use for MPEG tests. Unfortunately, this program is not useful for that - it creates too random patterns to be used for animations.  Still, it might give interesting results on still images.

There are no command line options defined specifically for ppmshift, but it recognizes the options common to all programs based on libnetpbm (See Common Options .)

Check this out: Save your favorite 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.

ppm(1), pamcut(1), pamflip(1), ppmdim(1), pnmcat(1)

Copyright (C) 1993 by Frank Neumann

This manual page was generated by the Netpbm tool 'makeman' from HTML source.  The master documentation is at

http://netpbm.sourceforge.net/doc/ppmshift.html

pamshuffle(1).