NAME

       ppm3d - convert two PPM images into an anaglyph (red/blue 3d glasses) PPM

SYNOPSIS

       ppm3d [-color] [-offset=horizontal_offset] leftppmfile rightppmfile

       Deprecated optional 3rd argument: horizontal_offset

DESCRIPTION

       This program is part of Netpbm(1).

       ppm3d  reads  two  PPM  images  as  input  and  produces  a PPM as output, with the images
       overlapping by the specified number of pixels in blue-green/red format.  The idea is  that
       if you look at the image with 3-D glasses (glasses that admit only red through one eye and
       only green or blue through the other), you see an image with depth.   This  is  called  an
       anaglyph stereogram.

       ppm3d  can  produce  either of two kinds of anaglyph stereogram: monochrome or color.  Use
       the -color option to choose.

       In the monochrome version, ppm3d ignores any color (actually, chrominance)  in  the  input
       images  and produces a result which is monochrome.  Viewed through red-green glasses it is
       yellow, but without any other color in the field, your brain tends to see it as grayscale.

       In the color version, ppm3d generates a  result  which  is  close  to  the  color  of  the
       original.   It's  not  great,  though,  because each eye necessarily cannot see the entire
       spectrum.  Red and cyan don't work well, but most other colors -- especially when  heavily
       saturated -- come out quite well.

       To  view  a  color anaglyph stereogram, you need glasses with a left lens that admits only
       red light and a right lens that admits only blue and green light.  (The right lens may  be
       called  a  cyan  lens  because  that  is  its pigment in white light; don't be misled into
       thinking that cyan is the only color that gets through it).  Your brain is wired  so  that
       even though the components of light are coming in through different eyes, they mix in your
       brain to form the same sensation as if you were looking at the combined  light  with  both
       eyes.

       The input PPMs must be the same dimensions.

       To  make  a different kind of stereogram, use pamstereogram.  That makes a stereogram that
       you view without special glasses, just by letting your eyes unfocus so that each eye  sees
       different parts of the image.

ARGUMENTS

       The mandatory arguments are file names of the left and right input images.

       An  optional third argument specifies the same thing as the value of the -offset argument,
       but is deprecated because -offset is easier to use and read.  Before Netpbm  10.38  (March
       2007), this third argument is the only way to specify the offset.

OPTIONS

       In addition to the options common to all programs based on libnetpbm (most notably -quiet,
       see
        Common Options ⟨index.html#commonoptions⟩ ), ppm3d recognizes the following command  line
       options:

       -offset=horizontal_offset
              This  option indicates the amount, in pixels, by which the left and image is offset
              to the right of the right image in the output.

              The effect of this option is to move the entire image forward (positive numbers) or
              backward  (negative  numbers).  With a zero offset, the main subject of the picture
              appears in the plane of the picture (i.e. if the image is projected  on  a  screen,
              the location of the screen).  The main subject is the subject at the location where
              the line of sight of the left camera intersects the line  of  sight  of  the  right
              camera  -- the main subject appears at the same location in both the left and right
              images.

              Default is zero.

              This option was new in Netpbm 10.38 (March  2007).   Before  that,  use  the  third
              argument instead.  Also, before Netpbm 10.38 the default is +30 pixels.

       -color This  option  causes ppm3d to generate a color anaglyph stereogram.  By default, it
              generates monochrome.

              This option was new in Netpbm 10.38 (March 2007).

SEE ALSO

       pamstereogram(1) ppm(1)

AUTHOR

       Copyright (C) 1993 by David K. Drum.

DOCUMENT SOURCE

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

              http://netpbm.sourceforge.net/doc/ppm3d.html