ppm3d(1) - Man pages

Ppm3d User Manual(1) General Commands Manual Ppm3d User Manual(1)

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, chromi-
nance) 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 neces-
sarily 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 im-
ages.

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 ]8;;index.html#commonoptions\ Common Options]8;;\ ), ppm3d recognizes the fol-
lowing 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 out-
put.

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 lo-
cation 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).