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Title
International cooperation and technology transfer
Author
Fras, Mojca Kosmatin

91
3. MAKING THE ANAGLYPH MAP
Such stereo-map is possible to be observed in all its
original colours but only with stereoscope. Smaller
part can be observed with special viewing methods
(parallel view method, cross-eye view method).
Merging of two stereo-pairs is possible, if they are
represented as an anaglyph. This method was first
used in 1858 from Spaniard d'Almeida. Later on
Rollman has introduced a method for projection of
diapositives of the stereogram, which was
successfully used by Louis Lumière in his stereo
cinema projection (additive anaglyph method).
3.1 Anaglyph Method
The anaglyph method uses colour to encode the
right and left image pairs. This method requires a
wear of special glasses with colour filters over each
eye. Best results we get, if used filters are of
complementary colours. International Stereoscopic
Union has chosen the red filter on left and the blue,
cyan or green filter on right for standard disposal. It
is also in coordination with the red used in
international marking of ships, planes and
politicians.
3.2 Anaglyph Types
The anaglyph image could be encode in three
different ways: colour (colour anaglyph), gray (gray
anaglyph*) and pure (pure anaglyph).
The pure anaglyph method converts the original
into a pure red/blue or red/green image
(depending on the type of glasses you have) -
with empty green or blue channel in RGB mode.
This method gives the best 3D effect, but
sacrifices the colour data and image intensity.
Gray anaglyph as same as pure anaglyph
represents the image but in grayscale version of
the original image coloured in red and blue or
green. Althought the colour information is not
preserved, this type of an anaglyph is most
common, because it is typically easier to view.
Colour anaglyph uses red and yellow colour for
the left stereopair and ussualy cyan for the right
stereopair of the image. Colour anaglyph tries to
preserve as much of the original image colour
as possible. Not all images are suitable for a
colour anaglyphs. Using of yellow colour allows
us to present the image in colours. All colours
can not be seen by observing an image with
special glasses.
Because of that, to present our map as colour
anaglyph, we should carefully choose the colours for
cartographical elements. With mixing the different
values cyan, red and yellow and using the red/blue
glasses a 3D impression of the map can be
achieved in wanted colour tints. Pure red or cyan
can not be used.
3.3 Making the Anaglyph
If we want to present a stereo-map as an anaglyph,
both stereopairs should be merged. The easiest way
to do it, is by help of computer:
1. Rasterise both stereo-pairs and present it in RGB
mode;
2. Delete the red channel (contents) from the image
of right stereo-pair;
3. Copy the red channel from the image of left
stereo-pair;
4. Paste the red channel of the left image into red
channel of the right image.
The result is an anaglyph map. Because of the RGB
mode this map could be observed with special
glasses only on the computer screen or projected
with datascope to the screen.
Figure 4: The anaglyph map
3.4 Reproduction the Anaglyph
Teoreticaly we could print the anaglyph map with
transformation of the image into CMYK mode. In
practice is better to print the anaglyph map in three
colours (red, green-blue and yellow for colour
anaglyph), because anaglyphs are very delicate on