Master Thesis - Hochschule Bonn-Rhein-Sieg

5. Algorithms Master Thesis Björn Ostermann page 64 of 126
a) b) c)
Figure 40: Reflection data, collected in a sample office environment
a) unmodified, b) scaled greyscale values, c) histogram analysis
5.1.2 Converting distance to colour
As already mentioned, the range data is to be depicted using colours. In the depiction of heat images
and stress images, it is common to use a colour-bar ranging from red to blue. This colour-bar, depicted
in Figure 41, arises from the use of the RGB Colour space.
0 m 7.5 m
Figure 41: Converting 0 to 7.5m into colour
It assigns the given range values to colour values from red over green to blue. For the maximum
distance of the used camera of 7.5 meters, the distribution would be as depicted in Figure 41. For
lower ranges the colour-bar can be adjusted, similar to the stretching algorithm explained in chapter
5.1.2. The actual range has to be adjusted in the source code, no interface to the GUI was installed (see
chapter 7.2).
The RGB Colour space consists of every colour a standard monitor can show by mixing red, green and
blue. Figure 42 shows the two used sides of the cube and the chosen path that leads to the colour-bar.
To make the differences in the used colour-bar as severe as possible, only the colours on the cube’s
edges are used.