Submitted version of the thesis - Airlab, the Artificial Intelligence ...

58 Chapter 5. Vision
The whole algorithm and script is found in Object’s Position section in
Appendix B.2
5.2 Color Definition
The camera we are currently using has a UXGA resolution CMOS and it is
set to 160x120 resolution for the blob search algorithm. One major problem
is the blob search algorithm. The algorithm used inside is unknown and
this forced us to define color information very precisely, since we cannot
eliminate the non-object blobs easily. We can eliminate the problem only
by using the area, perimeter and the circularity information which, in case
the target is a ball, is not enough for most cases to track the blob. So this
makes the color definition important. The color is defined in a RGB Cube,
using RGB444 format, and it is not very clear to understand the correctness
of the defined color from the color codes. In order to ease this process, the
color selection is made by theST software by selecting the desired color from
the image, or directly programming the rules if the color values are known.
Since the resolution is very low, the color consists of shadows, or existence
of blob not belonging to the searched object made us to improve the color
selection. The current ST software is sufficient to visualize the selected color
and test the blob search, but color definition is difficult since, in order to
define the color, the pixels should be selected one by one, is not possible
to select an area. Moreover, the rules (which is the additions and subtractions
of the color codes to RGB Cube) found by the ST software are not
in the compact form (the same rule for a color can be added or subtracted
more than one). To improve the color selection, we decided to use an offlinecalculator,
that calculates thehistogram for the selected object’s colors.
As a first step, we started by disabling automatic white balance and automatic
exposurecontrol. Before getting into the white balance, the concept
of color temperature needs to be introduced. Color temperature is just a
way of quantifying the color of light. It is measured in degrees Kelvin (K).
Normal daylight has a color temperature of around 6,500K. Warmer light
has a lower color temperature. The warm light that occurs late in the afternoon
might have a color temperature of around 4,000K. Cooler light has a
higher color temperature. Thebluish light that sometimes occurs in twilight
periods of the day might have a color temperature of about 7,500K. So, our
concept of warm and cool light is tied directly to the color temperature. The