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Searching for Blue
The first step in our tutorial is to spin in place while looking for a blue ball.
To do this we added an RGBFilter for the color blue. This module
is similar to the Color Filter but provides a quick way
to detect primary colors. This module works nicely in that it can detect a blue ball.
 
But in certain environments this is actually more problematic than one may expect as the color
blue is often
detected in shadow or dark areas (especially outside where shadows will contain blue areas
due to the reflection of the sky). Blue color detected in shadows have a flickering type quality to
them in that
they do not reliably detect the color blue in the same pixel per each frame. We used
the Flicker module to remove these areas of blue
that are not stable.
For example, notice the blue areas detected in the following image. The flicker module helps to
reduce this noise.
 
Additional problems arise when there are other blue colors seen while the robot is spinning around
looking for the blue ball. For example, if you happened to have the camera box lying around
an image like the following could occur.
 
But we can quickly see that the shape of the box is not quite like the shape of the ball.
To ensure that the NXT Tribot ignores the box we can use the blob filter to help us out.
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