Color histogramming

Color histogramming

Thresholding works well for objects which consist of one color or one dominant
color. A different COLOR technique popularized by Mike Swain, called color
HISTOGRAMMING histogramming, can be used to identify a region with several colors.137 Essentially,
color histogramming is a way to match the proportion of colors in a
region.

Because the color histogram of a current image can be matched with another
image, the technique appears to be model-based, or recognition. But
reactive systems do not permit recognition types of perception. Is this a contradiction?
No; a color histogram is an example of a local, behavior-specific
representation which can be directly extracted from the environment. For
example, a robot could be shown a Barney doll with its distinct purple color
with green belly as the percept for the goal for a move-to-goal behavior.
However, the robot will follow a purple triangle with a green region, because
the ratio of colors is the same. There is no memory and no inference,
just a more complex stimulus.
Note that the intersection can be considered to be ameasure of the strength
of the stimulus, which is helpful in reactive robotics. In one set of experiments,
a robot was presented a poster of Sylvester and Tweety. It learned the
histogram, then after learning the object (e.g., fixating on it), it would begin to
move towards it, playing a game of tag as a person moved the poster around.
The robot used a simple attractive potential fields-based move-to-goal behavior,
where the perceptual schema provided the location of the poster and
the percent intersection. The motor schema used the location to compute the
direction to the poster, but the intersection influenced the magnitude of the
output vector. If the person moved the poster into a dark area or turned it at
an angle, the intersection would be low and the robot would move slower.
If the match was strong, the robot would speed up. Overall, it produced a
very dog-like behavior where the robot appeared to play tag quickly (and
happily) until the human made it too difficult. Then if the human moved the
poster back to a more favorable position, the robot would resume playing
with no hard feelings.