Page 273 - Build Your Own Quadcopter_ Power Up Your Designs with the Parallax Elev-8

252 Bu il d Y o ur O w n Q u a d c o p t e r

in a window and tests them to determine if the average intensity differs from a preset value
or not. A radical change in value usually indicates that an edge is present at the center point
where the windowed pixels are located. This algorithm is applied over all the lines that
make up the image being processed. Figure 9.31 shows the Elev-8 snapshot processed to
extract an outline.
You can also see in the figure that I selected a window size of 4 pixels, which is a good
value. Any larger values will tend to make the edges less distinct, and smaller values will
make the edges too intermittent and choppy. Selecting the correct parameters is almost
always a process of trial and error, but that is in part why this field is so interesting.

Negative and Other Adjustments
Another interesting effect is the negative algorithm, an example of which is the negative
snapshot of the Elev-8 shown in Figure 9.32. This effect is found in the Adjust Content
category. The selections in the Adjust Content category are as follows:

• Camera_Properties
• Contrast
• Gamma
• Intensity
• Negative

Clicking on each one opens an additional variety of adjustments and settings that can be
made to optimize a specific video-capture device. I was very impressed with RoboRealm’s
functionality with regard to camera setting. While I am not suggesting that RoboRealm

Figure 9.31 Elev-8 outline edge extraction.