Recognition of facial expressions - Knowledge Based Systems ...
Recognition of facial expressions - Knowledge Based Systems ...
Recognition of facial expressions - Knowledge Based Systems ...
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Figure 22. Sobel edge detector applied on the initial image<br />
Because <strong>of</strong> the fact that the eye areas contain a sharp transition from the inner bright<br />
round to the surrounding black area, in the next stage only the pixels with high intensity<br />
are analyzed to be chosen as candidates for the eye positions. For removing the unwanted<br />
pixels, a threshold step is applied on the pixel map <strong>of</strong> the image. The threshold is so<br />
chosen as to let leave all the possible pixels for denoting the position <strong>of</strong> the eyes intact. It<br />
also has to be low enough for removing as many pixels as possible. The result is as in<br />
Figure 23.<br />
Figure 23. Threshold applied on the image<br />
At the moment there are still a lot <strong>of</strong> pixels that are to be considered as candidates for the<br />
eye locations. The next step is to separately analyze each <strong>of</strong> those pixels through a given<br />
procedure that computes the mean and the variation <strong>of</strong> the pixels’ intensity in a<br />
surrounding area. The searched area has to be far enough to the location <strong>of</strong> the pixel for<br />
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