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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Filtering in the domain <strong>of</strong> Spatial Frequency<br />
The filtering technique assumes the use <strong>of</strong> the Fourier transform for converting from<br />
image space domain to spatial frequency domain.<br />
G(u,v) = F(u,v)H(u,v)<br />
In the previous relation, F is Fourier transformation <strong>of</strong> input image and H is the filter<br />
function. The inverse Fourier transform applied on the filtering <strong>of</strong> spatial frequency can<br />
be used for recovering the initial image. The processing library used on the project<br />
included also support for filtering in the spatial frequency domain.<br />
Table 5. 3x3 window enhancement filters<br />
Low pass filters, high pass filters, band pass filters are filters with a criterion <strong>of</strong><br />
frequency control. Low pass filters which output only lower frequency image data, less<br />
than a specified threshold, were applied to remove high frequency, noise, in some cases<br />
in the images <strong>of</strong> the initial database, before training. In addition to that, the specified<br />
techniques were used also at the testing session <strong>of</strong> the recognition system. In the same<br />
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