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<p>be written as<br/>
:</p>

<p><big>Farid and Simoncelli derivatives</big></p>
<p>Farid and Simoncelli propose to use a pair of kernels, one for interpolation and another for differentiation (compare to Sobel above). These kernels, of fixed sizes 5 x 5 and 7 x 7, are optimized so that the <a href="page.php?w=Fourier_transform">Fourier transform</a> approximates their correct derivative relationship.</p>

<p>In <a href="page.php?w=MATLAB">Matlab</a> code the so called 5-tap filter is<syntaxhighlight lang="matlab">k  = [0.030320  0.249724  0.439911  0.249724  0.030320];d  = [0.104550  0.292315  0.000000 -0.292315 -0.104550];d2 = [0.232905  0.002668 -0.471147  0.002668  0.232905];</syntaxhighlight></p><p>
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