Martin Coath edited section_Methods_subsection_Algorithm_For__.tex  about 8 years ago

Commit id: f642e2f38d7b4323d55171597d7fd887afab18fd

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\begin{enumerate}  \item the number of pixels $m$ corresponding to half the required window size $w$ is calculated: $m = \mathrm{floor}(\frac{w}{2})$  \item hence the working window size is $n = 2 \cdot m+1$ even when this differs from $w$ by one  \item assemble the horizontal  vector $\vec{k}_{j}$ $\vec{k}_{h}$  of values for ahorizontal  window of $n$contiguous  pixels $k_{[i,j-m \: : \: i,j+m]}$ \item repeat with $\vec{k}_{i}$, $\vec{k}_{v}$,  a vector of values for a vertical window of $n$ pixels $k_{[i-m,j \: : \: i+m,j]}$ \item both vectors are normalized, so they can be treated as distributions, and the Skewness $\gamma$ of each distribution (\textit{i.e.} a measure of the asymmetry in the gray-scale values in both direction) is calculated, $\gamma_j$ $\gamma_h$  and $\gamma_i$ $\gamma_v$  \item the \textsc{skv} value of the pixel $\gamma_{i,j}$  is the larger mean  of the two values $\frac{\gamma_j + \gamma_i}{2}$ \end{enumerate}  In order to compare results from a range of pictures the window size will not be reported in pixels, but as the number of windows along the longest side of the image. For example, if a picture is 640 $\times$ 480 pixels and the \textsc{skv} is calculated with a window size of 64 pixels then this will be written as \textsc{skv}$_{10}$ as there are 10 windows along the longest side.