-\begin{description}
- \item[Horizontal:] composes a reflection of the right half-plane joined to the left half-plane. The axis of reflection is central and vertical (Reflection Center). It can be used together with Vertical to have 4 half-planes of reflection.
- \item[Swap LEFT-RIGHT side:] Swaps the two horizontal reflection half-planes, reversing their orientation. If this option is enabled, Enable Reflection Center is disabled.
- \item[Vertical:] composes a reflection of the top half-plane joined to the bottom half-plane. The axis of reflection is central and horizontal (Reflection Center). It can be used together with Horizontal to have 4 half-planes of reflection.
- \item[Swap TOP-BOTTOM side:] Swaps the two vertical reflection half-planes, reversing their orientation. If this option is enabled, Enable Reflection Center is disabled.
- \item[Enable Reflection Center:] allows shifting the half-plane along the X-axis and/or along the Y-axis, relative to the Reflection Center. You can enter the percentage value or act on the slider for a visual adjustment. Checking this option excludes the use of swap functions.
- \item[Reset] returns all values to the initial conditions, that is with only the Horizontal button enabled.
-\end{description}
+When the \textit{Enable Reflection Center} option is UNCHECKED, the used reflection is on the center of the image (i.e. $X=50\%$, $Y=50\%$) and the options about \textit{Reflection Center}, $X\%$ and $Y\%$, are disabled (grayed).
+The Horizontal option reflects the left side of the image on the right. If the \texttt{Swap LEFT-RIGHT side} option is checked then the right side to the left will be reflected.
+The Vertical option reflects the top on the bottom. If the \texttt{Swap TOP-BOTTOM side} option is checked then the bottom to the top will be reflected.
+There are special combinations when both Horizontal and Vertical checkboxes are enabled (and\textit{ Enable Reflection Center} is always UNchecked, of course). You can see those combinations in the figure~\ref{fig:mirror}.
+
+When the \textit{Enable Reflection Center} option is CHECKED the options about \textit{Reflection Center}, i.e. $X\%$ and $Y\%$, are enabled, and the two "Swap ... side" options are disabled and hidden. These two "Swap ... side" are disabled because the $X\%$ and $Y\%$ allow the swap side feature automatically. The $X\%$ and $Y\%$ positions move the center of the reflection to fit to the user's need.