编辑“︁Template:Overlay/doc”︁（章节）

===Purpose===
====Image overlay====
Allows image numbered, textual number, or colour tag overlays to be positioned over an image to indicate particular features in the image.

Up to 30 overlays can be positioned over the image.  Any overlay can be placed over the image up to 3 times, to indicate multiple locations of the same feature in the image.

The overlays can be coloured red, blue, or green, for example [[File:1 white, red rounded rectangle.svg|50x13px]], [[File:1 white, blue rounded rectangle.svg|50x13px]], [[File:1 white, green rounded rectangle.svg|50x13px]].  The default colour is red.  The colour of each overlay can be individually set.  Each overlay inherits its colour from the previous overlay, so only the first of any colour grouped overlays needs to have its colour set.

Each overlay is configurably wikilinkable by the template.

The overlays can be turned off by setting overlay to 'no', which will result in the only the image and legend being displayed.  This is particularly useful when the image itself already includes the overlays and-or colour tagging.  See [[#Spider's main organs (pre labelled image)|Spider's main organs]] below for example.

====Overlay legend====
A legend of the text for each overlay is displayed by default, in 3 columns, under the image.

The legend can be turned off by setting the number of columns to '0'.

The legend can be grouped into groups of overlays, explicitly up to 6 groups.  Each explicit legend grouping can optionally be given a title.

The number of overlay legend text items in each column is automatically balanced by the template across the columns within each legend grouping.

If the start overlay item for the first explicit grouping is after the first overlay item then the overlay text items from the first overlay up to but not including the first explicitly grouped overly item are displayed as an untitled grouping before the first explicit group.

If an end overlay item is specified for any explicit grouping and there is no following explicit grouping, then the remainder of the overlay items are displayed as an untitled grouping after the last explicit group.

By setting the start of the first explicit grouping after the first overlay item and the end of the sixth explicit grouping before the last overlay item, effectively 8 groupings can be configured, the first and eighth being untitled.