# வார்ப்புரு:Overlay/doc



## Function

### Name
This template is called **Overlay** in Wikipedia. It is called **Overlay legend** in Commons.  

In Wikipedia **Overlay legend** and **Legend overlay** redirect to **Overlay**.  

### 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.  

Typical colours of overlays are as follows:  
:{| cellpadding="5" padding="5"  
! Color name !! Example  
|-  
| red (default) || –  
|-  
| blue || –  
|-  
| green || –  
|-  
| brown || –  
|-  
| saddlebrown&nbsp; || –  
|-  
| yellow || –  
|}  

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 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 overlay 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.  

### Deficiences

#### Automatic column balancing
While the template will handle missing set overlay values at the start, that is the first overlay item does not have to be overlay1, the template treats intermediate missing overlays as though they exist for column balancing, and it does not allow for any text wrapped new lines within an overlay item's text.  

#### Undeterminable legend start and ends
If legend titles are provided without a corresponding start or end and the template cannot explicitly determine one from an adjacent legend then it will "guess" and unexpected results might be produced, which might not be stable with any template updates.  

Legend start and end ranges can be overlapped. This is either a deficiency or a feature depending on how you look at it. However, overlapping ranges might result in unexpected behaviour, which might not be stable with any template updates.  

#### Double quotes in pop up tips for overlays
Double quotes, **"**, cannot be placed in overlay tips when *form = text* or when *form = colour* are used. To include a double quote use its HTML coding, **&#38;#34;**.  

Double quotes are always allowed in the overlay, but if the overlay tip for that overlay is not set separately, the tip, which defaults to the same text as the overlay, will probably not display correctly. The overlay tip for an overlay with double quotes in it should always be set explicitly when *form = text* or when *form = colour* are used.  

## Usage

This is a colour/color friendly template. Either spelling can be used for any parameter value or any parameter name.  

### Skeleton
<pre>  

</pre>  

### Editing grid and coordinates
To assist in determining the position of each overlay a coordinate grid showing from the ordinates and from the top ordinates can be displayed by setting the grid parameter to yes:  

| grid = yes  

The coordinate grid is 900 x 900, so if the image is set to be smaller than this, the page content may be off scrolled, etc. The presentation will return to normal when the grid parameter is removed or set to a value other than yes.  

Note that the top ordinate is the position of the top of the overlay from the top of the image and the ordinate is the of the overlay from the of the image.  

### Form = colour
When setting  

| overlayNform = colour  

then the overlays still use up numbered positions within the list of overlays. Accordingly, if using a mixture of image and-or text forms with colour forms, then gaps will appear in the number sequence where a colour form overlay is specified.  

It might be generally best if colour form overlays are always set as the last overlays. See Spider's main organs below for example.  

### Full minimal skeleton
To assist editors, a full 30 overlays but minimal skeleton is provided below:  
| <pre></pre> | } |
| --- | --- |

## Examples
**Note:** The data in these examples is not necessarily correct.  

### Brisbane (with grid turned on)

| <pre></pre> | } |
| --- | --- |

### Charlotte Pass Village

| <pre></pre> | } |
| --- | --- |

### Spider's main organs (pre labelled image)

</pre>  
|}  

## Template parameters
| image | The image. If not set then only the legend is presented. | Image file name. |  |
| --- | --- | --- | --- |
| width | Width of the image in pixels. Defaults to 500. | Number. |  |
| height | Height of the image in pixels. Defaults to 500. | Number. |  |
| columns | The number of columns to display the legend in. Defaults to 3. Set to 0 to not display any legend. | Number == 0, 1, 2, 3, . . . |  |
| grid | Set to 'yes' to turn on the coordinate grid to allow easier determination of overlay coorindates while editing. Defaults to 'no'. All values other than 'yes' are equivalent to 'no'. |  |  |
| link | Set to 'yes' to turn on default linking of overlay and legend entry. Defaults to 'no'. All values other than 'yes' are equivalent to 'no'. |  |  |
| legendbox | Set to 'no' to turn off a box / around each legend group set of overlays. Defaults to 'yes'. All other values other than 'no' are equivalent to 'yes'. |  |  |
| float | Floats the image and legend. Defaults to centering the image and legend on the page. | Text == , . |  |
| overlay | Determines whether or not the overlays are presented when an image is available. Defaults to 'yes'. All values other than 'no' are equivalent to 'yes'. |  |  |
| Determines whether or not a is placed around the whole presentation. Defaults to 'yes'. All values other than 'no' are equivalent to 'yes'. |  |  |  |
| legend1title | Text for legend1 title. | Optionally linked text. |  |
| legend1start | The number of the first overlay to appear in legend1. Defaults to the first overlay set, otherwise to the previous legend end plus 1 if there is a previous legend. | Number == 1, . ., 30. |  |
| legend1end | The number of the last overlay to appear in legend1. Defaults to the next legend start less 1 if there is a next legend, otherwise to the last set overlay. | Number == 1, . ., 30. |  |
| Both legend starts and legend ends do not need to be provided. Legend starts only, or, legend ends only, for each legend may be provided. |  |  |  |
| overlay1form | The form of the overlays. The default form is an image number, for example, . Other settings allow textual numbers, for example, <span>1</span>, or coloured tags, for example, <span>&nbsp;&nbsp;</span>. Defaults to the previous overlay form, or to 'image' if no previous overlay form. | Text == image, text, colour/color. |  |
| overlay1 | Text for overlay1 for the legend. Defaults to overlay1tip if any. | Text. Do not link. The template will link. |  |
| overlay1colour | Colour of overlay1. Defaults to the previous overlay colour, or to 'red' if no previous overlay colour. | Text == , , . |  |
| overlay1tip | Pop up tool tip text to appear when the screen pointer is over overlay1. Defaults to overlay1. | Text. |  |
| overlay1left | Distance in pixels of the edge of overlay1 from the side of the image. | Number. |  |
| overlay1top | Distance in pixels of the top edge of overlay1 from the top side of the image. | Number. |  |
| overlay1link | Text to be used as a link for the overlay legend text. Defaults to overlay1 if link is not set to no. | Text. Do not link. |  |
| overlay1left1 | The same as overlay1left. | As per overlay1left. |  |
| overlay1top1 | The same as overlay1top. | As per overlay1top. |  |
| overlay1left2 | The ordinate for a second position of overlay1. | As per overlay1left. |  |
| overlay1top2 | The top ordinate for a second position of overlay1. | As per overlay1top. |  |
| overlay1left3 | The ordinate for a third position of overlay1. | As per overlay1left. |  |
| overlay1top3 | The top ordinate for a third position of overlay1. | As per overlay1top. | } |