This article shows how to create image maps using HTML. You’ll learn how to create client-side image maps, and we’ll touch on server-side image maps too.
Image maps explained
An image map is a way of defining “hot spot” links within an image on a Web page. This means that, rather than having the whole image behave as one link, you can have lots of different links within the one image.
Linking to an image map: The
How do you turn an image into an image map? Well, to associate an image map with an image, simply add the
usemap attribute to the
img tag for the image. In the above example, the image map is called
"shapes", so our
img tag looks like this:
<img src="images/shapes.jpg" width="375" height="102" style="border: none;" alt="Shapes" usemap="#shapes"/>
usemap="#shapes" attribute, that associates the image map with the image.
Creating an image map: The
The other half of the image map is the map definition itself. In this definition, you tell the browser where the hot spots are in the image, and what the hot spots need to link to.
The map is defined using the
<map></map> tag. In our example above, the
map tag looks like this:
map element is placed after the image in our HTML file. In fact, it can be placed anywhere within the HTML page body.
The general syntax for the
map element is:
<map name="map-name"> <area shape="area shape" coords="area coordinates" href="area hyperlink" or nohref="nohref" target="hyperlink target" title="area title" alt="alternate text"/> <area shape="area shape" ... </map>
So, each image map is given a name (
map-name), and one or more
area tags to specify the hot spots in the image.
area tag has the following attributes:
shape="rect | circle | poly | default"
Specifies the shape of the area. Possible values are:
rect(a rectangular shape),
circle(a circular shape),
poly(an arbitrary polygon, with 3 or more points), or
default(which represents the remaining area of the image not defined by any
Specifies the coordinates that define the corners of the shape. The coordinates depend on the shape specified in the
(The top left and bottom right corners of the rectangle)
(The centre and radius of the circle)
(The corners of the polygon)
Note that all coordinate values are relative to the top left corner of the image. In other words, the top left corner always has coordinates
Note also that the
default shape type does not need any coordinates.
This is the URL that you’d like to link the hot spot to. It works just like a standard
<a href=...> tag.
This is the optional target window or frame to open the linked URL in. Again, it works just like the
target attribute in a standard
<a href=...> tag.
This attribute allows you to give the area a title. When the mouse is rolled over this hot spot, the browser will usually pop up a tool tip displaying this title.
Server-side image maps
As an alternative to defining the whole image map in HTML for the browser to read, you can use server-side image maps. With this type of map, the browser simply sends the (x,y) coordinates of the point clicked on to a server-side script (such as a CGI script).
To define a server-side map, you simply include the
ismap attribute, and place an
<a href> tag around the image, specifying the server-side script to send the (x,y) information to:
<a href="shapemap.cgi"> <img src="images/shapes.jpg" width="375" height="102" style="border: none;" ismap="ismap"/> </a>
Then, when you click on the image, the browser sends the (x,y) coordinate of the point that you clicked on to the server-side script, which can then interpret these (x,y) values and take an appropriate action. The coordinates are appended as parameters to the end of the script URL:
For example, if you wanted the user to choose a country from a world map image, you could use the server-side script to calculate which country was clicked on, and then display information about that country.
Another way of creating a server-side image map is with the
image input type in web forms:
<form action="shapemap.cgi"> <input type="image" name="shapes_image" src="images/shapes.jpg" width="375" height="102" style="border: none;"/> </form>
In this case, the (x,y) coordinates are sent as form fields named
fieldname.y. So in the above example, the coordinates would be contained in the fields
It’s best to use a server-side map whenever the map has many areas, or where the areas are not easily defined by simple shapes such as circles, rectangles and polygons.
Working out image map coordinates
If you’re using a Web page editor such as Macromedia’s Dreamweaver you can draw image maps straight onto your images and let the editor work out the coordinates, but what if you’re editing your page by hand?
One easy way to work out coordinates is to change your image map from client-side to server-side temporarily, by changing the
usemap="mapname" attribute to
ismap="ismap", and adding a dummy
<a href> tag around the image, e.g.:
<a href="#"><img src="images/shapes.jpg" width="375" height="102" style="border: none;" alt="Shapes" ismap="ismap"/></a>
Then, as you roll the mouse over the image, you should see the coordinates appear after the “?” in the status bar of your browser! Try moving your mouse over the image below to see if this works:
If you can’t get that working, another technique is to open your image in a graphics package such as Adobe Photoshop. You can then move the mouse over the image and see the mouse coordinates in the Info Palette.
You now know how to create image maps in HTML. Happy mapping!