map element
(二)4.8.13 The area element
(三)4.8.14 Image maps
(一)4.8.14.1 Authoring
(二)4.8.14.2 Processing model
map element
name — Name of image maptoreference from the usemap attribute
Accessibility considerations:
For authors.
For implementers.
DOM interface:
[Exposed =Window ]
interface HTMLMapElement : HTMLElement {
[HTMLConstructor ] constructor ();
[CEReactions , Reflect ] attribute DOMString name ;
[SameObject ] readonly attribute HTMLCollection areas ;
};map element, in conjunction with an img element and any
area element descendants, defines an image map. The element
represents its children.
The name attribute gives
the map a name so that it can be referenced. The attribute must be present and must
have a non-empty value with no ASCII whitespace. The value of the name attribute must not be equal to the value of the name attribute of another map element in the same
tree. If the idattribute is also specified, both
attributes must have the same value.
map.areas
Returns an HTMLCollection of the area elements in the
map.
The areas
attribute must return an HTMLCollection rooted at the map element, whose
filter matches only area elements.
Image maps can be defined in conjunction with other content on the page, to ease maintenance.
This example is of a page with an image map at the top of the page and a corresponding set of
text links at the bottom.
<!DOCTYPE HTML>
< HTML LANG = "EN" >
< TITLE > Babies™: Toys</ TITLE >
< HEADER >
< H1 > Toys</ H1 >
< IMG SRC = "/images/menu.gif"
ALT = "Babies™ navigation menu. Select a department to go to its page."
USEMAP = "#NAV" >
</ HEADER >
...
< FOOTER >
< MAP NAME = "NAV" >
< P >
< A HREF = "/clothes/" > Clothes</ A >
< AREA ALT = "Clothes" COORDS = "0,0,100,50" HREF = "/clothes/" > |
< A HREF = "/toys/" > Toys</ A >
< AREA ALT = "Toys" COORDS = "100,0,200,50" HREF = "/toys/" > |
< A HREF = "/food/" > Food</ A >
< AREA ALT = "Food" COORDS = "200,0,300,50" HREF = "/food/" > |
< A HREF = "/books/" > Books</ A >
< AREA ALT = "Books" COORDS = "300,0,400,50" HREF = "/books/" >
</ P >
</ MAP >
</ FOOTER > area element
map element ancestor.
Content model:
Nothing.
Tag omission in text/html:
Noend tag.
Content attributes:
Global attributes
alt — Replacement text for use when images are not available
coords — Coordinates for the shape to be created in an image map
shape — The kind of shape to be created in an image map
href — Address of the hyperlink
target — Navigable for hyperlink navigation
download — Whether to download the resource instead of navigating to it, and its filename if so
ping — URLs to ping
rel — Relationship between the location in the document containing the hyperlink and the destination resource
referrerpolicy — Referrer policy for fetches initiated by the element
Accessibility considerations:
If the element has an href attribute: for authors; for implementers.
Otherwise: for authors; for implementers.
DOM interface:
[Exposed =Window ]
interface HTMLAreaElement : HTMLElement {
[HTMLConstructor ] constructor ();
[CEReactions , Reflect ] attribute DOMString alt ;
[CEReactions , Reflect ] attribute DOMString coords ;
[CEReactions , Reflect ] attribute DOMString shape ;
[CEReactions , Reflect ] attribute DOMString target ;
[CEReactions , Reflect ] attribute DOMString download ;
[CEReactions , Reflect ] attribute USVString ping ;
[CEReactions , Reflect ] attribute DOMString rel ;
[SameObject , PutForwards =value , Reflect="rel"] readonly attribute DOMTokenList relList ;
[CEReactions ] attribute DOMString referrerPolicy ;
// also has obsolete members
};
HTMLAreaElement includes HTMLHyperlinkElementUtils ;area element represents either a hyperlink with some text and a
corresponding area on an image map, or a dead area on an image map.
Anarea element with a parent node must have a map element
ancestor.
If the area element has an href
attribute, then the area element represents a hyperlink. In this case,
the alt attribute must be
present. It specifies the text of the hyperlink. Its value must be text that, when presented with
the texts specified for the other hyperlinks of the image map, and with the
alternative text of the image, but without the image itself, provides the user with the same kind
of choice as the hyperlink would when used without its text but with its shape applied to the
image. The alt attribute may be left blank if there is another
area element in the same image map that points to the same resource and
has a non-blank alt attribute.
If the area element has no href
attribute, then the area represented by the element cannot be selected, and the alt attribute must be omitted.
In both cases, the shape and coords attributes specify the area.
The shape attribute is
an enumerated attribute with the following keywords and states:
| Keyword | Conforming | State | Brief description |
|---|---|---|---|
circle
| Circle state | Designates a circle, using exactly three integers in the coords attribute.
| |
circ
| No | ||
default
| Default state | This area is the whole image. (The coords
attribute is not used.)
| |
poly
| Polygon state | Designates a polygon, using at-least six integers in the coords attribute.
| |
polygon
| No | ||
rect
| Rectangle state | Designates a rectangle, using exactly four integers in the coords attribute.
| |
rectangle
| No |
coords attribute
must, if specified, contain a valid list of floating-point numbers. This attribute
gives the coordinates for the shape described by the shape
attribute. The processing for this attribute is described as part of the image
map processing model.
In the circle state,
area elements must have a coords attribute
present, with three integers, the last of which must be non-negative. The first integer must be
the distance in CSS pixels from the left edge of the image to the
center of the circle, the second integer must be the distance in CSS
pixels from the top edge of the image to the center of the circle, and the third integer
must be the radius of the circle, again in CSS pixels.
In the default state,
area elements must not have a coords
attribute. (The area is the whole image.)
In the polygon state,
area elements must have a coords attribute
with at least six integers, and the number of integers must be even. Each pair of integers must
represent a coordinate given as the distances from the left and the top of the image in CSS pixels respectively, and all the coordinates together must represent the
points of the polygon, in order.
In the rectangle state,
area elements must have a coords attribute
with exactly four integers, the first of which must be less than the third, and the second of
which must be less than the fourth. The four points must represent, respectively, the distance
from the left edge of the image to the left side of the rectangle, the distance from the top edge
to the top side, the distance from the left edge to the right side, and the distance from the top
edge to the bottom side, all in CSS pixels.
When user agents allow users to follow hyperlinksordownload hyperlinks created using the
area element, the href, target, download, and ping attributes decide how the link is followed. The rel attribute may be used to indicate to the user the likely
nature of the target resource before the user follows the link.
The target, download, ping,
rel, and referrerpolicy attributes must be omitted if the
href attribute is not present.
If the itemprop attribute is specified on an
area element, then the href attribute must
also be specified.
N
element defining which referrer is sent when fetching the resource.">HTMLAreaElement/referrerPolicy
Support in all current engines.
Firefox50+Safari14.1+Chrome52+referrerPolicy must reflect the referrerpolicy content attribute, limited to
only known values.
img element, may be associated with an image map (in
the form of a map element) by specifying a usemap attribute on the img element. The
usemap attribute, if specified, must be a valid
hash-name reference to a map element.
Consider an image that looks as follows:
< p >
Please select a shape:
< img src = "shapes.png" usemap = "#shapes"
alt = "Four shapes are available: a red hollow box, a green circle, a blue triangle, and a yellow four-pointed star." >
< map name = "shapes" >
< area shape = rect coords = "50,50,100,100" > <!-- the hole in the red box -->
< area shape = rect coords = "25,25,125,125" href = "red.html" alt = "Red box." >
< area shape = circle coords = "200,75,50" href = "green.html" alt = "Green circle." >
< area shape = poly coords = "325,25,262,125,388,125" href = "blue.html" alt = "Blue triangle." >
< area shape = poly coords = "450,25,435,60,400,75,435,90,450,125,465,90,500,75,465,60"
href = "yellow.html" alt = "Yellow star." >
</ map >
</ p > img element has a usemap
attribute specified, user agents must process it as follows:
Parse the attribute's value using the rules for parsing a hash-name reference
to a map element, with the element as the context node. This will return either an
element (the map) or null.
If that returned null, then return. The image is not associated with an image
map after all.
Otherwise, the user agent must collect all the area elements that are
descendants of the map. Let areas be that list.
Having obtained the list of area elements that form the image map (the areas), interactive user agents must process the list in one of two ways.
If the user agent intends to show the text that the img element represents, then
it must use the following steps:
Remove all the area elements in areas that have no href attribute.
Remove all the area elements in areas that have no alt attribute, or whose alt
attribute's value is the empty string, ifthere is another area element in
areas with the same value in the href attribute and with a non-empty alt attribute.
Each remaining area element in areas represents a
hyperlink. Those hyperlinks should all be made available to the user in a manner
associated with the text of the img.
In this context, user agents may represent area and img elements
with no specified alt attributes, or whose alt
attributes are the empty string or some other non-visible text, in an
implementation-defined fashion intended to indicate the lack of suitable
author-provided text.
If the user agent intends to show the image and allow interaction with the image to select
hyperlinks, then the image must be associated with a set of layered shapes, taken from the
area elements in areas, in reverse tree order (so the last
specified area element in the map is the bottom-most shape, and
the first element in the map, in tree order, is the top-most shape).
Each area element in areas must be processed as follows to
obtain a shape to layer onto the image:
Find the state that the element's shape attribute
represents.
Use the rules for parsing a list of floating-point numbers to parse the
element's coords attribute, if it is present, and let the
coords list be the result. If the attribute is absent, let the coords list
be the empty list.
If the number of items in the coords list is less than the minimum number
given for the area element's current state, as per the following table, then the
shape is empty; return.
| State | Minimum number of items |
|---|---|
| Circle state | 3 |
| Default state | 0 |
| Polygon state | 6 |
| Rectangle state | 4 |
shape attribute's
state:
Circle state
Drop any items in the list beyond the third.
Default state
Drop all items in the list.
Polygon state
Drop the last item if there's an odd number of items.
Rectangle state
Drop any items in the list beyond the fourth.
If the shape attribute represents the rectangle state, and the first number in the list is
numerically greater than the third number in the list, then swap those two numbers around.
If the shape attribute represents the rectangle state, and the second number in the list is
numerically greater than the fourth number in the list, then swap those two numbers around.
If the shape attribute represents the circle state, and the third number in the list is less than
or equal to zero, then the shape is empty; return.
Now, the shape represented by the element is the one described for the entry in the list
below corresponding to the state of the shape attribute:
Circle state
Let xbe the first number in coords, ybe the second number, and rbe the third number.
The shape is a circle whose center is xCSS pixels
from the left edge of the image and yCSS pixels from
the top edge of the image, and whose radius is rCSS
pixels.
Default state
The shape is a rectangle that exactly covers the entire image.
Polygon state
Let xibe the (2i)th entry in coords, and yibe the (2i+1)th entry in coords (the first entry in coords being the one with index 0).
Let the coordinates be (xi, yi),
interpreted in CSS pixels measured from the top left of the image,
for all integer values of ifrom 0 to (N/2)-1,
where Nis the number of items in coords.
The shape is a polygon whose vertices are given by the coordinates, and whose
interior is established using the even-odd rule. [GRAPHICS]
Rectangle state
Let x1be the first number in coords, y1be the second number, x2be the third number, and y2be the fourth number.
The shape is a rectangle whose top-left corner is given by the coordinate (x1, y1) and whose
bottom right corner is given by the coordinate (x2,
y2), those coordinates being interpreted as CSS
pixels from the top left corner of the image.
For historical reasons, the coordinates must be interpreted relative to the
displayed image after any stretching caused by the CSS 'width' and
'height' properties (or, for non-CSS browsers, the image element's width and height attributes — CSS browsers map
those attributes to the aforementioned CSS properties).
Browser zoom features and transforms applied using CSS or SVG do not affect the
coordinates.
Pointing device interaction with an image associated with a set of layered shapes per the above
algorithm must result in the relevant user interaction events being first fired to the top-most
shape covering the point that the pointing device indicated, if any, or to the image element
itself, if there is no shape covering that point. User agents may also allow individual
area elements representing hyperlinks to be selected
and activated (e.g. using a keyboard).
Because a map element (and its area elements) can be
associated with multiple img elements, it is possible for an area
element to correspond to multiple focusable areas of the
document.
Image maps are live; if the DOM is mutated, then the user agent must act as if it
had rerun the algorithms for image maps.
4.8.8 The video element — Table of Contents — 4.8.15 MathML →