IMG - Inline Image

Syntax

<IMG>

Attribute Specifications

SRC=url (location of image)
ALT=Text (alternate text)
LONGDESC=url (link to long description)
WIDTH=Length (image width)
HEIGHT=Length (image height)
USEMAP=url (client-side image map)
ISMAP (server-side image map)
ALIGN=top|middle|bottom|left|right (image alignment)
BORDER=Length (link border width)
HSPACE=Pixels (horizontal gutter)
VSPACE=Pixels (vertical gutter)
[4.0] ID=string
[4.0] CLASS=string
[4.0] STYLE=string
[4.0] TITLE=string
[4.0] LANG=Language (i.e. RU - Russian)
[4.0] DIR=ltr|rtl
[4.0] SCRIPTING EVENTS=string

Contents

Empty

Contained in

Inline elements, block-level elements except PRE

SRC

The IMG element specifies an inline image. The required SRC attribute specifies the location of the image. The image can be any format, though browsers generally only support GIF and JPEG images. Support for the PNG image format is growing slowly.

ALT

The required ALT attribute provides alternate text for those not loading images. Effective ALT text should generally give the function of the image rather than a description of the image. For example, ALT="Welcome to XYZ Corp." would be more appropriate than ALT="XYZ Corp. Logo" for a company's logo on its welcome page. Good ALT text is crucial to the document's accessibility for the significant portion of users who do not load images; see Use of ALT texts in IMGs for a thorough discussion.

LONGDESC

The LONGDESC attribute gives the location of a long description of the image. This attribute should be used to provide a long description of an image where this would be useful. For example, a painting, graph, or corporate logo could be given a description so that blind and other text-only users can develop a mental picture of the image.

WIDTH & HEIGHT

The WIDTH and HEIGHT attributes are most useful when they specify the exact dimensions of the image in pixels. This allows image-loading browsers to reserve the proper amount of space for the image and continue to render the rest of the document, thus giving the appearance of a faster-loading page.

Unfortunately, many graphical browsers will use these dimensions when not loading images, which can cause the ALT text to be cut off if the image is small or the ALT text is large. In such cases, authors may wish to leave off the WIDTH and HEIGHT attributes, depending on the importance of the ALT text and the placement of the image on the page (an image towards the end of the document without WIDTH and HEIGHT attributes will generally not noticeably slow the rendering of the page).

Authors can also specify different dimensions for the WIDTH and HEIGHT attributes, in which case browsers should scale the image. Percentages, relative to the horizontal or vertical space available (not relative to the image's natural size) can also be specified, though these are not as widely supported as pixel lengths. Since browsers typically do a poor job of scaling images, authors should avoid using WIDTH and HEIGHT for this purpose as much as possible.

ALIGN

The ALIGN attribute, deprecated in HTML 4.0, specifies the alignment of the image. The values top, middle, and bottom specify the image's position with respect to surrounding content on its left and right.

ALIGN=middle aligns the center of the image with the current baseline. To center the image horizontally on the page, place the image in a centered block, e.g.,

<H1 ALIGN=center><IMG SRC="logo.gif" ALT="Welcome to XYZ Company"></H1>

The other ALIGN values, left and right, specify a floating image; the image is placed at the left or right margin and content flows around it. To place content below the image, use <BR CLEAR=left|right|all> as appropriate.

The vertical-align and float properties of Cascading Style Sheets provide more flexible methods of aligning images.

BORDER

The BORDER attribute, deprecated in HTML 4.0, specifies the width of the image's border. Specifying BORDER=0 will eliminate the border around a linked image in most browsers, though some allow the user to override this. Authors should only use BORDER=0 if the image would be clearly recognizable as a link, or as a method of de-emphasizing a link. For example:

<A HREF="reference/"><IMG SRC="icon/reference.gif" ALT="" WIDTH=90 HEIGHT=90 BORDER=0>Web Authoring Reference</A>

HSPACE & VSPACE

The deprecated HSPACE and VSPACE attributes allow an author to suggest horizontal gutters and vertical gutters, respectively, around the image. The value must be in pixels and applies to both sides of the image. Style sheets provide more flexibility in specifying the space around images.

USEMAP

The USEMAP attribute is used with client-side image maps to give the location of the map definition. While this value may be a full url--allowing a single map definition to be applied to multiple pages--Netscape Navigator will only find map definitions in the same file, effectively limiting the USEMAP value to a fragment identifier such as "#map".

ISMAP

The ISMAP attribute is used with server-side image maps. When the ISMAP attribute is included with a linked image and the user clicks the image, the image coordinates clicked are sent to the server, from which a location can be returned. The method of handling the coordinates is server-dependent, but the NCSA server's method is most common.

Server-side image maps are better supported than client-side image maps, but almost all browsers today support both methods. Client-side image maps are generally preferred since they do not require an extra request to the server (and so are faster), and since they allow a usable menu to be provided to text-only users. Using both methods in combination is a good approach, since browsers supporting client-side image maps will use that method while older browsers will use the server-side image map. An example follows:

<A HREF="/cgi-bin/imagemap/sitemap.map"><IMG SRC="sitemap.gif" ALT="Site Map" ISMAP USEMAP="#map" WIDTH=100 HEIGHT=100></A>

A MAP element named map would have to be included in the same document.

[4.0] ID

The ID attribute uniquely identifies an element within a document. No two elements can have the same ID value in a single document. The attribute's value must begin with a letter in the range A-Z or a-z and may be followed by letters (A-Za-z), digits (0-9), hyphens ("-"), underscores ("_"), colons (":"), and periods (".").

The following example uses the ID attribute to identify each of the first two paragraphs of a document:

<P ID=firstp>My first paragraph.</P>
<P ID=second>My second paragaph.</P>

The paragraphs in the example could have style rules associated with them through their ID attributes. The following Cascading Style Sheet defines unique colors for the two paragraphs:

P#firstp {
  color: navy;
  background: transparent
}

P#secondp {
  color: black;
  background: transparent
}

The paragraphs in the initial example could also be used as a target anchor for links:

<P>See <A HREF="#firstp">the opening paragraph</A> for more information.</P>

Note that most browsers do not support the ID attribute for link anchors. For current browsers, authors should use <A NAME>...</A> within the element instead of ID.

Since ID and NAME share the same name space, authors cannot use the same value for an ID attribute and a NAME attribute in the same document. Also note that while NAME may contain entities, the ID attribute value may not.

[4.0] CLASS

The CLASS attribute specifies the element to be a member of one or more classes. Classes allow authors to define specific kinds of a given element. For example, an author could use <CODE CLASS=Java> when giving Java code and <CODE CLASS=Perl> when giving Perl code.

Unlike with the ID attribute, any number of elements can share the same class. An element may also belong to multiple classes; the CLASS attribute value is a space-separated list of class names.

Note that most current browsers do not support multiple classes. Such browsers typically ignore a CLASS attribute that specifies multiple classes.

The CLASS attribute is particularly useful when combined with style sheets. For example, consider the following navigation bar:

<DIV CLASS=navbar>
<P><A HREF="/">Home</A> | <A HREF="./">Index</A> | <A HREF="/search.html">Search</A></P>
<P><A HREF="/"><IMG SRC="logo.gif" ALT="" TITLE="WDG Logo"></A></P>
</DIV>

This example's use of the CLASS attribute allows style rules to easily be added. The following Cascading Style Sheet suggests a presentation for the preceding example:

.navbar {
  margin-top: 2em;
  padding-top: 1em;
  border-top: solid thin navy
}

.navbar IMG { float: right }

@media print {
  .navbar { display: none }
}
[4.0] STYLE

The STYLE attribute allows authors to specify style rules inline for a single occurrence of an element. An example follows:

<P>A popular font for on-screen reading is <SPAN STYLE="font-family: Verdana">Verdana</SPAN>.</P>

When the STYLE attribute is used, a default style sheet language must be specified for the document by setting the Content-Style-Type HTTP header to the media type of the style sheet language. The previous example could use the following META element in the document's HEAD:

<META HTTP-EQUIV="Content-Style-Type" CONTENT="text/css">

In most cases, use of the CLASS or ID attributes is a better choice than using STYLE since ID and CLASS can be selectively applied to different media and since they provide a separation of content and presentation that often simplifies maintenance.

[4.0] TITLE

The TITLE attribute provides a title for an element and is commonly implemented as a "tooltip" on visual browsers, though many browsers lack support for TITLE. The attribute is most useful with A, LINK, IMG, and OBJECT elements, where it provides a title for the linked or embedded resource. Some examples follow:

TITLE is also helpful with the ABBR and ACRONYM elements to provide the long form of the abbreviation. Examples:

Internationalization Attributes

[4.0] LANG

The LANG attribute specifies the language of an element's attribute values and its content, including all contained elements that do not specify their own LANG attribute. While the LANG attribute is not widely supported, its use may help search engines index a document by its language while allowing speech synthesizers to use language-dependent pronunciation rules. As well, visual browsers can use the language's proper quotation marks when rendering the Q element.

The attribute value is case-insensitive, and should be specified according to RFC 1766; examples include en for English, en-US for American English, and ja for Japanese. Whitespace is not allowed in the language code.

Use of the LANG attribute also allows authors to easily change the style of text depending on the language. For example, a bilingual document may have one language in italics if rendered visually or a different voice if rendered aurally. The HTML of such a document might be as follows:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN"
   "http://www.w3.org/TR/REC-html40/strict.dtd">
<TITLE>Welcome - Bienvenue</TITLE>
<H1>
  <SPAN LANG=en>Welcome</SPAN> -
  <SPAN LANG=fr>Bienvenue</SPAN>
</H1>
<P LANG=en>This paragraph is in English.</P>
<P LANG=fr>Ce paragraphe est en français.</P>
...

A document's primary language may be set using the LANG attribute on the HTML element, or, alternatively, by using the Content-Language HTTP header.

[4.0] DIR

The DIR attribute specifies the directionality of text--left-to-right (DIR=ltr, the default) or right-to-left (DIR=rtl). Characters in Unicode are assigned a directionality, left-to-right or right-to-left, to allow the text to be rendered properly. For example, while English characters are presented left-to-right, Hebrew characters are presented right-to-left.

Unicode defines a bidirectional algorithm that must be applied whenever a document contains right-to-left characters. While this algorithm usually gives the proper presentation, some situations leave directionally neutral text and require the DIR attribute to specify the base directionality.

Text is often directionally neutral when there are multiple embeddings of content with a different directionality. For example, an English sentence that contains a Hebrew phrase that contains an English quotation would require the DIR attribute to define the directionality of the Hebrew phrase. The Hebrew phrase, including the English quotation, should be contained within a SPAN element with DIR=rtl.

[4.0] Scripting Events

A number of attributes that define client-side scripting events are common to most elements. The attribute value is a script--typically a function call or a few short statements--that is executed when the event occurs. The value may contain entities (e.g., &quot;).

The following example features JavaScript code to handle two events of a submit button, giving the user a reminder in the status bar when the mouse moves over the button and clearing the status bar when the mouse moves away. Note that the attribute values are delimited by single quotes since double quotes are used within them.

<INPUT TYPE=submit ONMOUSEOVER='window.status="Did you fill in all required fields?";' ONMOUSEOUT='window.status="";'>

When an event attribute is used, a default scripting language must be specified for the document by setting the Content-Script-Type HTTP header to the media type of the scripting language. The previous example could use the following META element in the document's HEAD:

<META HTTP-EQUIV="Content-Script-Type" CONTENT="text/javascript">

The common event attributes are device-dependent and largely tailored for the graphical user interface. The available events are as follows:

More Information

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