HTML The Definitive Guide (16 page)

Chapter 2

HTML Quick Start

2.8 Images Are Special

Image files are multimedia elements you may reference with anchors in your HTML document for separate download and display by the browser. But, unlike other multimedia, standard HTML has an explicit provision for image display "in line" with the text,[
5
] and images can serve as intricate maps of hyperlinks. That's because there is some consensus in the industry concerning image file formats -

specifically, GIF and JPEG - and the graphical browsers have built in decoders that integrate those image types into your document.

[5] Some browsers support other multimedia besides GIF and JPEG graphics for inline display. Internet Explorer, for instance, supports a tag that plays background audio. In addition, the HTML 4.0 standard provides a way to display other types of multimedia inline with HTML document text through a general tag.

2.8.1 Inline Images

The HTML tag for inline images is ; its required src attribute is the URL of the GIF or JPEG

image you want to insert in the document.
[, 5.2]

The browser separately loads images and places them into the text flow as if the image were some special, albeit sometimes very large, character. Normally, that means the browser aligns the bottom of the image to the bottom of the current line of text. You can change that with the special align attribute whose value you set to put the image at the top, middle, or bottom of adjacent
text. Examine Figures Figure 2.2 through Figure 2.4 for the image alignment you prefer. Of course,

wide images may take up the whole line, and hence break the text flow. Or you may place an image by itself, by including preceding and following division, paragraph, or line-break tags.

Figure 2.2: An inline image aligned with the bottom of the text (default)

Figure 2.3: An inline image specially aligned with the middle of the text
Figure 2.4: An inline image specially aligned with the top of the text
Experienced HTML authors use images not only as supporting illustrations, but also as quite small inline characters or glyphs, added to aid browsing readers' eyes and to highlight sections of the documents. Veteran HTML authors commonly add custom list bullets or more distinctive section dividers than the conventional horizontal rules. Images, too, may be included in a hyperlink, so that users may select an inline thumbnail sketch to download a full-screen image. The possibilities with inline images are endless.

2.8.2 Image Maps

Image maps are images within an anchor with a special attribute: they may contain more than one hyperlink.

One way to enable an image map is by adding the ismap attribute to an tag placed inside an