Animation in the web

Animation in the Web
Vishal Polley
IET Lucknow

Topics
 Text for the Web
 Images for the Web
 Animation for the Web
 Video for the Web
1

HTML Is a Markup Language
HTML stands for Hypertext Markup Language. The “Markup
Language” part of the name means that tags are used to do
such things as format text and embed media. The tags are
enclosed by angled brackets: <>. Some tags are bounding tags,
requiring both an opening tag and a closing tag. The closing
tag is indicated by a leading forward slash inside the angled
brackets. This example for bolded text illustrates the use of
the two tags:
<strong>This text is emphasized</strong>
Other tags, such as the tag for inserting an inline image, stand
by
themselves:
<IMG src="grey_ball.gif">
2

HTML and Multimedia
HTML provides tags for inserting media into HTML
documents:
the <IMG> tag for inline images
the <AUDIO> and <VIDEO> tags for multimedia
and the <EMBED> and <OBJECT> tags for compound
document embedding used to insert a “nonstandard”
item such as a Java applet or Flash animation into an
HTML document.

Text for the Web
By following some simple steps, you can ensure that your
pages are comprehensible.
• Use bullet points to deliver information
• Use clear headings and subheadings
• Headings should be descriptive and meaningful
• Write short sentences, in short paragraphs
• Be concise, clear, and use language that is simple and
to the point
• Highlight key words in your sentences. The reader
who is scanning the information will get the gist of it
from highlighted phrases.
Making Columns of Text
Flowing Text Around Images

Making Columns of Text
 The most powerful feature
of HTML may be found in
the <TABLE> tag.
 To the right, you’ll see how
to organize your text into
two columns, so it displays
more like a newspaper or a
magazine, using a table

Flowing Text Around Images
 As you can see in Figure, it is
possible (and easy) to “flow”
text around an image using
the ALIGN attribute of the
<IMG> tag. This is a quick and
simple method for mixing
text and images in a pleasing
layout.
 Add a <BR CLEAR="left"> tag
at the end of your text
paragraph, so that if there is
not enough text to fill the
entire vertical height of the
image, your next paragraph
will begin on a new line, left-
justified, and below the
image.

Images for the Web
GIF and PNG Images
JPEG Images
Using Photoshop
Backgrounds
Clickable Buttons

GIF and PNG Images
GIF images (Graphic Interchange File, also discussed in Chapter
3) are limited to 8 bits of color depth (256 colors). This is a
commercial image format developed by CompuServe
Information Services, an online PNG (for Portable Network
Graphics Specification) was developed as a new “open” format
(not requiring fees) to replace GIF. By allowing transparency by
single pixel or by alpha channel mask and a 24-bit indexed
palette, the PNG format is an improvement on the GIF format it
was intended to replace. But it does not support animation. And
because it only uses the RGB color model (not CMYK), PNG
images may not print well.

JPEG Images
JPEG (Joint Photographic Experts Group) images
may contain 24 bits of color depth (millions of
colors). JPEG uses a powerful but lossy compression
method that produces files as much as ten times more
compressed than GIF. Lossy means that information in
the original image is lost in the compression process
and cannot be retrieved. A lossless compression
method does not irretrievably discard the original
data.

Lossy compression schemes save disk space but can
also degrade an image. For the Web, line art is often
better saved in GIF, PNG, or SVG format than in JPEG.

GIF or JPEG?
Use JPEG for photo-realistic images containing many colors,
and avoid using it for images already forced into a 256-color
palette or for line drawings or 1-bit black-and-white images.
GIF compresses drawings and cartoons that have only a few
colors in them much better than JPEG, which may introduce
visible defects—sharp edges and lines that blur—especially
with small-size text.

Using Photoshop
Adobe’s Photoshop is the “tool of choice” for most
graphic artists, so it is worth taking some time to
provide a few suggestions for creating images for
use on the World Wide Web. If you use a different
image-editing application, follow the same logic and
use the commands appropriate for that application.
Always work in native Photoshop format using PSD
files—these images are typically in RGB mode and
use the maximum color depth.

Background Coloring
You can choose colors for backgrounds, text, and anchors to
URL links. Color controls for the entire page are attributes of
the <BODY> tag and are set using CSS:
body {background-color: #0000FF;}
where “#0000FF” is a hexadecimal red-green-blue triplet
used to specify the background color, in this case, blue.
Once you have chosen a background color, you will then want
to set the color of your text and establish proper contrasts.
Red on green shimmers, black on black is invisible. By setting
styles in the <BODY> tag, you set default styles for the entire
document. For white text on a blue background, the CSS
code would be:
body {color: #FFFFFF;}

Background Images
Background images are by default tiled, or repeated,
across and down the page until the page or page
element is filled, so a randomly distributed “sandy”
background image (see Figure) can easily be made
from a very small source image. Load a background
image into a document by specifying its URL (if it is
available somewhere on the Web) or its relative file
path (if it is on the same server as the page) in the
CSS attributes for the <BODY> tag, for example:
body {background-image: url('paper.gif');}

Clickable Buttons
To make a graphic image “clickable” so that it links to another
document, simply include the image tag inside the bounding tags
of an HTML anchor that points to that document’s URL:
<a href="documentToGoTo.html">
<img src="greenButton.gif" border="0"> </a>
You can also use the <A> tag to provide a link
to a larger graphic or even to a video clip from a
small, thumbnail-sized image:
<a href="bigPicture.jpg"><img src="thumbnail.gif"
border="0"></a>

Sound for the Web
As the Web has developed, sound has become more important,
and most browsers allow embedding of sounds into documents
using the <AUDIO> tag. Inside this tag, the autoplay
attribute, if present, starts the audio playing as soon as
it is ready. If controls is present, a play/pause and other
controls will be displayed. When preload is present, the
audio will load when the page does and be ready to run. Text
can be included in the tag that will be ignored unless the
user’s browser cannot understand the <AUDIO> tag:
<audio src="LizLaugh.aiff" preload autoplay controls loop>
Sorry, your browser does not support the HTML audio element.
</audio>
The <A> anchor tag and <EMBED> tag can also be used to play sound files:
Click <a href="LizLaugh.aiff">here</a> to play sound file.
<embed src="Mozart.mid" autostart="true" loop="false" width="120" height="50"
hidden></embed>

Animation for the Web
HTML makes no provision for animation, by itself
delivering only a static page of text and graphics.
Boring, many people said, and programmers went to
work devising methods to liven up the view. JavaScript
can dynamically change a web page without needing to
reload it. JavaScript with XML features, combined into
Ajax (Asynchronous JavaScript and XML) , is used for
powerful interactive applications such as Google’s
“Office.” The Flash plug-in for browsers offers
animation and interaction.

GIF89a
Browsers implement a little-known animation feature in the final 1989
revision “a” of the GIF file format specification. It is possible to make
simple animations by putting multiple images, or frames, into a single
GIF89a file and display them with programmable delays (in 100ths of a
second) between them.
When you use the <IMG> tag to embed a GIF89a multiframe
Image , the browser downloads the file and stores it in the cache folder
of your local hard disk. Once fully downloaded, the browser plays each
frame of the image quickly and smoothly. Limit animated GIFs to small
images, and use a more capable plug-in like Flash for animations over
larger areas.

Video for the Web
Introduction of the HTML5 <VIDEO> tag is a push in the
direction of a standardized few technologies and methodologies
that will work for most everyone on the Internet. The most
commonly used codecs are H.264, Theora, and VP8 within MP4,
Ogg, and WebM containers. Unfortunately, no one of these will
necessarily play in every HTML5-compliant browser. To
guarantee playability by all browsers, you may need to encode
four separate versions of your video file, including a Flash .flv
format as a fallback, and program your HTML <VIDEO> tag
with all four.

Animation in the web

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