2. Graphics
Good design is clear thinking made visible.
Good diagrams and interesting illustrations are visually arresting and
create documents that are distinct and memorable.
3. The Role of Web Graphics
Graphics as a Content
Illustrations: Graphics can show you things, bringing pieces of the world into
your document
Diagrams: Quantitative graphics and process diagrams can explain concepts
visually
Quantitative data: Numeric charts can help explain financial, scientific, or other
data
Analysis and causality: Graphics can help take apart a topic or show what
caused it
Integration: Graphics can combine words, numbers, and images in a
comprehensive explanation
4. Characteristics of Web Graphics
Color displays
Screen Resolution
Gamma
Graphics and bandwidth
5. Graphic File Formats
The primary web file formats are GIF (pronounced “jiff”), JPEG (“jay-peg”), and, to a much
lesser extent, PNG (“ping”) files.
GIF Graphics
JPEG Graphics
PNG Graphics
6. GIF Graphics
Many images on the web are in GIF format, and virtually all web browsers that
support graphics can display GIF files. GIF files are 8-bit graphics and thus can only
accommodate 256 colors.
GIF file compression
7. GIF Graphics
Dithering : GIF images can contain no more than 256 colors. The process
of reducing many colors to 256 or fewer is called dithering.
9. Advantages of GIF files
GIF is the most widely supported graphics format on the web
GIFs of diagrammatic images look better than JPEGs
GIF supports transparency and interlacing
10. JPEG Graphics
JPEG images are full-color images that dedicate at least 24 bits of memory to each pixel, resulting in
images that can incorporate 16.8 million colors. JPEG images are used extensively among photographers,
artists, graphic designers, medical imaging specialists, art historians, and other groups for whom image
quality and color fidelity is important.
11. Advantages of JPEG images
JPEG achieves huge compression ratios, which mean faster downloads
JPEG produces excellent results for most photographs and complex images
JPEG supports full-color (24-bit, true-color) images
12. PNG Graphics
PNG is an image format developed by a consortium of graphic software
developers as a nonproprietary alternative to the GIF image format.
PNG graphics were designed specifically for use on web pages, and they
offer a range of attractive features, including a full range of color depths,
support for sophisticated image transparency, better interlacing, and
automatic corrections for display monitor gamma.
PNG supports full-color images and can be used for photographic images
15. Graphics Markup
Height and width tags : Graphic source tags tell the browser how much space to devote to a
graphic on a page, and they instruct the browser to lay out your web page even before the
graphics files have begun to download.
Alt text: HTML has several built-in fallbacks designed to allow web pages to work under
different conditions. One of these is the “alt” attribute of the <img>tag. The alt attribute
allows us to supply an alternate text description with any images we place on our page.
Colored Backgrounds: Web colors offer a zero-bandwidth means to change the look of your
pages without adding graphics. They also allow you to increase the legibility of your pages,
tune the background color to complement foreground art, and signal a broad change in
context from one part of your site to another.
Background colors and legibility: A primary factor affecting legibility is the contrast
between text and background. Low-contrast type diminishes the reader’s ability to
differentiate between the color of the background and the text, which in turn makes it
difficult to distinguish letterforms
16. Graphics Markup
Background Graphics : Cascading Style Sheets offer powerful tools for
designing layouts that include background graphics. With css, you can set
a background graphic and define where it displays, whether it repeats, and,
if so, in what direction, whether the image is fixed in place or scrolls with
the page, and more. Background graphics can be attached to the entire
page or to individual elements, such as the banner, navigation, or content
area
