LIS 341. Summer, 1996. Adding Images

the university of texas at austin
GRADUATE SCHOOL OF LIBRARY & INFORMATION SCIENCE

Adding Images

You have probably already used clip art images, or downloaded "free art" from one of the many sites on the Web. But you can also create your own images using a program like Photoshop, Photostyler, Painter, etc. or scanning in photographs, drawings, etc.

GIF (Graphics Interchange Format) files are displayed by all browsers, and nowadays, only a few browsers need a helper application to display JPEG (Joint Photographic Experts Group) images. GIF works with 8 bit color, that is, it can display 256 colors. JPEG offers 24 bit color, which means that it can work with millions of colors, and is mostly used for photographs. In general, your images should follow the following guidelines to be "web friendly":

Keep image resolution to 72 DPI (dots per inch)
After you create or scan in an image, reduce its dimensions. The most common screen size is 640 x 480 pixels
Total size should not exceed 30 Kbytes. As a rule of thumb, you can estimate 1 second per Kbyte of downloading time-- you don't want your users to wait longer than 30 seconds for an image!
Modify your image in RGB mode, but save as indexed color. If you can, choose the system palette, and diffusion dithering if you wish to diffuse sharp edges. You may also specify less than 8 bits if you are using a few colors- this saves some space.
Remember to use alt="Text" for users who are not viewing images
If your pages rely heavily on images, you should consider creating a parallel "text only" version
See also Tips on Creating Graphics at UT Austin

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