Building 3D Models for the Web Technical Details of 2D Web Graphics

Portability Issues

DOS/Windows computers have a gamma setting of 2.5, making them darker than Macintoshes with a gamma setting of 1.8. Unix workstations vary. Silicon Graphics workstations have a gamma setting 0f 1.7.

If you are developing Web graphics on a Macintosh, make them a little lighter. Conversely, if developing graphics on a DOS/Windows computer, make them a little darker. Test your graphics on both platforms.

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Color Depth

8 bit color

256 simultaneous colors. Common on older Windows and Macintosh computers. Macintosh, Windows and Windows 95 have 216 colors in common in their 256 color palettes. Any additional colors in your graphics will be dithered.

16 bit color

65,536 simultaneous colors. Called "thousands of colors" on the Macintosh.

24 bit color

8 bits assigned to each of red, green, and blue. 16,777,216 simultaneous colors. Common on newer Windows and Macintosh computers. Called "millions of colors" on the Macintosh.

32 bit color

24 bit color plus 8 bits for transparency. 16,777,216 simultaneous colors with 256 levels of transparency.

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Screen Resolution

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Accessibility

Color blindness:

View your Web pages on a 256 gray scale monitor to be certain that it has a broad range of values (from dark to light).

Vision impaired:

Do not use small text on graphics images, such as buttons or clickable images, without offering an alternative page with plain text.

Blind:

Use ALT tags for all of your images. Complex pages (frames, multiple columns) are difficult for screen reading applications for the blind.

Hearing impaired:

Include transcriptions of any audio clips.

References

• WGBH National Center for Accessible Media
• Web Accessibility Initiative
• Microsoft Accessibility and Disabilities page

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