If no good match can be found, color may be simulated with dithering, in which pixels of two or more colors are intermingled to produce an optical representation of a color that is not physically present. In fact it is very likely that at least some of the vibrant, solid colors you see on your computer screen will be unavailable on a given viewer’s system, causing the closest matching colors to be used in their place. If you create 8-bit images using a system-specific palette, a custom palette, or an adaptive palette, there is no guarantee that what you see on your screen will be what the viewers see on theirs. And browser programs, such as Internet Explorer and Netscape, contribute to the problem by reserving specific (and different) colors for their interface elements. Here’s the rub: The Windows and Mac OS’s don’t use the same system color palette. If you - or your client - want to play it safe and build a site that looks good on those older computers (and thus reach the maximum number of customers), you’ll have to learn to design within a limited palette and save your images in an 8-bit Web-compatible format, such as GIF. Virtually all computer systems sold today come equipped with graphics cards that support true-color modes, but there is a huge installed base of older computers that are only capable of displaying 8 bits of data per pixel, which delivers a palette of only 256 simultaneous colors. Specifically, I’ll explain how different system palettes and overall gamma settings can affect the colors on your Web page.Īs a designer you probably run your graphics card in true-color mode - at either 24 bits or 32 bits of data per pixel - which gives you the ability to view the full RGB spectrum of 16.7 million colors.
This time, I’ll focus on cross-platform color challenges and how to get around them. In the first part of this two-part column, I explored the differences in how fonts are displayed on the two platforms.
Designing Web pages that look the same whether viewed on a Mac or a PC is no easy task: The Mac OS and Windows handle certain fundamental operations differently, and the differences have their implications.