

ATTENTION MAC USERS: Free & Clear does run on Macs under Virtual PC with Windows 95/98. I won't be creating a Mac-specific version of the freeware demo, but you can see for yourself (from the samples above) how it looks on your Mac, and you can play with it if you have Virtual PC.





Limitations of Sub-Pixel Rendering Terrific as sub-pixel rendering is, it has a few limitations that need to be kept in mind: ONLY LCD's . . . not CRT's! While the application of Sub-Pixel Graphic Rendering will absolutely benefit virtually all users of LCD displays, it's important to understand that this technique is not applicable to high-resolution Cathode Ray Tube (CRT) displays. Yes, I know, the sample above looked really great on your CRT, but that's mostly because any mature sub-pixel rendering technology also incorporates aspects of anti-aliasing (as we'll see on the next page of this little web zone.) And it's well known that anti-aliasing helps tremendously with the display of text. So even though sub-pixel rendering is better than nothing on CRT's, its "colorized" aspects only really work on LCD displays. Black and White Images are Best As we've seen, the success of sub-pixel rendering depends upon using part of an adjacent pixel to extend an existing pattern of sub-pixels which the eye perceives as a slightly larger white or black pixel. While this approach can also be employed with low-saturation (pastel) colors, it will always be most effective when displaying high contrast white and black images. Dark colored text on a white background will be effective, as would white text on a dark colored background. But black & white best shows off what this technology can do. ONLY Landscape . . . not Portrait! As we've seen, sub-pixel rendering only enhances the horizontal resolution of LCD panels. It's incredibly convenient that 'horizontally' is precisely where text needs the most help! Emboldening stretches text only horizontally, kerning and micro-justification only shift text horizontally, and italicizing slants type by skewing it horizontally. However, this means that existing color LCD panel technology can not be used with sub-pixel text rendering when the panel is used in a vertical, or portrait, orientation. It seems to me that this significantly cools off our excitement about the application of our existing hardware for eBooks, since eBooks utilize the traditional book's familiar vertical orientation which is completely incompatible with existing color LCD construction for under sub-pixel rendering. However, there is certainly nothing to prevent the creation of a new breed of LCD panels specifically for eBooks. They would be longer vertically than horizontally (for portrait orientation), while orienting their sub-pixels horizontally like existing LCD panels. Such a new style display would indeed be a fabulous eBook component since it could display color images clearly while simultaneously employing sub-pixel rendering for its page's text. Sub-Pixel Order Sensitivity Since sub-pixel rendering depends heavily upon the physical proximity of adjacent sub-pixels, the rendering algorithm must know whether the pixels are ordered Red-Green-Blue or Blue-Green-Red. (Those are the only two sequences occurring on LCD panels.) If the sub-pixel rendering algorithm gets the sequencing backwards (as shown in this example) the result is as bad as getting it right is good. Since a few LCD panels have their sub-pixels arranged in B-G-R instead of R-G-B order, any industrial strength delivery of sub-pixel rendering technology will require a user-settable (or operating system readable) option to inform the system's LCD rendering engine whether the sub-pixels are arranged in 'forward' or 'reverse' order.