HP TextSmart Technology

When Hewlett-Packard set out to create a low-cost color copier, one of the fundamental challenges it faced was achieving high-quality reproduction of both black on white text and color images. While this is not difficult when a page contains only black on white text or only color images, a page containing both is harder to reproduce because optimizing the reproduction process for images causes text quality to suffer, and vice versa. Ideally, the areas on the page containing black on white text should be processed one way while the areas containing color images should be processed another way to get the best overall reproduction.

HP TextSmart Technology was developed specifically for the new HP Nike Color Printer-Copier to alleviate the gray, fuzzy text characters commonly associated with color copiers. It enhances the quality of black on white text to produce crisper, blacker characters while maintaining optimal reproduction of color images. As a result, the HP Nike Color Printer-Copier is able to produce high-quality reproductions using low-cost scanning and printing technology.

Scanning is Not Seeing

A color scanner "sees" a page very differently from the way a person sees a page. First, it sees only an approximation of the page represented by a mesh of individual pixels of varying intensities and hues. Second, the scanner sees color very literally, and makes no attempt to adjust the color information it senses to fit common-sense notions of what black on white text should look like. Lastly, because each color is scanned separately, slight discrepancies occur in the relative positions of the color components (misregistration) due to the inherent limitations of all scanning mechanisms.

When black on white text is scanned, the pixels solidly over a character register dark and the pixels solidly over the background register light. The pixels straddling the boundary, covering part of the character and part of the background, register as various shades of gray depending on the proportion of black to white. What's more, the color misregistration causes these border pixels to also take on different hues.

As a result, the scanner does not see crisp, black characters on a pure white background, and this effect is especially noticeable with small characters. To the scanner, characters appear dark gray. Instead of sharp edges, characters appear fuzzy with a colored fringe around them. And instead of white, the background appears to be light yellow. This is exactly how the text would print if the raw data from the scanner were simply passed through to the print mechanism unaltered.

Separating Text from Images

If the page contained only black on white text, it would be a simple matter to snap all dark areas to black and all light areas to white (this is essentially how a fax machine works). Obviously, however, this would create significant distortions to any images that might be on the page.

HP TextSmart technology provides the HP Nike Color Printer-Copier with the intelligence to discern the difference between black on white text and color images and adjust the color information accordingly. Raw data from the scanner is first processed by a sharpening filter to improve the quality of both the text and images. Then, using sophisticated statistical techniques developed by HP Labs and algorithms based on HP's AccuPage technology, HP TextSmart technology analyzes the sharpened data, identifies those portions of the page likely to contain text and separates them from those likely to contain images.

Different Strokes for Different Folks

Once the text and images have been separated, individual characters between about 6 and 20 points in size are identified. Further processing establishes the nominal shape for each character, snaps those pixels to black, and then creates a white border around it to improve its sharpness. The enhanced text is recombined with the sharpened images and the page is ready for printing.

HP's TextSmart technology improves the overall page appearance by treating text and images separately. Images retain their colors and shading while these same attributes are virtually eliminated from the black on white text. Characters print blacker and appear more well defined. HP's TextSmart technology sets a new standard for low-cost color copying.