HP DeskWriter C printer driver development - development of Macintosh driver for HP color ink-jet printer - Technical

Hewlett-Packard Journal, August, 1992 by William J. Allen, Toni D. Courville, Steven O. Miller

Because most computers have limited RAM, and rasterizing a 300-dpi page can take a lot of memory (up to 32 megabytes to represent a full color page), the driver usually rasterizes a portion of the page at a time in what is called banding. Banding is pictured in Fig. 3. The less available RAM the computer has, the more bands it takes to rasterize the whole page, and the longer it takes to complete the whole page, because there is a fixed overhead in rasterizing each band. Each object must be examined to determine if it falls within the band. If it does then it is rasterized (drawn) into the band. Otherwise, it is ignored (clipped). Objects that cross band boundaries must be rasterized for each band that they touch. For most common documents, banding adds little or nothing to the print time. Only for very complex documents that have a large number of objects, or for very low-memory conditions, which increase the number of bands, does banding significantly affect the time to rasterize the whole page.

User Interface

This product had a wide range of human factors issues and challenges, all of which were analyzed, designed, and tested. The issues included defining a conceptual use model of the product, hardware design, and integrating aspects of color imaging into a simple driver interface.

To design a product that meets the requirements of our users, we needed to find out who our users are. The key data point returned from market research was that the HP DeskWriter C should be designed for home and business users who do not currently use color, and who do not want to struggle with their computer or printer. Initial market research and human factors concept testing pointed strongly to the necessity for a user-friendly product with good print quality.

Usability studies and iterations of the user interface followed and continued for the next six months. Usability studies are more detailed than concept testing, and are designed to test users' reactions to specific aspects of a prototyped product. To test the user interface, subjects were asked to perform numerous printing tasks in a number of different scenarios. The users were questioned regarding verbiage, ease of use, and functionality offered. Our goal was to design a usable driver without compromising functionality and without creating confusion for less-technical users. We had three formal usability studies during the product design phase, which required a number of iterations to the driver's interface. The results from each study were published by our human factors engineer along with design recommendations for the next iteration. These design recommendations were based on the users' responses to questions, task completion successes or failures, and other observed data.

Dialog Boxes

Fig. 4 shows the final dialog boxes of the user interface. The first two dialog boxes, Print and Page Setup, are accessed from the menu bar. A key design objective was to make these screens as simple and uncluttered as possible. It was decided that only those functions for which frequent change was required would be in the two main dialog boxes. The more technical functions were put into the Colors and Options screens. This was done to decrease confusion for the typical user who would rarely have use for the added features. The defaults were chosen such that most users would not require the Colors and Options dialog boxes.