Professor Allebach’s primary areas of research have concerned various aspects of image acquisition and reproduction. He has done important work in a number of areas, including the theory of sampling and quantization, color imaging, modeling of human vision, and image quality assessment. However, the area where his work has had the greatest impact in terms of practical applications is digital halftoning. This is the process whereby continuous-tone images possessing a full range of gray values from shadow to highlight can be reproduced using output devices, especially printers, that can only reproduce a small number of widely spaced gray values. Digital halftoning is a critical technology that makes it possible today to obtain near-photographic quality color and black-and-white images from low-cost inkjet and laser (electrophotographic) printers.
Allebach’s seminal contributions to digital halftoning occurred in two primary phases. First, he pioneered the design of very high-quality digital halftone images using computer-aided processes and models for the human visual system. This ultimately led to the algorithm known as direct binary search (DBS), which is very computationally intensive, but which generates halftone images of unparalleled visual quality. During the second phase of his work, Allebach used DBS to train halftoning algorithms that can be practically implemented in low-cost devices, and that yield visual quality essentially equivalent to that of DBS. These algorithms can be found in HP products ranging from the large Indigo digital press to tiny photo-printers.
Today Allebach leads an interdisciplinary research program in digital printing and imaging at Purdue that involves 8 faculty members in 4 different academic units and over 20 half-time graduate research assistants. This activity is sponsored by DuPont, HP, NSF, Samsung, and Xerox. The outstanding success of the HP-Purdue relationship, in particular, was the basis for the Purdue College of Engineering Team Award that his group received in 2006. This year the Purdue College of Engineering has recognized Allebach with its 2008 Excellence in Mentoring Award given for his work in mentoring graduate students and junior faculty members.
Professor Allebach has received many forms of external recognition for his work. He is a Fellow of three different technical societies, and was named 2004 Electronic Imaging Scientist of the Year. Of particular note is the Honorary Membership that he received from the Society for Imaging Science and Technology in 2007 “for many and diverse contributions to imaging science; including halftoning, digital image processing, color management, visual perception, and image quality.” This is the highest award that IS&T bestows. Previous recipients include Edwin Land (1955), inventor of Polaroid photography; Chester Carlson (1962), inventor of the Xerox machine; and Gary Starkweather (2004), inventor of the laser printer.