Blog: June 10, 2016
Topics: Innovation

A colorful collaboration

Purdue University and HP: Decades of imaging innovation


In our previous issue we touched on the long-standing research collaboration HP has with Purdue University. This 25-year collaboration has paved the way for amazing innovation in imaging, and is now setting the stage for advancements in ambient computing technology for home and office applications.

The collaboration between Purdue and HP started in 1992. While Qian Lin was an intern at HP Labs during her PhD program at Stanford University, she invited Professor Jan Allebach and his colleague Professor Charles Bouman to give a presentation at HP Labs. Professor Allebach was Qian’s former advisor at Purdue University when she was working on her Master’s degree in Electrical Engineering. Professors Allebach and Bouman were well-known researchers in the area of electronic imaging and Qian thought they would provide valuable insights to the HP team. This was the start of a collaboration between Purdue University and HP that included HP Labs, and printer divisions in Boise, ID, Vancouver, WA, Israel (Indigo and Scitex), and Barcelona, Spain, that has continued through present day. Professor Allebach himself spent six summers as a Visiting Researcher at HP Labs, and later did a sabbatical there. One result of this strong engagement with HP was Professor Allebach’s contribution to the development of HP’s Color Smooth Dither technology.

Dithering means creating the illusion of colors and shades by varying the dots in an image. In printing, dithering is usually called halftoning, and shades of gray are called halftones. Halftoning is a key component in the printing pipeline that directly affects the print image quality. While working on a research project in digital holography, Professor Allebach developed an algorithm called Direct Binary Search to design holograms. During one of his summers at HP Labs, he collaborated with Qian, a renowned researcher in halftone algorithms for HP printers. Applying Jan’s direct binary search ideas to those algorithms led them to the design of halftone dither matrices called “Color Smooth Dither” that were shipped in HP Inkjet and large format printers.

Many other technologies developed in the collaboration between HP and Purdue can be found in a wide range HP’s printer products. Over two dozen patent applications have been filed by HP to protect this work. Sixteen faculty members and over 60 graduate students from four different departments at Purdue have participated in this research.


Acknowledging the contributions from Purdue professors and researchers, HP endowed the Hewlett-Packard Professorship in 2006, which is presently held by Professor Jan Allebach. The Purdue and HP collaboration continues to grow in the quest to solve some of the complex problems involving multi-disciplinary research. As an example, a new research project explores using deep learning to recognize objects in images in real time for ambient computing applications.

The image on the left uses the same dither matrix for all colors. The image on the right uses Color Smooth Dither which distributes cyan, magenta, and yellow dots stochastically. This results in a less grainy appearance.

About HP

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