EE381K Multidimensional DSP - Halftoning

Announcement

• Mr. Vishal Monga, The University of Texas at Austin, "Perceptually Based Methods for Robust Image Hashing", Wednesday, April 13th, 9:00 AM, ENS 637. This is Ph.D. defense.
• Dr. Shen-ge Wang, Xerox Laboratories, Webster, NY, "Glossmark Technology: Beyond Halftone Frequencies", Wednesday, April 13th, 12:00 PM, SEA 4.244.

Lecture

• Digital halftoning is the process by which a continuous-tone image is converted to a binary image, or halftone, for printing or display on binary devices.
• Throughput calculations for a high-end laser printer for printing 8.5" by 11" pages at 24 pages per minute:
  • 600 dots per inch: 13.464 Mpixels/s
  • 1200 dots per inch: 53.856 Mpixels/s
• Compare this to NTSC video
  • 704 by 576 frames at 30 frames/s for 3 colors/frame: 36.495 Mpixels/s
• Dots per inch or lines per inch? Dots per inch is a marketing ploy. The way that dots per inch is computed by first printing a line of four dots, then printing a line of three dots right under it, and the difference in lengths is taken as the size of one dot. At 600 dpi and higher, a printer is not really able to render an isolated single dot.
• Halftone comparison
• Halftoning by screening
• Talk on Halftoning available in PowerPoint and PDF formats.

References

• T. D. Kite, B. L. Evans, and A. C. Bovik, "Modeling and Quality Assessment of Halftoning by Error Diffusion", IEEE Transactions on Image Processing, vol. 9, no. 4, pp. 909-922, May 2000.
• T. D. Kite, N. Damera-Venkata, B. L. Evans, and A. C. Bovik, "A Fast, High-Quality Inverse Halftoning Algorithm for Error Diffused Halftones", IEEE Transactions on Image Processing, vol. 9, no. 9, pp. 1583-1592, Sep. 2000.

Last updated 04/12/05. Send comments to bevans@ece.utexas.edu