Hardcopy Imaging Systems

Embedded Multilevel Error Diffusion

Adaptive Filtering for Error-Diffusion Quality Improvement

Hybrid Halftoning for Color Moire Reduction

Displaying True Color Images Using a Limited-Depth Frame Buffer

A Study on Entropy Reduction of Bi-Level Color Image Quantized by the Minimized Average Error Method

Entropy-Constrained Error Diffusion

New Group-3 Color-Facsimile Standard: Protocol Testing and Performance

Bi-Level Image-Quality Improvement for Mixed-Color Facsimile

Color Calibration for Color Facsimile

A System for Overhead-Projection-Transparency Reuse



Embedded Multilevel Error Diffusion
J. R. Goldschneider, E. A. Riskin
University of Washington, Seattle, WA
P. W. Wong
Hewlett-Packard Laboratories, Palo Alto, CA
full paper

Two methods for embedding the output of binary Floyd and Steinberg error diffusion into the output of K level error diffusion are discussed. The first method uses two K/2 level scalar quantizers. The output of the binary error diffusion determines which of the two quantizers to use. The embedding can be done in any bit of the output depending on the choice of quantizers. The second method, fully embedded multilevel error diffusion, uses K-1 binary scalar quantizers. The output of this method is fully embedded, so that if one bit is removed from the output, the results of the K/2 level error diffusion are preserved. The full embedding can be done in either the most or least significant bits of the output depending on the choice of quantizers.



Adaptive Filtering for Error-Diffusion Quality Improvement
J. Shu
Epson Palo Alto Lab, Palo Alto, CA
full paper

A novel adaptive filtering approach to improve error diffusion halftone quality is presented. This technique employs a set of error filters having different sizes and/or associated weighted coefficients for diffusing quantization errors among neighboring pixels in predetermined tonal areas of an image. Both "worm" and "graininess" artifacts in halftone images were reduced to achieve high-quality smooth halftone images.



Hybrid Halftoning for Color Moire Reduction
D. Knox, Y. Holladay, R. Eschbach
Xerox Digital Imaging Technology Center, Webster, NY
full paper

A hybrid approach for the reduction of color moiré in four color printing is described. In this hybrid approach, periodic and non-periodic halftoning techniques are combined in order to reduce the intermodulation frequencies between the different color separations.



Displaying True Color Images Using a Limited-Depth Frame Buffer
A. C. Barkans
Hewlett-Packard Co., Ft. Collins, CO
full paper

A method to display images with millions of colors in an interactive environment from a limited-depth frame buffer is discussed. In place of the conventional dithering techniques for 8-bit color displays, a new digital-signal-processing (DSP) based scheme was used to reconstruct the original color image.



A Study on Entropy Reduction of Bi-Level Color Image Quantized by the Minimized Average Error Method
F. Ogawa, I. Ueno, M. Matsumoto, T. Semasa, N. Tanabe, F. Ono
Mitsubishi Electric Corp., Kanagawa, Japan
full paper

The Markov entropy was evaluated for high-efficiency encoding of a bi-level color image quantized by the minimized average error method (MAEM). An optimum-efficiency reference pixel encoding template was created. The extent of entropy reduction and the range of applicability of this method is demonstrated.



Entropy-Constrained Error Diffusion
P. W. Wong, H. Nguyen
Hewlett-Packard Laboratories, Palo Alto, CA
full paper

While traditional error diffusion generates very high quality halftones from continuous tone images, the resulting binary images are not amenable to lossless compression. An algorithm is proposed that incorporates an entropy constraint and a delayed decision procedure for generation of halftone images that are more amenable to lossless compression. In essence, distortion is traded off with compression ratio as in rate-distortion theory.



New Group-3 Color-Facsimile Standard: Protocol Testing and Performance
G. B. Beretta, E. F. Chan, K. Konstantinides, D. T. Lee, H. J. Lee, A. H. Mutz
Hewlett-Packard Laboratories, Palo Alto, CA
full paper

Results on the implementation of new color-facsimile standard, protocol testing, and performance are presented. System issues and extensions to continuous-tone color capabilities are discussed.



Bi-Level Image-Quality Improvement for Mixed-Color Facsimile
H. Mizumachi
NTT Human Interface Laboratories, Yokosuka, Japan
M. Matsuki
NTT Printec Corp., Saitama, Japan
full paper

In mixed color facsimile system, the image quality of the bi-level image area is slightly lower than that of continuous-tone area. In order to improve the image quality, a system that manages different resolutions of each image block in one page was developed. A scanning and printing system that supports this feature is described.



Color Calibration for Color Facsimile
F. Schmitt, J.-P. Crettez
ENST, Paris, France
Y. Wu
ENST, Paris, France, and OCE Graphics, Créteil, France
G. Boulay
SEPT, Caen, France
full paper

A complete methodology is proposed for the control of the color responses of the input/output devices for color facsimile. It employs models developed from the initial calibration of the input/output devices using 3D non-linear transformations linking their specific RGB/CMYK with standard CIELab color space. The transformations were calculated using tri-linear interpolator with 3D look-up tables.



A System for Overhead-Projection-Transparency Reuse
Y. Okada, Y. Nishioka, Y. Okabe, F. Nakagawa
Oki Electric Industry Co., Ltd., Tokyo, Japan
full paper

In this system overhead-projection (OHP) transparencies were produced with thermo-reversible recording material consisting of polyvinyl acetal and a higher fatty acid, that records negative images. The material can take two states, transparent and opaque, depending on the difference in cooling rate after heating. The thermo-reversible mechanism of the material is responsible for the miscibility and immiscibility. Recorded OHP transparencies made from the material could be reused by passing through a heated-roller-based erasing subsystem.