Hewlett-packard Company

Hewlett-packard Development Company, L.P.

Irwin Sobel

Doron Shaked

Will Allen

Nur Arad

Andrew E Fitzhugh

An-Chung Robert Lin

Michael D McGuire

A special ink consists of water and a humectant. A reusable paper includes a surface darkened by a water-insoluble material and a coating covering the darkened surface. The coating is made of a material that scatters light when dry and that becomes at least translucent when wetted by water. If the special ink is used to print on the reusable paper, the print will be visible for a limited period of time (e.g., half an hour). By the end of that time period, however, the special ink will have evaporated and the print will have disappeared completely from the reusable paper. The special ink may be applied to the reusable paper by an inkjet printer. An inkjet cartridge for such a printer includes a casing filled with the special ink.

Inking system including reusable paper and water-humectant ink

Error diffusion algorithms such as the celebrated Floyd Steinberg error-diffusion algorithm are high-performance halftoning methods in which quantization errors are diffused to 'future' pixels. Originally intended for grayscale images, they are traditionally extended to color images by error-diffusing each of the three color planes independently (separable error-diffusion). Adding a design rule which is based on certain characteristics of human color perception to the error-diffusion paradigm results in a color halftoning algorithm having output of considerably higher quality when compared to separable error-diffusion. These benefits are achieved by adding the Minimum Brightness Variation Criterion (MBVC) to the design rules of color error-diffusion halftoning methods. Halftone values are constrained to be vertices of a Minimum Brightness Variation Quadruple (MBVQ) associated with each pixel of the color image being processed. The algorithm presented requires no additional memory and entails a reasonable increase in run-time.

Color halftone error-diffusion with local brightness variation reduction

Current methodologies for color image halftoning produce prominent halftoning noise. Brightness variations between color dots placed at neighboring locations are a primary cause of color halftone noise. To correct this flaw, an Ink Relocation Postprocess to halftoning algorithms relocates ink drops between neighboring drop locations in order to reduce local brightness variations. Due to the intrinsic blurring side-effect of ink relocation, some enhancement may be desired. Two application-specific enhancement procedures are presented. In the first enhancement, ink relocation is suppressed in areas of fine detail. In the second enhancement, edge sharpening is performed after ink relocation.

Ink relocation for color halftones

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Menlo Park, CA, United States of America

Irwin Sobel