Hewlett-packard Company

Other

Michael D McGuire

Andrew E Fitzhugh

Doron Shaked

Ricardo Jansson Motta

Nur Arad

Irwin Sobel

Stephen J Boulanger

Gary J Dispoto

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

Error distribution in printing and information processing systems is accomplished according to combined internal and external super-pixel error diffusion techniques, effective for distributing whole or fractional error contributions both within and without a selected super-pixel. For a particular super-pixel, error amounts of a selected internal subject pixel are provided to another internal subject pixel until a determined or selected final pixel error value within the selected super-pixel has been determined. This final, internal error value is distributed fractionally or wholly among selected super-pixels within a predetermined super-pixel neighborhood.

Pixel error diffusion method

A system selectively enables a printer to deposit on a sheet C, M, Y and K color dots at each of the plurality of pixel locations to produce a color image. The system comprises a memory for storing C, M, Y and K color values for each pixel in the color image and a processor for controlling selective deposition of the C, M, Y and K colors. The processor determines a gray value for each pixel location from values stored in the C, M, and Y color planes. The processor subtracts the determined gray value from the C, M, and Y values which correspond to the pixel location and then determines a relationship of the gray value to a non-linear function and in dependence upon the relationship alters the C, M and Y pixel values accordingly. The processor either (1) adds the gray value back to the C, M, and Y values for the pixel location, or (2) adds a first portion of the gray value to the C, M, and Y values for the pixel location and a second portion of the gray value to the K value for the pixel location; or (3) adds all of the gray value to a K value for the pixel location. As a result, the C, M, Y and K values are altered in accordance with the determined gray value. The altered color values are then prioritized and the processor determines which colors should be printed at each pixel location and diffuses color error values to neighboring pixel locations after such determination. The prioritization procedure enables print priority to be given to either the brightest color dot or to the color dot that is most visible to the human eye.

Bi-level digital color printer system exhibiting improved undercolor

A lock for a sliding panel such as a sliding glass door includes a chain which bends in only one direction. The chain, when latched, forms an incompressible column between the openward edge of the panel and the door frame. Unlatching allows the chain to bend in its allowed direction and fall vertically along side the door frame, thus allowing the panel to open.

Chain lock for sliding door

A self-aligning neck joint for releasably securing the neck of an electric guitar to the guitar body and maintaining the neck in fixed proper alignment with the body. The neck joint includes a first bracket secured in a channel in the underside of the upper end of the neck and a second bracket secured in a neck pocket in the guitar body such that upon securing the brackets together the neck is secured to and fixed in proper alignment with the guitar body. The brackets each define a pair of rows of interlocking undercut teeth with one of the rows of teeth on the second bracket being moveable in a transverse direction for selective engagement and disengagement with the mating teeth on the first bracket to allow the brackets to be moved out of engagement and the neck separated from the guitar body. A moveable screw driven wedge is provided on the second bracket to urge the moveable teeth thereon outwardly into fixed engagement with the mating teeth on the first bracket and thereby tightly lock the neck to the body of the guitar in proper alignment.

Growing community of inventors

Palo Alto, CA, United States of America

Michael D McGuire