A method and a printing system are described capable of rendering more than 2 density levels at the device pixel level using precalculated rectangular screening tiles of finite size that define a spatially repetitive screening operation according to geometric clustered dot screen definitions for first, second and third separation screens that has the following characteristics: (A) the set of at least three separation screens is free of second order moire; (B) the set of at least three separation screens consists of screens that have no internal moire and/or screens that have a reduced sensitivity to amplification by process instability of any remaining level of intrinsic internal moire; and (C) the screens have an optimized and balanced rosette structure leading to a reduction of visible patterning in overlays of the separation screens.

Multilevel clustered dot screening method with improved detail and reduced image noise

An image processing system includes a printing device configured to print a halftone dot using multi-tone levels. The halftone dot is made up of a plurality of pixels, and each pixel is associated with a corresponding tone level. The image processing system further includes a processor. The processor is configured to receive a request to print a bitmap including one or more colors and to identify a grey level for each of the one or more colors. One of the multi-tone levels is associated with the identified grey level, and a halftone matrix is selected for the associated multi-tone level. Each of the multi-tone levels is associated with a different halftone matrix. The processor is further configured to compare the identified grey level with a plurality of pixel threshold values of the selected halftone matrix to determine the corresponding tone level of each of the plurality of pixels.

Partition halftone for multi-tone level output device

An image processing apparatus that converts input image data into printable image data is provided. The apparatus performs screen processing on the input image data, and determines whether moire occurs in screen image data generated by the screen processing unit for a target pixel in the input image data. Depending on the determination result made by the determination unit, the apparatus outputs one of a screen pixel value in the screen image data for the target pixel and a value obtained by converting an input pixel value into a printable pixel value based on intermediate data, as a value of the target pixel in the printable image data, the intermediate data being generated by replacing a screen pixel in the screen image data that is determined to have moire by the determination unit with the input pixel value in the input image data.

Image processing apparatus and control method thereof

A method for generating a clustered halftone representation of a continuous-tone image for printing includes applying a search technique. In the search technique, evaluation of a similarity between an initial halftone and the continuous-tone image includes application of an initialization filter to an initial error image that represents a difference between the initial halftone and the continuous-tone image. Evaluation of a similarity between each updated halftone, formed by modifying a previously-evaluated halftone, and the continuous-tone image includes application of an update filter that is different from the initialization filter to an updated error image that represents a difference between the updated halftone and the continuous-tone image. Relating computer program product and data processing system are also disclosed.

Clustered halftone generation

A special-purpose image processor can convert an electronic file into a bitmap by generating printing halftone dots within the bitmap based on locations of colors within the electronic file, and generating non-printing dots within the bitmap. A printing apparatus can print the bitmap, by not print marking materials where the non-printing dots are positioned within the bitmap. The special-purpose image processor can generate the non-printing dots within the bitmap by increasing the size of the printing halftone dots until they contact one another, or generating printing lines that connect the printing halftone dots to each other within the bitmap. Also, the special-purpose image processor can generate, as each printing halftone dot, a higher frequency pattern of printing dots, where the non-printing dots are generated to have a lower frequency pattern relative to that higher frequency.

Non-printing dot halftone patterns

The design of periodic screens for halftone patterns is based upon a series of constrained optimization problems. For each of a number of input levels, a pattern is found that minimizes a cost function. The cost function is a spatial-frequency weighted difference between an ideal, continuous-space pattern and a predicted reconstructed pattern. The frequency weighting is a parameterized trade-off between the preservation of periodic components and the introduction of non-harmonic components.

Kenneth R. Crounse

Papers

Method and system for reducing auto-moire artifacts in periodic halftone screening