Screening

Artifex offers three high-performance screening technologies: Even Toned Screening, Error Diffusion Screening and Threshold Array Screening.

Even Toned Screening

Even Toned Screening (ETS), our proprietary technology, is a variant of error diffusion. It is well suited for use in inkjet printers and provides significant visual improvements over standard error diffusion methods.

ETS provides unparalleled fidelity in reproducing fine detail by:

• Eliminating moiré.
• Eliminating “wormy” textures in highlights and shadows.
• Eliminating “tearing” adjacent to high-contrast areas.
• Supporting multiple color sets and multiple dot sizes.
• Reducing artifacts in locations like smooth gradients.

This high-quality technique adds output-dependent feedback to the conventional error diffusion halftone, improving these halftones significantly.

While ETS can be applied to both highlight and shadow dots, on inkjet printers only the highlights cause visually noticeable patterns because of the ink spread. Thus, applying the output dependent feedback to only highlight textures, processing speeds are significantly optimized.

Threshold Array Screening

Ordered Dither & Dispersed Dot Stochastic Dither

Artifex offers two Threshold Array Screening options: Ordered dither, using traditional parameters for lines per inch (screen resolution), angle, and spot shape, and Dispersed dot stochastic dither screen.

Both technologies allow for independent horizontal and vertical device resolution and the abilities to generate screens with at least 256 levels.

In the ordered dither screen, a supercell is used consisting of an array of multiple dots within the screen to provide enough gray levels, using stochastic dot growth to prevent moiré patterns. The threshold array dimensions will be those of the supercell.

The dispersed-dot stochastic dither threshold array can be generated for any specified width and height, and the number of levels is 1+(width*height). This technology also allows for a ‘minimum dot’ setting when generating dispersed dots to allow the resultant screens to be practical on printing engines that cannot reliably image true ‘dispersed dot’ screens. This is sometimes referred to as a ‘green screen’ in that the peak spatial frequency at a particular level is lower than a blue noise distribution or that of error diffusion, but the perceived visual quality may be better than an ordered dither screen.

The dispersed dot approach relies on a seed or simple spatial rotation, rather than the screen angle in order to prevent correlation among individual screens for each color channel (e.g., CMYK). This prevents color shifts if the print engine registration among color channels changes within the page or page to page.

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