HALFTONING SCREEN GENERATING APPARATUS AND METHOD, AND HALFTONING SCREEN GROWING APPARATUS, AND IMAGE FORMING APPARATUS USING THE SAME, AND COMPUTER READABLE MEDIUM

摘要

A halftoning screen generating apparatus and method, and a halftoning screen growing apparatus, and an image forming apparatus using the same, and a computer readable medium are provided to generate a halftoning screen that includes the characteristics to reproduce both the smooth and detailed tones, by adaptively varying the LPI according to the applied level ranges. A halftoning screen generating apparatus(100) includes a dot center determining unit(110) and a screen generating unit(120). The halftoning screen generating apparatus is an image forming apparatus such as a printer, or an external host device, such as a PC, having a printer driver program installed therein. The dot center determining unit sets the locations of dot centers according to grey levels of print data. The grey levels include 0 through 255. The dot center determining unit divides the entire grey level into a plurality of sub-levels, and set the locations of the dot centers according to each of the sub-levels. The dot center determining unit sets the locations of the dot centers based on a plurality of predetermined LPI values. The screen generating unit grows the dots based on the locations of the dot centers determined by the dot center determining unit and outputs a halftone screen. That is, the screen generating unit grows the dots based on the locations of the dot centers that are differently set according to the respective grey levels. The dot center setting unit includes a first dot center setting unit(112), a level range determining unit(114), and a second dot center setting unit(116). The first dot center setting unit sets the location of a first dot center that corresponds to a first LPI value. The first LPI value is 200 LPI. For example, the first dot center setting unit sets the location of the first dot center based on a 200 LPI value. The level range determining unit determines grey level ranges to which to apply a first LPI value and a second LPI value from a total of 256 grey levels, numbered from 0 through 255. The level range determining unit classifies the entire grey level range from 0 through 255 into two sub-ranges, and determine a grey level range for each sub-range to which to apply the first and second values, respectively.