Patent ID: 8004720
Filing Date: 2011-08-23
Classification: H04N

Abstract:
1. Method for adaptive screening a continuous tone original, presented by the multilevel sampling values of optical parameter (tone value) of its areas of relatively low spatial frequency, on a substrate, said method comprising: dividing the copy substrate areas, corresponding to the areas of the original, into elements of relatively high spatial frequency; assigning each element of a substrate one of the first weight values, all normalized in accordance with a multilevel sampling scale and selected so as to achieve the desired smooth tone rendition; ascertaining the presence of detail on an original area corresponding to a given substrate area; with no detail being present in the original area, each element of said substrate area is formed dark if its first weight exceeds the optical parameter sampling value of said area of an original and is formed light if the first weight of said element doesn't exceed the value of said area while; with the detail being present in said original area each element of the given copy area is assigned one of second weight values, all normalized in accordance with a multilevel sampling scale and selected so as to achieve accuracy of detail geometry reproduction; determining a first and a second supplementary tone value S forming each element of the corresponding copy area dark or light as result of comparison of a first weight of the element with a first supplementary tone value S wherein the presence of detail comprised of one or two boundaries dividing the given area on its darker and lighter parts is ascertained; with a detail being present by two boundaries, there is ascertained if the section located between said boundaries is darker or lighter than the outer to these boundaries part; in the event of the detail comprising one dividing boundary and the original area sampling tone value S where S each element of the corresponding copy area is formed dark if its first weight exceeds the first supplementary tone value S otherwise the element is formed light; in the event of the detail comprising one dividing boundary and the original area sampling tone value S where min(S) is minimum value of tone values of an adjacent sampling areas, and each element of the corresponding copy area is formed dark if its first weight exceeds the first supplementary tone value S otherwise the element is formed light.