US 2003/0189729 A1 · Method and apparatus for converting brightness level of image

Abstract

An image brightness level conversion method and apparatus which converts a multi-valued brightness level of an input pixel to a bi-valued brightness level using a threshold value. If the input pixel is determined to belong to an edge area, a predetermined reasonable distance by which dots should be isolated is reduced by a noise component and the threshold value is produced using the reduced distance. If the input pixel is determined not to belong to the edge area, the threshold value is produced without using the noise component. The method provides a uniform distribution of dots on the 2-dimensional space, a decrease in a generation of a void region where no dots appear around the edge area, a reduction of unpleasant appearing fixed patterns between dots, and a decrease in the generation of a typical pattern in which dots with a same color are diagonally arrayed.

Claims20

Dependent claims

A method of converting a multi-valued brightness level of an input pixel to a bi-valued brightness level using a threshold value, the method comprising;

determining whether the input pixel belongs to an edge area;
decreasing a predetermined distance by which dots are to be isolated by a first noise component and producing the threshold value using the decreased distance, in response to determining that the input pixel belongs to the edge area;
producing the threshold value using the decreased distance;
and
producing the threshold value without using the first noise component in response to determining that the input pixel does not belong to the edge area, wherein each of the dots has the converted bi-valued brightness level.

2 more elements

An apparatus for converting a multi-valued brightness level of an input pixel to a bi-valued brightness level using a threshold value, the apparatus comprising:

an edge checking unit which checks present and previous bi-valued brightness levels whether the input pixel corresponding to a current bi-valued brightness level belongs to an edge area and outputs a checked result;
and
a threshold value producing unit which decreases a predetermined distance by which dots are to be isolated by a first noise component to produce the threshold value in consideration of the decreased dot distance, in response to the checked result,
wherein each of the dots has the converted bi-valued brightness level.

1 more element

Dependencies are inferred from the claim text.

Method and apparatus for converting brightness level of image

Life of this patent

Method and apparatus for converting brightness level of image

Life of this patent

Abstract

Claims20