Patent ID: 7881553

Claim:
An image processing apparatus that receives image information and determines an output gray-scale value of the image information, the image processing apparatus comprising: a corrected input-value calculating unit to calculate a corrected input value by assigning a predetermined weight to an error value near a target pixel of the image information and adding the error value to an input gray-scale value; a threshold selecting unit to select a threshold based on an input gray-scale value of at least one of the target pixel of the image information and a pixel near the target pixel; an output gray-scale value determining unit to determine an output gray-scale value based on the corrected input value calculated by the corrected input-value calculating unit and the threshold selected by the threshold selecting unit; and an error calculating unit to calculate a difference between the output gray-scale value determined by the output gray-scale value determining unit and the corrected input value as an error value, and transmit the calculated error value to the corrected input-value calculating unit, wherein the threshold selecting unit selects one of at least two types of threshold tables based on the input gray-scale value of at least one of the target pixel and the pixel near the target pixel and selects a threshold from selected one of the threshold tables, and wherein the threshold tables have a same period and different degrees of flexibility, where the degree of flexibility is defined as representing a number of pixels that can take different output values as a result of threshold processing on an input image formed only with a predetermined gray-scale value.