Patent ID: 7463387
Filing Date: 2008-12-09
Classification: H04N

Abstract:
1. A multilevel value output device, comprising: a relative density value storage portion that prestores therein at least three relative density values for at least three multilevel output values in one-to-one correspondence with each other, the at least three relative density values being defined dependently on a predetermined maximum density that is defined for a highest relative density value among the at least three relative density values; an input portion that receives an input value indicative of density of a pixel in an input image; a corrected value calculation portion that calculates a corrected value by adding to the input value at least a part of an error value that has been generated by at least one pixel near to the subject pixel; an output value generation portion that compares the corrected value with at least one of the at least two threshold values, that converts the corrected value into one of the at least three multilevel values based on the compared results, and that outputs a resultant multilevel output value, the output value generation portion referring to the threshold value storage portion and setting one relative density value that corresponds to the output value, the output value generation portion calculating a difference between the corrected value and the relative density value and setting the calculated result as an error value for the subject pixel; and an output-value generation control portion that, when the corrected value is close to at least one of the at least three relative density values, reduces a frequency, at which the output value generation portion converts the corrected value into one multilevel output value that corresponds to the subject relative density value, thereby reducing a frequency at which the error value for the subject pixel becomes close to zero.