GRAY-LEVEL CORRECTION METHOD, THRESHOLD DETERMINATION DEVICE FOR EPSILON-FILTER, AND METHOD THEREFOR

摘要

[Problem] To correct a gray level so as to satisfy both a halo and a retinex operation effect. [Solution] A corresponding JND value is obtained for a brightness value in an obtained panel unit gray level. A pixel value corresponding to the JND value is obtained for each panel unit gray level (fig. 3B). A threshold (epsilon) is obtained from an identifiable JND value for each panel unit gray level, by inverse-gamma-correcting the ratio of said JND values to the maximum output value of the panel (fig. 3C). An approximate result from a linear function is calculated using the method of least squares (fig. 3D). The threshold (epsilon) is identified as an increasing function of the pixel value, on the basis of the number of allowable JND steps. The threshold (epsilon) is changed using such a function. Hence, it is possible to vary the threshold (epsilon) according to a center pixel value.