IMAGE PROCESSING DEVICE AND IMAGE PROCESSING METHOD

If a false edge will possibly occur at a portion in an image where the input pixel value. Iin is equal to the value (Rj+F), where j=N, S, M, or L, the noise value N is generated when the input pixel value Iin is around the value (Rj+F). The noise value N has a value equal to a product of a random number, the value “rate”, and the value “coefficient”. The value “rate” becomes the maximum value (1) when the input pixel value Iin is equal to the value (Rj+F), and becomes zero (0) when the input pixel value Iin is smaller than or equal to the value (Rj+F)−Range and when the input pixel value Iin is greater than or equal to the value (Rj+F)+Range. The value “coefficient” ensures that the value (Iin+N) will not become smaller than an input minimum value Imin or a threshold that corresponds to another relative value that is smaller than and next to the subject relative value Rj and will not exceed the input maximum value Imax or another threshold that corresponds to still another relative value that is greater than and next to the subject relative value Rj.