A digitized luminance signal, representing the luminance component of a picture signal, is adjusted according to data stored in a memory. The data are output according to the value of the digitized luminance signal and multiplied by a weighting signal generated according to the amount of black area represented by the digitized luminance signal. The digitized luminance signal is then multiplied by a value obtained from the weighted product data. Use of the weighting signal enables the luminance scale to be stretched and compressed according to various different control characteristics without the need to store separate data for each characteristic in the memory.