Filtration of an input signal implemented in the horizontal or vertical
direction may disorder the gradation in oblique directions, so that oblique lines
may become jagged. To deal with this situation, the following components are provided
to process the input signal: a waveform correcting means (6) having a correcting
characteristic that the slope for correction in the medium-luminance range is greater
than that in the high-luminance range or in the low-luminance range; a processing
means (7) for extracting the deviation of the input signal processed by
the waveform correcting means; a picture edge strength detecting means (1);
and a processing means (8) for performing operations based on the deviation
of the input signal and the picture edge strength.
