A contour emphasizing circuit which comprises a contour pick-up unit 10
for picking up a contour component HE from an input luminance signal Y, a
level judging unit 15 for judging the luminance level of the input
luminance signal Y, a coefficient control unit 17 for changing the
coefficient in a plurality of steps depending upon a judgment signal and
multiplying the contour component HE by the coefficient to output the
product, and an adder 14 for adding the contour component outputted from
the coefficient control unit 17 to the input luminance signal Y to output
an emphasized-contour luminance signal. The coefficient to be multiplied
by the contour component HE is changed in a plurality of steps depending
upon the luminance level of the input luminance signal Y, and the contour
component HE to be added to the input luminance signal Y is controlled to
have a magnitude appropriate to the luminance level of the input
luminance signal Y. As a result, the contour is emphasized according to
the luminance level of the input luminance signal Y without causing
excessive contour emphasis by adding a large contour component to a dark
image of a small luminance level, thus preventing formation of unnatural
images.