Image signal processing device to emphasize contrast

An image signal processing device comprising:

• a luminance signal input unit, configured to be supplied with a luminance signal representing an image;
• a representative luminance calculating unit, configured to detect a representative luminance in a predetermined area of the image represented by the luminance signal inputted via the luminance signal input unit;
• a first correction unit, configured to
• associate the predetermined area of the image to a brightness area of the image, wherein a plurality of brightness areas include:
• a dark area, an ordinary area, and a bright area, wherein each brightness area has a respective input-output characteristic function, and wherein at least the input-output characteristic function of the dark area is different from the input-output characteristic function of the bright area, and
• correct the luminance signal inputted via the luminance signal input unit, according to an output of the representative luminance calculating unit, by use of the respective input-output characteristic function, by:
• gradually adjusting the respective input-output characteristic function of the input luminance signal for the predetermined area of the image, and
• suppressing any abrupt change of the input-output characteristic functions due to noise, thereby inhibiting a rupture of the image generated when an input-output characteristic function is discontinuous;
• a second correction unit, configured to correct the luminance signal corrected by the first correction unit, by use of input-output characteristic functions which are uniform in a screen;
• a luminance signal output unit, configured to output the luminance signal corrected by the first correction unit and the second correction unit;
• a chrominance signal input unit, configured to be supplied with a chrominance signal;
• a third correction unit, configured to correct the chrominance signal inputted via the chrominance signal input unit, by use of a ratio between:
• the luminance signal inputted from said luminance signal input unit, and the luminance signal corrected by said second correction unit;
• and
• a chrominance signal output unit, configured to output the chrominance signal corrected by the third correction unit.

An image signal processing device comprising:

• a luminance signal input means for receiving a luminance signal representing an image;
• a representative luminance calculating means for detecting a representative luminance in a predetermined area of the image represented by the luminance signal inputted via the luminance signal input means;
• a first correction means, for
• associating the predetermined area of the image to a brightness area of the image, wherein a plurality of brightness areas include:
• a dark area, an ordinary area, and a bright area, wherein each brightness area has a respective input-output characteristic function, and wherein at least the input-output characteristic function of the dark area is different from the input-output characteristic function of the bright area, and
• correcting the luminance signal inputted via the luminance signal input means, according to an output of the representative luminance calculating unit, by use of the respective input-output characteristic function, by:
• gradually adjusting the respective input-output characteristic function of the input luminance signal for the predetermined area of the image, and
• suppressing any abrupt change of the input-output characteristic functions due to noise, thereby inhibiting a rupture of the image generated when an input-output characteristic function is discontinuous;
• a histogram detecting means for detecting a luminance distribution of the luminance signal inputted via the luminance signal input means;
• a second correction means for correcting the luminance signal corrected by the first correction means, by use of input-output characteristic functions which are uniform in a screen, according to the luminance distribution detected by the histogram detecting means;
• a luminance signal output means for outputting the luminance signal corrected by the first correction means and the second correction means;
• a chrominance signal input means for receiving a chrominance signal;
• a third correction means for correcting the chrominance signal inputted via the chrominance signal input means, by use of input-output characteristic functions which are set according to change of the luminance signal calculated from the input-output characteristic functions used in the first correction means and the input-output characteristic functions used in the second correction means;
• and
• a chrominance signal output means for outputting the chrominance signal corrected by the third correction means.