Color adjustment apparatus, image display apparatus, and color adjustment method

A color adjustment apparatus that adjusts color in a manner to increase saturation of a color image represented by an image signal, comprising:

• a storage section that stores parameters;
• a section for acquiring a luminance value of each pixel from the image signal that includes RGB color signal values for expressing, in combination with a plurality of colors, the color of each pixel forming the color image;
• a saturation correspondence value calculating section that calculates a saturation correspondence value corresponding to the saturation of each pixel, from the image signal;
• a saturation adjusting section that calculates an adjustment coefficient corresponding to the saturation correspondence value calculated by the saturation correspondence value calculating section, based on the parameters;
• and
• an image generating section for generating a color image with an image signal expressing the color image in which the color has been adjusted by, for each of the RGB color signal values, multiplying a value obtained by subtracting the luminance value from the color signal value before color adjustment by the adjustment coefficient calculated by the saturation adjusting section and then adding the luminance value to the result of the multiplication to calculate the color signal value after color adjustment, wherein
• the parameters are determined to define a maximum value of the adjustment coefficient calculated by the saturation adjusting section to be a value that causes all of the RGB color signal values after color adjustment to be less than or equal to a maximum value that can be realized by each signal value, and
• the saturation adjusting section calculates the adjustment coefficient to be a value that causes all of the RGB color signal values after color adjustment to be less than or equal to a maximum value that can be realized by each signal value.

A color adjustment method for adjusting color of a color image represented by an image signal, comprising:

• determining parameters including a lower limit value S1 and an upper limit value S3 for saturation to be adjusted within a saturation before color adjustment, a maximum setting value S2 between S1 to S3 determining a saturation whose change amount is to be greatest within the saturation before color adjustment, and a saturation Se after color adjustment in a case where the saturation before color adjustment is equal to S2;
• saturation correspondence value calculation of calculating the saturation S_in before color adjustment of each pixel forming the color image, from the image signal;
• saturation adjustment of calculating the saturation S_out after color adjustment corresponding to the saturation S_in before color adjustment calculated in the saturation correspondence value calculation, based on the parameters;
• and
• generating a color image with an image signal representing the color image in which the color has been adjusted, according to the saturation S_out after color adjustment calculated in the saturation adjustment, wherein
• the saturation adjustment (i) increases S_in in the range from S1 to S2 such that the saturation increase amount increases according to the increase of S_in and increases S_in in the range from S2 to S3 such that the saturation increase amount decreases according to the increase of S_in, or (ii) decreases S_in in the range from S1 to S2 such that the saturation decrease amount increases according to the increase of S_in and decreases S_in in the range from S2 to S3 such that the saturation decrease amount decreases according to the increase of S_in, and
• when the saturation is less than or equal to S1, S_out is equal to S_in.

A color adjustment method for adjusting color in a manner to increase saturation of a color image represented by an image signal, comprising:

• determining parameters;
• acquiring a luminance value of each pixel from the image signal that includes a plurality of RGB color signal values for expressing, in combination with a plurality of colors, the color of each pixel forming the color image;
• saturation correspondence value calculation of calculating a saturation correspondence value corresponding to the saturation of each pixel, from the image signal;
• saturation adjustment of calculating an adjustment coefficient corresponding to the saturation correspondence value calculated in the saturation correspondence value calculation, based on the parameters;
• and
• image generation of generating a color image with an image signal expressing the color image in which the color has been adjusted, by, for each of the RGB color signal values, multiplying a value obtained by subtracting the luminance value from the color signal value before color adjustment by the adjustment coefficient calculated in the saturation adjustment and then adding the luminance value to the result of the multiplication to calculate the color signal value after color adjustment, wherein
• the parameters are determined to define a maximum value of the adjustment coefficient calculated in the saturation adjustment to be a value that causes all of the RGB color signal values after color adjustment to be less than or equal to a maximum value that can be realized by each signal value, and
• the saturation adjustment includes calculating the adjustment coefficient to be a value that causes all of the RGB color signal values after color adjustment to be less than or equal to a maximum value that can be realized by each signal value.