Image processing apparatus and image processing method

An image processing method, comprising:

• first generating, from input image data, color component data of a predetermined color space for luminance output;
• second generating, from input image data, color component data of the predetermined color space for color difference output;
• first converting a tone of each piece of the color component data for luminance output generated by the first generating;
• second converting a tone of each piece of the color component data for color difference output generated by the second generating;
• combining each piece of the color component data obtained by the conversion by the first converting and each piece of the color component data obtained by the conversion by the second converting, and generating respective pieces of combined color component data;
• respectively separating luminance data and color difference data from each piece of color component data obtained by the combining;
• and
• correcting a tone of each of piece of the luminance data and color difference data obtained by the separating,
• wherein the second converting has a conversion characteristic for outputting, for each piece of color component data, a non-negative value in a range, of negative infinity to a positive threshold set in advance, that input data can take.

A non-transitory computer-readable storage medium storing a program which, when read and executed by a computer, causes the computer to perform the steps of an image processing method, the method comprising:

• first generating, from input image data, color component data of a predetermined color space for luminance output;
• second generating, from input image data, color component data of the predetermined color space for color difference output;
• first converting a tone of each piece of the color component data for luminance output generated by the first generating;
• second converting a tone of each piece of the color component data for color difference output generated by the second generating;
• combining each piece of the color component data obtained by the conversion by the first converting and each piece of the color component data obtained by the conversion by the second converting, and generating respective pieces of combined color component data;
• respectively separating luminance data and color difference data from each piece of color component data obtained by the combining;
• and
• correcting a tone of each of the luminance data and color difference data obtained by the separating,
• wherein the second converting has a conversion characteristic for outputting, for each piece of color component data, a non-negative value in a range, of negative infinity to a positive threshold set in advance, that input data can take.

An image processing apparatus, comprising:

• a first generation unit configured to generate, from input image data, color component data of a predetermined color space for luminance output;
• a second generation unit configured to generate, from input image data, color component data of the predetermined color space for color difference output;
• a first conversion unit configured to convert a tone of each piece of the color component data for luminance output generated by the first generation unit;
• a second conversion unit configured to convert a tone of each piece of the color component data for color difference output generated by the second generation unit;
• a combining unit configured to combine each piece of the color component data obtained by the conversion by the first conversion unit and each piece of the color component data obtained by the conversion by the second conversion unit, and generate respective pieces of combined color component data;
• a third conversion unit configured to convert a tone of each piece of color component data obtained by the combining unit,
• wherein at least one of the second conversion unit and the third conversion unit has a conversion characteristic for outputting, for each piece of color component data, a non-negative value in a range, of negative infinity to a positive threshold set in advance, that input data can take.

An image processing method, comprising:

• first generating, from input image data, color component data of a predetermined color space for luminance output;
• second generating, from input image data, color component data of the predetermined color space for color difference output;
• first converting a tone of each piece of the color component data for luminance output generated by the first generating;
• second converting a tone of each piece of the color component data for color difference output generated by the second generating;
• combining each piece of the color component data obtained by the conversion by the first converting and each piece of the color component data obtained by the conversion by the second converting, and generating respective pieces of combined color component data;
• third converting a tone of each piece of color component data obtained by the combining,
• wherein at least one of the second converting and the third converting has a conversion characteristic for outputting, for each piece of color component data, a non-negative value in a range, of negative infinity to a positive threshold set in advance, that input data can take.

A non-transitory computer-readable storage medium storing a program which, when read and executed by a computer, causes the computer to perform the steps of an image processing method, the method comprising:

• first generating, from input image data, color component data of a predetermined color space for luminance output;
• second generating, from input image data, color component data of the predetermined color space for color difference output;
• first converting a tone of each piece of the color component data for luminance output generated by the first generating;
• second converting a tone of each piece of the color component data for color difference output generated by the second generating;
• combining each piece of the color component data obtained by the conversion by the first converting and each piece of the color component data obtained by the conversion by the second converting, and generating respective pieces of combined color component data;
• third converting a tone of each piece of color component data obtained by the combining,
• wherein at least one of the second converting and the third converting has a conversion characteristic for outputting, for each piece of color component data, a non-negative value in a range, of negative infinity to a positive threshold set in advance, that input data can take.