Color expressing method and image processing apparatus thereof

A color expression method comprising the steps of:

• obtaining first color signal data expressed by a combination of three stimulus data corresponding to vertices of a triangle, wherein the triangle formed by connecting these three points circumscribes a spectrum locus on xy chromaticity coordinates approximately at 505 nm and 525 nm, and one side of the triangle includes a purple boundary connecting two points at 380 nm and 780 nm;
• and
• obtaining second color signal data by performing a non-linear transformation on the first color signal data,
• wherein the nonlinear transformation is a transformation such that a quantizing step becomes larger as the luminance of the first color signal data is higher.

An image processing apparatus comprising:

• means for obtaining first color signal data expressed by a combination of a three stimulus data corresponding to vertices of a triangle, wherein the triangle formed by connecting these three points circumscribes a spectrum locus on xy chromaticity coordinates approximately at 505 nm and 525 nm, and one side of the triangle includes a purple boundary connecting two points at 380 nm and 780 nm;
• means for independently performing a nonlinear transformation on the color signal data;
• and
• data transform means for obtaining a color separation signal from a difference of a signal value after the nonlinear transformation,
• wherein the color separation signal is transformed to predetermined color component data as image information and the obtained image information is outputted as a visual output.

A color expression method comprising the steps of:

• obtaining first color signal data expressed by a combination of three stimulus data corresponding to vertices of a triangle, wherein the triangle formed by connecting these three points circumscribes a spectrum locus on xy chromaticity coordinates approximately at 505 nm and 525 nm, and one side of the triangle includes a purple boundary connecting two points at 380 nm and 780 nm;
• performing a nonlinear transformation independently on the obtained color signal data;
• obtaining a color separation signal from a difference of a signal value after the nonlinear transformation;
• and
• transforming the color separation signal to predetermined component data,
• wherein the nonlinear transformation is a transformation such that a number of quantizing bits of the color separation signal is less than the number of quantizing bits of R, G, B signals.

A color expressing apparatus comprising;

• means for obtaining first color signal data expressed by a combination of three stimulus data corresponding to vertices of a triangle, wherein the triangle formed by connecting these three points circumscribes a spectrum locus on xy chromaticity coordinates approximately at 505 nm and 525 nm, and one side of the triangle includes a purple boundary connecting two points at 380 nm and 780 nm;
• means for obtaining second color signal data by performing nonlinear transformation on the first color signal data;
• and
• means for transforming said second color signal data to predetermined color component data,
• wherein the nonlinear transformation is such that a quantizing step becomes larger as the luminance of the first color signal data is higher.

An image processing method comprising the steps of:

• obtaining first color signal data expressed by a combination of three stimulus data corresponding to vertices of a triangle, wherein the triangle formed by connecting these three points circumscribes a spectrum locus on xy chromaticity coordinates approximately at 505 nm and 525 nm, and one side of the triangle includes a purple boundary connecting two points at 380 nm and 780 nm;
• independently performing a nonlinear transformation on the color signal data;
• and
• transforming data for obtaining a color separation signal from a difference of a signal value after the nonlinear transformation,
• wherein the color separation signal is transformed to predetermined color component data as image information and the obtained image information is outputted as a visual output.

A color expressing apparatus comprising:

• means for obtaining first color signal data expressed by a combination of three stimulus data corresponding to vertices of a triangle, wherein the triangle formed by connecting these three points circumscribes a spectrum locus on xy chromaticity coordinates approximately at 505 nm and 525 nm, and one side of the triangle includes a purple boundary connecting two points at 380 nm and 780 nm;
• means for performing nonlinear transformation independently on the color signal data;
• means for obtaining a color separation signal from a difference of a signal value after the nonlinear transformation;
• and
• means for transforming the color separation signal to predetermined component data,
• wherein the nonlinear transformation is such that a number of quantizing bits of the color separation signal is less than the number of quantizing bits of R, G and B signals.