Color processing apparatus, color processing method, and non-transitory computer readable medium

A color processing method comprising:

• performing a first calculation process by calculating a second color signal from a first color signal by using successive approximation, the first color signal being given by repeatedly calculating a first successive solution using an inverse matrix of a sensitivity matrix of an input/output characteristic function of an output device;
• determining whether or not the first successive solution calculated in the first calculation process is divergent;
• and
• performing a second calculation process by calculating a second successive solution using a method different from a method used in the first calculation process when it is determined in the determining that the first successive solution is divergent, the second calculation process including
• (i) generating a plurality of linear equations with changing unknown numbers to be fixed, each of the plurality of linear equations being a linear equation in which an unknown number in a linear equation using the sensitivity matrix is set to a fixed value,
• (ii) fixing the unknown number so that a color signal representing a boundary of a color gamut reproduced by the output device is obtained,
• (iii) determining a solution that minimizes each of the linear equations,
• (iv) predicting a color signal corresponding to each solution using the input/output characteristic function on the basis of the solutions that minimize the linear equations, and
• (v) selecting a linear equation that minimizes a difference between the predicted color signal and the first color signal, and that uses the solution obtained by the selected linear equation as the second successive solution.

A non-transitory computer readable medium storing a program causing a computer to execute a process for performing color processing, the process comprising:

• performing a first calculation process by calculating a second color signal from a first color signal by using successive approximation, the first color signal being given by repeatedly calculating a first successive solution using an inverse matrix of a sensitivity matrix of an input/output characteristic function of an output device;
• determining whether or not the first successive solution calculated in the first calculation process is divergent;
• and
• performing a second calculation process by calculating a second successive solution using a method different from a method used in the first calculation process when it is determined in the determining that the first successive solution is divergent, the second calculation process including
• (i) generating a plurality of linear equations with changing unknown numbers to be fixed, each of the plurality of linear equations being a linear equation in which an unknown number in a linear equation using the sensitivity matrix is set to a fixed value,
• (ii) fixing the unknown number so that a color signal representing a boundary of a color gamut reproduced by the output device is obtained,
• (iii) determining a solution that minimizes each of the linear equations,
• (iv) predicting a color signal corresponding to each solution using the input/output characteristic function on the basis of the solutions that minimize the linear equations, and
• (v) selecting a linear equation that minimizes a difference between the predicted color signal and the first color signal, and that uses the solution obtained by the selected linear equation as the second successive solution.