Color measuring device, image capturing device, image forming apparatus, color measurement method, and computer program product

A color measurement method comprising:

• capturing a reference chart and a subject to be a target for color measurement simultaneously to acquire RGB values of the reference chart and RGB values of the subject, a plurality of colors constituting the reference chart being stored in advance as colorimetric values in a predetermined color space that is device-independent, respectively;
• searching for at least RGB values of four points corresponding to vertices of a polyhedron in the reference chart, the polyhedron including a specified RGB value of the subject in an RGB color space;
• calculating a linear transformation matrix for converting the RGB values of the four points in the reference chart into the colorimetric values corresponding to the RGB values of the four points;
• and
• converting the specified RGB value of the subject into a colorimetric value corresponding to the specified RGB value of the subject in the predetermined color space based on the linear transformation matrix.

A computer program product comprising a non-transitory computer readable medium including programmed instructions, wherein the instructions cause a computer to execute:

• capturing a reference chart and a subject to be a target for color measurement simultaneously to acquire RGB values of the reference chart and RGB values of the subject, a plurality of colors constituting the reference chart being stored in advance as colorimetric values in a predetermined color space that is device-independent, respectively;
• searching for at least RGB values of four points corresponding to vertices of a polyhedron in the reference chart, the polyhedron including a specified RGB value of the subject in an RGB color space;
• calculating a linear transformation matrix for converting the RGB values of the four points in the reference chart into the colorimetric values corresponding to the RGB values of the four points;
• and
• converting the specified RGB value of the subject into a colorimetric value corresponding to the specified RGB value of the subject in the predetermined color space based on the linear transformation matrix.