Method and apparatus for providing improved human observer xyz functions and calculations for cielab

A method for determining color matching functions, comprising:

• obtaining spectral data originating from color matching experiments and from metameric pairs;
• defining color matching functions from a set of parameters;
• and
• defining an error function that indicates error due to perceptual differences between the parameterized color matching functions and the color matching experiments, wherein the number of parameters is less than 96.

A method for optimizing the definitions of XYZ human observer functions, comprising:

• defining parameters and parametric equations that are substantially similar to current definitions for LMS cone response functions based on the CIE XYZ observer functions;
• converting the parameters and parametric equations to XYZ human observer functions;
• adjusting the parameters to maintain the similarity to the current definitions for the LMS cone response functions;
• and
• adjusting the parameters and parametric equations to maintain substantial similarity to the XYZ human observer functions while reducing the calculated delta E (ΔE) errors between matching pairs of metameric functions.

A method for defining improved definitions of CIELAB, comprising:

• (a) defining parameters and parametric equations that are substantially similar to current definitions for LMS cone response functions based on CIE XYZ observer functions;
• (b) converting the parameters and parametric equations to XYZ human observer functions;
• and
• (c) substituting values in the CIE XYZ observer functions for CIELAB with values of XYZ human observer functions from (b).

A system, comprising:

• means for receiving measured spectral data associated with a list of device code values;
• means for converting the spectral data to XYZ or LAB data by:
• (a) defining parameters and parametric equations that are substantially similar to current definitions for LMS cone response functions based on CIE XYZ observer functions;
• (b) converting the parameters and parametric equations to XYZ human observer functions;
• (c) substituting values in the CIE XYZ observer functions for CIELAB with values of XYZ human observer functions from (b);
• and
• means for generating an ICC profile using the XYZ or LAB data.

A method for defining human observer functions, comprising:

• obtaining a set of measured spectra from a set of color samples;
• parameterizing a conversion from cone response functions to human observer functions;
• converting from the human observer functions to a perceptually uniform space;
• and
• optimizing the parameters obtained during the parameterizing in order to obtain improved correspondence between Euclidean differences and magnitudes of visual difference between the color samples.

A method for optimizing the coefficients used in conversion from LMS to XYZ, comprising:

• obtaining measured color data from sequences of colors wherein the visual differences between colors within each sequence is substantially similar;
• calculating a delta E (ΔE) difference between adjacent pair of colors within each sequence;
• calculating the differences in delta E (ΔE) between each pair of adjacent colors within each sequence;
• summing the differences in delta E (ΔE) in order to obtain an error function;
• and
• optimizing the coefficients used in the conversion of LMS to XYZ in order to minimize the error function.

A method for optimizing coefficients used for calculating CIELAB, comprising:

• obtaining measured color data from sequences of colors wherein the visual differences between colors within each sequence is substantially similar;
• calculating a delta E (ΔE) difference between adjacent pair of colors within each sequence;
• calculating the differences in delta E (ΔE) between each pair of adjacent colors within each sequence;
• summing the differences in delta E (ΔE) in order to obtain an error function;
• and
• optimizing the coefficients used in the calculation of CIELAB in order to minimize the error function.

A method for optimizing the coefficients used in conversion from LMS to XYZ and the coefficients used for calculating CIELAB, comprising:

• obtaining measured color data from sequences of colors wherein the visual differences between colors within each sequence is substantially similar;
• calculating a deltaE (ΔE) difference between each adjacent pair of colors within each sequence;
• calculating the differences in deltaE (ΔE) between each pair of adjacent colors within each sequence;
• summing the differences in deltaE (ΔE) in order to obtain an error function;
• and
• optimizing the coefficients used in conversion from LMS to XYZ and in the calculation of CIELAB in order to minimize the error function.

A method for defining a color order system, comprising:

• obtaining measured color data from sequences of colors wherein the visual differences between colors within each sequence is substantially similar;
• calculating a deltaE (ΔE) difference between each adjacent pair of colors within each sequence;
• defining the sequences of colors in directions of lightness, hue, and chroma;
• and
• wherein adjacent colors within each sequence differ by the same value of calculated deltaE (ΔE).