Image-based matching of color and appearance of coatings containing effect pigments, using a cosine comparison methodology

At least one non-transitory machine-readable storage medium that stores instructions executable by at least one processor, the instructions configurable to cause the at least one processor to perform a method of matching color and appearance of coatings containing at least one effect pigment, the method comprising:

• obtaining, for a coating sample to be matched, sample color image data comprising pixel-specific color model properties, wherein the sample color image data is based on a digital image of the coating sample to be matched, as captured by a digital image capture system;
• generating a characterizing histogram for the sample color image data, the characterizing histogram comprising N distinct bins to obtain N bin counts, wherein the characterizing histogram represents an appearance feature descriptor of the coating sample to be matched;
• creating a sample histogram vector from the characterizing histogram, wherein the sample histogram vector is an N-dimensional vector comprising the N bin counts;
• retrieving a specimen histogram vector for comparison against the sample histogram vector, wherein the specimen histogram vector is an N-dimensional vector derived from pixel-specific color model properties obtained for a candidate coating specimen in response to a captured digital image of the candidate coating specimen;
• and
• calculating a cosine similarity value from the sample histogram vector and the specimen histogram vector as a measure of an angle between the sample histogram vector and the specimen histogram vector, wherein the cosine similarity value indicates how well the candidate coating specimen matches the coating sample to be matched.

A computing system operable to match color and appearance of coatings containing at least one effect pigment, the computing system comprising:

• at least one processor;
• and
• at least one non-transitory machine-readable storage medium that stores instructions executable by the at least one processor, the instructions configurable to cause the at least one processor to perform a method comprising the steps of:
• obtaining, for a coating sample to be matched, sample color image data comprising pixel-specific color model properties, wherein the sample color image data is based on a digital image of the coating sample to be matched, as captured by a digital image capture system;
• generating a characterizing histogram for the sample color image data, the characterizing histogram comprising N distinct bins to obtain N bin counts, wherein the characterizing histogram represents an appearance feature descriptor of the coating sample to be matched;
• creating a sample histogram vector from the characterizing histogram, wherein the sample histogram vector is an N-dimensional vector comprising the N bin counts;
• retrieving a specimen histogram vector for comparison against the sample histogram vector, wherein the specimen histogram vector is an N-dimensional vector derived from pixel-specific color model properties obtained for a candidate coating specimen in response to a captured digital image of the candidate coating specimen;
• and
• calculating a cosine similarity value from the sample histogram vector and the specimen histogram vector as a measure of an angle between the sample histogram vector and the specimen histogram vector, wherein the cosine similarity value indicates how well the candidate coating specimen matches the coating sample to be matched.

A method of matching color and appearance of coatings containing at least one effect pigment, the method comprising:

• obtaining, for a coating sample to be matched, sample color image data comprising pixel-specific hue values, wherein the sample color image data is based on a digital image of the coating sample to be matched, as captured by a digital image capture system;
• generating a hue histogram for the pixel-specific hue values, wherein the hue histogram arranges the pixel-specific hue values into N distinct hue value bins to obtain N bin counts, and wherein the hue histogram represents an appearance feature descriptor of the coating sample to be matched;
• creating a sample histogram vector from the hue histogram, wherein the sample histogram vector is an N-dimensional vector comprising the N bin counts;
• retrieving a specimen histogram vector for comparison against the sample histogram vector, wherein the specimen histogram vector is an N-dimensional vector derived from pixel-specific hue values obtained for a candidate coating specimen in response to a captured digital image of the candidate coating specimen;
• and
• calculating a cosine similarity value from the sample histogram vector and the specimen histogram vector as a measure of an angle between the sample histogram vector and the specimen histogram vector, wherein the cosine similarity value indicates how well the candidate coating specimen matches the coating sample to be matched.