Method and system for color grading of gemstones
First Claim
1. A method for color grading of a gemstone using a system with a computer program product, comprising:
- calibrating a display element to a specification of a white point of a CIE standard illuminant at a brightness level with a γ
correction;
observing an average color of said gemstone by the 45/0 condition under a standard CIE daylight simulator against a neutral background and surround;
adjusting a hue, a lightness and a saturation value continuously to change a reference color of the display element by a color grader;
calculating a color coordinate and a color notation from said hue, said lightness and said saturation value;
applying said γ
correction to a RGB tristiumlus value;
calculating a RGB digital counts;
assigning a corresponding color name from said calculated color coordinates by checking a color name look-up table;
making a logical decision;
displaying said assigned color name and said calculated color coordinates; and
displaying a reference color on said display element.
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Abstract
A method and system, including a computer program product, implementing a color terminology for accurate color grading of gemstones are provided. The method includes generating a reference color to match that of a graded gemstone under the standard viewing environment, processing color data in different color spaces, assigning a color grade to specify the color of the gemstone graded. The reference color can be continuously changed by adjusting the hue, lightness and saturation values. The color grade comprises a color name and one or more corresponding color coordinates and/or one or more corresponding color notations, in the form of Color Name (Color Coordinates). The color name is used for verbal description of the color, and the color coordinate or color notation is for accurate color communication in the jewelry industry.
25 Citations
20 Claims
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1. A method for color grading of a gemstone using a system with a computer program product, comprising:
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calibrating a display element to a specification of a white point of a CIE standard illuminant at a brightness level with a γ
correction;observing an average color of said gemstone by the 45/0 condition under a standard CIE daylight simulator against a neutral background and surround; adjusting a hue, a lightness and a saturation value continuously to change a reference color of the display element by a color grader; calculating a color coordinate and a color notation from said hue, said lightness and said saturation value; applying said γ
correction to a RGB tristiumlus value;calculating a RGB digital counts; assigning a corresponding color name from said calculated color coordinates by checking a color name look-up table; making a logical decision; displaying said assigned color name and said calculated color coordinates; and displaying a reference color on said display element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 20)
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14. A computer program product stored on a machine-readable medium for processing color grading of a gemstone, the product comprises of instructions operable to cause a programmable data processor to:
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receive an input hue, an input lightness and an input saturation value; calculate a color coordinate from said input hue, said input lightness and said input saturation value for adjusting a reference color, apply a γ
correction to RGB tristimulus values;calculate a RGB digital count; assign a corresponding color name from said calculated color coordinate by checking a color name lookup table; and instruct said programmable data processor to drive a display element to show said reference color. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification