| CPC G06T 1/0021 (2013.01) [G01J 3/462 (2013.01); G01J 3/463 (2013.01); G06T 7/90 (2017.01); G06T 11/001 (2013.01)] | 13 Claims |

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3. An apparatus comprising:
an input to obtain a reflectance value representing an image pixel or group of image pixels within a wavelength range, the image pixel representing artwork including a cyan value, a magenta value, and a yellow value;
means for altering the reflectance value according to an information carrying signal, said means for altering yielding a target reflectance value within the wavelength range;
means for changing, in a first direction, the cyan value to achieve the target reflectance value, said means for changing yielding changed pixel color values;
means for evaluating a luminance (L*) value of the changed pixel color values relative to a luminance (L*) value of the image pixel or group of image pixels;
means for changing, in a second direction opposite of the first direction, a magenta value of the changed pixel color values to minimize a change in luminance (*L) between the luminance (L*) value of the changed pixel color values relative to the luminance (L*) value of the image pixel or group of image pixels while maintaining the target reflectance value within 0-5%.
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