There is provided an apparatus and method for determining metameric settings for a nonlinear light source comprising a set of N primaries. Spectral data indicative of a spectral output of each of the N primaries at each of a plurality of predetermined intensity values is received. The method comprises determining, in dependence on the received data, a relationship for each of the N primaries between intensity and spectral output over at least a portion of a visible spectrum; determining a first activation corresponding to activation of a first photoreceptor type and a second activation corresponding to activation of a second photoreceptor type in dependence on the determined relationship for each of the N primaries; and selecting a background set of intensity values and a modulation set of intensity values of the N primaries. The background set and modulation set are selected such that a difference between the determined first activation corresponding to the background set and the determined first activation corresponding to the modulation set is according to a first criteria; and a difference between the determined second activation corresponding to the background set and the determined second activation corresponding to the modulation set is according to a second criteria.

Disclosed is a method for organizing a substantially uniform system of colorimetry comprising the steps of (i) taking a pseudoinverse of a matrix containing intensity values for an existing non-uniform color-matching functions; (ii) optionally normalizing the pseudoinverse matrix from step (i); (iii) empirically determining an opponency transformation matrix based on a plurality of substantially uniformly spaced color standards; (iv) transforming the matrix from step (ii) to a color opponency color coordinate utilizing the opponency transformation matrix from step (iii) to obtain a Red-Green, Yellow-Blue and Lightness (RG, YB and LT) color matching functions; and (v) transforming the RG, YB and LT color matching functions from step (iv) non-linearly to color matching functions that produce colors recognizable as being uniform by human vision; wherein after step (v) the existing non-uniform color matching functions are transformed into substantially uniform color matching functions.

An image forming apparatus that prints an adjustment pattern on a sheet includes a generator and an image former. The adjustment pattern is for correcting a color value obtained by reading a second patch region on the sheet with a second reader based on a color value obtained by reading a first patch region on the sheet with a first reader. The generator generates image data of the adjustment pattern, and the image former performs printing based on the image data. The adjustment pattern includes a first patch printed in the first patch region and a second patch printed in a region other than the first patch region in the second patch region. The second patch includes a common color patch in a same color as a color of the first patch, and a size of the first patch is larger than a size of the second patch.

The present disclosure relates generally to signal encoding for printed objects such as product packaging, labels and hangtags. One implementation obtains a color image representing CMY color channels, and alters the color image to include an encoded signal by altering values representing CIELAB a* and b*, all the while keeping L* on or within a predetermined tolerance of a contour representing a constant value. Other implementations are provided.

A method for determination of a cross-manufacturer hair coloration agent recommendation is provide. The method includes the allocation of a number of hair coloration agents to respectively one standard source hair color of a number of source hair colors, a coloration of hair samples with the number of hair coloration agents, a colorimetric measurement of the number of hair samples, a determination of a color difference between each of the number of colors, an allocation of each of the hair coloration agents with unknown composition to one of the hair coloration agents with known composition in such a way that the color difference is minimized, a determination of the user source hair color, a determination of the user's desired hair color, a determination of a first recommended hair coloration agent from the number of hair coloration agents of known composition and of a second recommended hair coloration agent.

Certain examples described herein relate to color spaces. In some cases, data representing a set of color values is obtained. Each color value has, for each of first, second and third axes defining a three-dimensional color space, a respective coordinate value. In some cases, for each of the set of color values, the coordinate value for the first and/or second axis is transformed dependent on the coordinate value for the third axis, to generate data representing a transformed set of color values. A set of output color values in an output color space is derived using the generated data. Output data associating the set of output color values in the output color space with a set of further color values in a further color space is generated.

A color table is modulated. The color table includes nodes that correspond with a color input in a first color space and provides a print substance formulation in a second color space. For a set of the nodes, a determination is made as to whether a color amount based on the print substance formulation is outside of threshold value. For each node in which the color amount for the node is outside the threshold value, the print substance formulation is replaced with a replacement print substance formulation having a color amount that is within the threshold value.

A method for generating color conversion information including providing a user with color sample information for determining a color sample of which color characteristic information is known, receiving, from the user, an image including the color sample determined by the color sample information in a lighting environment, and generating color conversion information which corresponds to the lighting environment and is correlated with the user, based on the image and the color characteristic information of the color sample determined by the color sample information. The color conversion information converts between color information and color characteristic information, the color information is information which corresponds to a lighting environment and indicates colors of an object in the lighting environment, and the color characteristic information indicates color characteristics of the object.

Method of color measuring a color of a rendered copy of a digital image, by a color-measuring-device (3000) for color measuring in a plurality of spectral ranges (r.sub.1 . . . r.sub.Q); wherein said method comprises the step: measuring said color is measured in a sub-set (s.sub.1 . . . s.sub.M; .sub.3305) of said plurality of spectral ranges (r.sub.1 . . . r.sub.Q); and wherein said sub-set (s.sub.1 . . . s.sub.M) is determined by: selecting a color of a gamut boundary of said digital image (1200); and determining of said color for said plurality of spectral ranges (r.sub.1 . . . r.sub.Q) corresponding spectral reflectance factors (v.sub.1 . . . v.sub.Q); and adding a spectral range (r.sub.i), having a minimum and maximum spectral reflectance factor, to said sub-set (s.sub.1 . . . s.sub.M) wherein its corresponding spectral reflectance value (v.sub.i) is larger than 10% of said maximum spectral reflectance factor minus said minimum spectral reflectance factor.

A system and method for generating a colour filter for modifying the spectral response of a vision system are disclosed. The method includes receiving an RGB spectral response of the vision system for a colour target under predetermined illumination and executing, by a processor of a computer system, computer program instructions configured to apply the RGB spectral response to a bilinear optimisation problem that simultaneously determines: i) a colour correction matrix to transform the RGB spectral response to XYZ colour space; and, ii) parameters of the colour filter. The method further executes computer program instructions configured solving the bilinear optimisation problem; and then provides the parameters or causes a colour filter to be formed using the parameters.