The ICC specification defines that the white point for the profile connection space is D50 and this is specified in the ICC profile. However, the same specification states that D50 should have certain XYZ coordinates when ICC profiles round the coordinates and most color engines adopt that or close to it. In addition, RGB coordinates at 255, 255, 255 should be neutral white, but in some profiles that is simply not the case, however, it can be used to infer that. Many profiles in use do not strictly adhere to the definitions, and although it is possible to construct them so that they do, color engines vary in the method used to interpret the results.
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