Abstract: An inkjet ink having sufficient water resistance on a recording sheet but having excellent re-solubility in an ink in a head portion and excellent ejection stability through a nozzle, the inkject ink comprising an aqueous liquid, a pigment and a water-soluble resin, the water-soluble resin being a terpolymer obtained from acrylic acid, styrene and .alpha.-methyl styrene and having a weight average molecular weight of 2,000 to 8,000 and an acid value of 90 to 130, and a process for the production of the inkjet ink, which comprises preparing a concentrated aqueous dispersion of a pigment and a terpolymer obtained from acrylic acid, styrene and .alpha.-methylstyrene, adding water and an additive to the concentrated dispersion to dilute the concentrated dispersion and maintaining the diluted dispersion at a temperature between 60.degree. C. and 80.degree. C. for 5 to 48 hours.

Abstract: A neural network is made to undergo learning such that at least three characteristic parameters, which correspond to an inputted set of color information values when the set of color information values, including at least three color information values, is inputted and which are obtained by multivariate analysis of the spectral reflectance distribution or the spectral transmittance distribution, are outputted. A subject set of color information values is transformed into the characteristic parameters by using the neural network which has completed learning, and a spectral reflectance distribution or a spectral transmittance distribution is estimated by linear polynomial approximation using the transformed characteristic parameters, eigenvectors obtained by the multivariate analysis, and a mean vector of the spectral reflectance distribution or the spectral transmittance distribution.