Image processing apparatus and image processing method

An image processing apparatus for printing an image on a print medium with use of multiple color materials, the image processing apparatus comprising:

• a data acquisition unit configured to acquire pieces of multivalued data of a target pixel, the pieces of multivalued data respectively corresponding to the multiple color materials;
• a threshold value acquisition unit configured to, from among multiple threshold value matrices each configured to include arrayed multiple threshold values, set one threshold value matrix for each of the multiple color materials, and from the set threshold value matrix, acquire a first threshold value corresponding to the target pixel;
• a reference color setting unit configured to, from among the pieces of multivalued data respectively corresponding to the multiple color materials, set reference data that is referred to in order to perform a predetermined process on the first threshold value acquired by the threshold value acquisition unit for that color material;
• a calculation unit configured to, for that color material, perform the predetermined process on the first threshold value on a basis of the reference data set by the reference color setting unit and thereby calculate a second threshold value;
• and
• a generation unit configured to, for that color material, generate quantization data for printing a dot by comparing a corresponding one of the pieces of multivalued data and the second threshold value, wherein
• the threshold value acquisition unit and the reference color setting unit set the threshold value matrix and the reference data for that color materials so as to make graininess of a dot pattern of that color material lower than graininess of a mixed color dot pattern obtained by mixing respective dot patterns of the multiple color materials, the dot pattern being determined by the quantization data.