Image processing apparatus to improve dot dispersibility with N-gradation multi-valued data, image processing method, and storage medium

An image processing apparatus comprising:

• one or more processors and at least one memory in a recording apparatus having ink with ink colors, the at least one memory being coupled to the one or more processors and having stored thereon instructions executable by the one or more processors, wherein at least one of the one or more circuits or the execution of the instructions cause the image processing apparatus to function as:
• an inputting unit configured to input image data having a plurality of pixels in a region of interest, the plurality of pixels corresponding to ink colors in the recording apparatus,
• a color separation unit configured to separate the image data into N-gradation multi-valued data of each ink color of the recording apparatus, where N≥4, representing pixel values of the plurality of pixels,
• a determination unit configured to determine whether the pixel values have a split distribution in which the pixel values are distributed, in a predetermined range, over two adjacent split regions separated by a quantization representative threshold, and
• a generation unit configured to generate M-gradation quantization data represented by an M-gradation quantization value, where 3≤M<N, based on the N-gradation multi-valued data and the split distribution,
• wherein in a case where the pixel values have the split distribution, the generation unit generates the M-gradation quantization data in a correction process so that each of almost all the plurality of pixels has a value that is one of two consecutive values of the M-gradation quantization values, and has no value other than the two consecutive values among the M-gradation quantization values, in the generated M-gradation quantization data, and records the M-gradation quantization values on a recording medium.