1. An image processing system for image forming with an electrophotographic image forming device, comprising: a memory that stores correspondence information associating features of a region of image data with a colorless pattern to be formed with colorless toner in electrophotographic image forming, the correspondence information including pile height criteria information restricting a pile height of the colorless toner in association with a set of the features and the colorless pattern; and a processor configured by execution of a program of instructions to include: an image segmenter part that segments input image data into a plurality of regions; a features extractor part that obtains features of at least one of the plurality of regions segmented from the input image data; and a colorless data generator part that determines a specific colorless pattern based on the correspondence information and the pile height criteria information that corresponds to the features obtained for the at least one of the plurality of regions of the input image data, and generates colorless image data using the colorless pattern, for controlling electrophotographic image forming using the colorless toner, wherein the memory stores keyword parameter correspondence information that associates a plurality of keywords each reflecting features of a colorless pattern with a plurality of pattern parameters each specifying the features of the colorless pattern, the processor configured by execution of the program of instructions causes a user interface to display a list of the plurality of keyword to a user to allow the user to select one of the plurality of keywords, and the processor is further configured by execution of the program of instructions to include a region segmentor part that refers to the keyword parameter correspondence information to obtain a pattern parameter that corresponds to the selected keyword, and generates the colorless pattern using the obtain pattern parameter.