1. An image processing apparatus, comprising: a color converting unit converting input image data into image forming data used for image formation; a control unit, via implemented using a processor to control the image formation by the image forming data, wherein the color converting unit converts each of a plurality of set colors that are difficult for colorblind people to mutually distinguish among colors included in a color space of the input image data, as difficult colors for colorblind people, into a same color in a color space of the image forming data, while an ordinary color-vision person can recognize the difficult colors in the image forming data; and an output-form designating unit receiving printing modes that includes a normal printing mode and a color-scheme warning printing mode, wherein when the color-scheme warning printing mode is selected, the output-form designating unit displays on a display device a notification that an image simulating a view of the colorblind people is to be printed and displays a message that represents an oral explanation by pointing to a portion in which the color difference cannot be recognized.