The control unit 18 includes, for example, a central processing unit (CPU), a read-only memory (ROM) that stores programs and various data, and a random-access memory (RAM) that is used as a work area of the CPU. The CPU executes the program stored in the ROM or the storage unit 17.

By executing the image forming program 17a stored in the storage unit 17, the control unit 18 functions as a range accepting unit 18a, a color conversion unit 18b, and a table generating unit 18c. The range accepting unit 18a accepts a designation of the radius-ratio acceptable range. The color conversion unit 18b converts an input image into an output image by using the RGB-to-Lab-to-CMYK table 17b or the RGB-to-CMYK table 17c. The table generating unit 18c generates the RGB-to-CMYK table 17c.

Next, a description will be given of operations of the MFP 10.

First, a description will be given of operations of the MFP 10 when setting the radius-ratio acceptable range.

Instruction of a start of setting the radius-ratio acceptable range via the operation unit 11 causes the control unit 18 to execute the operations illustrated in FIG. 2.

FIG. 2 illustrates the operations of the MFP 10 when setting the radius-ratio acceptable range.

As illustrated in FIG. 2, the range accepting unit 18a displays a range-setting screen 20 (see FIG. 3) for setting the radius-ratio acceptable range in the display 12 (Step S101).