1. A development processing device that develops undeveloped image data, the development processing device comprising: a development processing unit that generates image data of a predetermined format for which development is completed from the undeveloped image data by performing a development process for the undeveloped image data; a parameter determining unit that determines at least two initial parameters of a first initial parameter and a second initial parameter that are used for the development process; a change screen displaying unit that displays a parameter changing screen on a display screen; and an acceptance unit that accepts designation of a first user parameter corresponding to the first initial parameter and a second user parameter corresponding to the second initial parameter from a user, wherein the change screen displaying unit displays; a first number line corresponding to the first initial parameter and a second number line corresponding to the second initial parameter, wherein each of the number lines has a length corresponding to a settable range of the corresponding parameter; a reference line that intersects the first number line in a position corresponding to the first initial parameter and intersects the second number line in a position corresponding to the second initial parameter; a first marker that represents a position corresponding to the first user parameter on the first number line, and a second marker that represents a position corresponding to the second user parameter on the second number line on the parameter changing screen, wherein the development processing unit performs the development process based on at least the first user parameter and the second user parameter; and wherein the change screen displaying unit allows the number line and the reference line to intersect each other in a position of a determined initial parameter by moving the number line corresponding to the determined initial parameter after the parameter determining unit determines the initial parameter.