Image forming apparatus and image forming method

An image forming apparatus comprising:

• an image forming unit that forms an image;
• a color measuring unit that measures a color of the image;
• a measured-value acquiring unit that acquires a measured value that is measured by the color measuring unit;
• and
• a feed-back unit to feed back the measured value;
• a set-value deciding unit that decides a set value with reference to a process parameter related formation of the image according to an operation amount decided on a difference between the measured value that has been fed-back and a present target value, wherein
• the set-value deciding unit determines the set value so that the image approaches a reference value in a period from a current state of the image to desired state of the image while optimizing a constraint evaluation function related to a constraint condition for the formation of the image by using an estimation equation for approximating time-series variation in a state of the image,
• the estimation equation includes a matrix that represents an output change in accordance to a change of the process parameter, and
• the matrix is charged in accordance with the set value regarding to the latest process parameter.