Patent ID: 8610982

Claim:
An image forming apparatus comprising: an image output unit that forms a gradation test image on a recording sheet and outputs the recording sheet having the gradation test image formed thereon; an image reader that covers the recording sheet placed on a reading surface of the image reader with an openable cover plate and optically reads the recording sheet to obtain read data of the gradation test image and read data of a detecting area of the recording sheet; a detecting unit that detects, when the image reader optically reads the recording sheet, an opened/closed state of the openable cover plate by reading the detecting area of the recording sheet and using the read data of the detecting area that is inside a portion of the recording sheet; and a gradation correction unit that, when the detecting unit detects that the openable cover plate is in the closed state, conducts a gradation correction of the image forming apparatus using the read data of the gradation test image; wherein the detecting unit detects the opened/closed state of the openable cover plate by comparing the read data of the detecting area that is inside the portion of the recording sheet with a threshold value indicating the closed state of the openable cover plate.