Image forming device and method

An image forming device comprising:

• an image former configured to form in advance a reference mark indicating an orientation of a sheet to be placed on a platen, and an adjustment pattern filled in with black or a highly concentrated color in an area folded by or an area in which a crease is formed by a post processor,
• wherein the sheet is configured for identifying a position of a fold line or a crease of the post processor that performs post processing to execute folding or form a crease on paper,
• wherein the orientation of the sheet to be placed on the platen is changed according to the post processing or paper characteristics of the sheet, and
• wherein the position of a fold line or a crease is identified by reading an image of the sheet with the sheet unfolded and placed on the platen.

A method comprising:

• performing post processing to execute folding or form a crease on an adjustment sheet in which a reference mark and an adjustment pattern filled in with black or a highly concentrated color are formed, across the adjustment pattern using a predetermined reference position;
• reading an image of the adjustment sheet if an orientation of the adjustment sheet placed on a platen is changed according to a type of the post processing or paper characteristics of the adjustment sheet, and the adjustment sheet, on which the post processing has been performed, is placed on the platen so that the reference mark is located in a predetermined direction on the platen;
• identifying a position of a fold line or a crease using the fold line or the crease that appears in the image of the adjustment sheet;
• and
• adjusting a fold position or a position of a crease of the post processor using a difference between a position of the fold line or the crease and the reference position.