Abstract: In an image forming device including a document platen, a scanning mechanism, and a controller, a preview screen is small and difficult to see, and it is not possible to adjust position and size on the preview screen after scanning. The document platen has a document platen display unit controlled by the controller. The scanning mechanism can read an image of a document placed on the document platen and transmit read initial image data to the controller. The controller can cause the document platen display unit to display image data based on the initial image data. The controller realized as an LSI includes a device interface for controlling the scanning mechanism and receiving the read initial image data from the scanning mechanism and a document platen display unit interface for causing the document platen display unit to display image data based on the initial image data.