Abstract: An original image comprises a printed region on which a predetermined printed matter is realized and a background region on which no printed matter is realized. The shape of a peripheral zone in the original image comprises the shape of the background region, which shape exists particularly at the peripheral region of said original image. It is determined whether or not the original image comprises the special document by detecting the peripheral zone. Further, the original image has an outer-frame region, having a predetermined shape at the peripheral region of the original image. The determination is carried out using a result of measuring the width of the outer-frame region. Further, the width of the outer-frame region comprises a width along a direction substantially perpendicular to a direction extending along the outline of the original image.

Abstract: An original image comprises a printed region on which a predetermined printed matter is realized and a background region on which no printed matter is realized. The shape of a peripheral zone in the original image comprises the shape of the background region, which shape exists particularly at the peripheral region of said original image. It is determined whether or not the original image comprises the special document by detecting the peripheral zone. Further, the original image has an outer-frame region, having a predetermined shape, at the peripheral region of the original image. The determination is carried out using a result of measuring the width of the outer-frame region. Further, the width of the outer-frame region comprises a width along a direction substantially perpendicular to a direction extending along the outline of the original image.

Abstract: A digital copier or a complex copier having a facsimile function is provided with a security function for keeping a record of persons who copied or transmitted images, the dates of copying or transmission and the kinds of the images in a manner which is not known to a third person. When a scanner included in the copier is used, a document image is electrically or magnetically recorded in a security unit removably mounted on the copier. The document image is thinned or otherwise reduced in scale before written to the security unit. A keyword, password or similar information identifying a person is input on the copier. The document image is recorded in the security unit together with the person's identification and the date and time when the scanner is used. A plurality of such document images stored in the security unit are printed on a single paper at the same time.

Abstract: The present invention provides an invisible light image detecting means for detecting an invisible light region image formed by using colorless paint in an invisible light region, and a discriminating means for discriminating a general document from a specific one by using the image data detected by said invisible light image detecting means, thus discrimination between a general document and a specific one being executed accurately and without fail.

Abstract: An image forming apparatus including an image reading unit for reading an original and for outputting image data corresponding to the original, an image processing unit for processing the image data supplied from the image reading unit in accordance with a predetermined method and for outputting printing image data, a printer unit for printing an image corresponding to the printing image data supplied from the image processing unit, and an image adding unit for adding an identification information to the recording sheet on which the image is formed by the printer unit, the identification information identifying the image forming apparatus in order to prevent forgery of securities, confidential documents or backnotes. A detector detects the presence or absence of the image adding unit and disables the copying functions when the image adding unit is absent.