Patent Publication Number: US-2009219558-A1

Title: Image processing apparatus and image processing method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 61/032,384, filed Feb. 28, 2008. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an image processing apparatus such as a digital multifunction peripheral including processing units such as a scanner, a printer, a network interface, and a facsimile interface and an image processing method. 
     BACKGROUND 
     A digital multifunction peripheral includes an image scanning apparatus (a scanner), an image forming apparatus (a printer), a network communication unit (a network interface), and a facsimile communication unit (a facsimile interface). The digital multifunction peripheral including such hardware copies an image on an original document to a sheet, transmits image data through a network, and transmits image data by facsimile. The digital multifunction peripheral functions as an image processing apparatus that processes input image data of, for example, an image scanned by the scanner. The digital multifunction peripheral has, as an image processing function for the image scanned by the scanner, an outside-of-document erasing function for erasing an unnecessary area (a black image portion) on the outside of an original document image. The outside-of-document erasing function is effective for image data obtained by the scanner scanning an original document in a state in which a document cover is opened. U.S. Pat. No. 5,629,777 discloses a technique for erasing an area on the outside of an original document from image data of the original document scanned in a state in which a document cover is opened in a monochrome digital multifunction peripheral. A method disclosed in U.S. Pat. No. 5,629,777 is a method of determining whether a density value of each of pixels in monochrome image data scanned by the scanner is likely to be a density value of pixels on the outside of the original document. With the method disclosed in U.S. Pat. No. 5,629,777, an area on the outside of the original document in the scanned image data is detected on the basis of a result of the determination and an image in an area determined as the outside of the original document is erased. 
     However, in the method disclosed in U.S. Pat. No. 5,629,777, a density value of each of pixels in a scanned image of an original document and a threshold are simply compared. Therefore, in the method disclosed in U.S. Pat. No. 5,629,777, an area crowded with pixels having a large density value in image data in an original document may be determined as an area on the outside of the original document by mistake. Further, in recent years, a color digital multifunction peripheral (color MFP) is widely spread. In the color digital multifunction peripheral, an image of an original document is scanned as a color image. In such a color digital multifunction peripheral, it is also necessary to distinguish an area on the outside of the original document and the other areas in color image data obtained as a scanned image of the original document. 
     SUMMARY 
     It is an object of an embodiment of the present invention to provide an image processing apparatus and an image processing method for processing an input image to obtain the same level of a processing result irrespective of an operation mode. 
     According to an aspect of the present invention, there is provided an image processing apparatus including: a scanner that scans an image of an original document; plural processing units that process image data according to various operation modes; plural image converting units that convert image data scanned by the scanner into image data to be processed in processing units corresponding to the operation modes; an outside-of-document erasing unit that erases, as an area on the outside of the original document image, the same area irrespective of content of image conversion processing in the respective image converting units from the image data; and a control unit that supplies the image data from which the area on the outside of the original document image is erased by the outside-of-document erasing unit and that is processed by the image converting unit corresponding to an operation mode designated by a user to the processing unit corresponding to the operation mode. 
     According to another aspect of the present invention, there is provided an image processing method including: acquiring image data; converting the acquired image data into image data corresponding to an operation mode designated by a user; erasing an area on the outside of an original document image from the acquired image data with outside-of-document erasing processing for erasing, as an area on the outside of an original document image, the same area irrespective of content of conversion processing for image data corresponding to various operation modes; and performing, using the image data from which the area on the outside of the original document image is erased and that is converted into the image data corresponding to the operation mode designated by the user, processing corresponding to the operation mode. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a schematic diagram of an external configuration of a digital multifunction peripheral; 
         FIG. 2  is a block diagram of the digital multifunction peripheral according to a first configuration example; 
         FIG. 3A  is a diagram of an example of an image scanned in a state in which a document cover is opened; 
         FIG. 3B  is a diagram of an example of an image obtained by erasing an area determined as the outside of an original document from the image shown in  FIG. 3A ; 
         FIG. 4A  is a diagram of a spread-page book placed on a glass table in the state in which the document cover is opened; 
         FIG. 4B  is a diagram of an example of an image obtained by scanning the book placed in the spread state shown in  FIG. 4A ; 
         FIG. 4C  is an example of an image obtained by erasing an area determine as the outside of the original document from the image shown in  FIG. 4B ; 
         FIG. 5  is a diagram of a configuration example of an outside-of-document erasing unit; 
         FIG. 6  is a diagram of contents of input and output signals in a monochromization module; 
         FIG. 7  is a diagram of contents of input and output signals in a binarization module; 
         FIG. 8  is a diagram of contents of input and output signals in an outside-of-document erasing module; 
         FIG. 9  is a flowchart for explaining a flow of processing in the digital multifunction peripheral according to the first configuration example; 
         FIG. 10  is a block diagram of a digital multifunction peripheral according to a second configuration example; 
         FIG. 11  is a diagram of a configuration of an outside-of-document erasing unit in the digital multifunction peripheral according to the second configuration example; 
         FIG. 12  is a diagram of a setting example of binarization thresholds for respective operation modes in the digital multifunction peripheral according to the second configuration example; 
         FIG. 13  is a flowchart for explaining a flow of processing in the digital multifunction peripheral according to the second configuration example; 
         FIG. 14  is a block diagram of a digital multifunction peripheral according to a third configuration example; 
         FIG. 15  is a flowchart for explaining a flow of processing in the digital multifunction peripheral according to the third configuration example; 
         FIG. 16  is an external view of an overall configuration of an operation panel serving as an operation unit; 
         FIG. 17  is a diagram of an example of a setting screen for a user to designate intensity for determining the outside of an original document; and 
         FIG. 18  is a diagram of an example of a setting screen having a preview screen that displays an image showing an area on the outside of an original document to be erased by outside-of-document erasing processing. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention are explained below with reference to the accompanying drawings. 
       FIG. 1  is a schematic diagram of an overall configuration example of a digital multifunction peripheral  1 . 
     The digital multifunction peripheral  1  shown in  FIG. 1  is an image processing apparatus that functions as a copying machine, a scanner, a printer, a facsimile, and a network communication machine. In the configuration example shown in  FIG. 1 , the digital multifunction peripheral  1  includes a main control unit  10 , a scanner  11 , a printer  12 , a facsimile communication unit (a FAX unit)  13 , a network communication unit (an NW unit)  14 , and an operation unit  15 . 
     The main control unit  10  controls the entire digital multifunction peripheral  1 . The main control unit  10  receives an operation instruction from a user in the operation unit  15  and controls the scanner  11 , the printer  12 , the facsimile communication unit  13 , the network communication unit  14 , and the operation unit  15 . The main control unit  10  further includes an image processing unit that processes image data. 
     The scanner  11  scans an image on a recording medium (an original). The scanner  11  includes a not-shown scanning unit, a glass table  11   a  as a document placing table, a document cover  11   b  that covers the document placing table, and an open and close detector  11   c  that detects open and closed states of the document cover  11   b.    
     The scanning unit is provided below the glass table  11   a . The scanning unit converts an image of an original document set on the glass table  11   a  into image data. The scanning unit supplies the scanned image data to the main control unit  10 . For example, the scanning unit includes a driving mechanism, a CCD line sensor, and a signal processing unit (all of which are not shown in the figure). The scanning unit is moved in a sub-scanning direction below the glass table  11   a  by a driving mechanism. The scanning unit scans, with the CCD line sensor, the image of the original document on the glass table  11   a  while moving in the sub-scanning direction. The CCD line sensor includes plural CCD sensors arranged in a main scanning direction with respect to the original document. The CCD line sensor converts reflected light from the original document into an analog image signal. The signal processing unit converts the analog image signal scanned by the CCD line sensor into a digital image signal. 
     In this embodiment, the scanner  11  scans the image of the original document as color image data formed by values of red (R), green (G), and blue (B) signals (pixel values of primary colors). In this embodiment, respective pixels (colors of the respective pixels) of the image data scanned by the scanner  11  are represented by a density value of R (hereinafter simply referred to as R), a density value of G (hereinafter simply referred to as G), and a density value of B (hereinafter simply referred to as B). 
     The glass table  11   a  functions as an original placing table for holding an original document to be scanned. The document cover  11   b  is configured such that the user can open and close the document cover  11   b . In a closed state, the document cover  11   b  covers the entire glass table  11   a . The document cover  11   b  also functions as a pressing member for pressing an original document placed on the glass table  11   a . Open and closed states of the document cover  11   b  are detected by the open and close detector  11   c . An auto document feeder (ADF) that feeds original documents one by one may be used as the document cover  11   b.    
     A surface of the document cover  11   b  on the glass table  11   a  side is colored in, for example, white. Therefore, in a state in which the document cover  11   b  is closed, the CCD line sensor of the scanning unit can obtain reflected light having a minimum density value (maximum luminance) from an area on the outside of an original document (i.e., the white surface of the document cover  11   b ). Therefore, in the state in which the document cover  11   b  is closed, the CCD line sensor of the scanning unit scans the area on the outside of the original document as an image in which a density value is “minimum” (a luminance value is “maximum”). In other words, in the state in which the document cover  11   b  is closed, the scanning unit scans the area on the outside of the original document as white. 
     On the other hand, in a state in which the document cover  11   b  is opened, the CCD line sensor of the scanning unit cannot obtain reflected light from the area on the outside of the original document (reflected light from the original document). Therefore, in the state in which the document cover  11   b  is opened, the scanning unit scans the area on the outside of the original document on the glass table  11   a  as black. In other words, in the state in which the document cover  11   b  is opened, the scanning unit scans the area on the outside of the original document as a black image in which a density value is “maximum” (a luminance value is “minimum”). 
     The printer  12  forms a print image on an image formation medium. For example, when copying is performed, the main control unit  10  converts an image of an original document scanned by the scanner  11  into image data for printing. The printer  12  prints the image data of the original document processed for printing by the main control unit  10  on a copy sheet. A printer of an arbitrary image formation system can be applied as the printer  12 . For example, the printer  12  may be a laser printer or may be an ink jet printer. 
     The facsimile communication unit (the FAX unit)  13  is an interface that performs transmission and reception of image data as facsimile data. The FAX unit  13  is connected to a telephone line. The FAX unit  13  transmits and receives the image data via the telephone line according to a facsimile transmission system. In this embodiment, the FAX unit  13  of the digital multifunction peripheral  1  transmits and receives monochrome image data. For example, when an image of an original document is transmitted by facsimile, the main control unit  10  converts the image of the original document scanned by the scanner  11  into image data for facsimile transmission. The FAX unit  13  transmits by facsimile the image data for facsimile transmission to a telephone number of a destination designated on the operation unit  15  according to the control by the main control unit  10 . 
     The network communication unit (the NW unit)  14  is an interface for performing network communication of a LAN and the like. The NW unit  13  is connected to a network formed by a communication line or radio communication. For example, when the digital multifunction peripheral  1  is used as a network scanner, the main control unit  10  converts an image of an original document scanned by the scanner  11  into scan image data of a designated format. The NW unit  14  transmits the scan image data processed by the main control unit  10  to an apparatus (e.g., a user terminal) at a destination on a network designated on the operation unit  15 . 
     The operation unit  15  is an operation unit on which the user inputs an operation instruction or guidance is displayed for the user. The operation unit  15  includes a display device and operation keys. For example, the operation unit  15  includes a liquid crystal display device incorporating a touch panel and hard keys such as a ten key. 
     The digital multifunction peripheral  1  according to a first configuration example of the digital multifunction peripheral is explained below. 
       FIG. 2  is a block diagram of the digital multifunction peripheral  1  and the main control unit  10  according to the first configuration example. 
     As shown in  FIG. 2 , the main control unit  10  includes a CPU  21 , a main memory  22 , an HDD  23 , a scanner-system image processing unit (an input image processing unit)  24 , a page memory  25 , and a printer-system image processing unit (an output image processing unit)  26 . 
     The CPU  21  manages control of the entire digital multifunction peripheral  1 . The CPU  21  realizes various functions by executing, for example, programs stored in a not-shown program memory. The main memory  22  is a memory in which work data and the like are stored. The CPU  21  realizes various kinds of processing by executing various programs using the main memory  22 . 
     For example, the CPU  21  realizes copy control by controlling the scanner  11  and the printer  12  according to a program for copy control. In other words, when the CPU  21  executes the program for copy control, the digital multifunction peripheral  1  functions as a copy machine. The CPU  21  realizes a facsimile function by controlling the scanner  11  and the facsimile communication unit  13  according to a program for facsimile control. In other words, when the CPU  21  executes the program for facsimile control, the digital multifunction peripheral  1  functions as a facsimile apparatus. Further, the CPU  21  realizes network scan by controlling the scanner  11  and the network communication unit  14  according to a program for network scan control. In other words, when the CPU  21  executes the program for network scan control, the digital multifunction peripheral  1  functions as a network scanner. 
     The HDD (hard disk drive)  23  is a nonvolatile large-capacity memory. For example, the HDD  23  stores image data. The HDD  23  stores setting values (default setting values) in various kinds of processing. Further, the HDD  23  may store programs to be executed by the CPU  21 . 
     The input image processing unit  24  processes an input image. In the first configuration example shown in  FIG. 2 , the scanner  11  functions as a scanner-system image processing unit that processes, as an input image, an image scanned by the scanner  11 . The input image processing unit  24  processes, according to an operation mode of the digital multifunction peripheral  1 , the image data scanned by the scanner  11 . The CPU  21  indicates processing content corresponding to the operation mode to the input image processing unit  24 . 
     Various kinds of image processing by the input image processing unit  24  may be realized by the CPU  21  executing a program for image processing. An image input to the input image processing unit  24  is not limited to image data input from the scanner  11 . For example, the input image processing unit  24  may process, as an input image, image data received by the NW unit  14  through the network or image data received by the FAX unit  13  through facsimile communication. 
     The page memory  25  is a memory that stores image data to be processed. For example, the page memory  25  stores color image data for one page. The page memory  25  is controlled by a not-shown page memory control unit. In the configuration example shown in  FIG. 2 , the page memory  25  stores image data as a result of the processing by the input image processing unit  24 . 
     The output image processing unit  26  processes an output image. In the configuration example shown in  FIG. 2 , the output image processing unit  26  functions as a printer-system image processing unit that generates image data to be printed on a sheet by the printer  12 . For example, the output image processing unit  26  converts the image data stored in the page memory  25  into image data for printing. Various kinds of image processing by the output image processing unit  26  may be realized by the CPU  21  executing a program for image processing. 
     The input image processing unit  24  includes an outside-of-document erasing unit  31  and various image processing modules  32   a ,  32   b , and  32   c.    
     The outside-of-document erasing unit  31  erases an image area other than an original document image in image data (converts the image area into a white image). In the configuration example shown in  FIG. 2 , the outside-of-document erasing unit  31  detects an area on the outside of an original document in image data scanned by the scanner  11  and outputs the image data from which the detected area on the outside of the original document is erased. A configuration and operations of the outside-of-document erasing unit  31  are explained in detail later. 
     The image processing modules  32   a ,  32   b , and  32   c  function as image converting units corresponding to various operation modes in the digital multifunction peripheral  1 . The image processing modules  32   a ,  32   b , and  32   c  process (convert) input image data according to processing contents corresponding to the operation modes, respectively. For example, the image processing module for copying  32   a  is an image converting unit corresponding to a copy mode as an operation mode of the digital multifunction peripheral  1 . The image processing module for NW  32   b  is an image converting unit corresponding to a network scan mode as an operation mode of the digital multifunction peripheral  1 . The image processing module for FAX  32   c  is an image converting unit corresponding to a facsimile mode as an operation mode of the digital multifunction peripheral  1 . 
     In the first configuration example shown in  FIG. 2 , when the digital multifunction peripheral  1  is in the copy mode, in the input image processing unit  24 , the image processing module for copying  32   a  converts image data supplied from the outside-of-document erasing unit  31  into image data for copying (for printing). When the digital multifunction peripheral  1  is in the network scan mode, in the input image processing unit  24 , the image processing module for NW  32   b  converts image data supplied from the outside-of-document erasing unit  31  into image data for a network (image data as a scan result to be transmitted to an external apparatus via the network). When the digital multifunction peripheral  1  is in the facsimile mode, in the input image processing unit  24 , the image processing module for FAX  32   c  converts image data supplied from the outside-of-document erasing unit  31  into image data for facsimile transmission (facsimile data to be transmitted to an external apparatus via a facsimile line). 
     The image processing module for copying  32   a  has image processing functions such as shading correction, gradation conversion, inter-line correction, color conversion, and compression. The shading correction is processing for correcting image data according to sensitivity fluctuation in respective photoelectric conversion elements in the scanner  11  or a light distribution characteristic of a lamp (not shown) for illuminating an original document. The gradation conversion is processing for converting values of respective pixels forming image data (e.g., values of R, G, and B signals) according to a not-shown lookup table (LUT). The inter-line correction is processing for correction physical positional deviation of respective CCD sensors for R, G, and B in the scanner  11 . The color conversion is processing for converting image data formed by R, G, and B pixel signals into image data formed by C, M, and Y pixel signals (image data for printing). Filtering, gamma correction, gradation correction, or the like may be performed as processing corresponding to a characteristic of a printer together with the color conversion. The compression is processing for encoding image data. 
     The outside-of-original erasing processing in the outside-of-original erasing unit  31  is explained in detail below. 
       FIG. 3A  is a diagram of an example of an image obtained by scanning an original document set on the glass table  11   a  in a state in which the document cover  11   b  is opened.  FIG. 3B  is a diagram of an image obtained by erasing a black image on the outside of the original document from the scanned image shown in  FIG. 3A . In the image shown in  FIG. 3B , only the black image on the outside of the original document is erased. Conversion of the image shown in  FIG. 3A  into the image shown in  FIG. 3B  is the outside-of-document erasing processing. 
       FIG. 4A  is a diagram of a spread book B placed on the glass table  11   a  in a state in which the document cover  11   b  is opened.  FIG. 4B  is a diagram of an example of an image obtained by scanning the spread book B placed on the glass table  11   a  as shown in  FIG. 4A . The image shown in  FIG. 4B  includes a black image area on the outside of an original document and an area of an original document image. Further, the image shown in  FIG. 4B  includes an area of pixels close to black (having high density values) (hereinafter also referred to as high-density area in the center) near a center line with respect to the left to right direction (an area including a boundary of spread two pages). In general, the high-density area in the center in the scanned image shown in  FIG. 4B  is densest in the center line as the boundary and becomes thinner away from the center line. This is because, when a spread book is placed on the glass table  11   a , usually, a center line (a boundary of pages) portion of the book is farthest away (lifted) from the glass table  11   a.    
       FIG. 4C  is a diagram of an example of an image obtained by applying the outside-of-document erasing processing to the image data shown in  FIG. 4B . The image shown in  FIG. 4C  is an image obtained by erasing an area formed by pixels having density values equal to or higher than a density value as a determination criterion from the image data shown in  FIG. 4B . In the image shown in  FIG. 4C , the black image area on the outside of the original document and the high-density area in the center in the original document image shown in  FIG. 4B  are erased. A density value of the high-density area in the center is not fixed. In the outside-of-document erasing processing for the high-density area in the center, if a reference value (intensity) for determining that an area is on the outside of the original document fluctuates, an area determined as the outside of the original document also changes. Therefore, in the digital multifunction peripheral  1 , it is difficult to unconditionally set a level (intensity) for determining an area on the outside of the original document. Therefore, in the digital multifunction peripheral  1 , the reference value indicating the level (intensity) for determining an area as an area on the outside of the original document is adjusted (set) according to an instruction by the user. 
     A configuration of the outside-of-document erasing unit  31  is explained below. 
       FIG. 5  is a diagram of a configuration example of the outside-of-document erasing unit  31 . 
     In the configuration example shown in  FIG. 5 , the outside-of-document erasing unit  31  has a monochrome conversion unit  41 , an outside-of-document detecting unit  42 , and an erasing unit  43 . 
     The monochrome conversion unit  41  converts an input image into a binary monochrome image data. The monochrome conversion unit  41  includes a monochromization module  51  and a binarization module  52 . The monochromization module  51  is a module that monochromizes input image data. When color image data formed by pixels having values (R, G, B) of R, G, and B signals is supplied from the scanner  11 , the monochromization module  51  monochromizes respective color pixels forming the color image data. For example, the monochromization module  51  converts color pixels having R, G, and B pixels values into a monochromized pixel value (BK) according to Formula (A1). 
         BK=α×R+β×G+γ×B   (A1) 
     α, β, and γ in Formula (A1) are coefficients satisfying a condition (B1) “0≦α, β, γ≦1 (B1)”. For example, it is conceivable that the monochromization module  51  calculates the monochrome pixel value (BK) from the color pixel values according to BK=(R+G+B)/3. In this case, each of the coefficients α, β, and γ is “0.333 . . . ”. The coefficients α, β, and γ are desirably values that make it easy to separate a black image in an original document (hereinafter also referred to as black image in the inside of the original document) and a black image as an image on the outside of the original document in a document cover open state (hereinafter also referred to as black image on the outside of the original document). 
     The black image on the outside of the original document indicates a state in which reflected light from the original document is not made incident on a CCD sensor. Therefore, it is expected that, in the black image on the outside of the original document, all the R, G, and B signals of the respective color pixels have values close to a maximum density value. On the other hand, it is expected that, in the black image in the original document, the R, G, and B signals of the respective color pixels have a tendency corresponding to a characteristic of the entire original document. In order to highly accurately separate the black image on the outside of the original document and the other images, it is desirable to set the coefficients α, β, and γ corresponding to such a characteristic. 
     For example, when a density value of the R signal tends to be large in the black image in the original document, if a value of the coefficient α is set to a relatively small value compared with the coefficients β and γ, a BK value in the black image in the original document has a density value smaller than a simple average of the R, G, and B signals. As a result, it is easy to separate the black image in the original document and the black image on the outside of the original document. 
     The binarization module  52  binarizes the pixels monochromized by the monochromization module  51 . The binarization module  52  binarizes a BK value according to a threshold (a reference value given from the CPU) for separating the black image on the outside of the original document and the images in the other areas. For example, the binarization module  52  converts pixels having BK values equal to or larger than the threshold into “1” and converts pixels having BK values smaller than the threshold into “0”. In this case, the binarization module  52  discriminates that the pixels having the BK values equal to or larger than the threshold are likely to be the black image on the outside of the original document and discriminates that the pixels having the BK values smaller than the threshold is likely to be other than the black image on the outside of the original document. 
     The outside-of-document detecting unit  42  determines whether pixels are the pixels from the image on the outside of the original document. The outside-of-document detecting unit  42  includes an outside-of-document determination module  53  and a correction module  54 . 
     The outside-of-document determination module  53  determines whether the pixels are the pixels on the outside of the original documents according to pixel values binarized by the binarization module  52 . For example, in the example explained above, the pixels having the binarized value “1” are the pixels on the outside of the original document and the pixels having the binarized value “0” are the pixels other than those on the outside of the original document (the pixels in the original document). In this case, the outside-of-document determination module  53  determines that the pixels having the binarized value “1” are on the outside of the original document and the pixels having the binarized value “0” are in the original document. However, the black image on the outside of the original document is considered to be distributed around the image in the original document. Therefore, the correction module  54  may determine whether positions where the pixels are present (an area where the pixels are present) are also likely to be on the outside of the original document. For example, if all adjacent pixels are the pixels in the original document, the correction module  54  corrects a determination result to determine even the pixels having the binarized value “1” are determined as being in the original document. 
     The erasing unit  43  erases the area determined as the outside of the original document. The erasing unit  43  includes an outside-of-document erasing module  55 . The outside-of-document erasing module  55  erases an image of the area determined as the outside of the original document by the outside-of-document detecting unit  42 . In other words, information indicating the area on the outside of the original document in the input image detected by the outside-of-document detecting unit  42  is given to the outside-of-document erasing module  55 . The input image data (the color image data scanned by the scanner  11 ) itself is also supplied to the outside-of-document erasing module  55 . The outside-of-document erasing module  55  erases the image of the area on the outside of the original document in the color image data as the input image according to the information indicating the area on the outside of the original document given from the outside-of-document detecting unit  42 . The outside-of-document erasing module  55  outputs, as a processing result, the color image data from which the image of the area on the outside of the original document is erased. 
     A flow of signals in the outside-of-original erasing unit  31  is explained in detail below. 
     The modules  51  to  55  in the outside-of-original erasing unit  31  have input and output signals shown in  FIG. 5 . As shown in  FIG. 5 , the modules  51  to  55  in the outside-of-document erasing unit  31  operate according to a reset signal (RESET) and a main clock signal (MCLK 1 ) from the CPU  21 . 
       FIG. 6  is a diagram of contents of input and output signals in the monochromization module  51 . As shown in  FIG. 6 , input pixel signals (IRDT, IGDT, and IBDT) are input to the monochromization module  51  together with a vertical synchronization signal (IVDEN) and a horizontal synchronization signal (IHDEN). The input pixel signals (IRDT, IGDT, and IBDT) are R, G, and B signal of color pixels in a color image such as a scanned image by the scanner  11 . The input pixel signals are supplied to the monochromization module  51  and the outside-of-original erasing module  55  in the outside-of-original erasing unit  31 . 
     Input pixels signals (IRDT, IGDT, and IBDT) indicating R, G, and B signals of color pixels forming input image data are input to the monochromization module  51  together with a vertical synchronization signal (IVDEN 0 ) and a horizontal synchronization signal (IHDEN 0 ). The CPU  21  supplies values (MONOR, MONOG, and MONOB) of the coefficients α, β, and γ for monochromizing three signals of R, G, and B to the monochromization module  51 . 
     The monochromization module  51  multiplies the three signals (IRDT, IGDT, and IBDT) as the input pixel signals with the coefficients α, β, and γ, respectively, and calculates a total value of the multiplied values. This calculated total value is a BK value (IDT) as a monochrome pixel value obtained by monochromizing the input pixel signals. As shown in  FIG. 7 , the monochromization module  51  outputs the calculated BK value (IDT) to the binarization module  52  in synchronization with timing of a vertical synchronization signal (IVDEN 0 _ 0 ) and a horizontal synchronization signal (IHDEN 0 _ 0 ). 
       FIG. 7  is a diagram of contents of input and output signals in the binarization module  52 . The binarization module  52  binarizes the BK value (IDT) supplied from the monochromization module  51 . The CPU  21  supplies a threshold (GGSTH) for binarizing the BK value (IDT) to the binarization module  52 . The binarization module  52  determines whether the BK value (IDT) is equal to or larger than the threshold (GGSTH). For example, the binarization module  52  converts a BK value equal to or larger than the threshold into “1” and converts a BK value smaller than the threshold into “0”. In other words, the binarization module  52  converts pixels of an input color image into a binarized pixel value (IMGB). The binarization module  52  outputs the binarized pixel value (IMGB) to the outside-of-document determination module  53  in synchronization with a vertical synchronization signal (IVDEN 0 _ 1 ) and a horizontal synchronization signal (IHDEN 0 _ 1 ). 
     The binarized pixel value (IMGB) is input to the outside-of-document determination module  53  together with a vertical synchronization signal (IVDEN 0 ) and a horizontal synchronization signal (IHDEN 0 ). The binarization module  52  converts pixels equal to or larger than the threshold into “1” and converts pixels smaller than the threshold into “0”. In this case, the outside-of-document determination module  53  determines that pixels having the binarized pixel value (IMGB) “1” is on the outside of the original document and pixels having the binarized pixel value (IMGB) “0” is in the original document. The outside-of-document determination module  53  supplies information (MAREA) indicating a determination result based on the binarized pixel value (IMGB) to the correction module  54  at timing indicated by a vertical synchronization signal (IVDEN 0 _ 2 ) and a horizontal synchronization signal (IHDEN 0 _ 2 ). The information (MAREA) indicating the determination result is, for example, information indicating positions of the pixels determined as an area on the outside of the original document. 
     The information (MAREA) indicating the determination result based on the binarized pixel value is supplied to the correction module  54  in synchronization with the vertical synchronization signal (IVDEN 0 _ 2 ) and the horizontal synchronization signal (IHDEN 0 _ 2 ). The correction module  54  corrects the information (MAREA) indicating the determination result. For example, the correction module  54  checks whether the positions of the pixels determined as being on the outside of the original document are an area on the outside of the original document. 
     When the correction module  54  determines that the determination result (MAREA) by the outside-of-original determination module  53  is positionally likely, the correction module  54  outputs the information (MAREA) indicating the determination result to the outside-of-document erasing module  55  as a final determination result (MAR 1 ). When the correction module  54  determines that the determination result (MAREA) by the outside-of-document determination module  53  is positionally unlikely, the correction module  54  outputs a determination result obtained by correcting the information (MAREA) indicating the determination result to the outside-of-document erasing module  55  as the information (MAR 1 ) indicating a final determination result. 
       FIG. 8  is a diagram of contents of input and output signals in the outside-of-document erasing module  55 . As shown in  FIG. 8 , the information (MAR 1 ) indicating final results for respective pixels is supplied to the outside-of-document erasing module  55  in synchronization with a vertical synchronization signal (IVDEN 0 _ 3 ) and a horizontal synchronization signal (IHDEN 0 _ 3 ). Further, input pixel signals (IRDT, IGDT, and IBDT) as pixel data forming an input image (color image data) supplied to the outside-of-document erasing unit  31  are also supplied to the outside-of-document erasing module  55 . 
     Therefore, the information (MAR 1 ) indicating whether the pixels are on the outside of the original document is supplied to the outside-of-document erasing module  55  together with the input pixel signals (IRDT, IGDT, and IBDT). The input pixel signals (IRDT, IGDT, and IBDT) supplied to the outside-of-document erasing module  55  and the information (MAR 1 ) indicating a determination result correspond to each other. For example, the input pixel signals (IRDT, IGDT, and IBDT) are delayed by a not-shown delay circuit and input to the outside-of-document erasing module  55  to correspond to the information (MAR 1 ) indicating a determination result of the pixels. 
     The outside-of-document erasing module  55  outputs, as output pixel signals (ORDT, OGDT, and OBDT), image data from which the area on the outside of the original document is erased. In other words, when the information (MAR 1 ) indicating a determination result indicates that the pixels are not pixels on the outside of the original document, the outside-of-document erasing module  55  directly outputs the input pixel signals (IRDT, IGDT, and IBDT) as the output pixel signals (ORDT, OGDT, and OBDT). When the information (MAR 1 ) indicating a determination result indicates that the pixels are pixels on the outside of the original document, the outside-of-document erasing module  55  outputs a pixel value (a pixel value of white), with which all the R, G, and B signals have minimum density values, as the output pixel signals (ORDT, OGDT, and OBDT) in order to erase the pixels (the pixels forming the black image on the outside of the original document). 
     A flow of processing in the digital multifunction peripheral  1  according to the first configuration example shown in  FIG. 2  is explained below. 
       FIG. 9  is a flowchart for explaining a flow of processing including processing for scanning an original document image in the digital multifunction peripheral  1  according to the first configuration example. 
     First, it is assumed that the digital multifunction peripheral  1  operates in any one operation mode among a copy mode, a network scan mode, and a facsimile mode. The outside-of-document erasing processing may be set to be valid as default or may be set to be valid only when the user designates the processing. 
     First, when the user performs copying, network scan, or facsimile transmission, the user sets an original document in the scanner  11 . For example, the user sets the original document on the glass table  11   a . After setting the original document, the user designates an operation mode using the operation unit  15 . In designating an operation mode, the user can also designate whether the outside-of-document erasing processing should be set valid or invalid. The CPU  21  sets the operation mode and valid and invalid of the outside-of-document erasing processing according to the designation by the user (Act  11 ). 
     After designating the operation mode, the user enters a start key for instructing the start of scanning of the original document in the operation unit  15 . When the CPU  21  detects the enter of the start key, the CPU  21  starts the scanning of the original document. When the scanning of the original document is started (Act  12 , YES), the CPU  21  determines whether the outside-of-document erasing processing is valid (Act  13 ). The CPU  11  may check whether the outside-of-document erasing processing is valid or invalid at every predetermined interval until the start of scanning of the original document is instructed. 
     If the outside-of-document erasing processing is valid at the start of the scanning (Act  13 , YES), the CPU  11  determines on the basis of a detection signal of the open and close detector  11   c  whether the document cover  11   b  is in the open state (Act  14 ). When it is determined that the document cover  11   b  is in the open state (Act  14 , YES), the CPU  11  scans the original document on the glass table  11   a  using the scanner  11  (Act  15 ). In this case, the main control unit  10  supplies an image scanned by the scanner  11  to the outside-of-document erasing unit  31 . The outside-of-document erasing unit  31  erases an image area on the outside of the original document from image data supplied from the scanner  11  (Act  16 ). 
     The CPU  21  supplies the image data from which the image area on the outside of the original document by the outside-of-document erasing unit  31  to the image processing module  32   a ,  32   b , or  32   c  corresponding to the operation mode. 
     When the operation mode of the digital multifunction peripheral  1  is the copy mode (Act  17 , YES), the CPU  21  supplies the image data (the image data from which the image area on the outside of the original document is erased) output from the outside-of-document erasing unit  31  to the image processing module for copying  32   a . The image processing module for copying  32   a  generates, according to image processing for printing (for copying) (e.g., color conversion to C, M, and Y signals), image data for printing (for copying) from the image data from which the area on the outside of the original document is erased (Act  18 ). The image processing module for copying  32   a  stores the generated image data for printing in the page memory  25  (Act  19 ). When the image data for printing is stored in the page memory  25 , the CPU  21  processes the image data for printing stored in the page memory  25  using the output image processing unit  26  and prints (copies) the image data on a sheet using the printer  12  (Act  20 ). 
     When the operation mode of the digital multifunction peripheral  1  is the network scan mode (Act  21 , YES), the CPU  21  supplies the image data (the image data from which the image area on the outside of the original document) output from the outside-of-document erasing unit  31  to the image processing module for NW  32   b . The image processing module for NW  32   b  generates, according to image processing for network scan (e.g., resolution conversion or image compression corresponding to user designation), image data for network scan (image data as a scan result) from the image data from the area on the outside of the original document is erased (Act  22 ). The image processing module for NW  32   b  stores the generated image data for network scan in the page memory  25  (Act  23 ). When the image data for network scan is stored in the page memory  25 , the CPU  21  transmits, through the network interface  14 , the image data for network scan stored in the page memory  25  to a destination designated by the user as a scan result (Act  24 ). 
     When the operation mode of the digital multifunction peripheral  1  is the facsimile mode (Act  25 , YES), the CPU  21  supplies the output (the image data from which the image area on the outside of the original document is erased) from the outside-of-document erasing unit  31  to the image processing module for FAX  32   c . The image processing module for FAX  32   c  generates, according to image processing for facsimile transmission (e.g., monochrome conversion), image data for facsimile transmission from the image data from which the area on the outside of the original document is erased (Act  26 ). The image processing module for FAX  32   c  stores the generated image data for facsimile transmission in the page memory  25  (Act  27 ). When the image data for facsimile transmission is stored in the page memory  25 , the CPU  21  transmits, through the facsimile interface  13 , the image data for facsimile transmission stored in the page memory  25  to a destination of a telephone number designated by the user (Act  28 ). 
     When the outside-of-document erasing processing is set invalid (Act  13 , NO) or when the document cover  11   b  is closed (Act  14 , NO), the CPU  21  omits the processing by the outside-of-document erasing unit  31  applied to the image data scanned by the scanner  11 . In other words, when the outside-of-document erasing processing is unnecessary, the CPU  21  directly supplies the image data scanned by the scanner  11  to the image processing module  32   a ,  32   b , or  32   c  corresponding to the operation mode. In this case, the image processing module  32   a ,  32   b , or  32   c  selected according to the operation mode generates image data corresponding to the operation mode from the image data not subjected to the outside-of-document erasing processing. 
     As explained above, in the digital multifunction peripheral  1  according to the first configuration example, the outside-of-document erasing unit  31  is provided before the image data scanned by the scanner  11  is supplied to the image processing modules corresponding to the various operation modes. As a result, in the digital multifunction peripheral  1  according to the first configuration example, it is possible to prevent fluctuation from occurring in a result of the outside-of-document erasing processing depending on an operation mode. In other words, in the digital multifunction peripheral according to the first configuration example, it is possible to apply the same outside-of-document erasing processing to input image data irrespective of an operation mode. 
     A digital multifunction peripheral and a main control unit according to a second configuration example are explained below. 
       FIG. 10  is a block diagram of a digital multifunction peripheral  101  and a main control unit  110  according to the second configuration example. 
     As shown in  FIG. 10 , the digital multifunction peripheral  101  according to the second configuration example includes the main control unit  110 , a scanner  111 , a printer  112 , a facsimile communication unit (a FAX unit)  113 , a network communication unit (a NW unit)  114 , and an operation unit  115 . The scanner  111 , the printer  112 , the facsimile communication unit (the FAX unit)  113 , the network communication unit (the NW unit)  114 , and the operation unit  115  are the same as the scanner  11 , the printer  12 , the FAX unit  13 , the NW unit  14 , and the operation unit  15  in the digital multifunction peripheral  1  according to the first configuration example shown in  FIGS. 1 and 2 . Therefore, detailed explanation is omitted concerning the scanner  111 , the printer  112 , the FAX unit  113 , the NW unit  114 , and the operation unit  115 . 
     The main control unit  110  according to the second configuration example shown in  FIG. 10  has basic functions same as those of the main control unit  10  shown in  FIG. 2  explained in the first configuration example. However, a flow of processing for input image data is different in the main control unit  110  according to the second configuration example and the main control unit  10  according to the first configuration example. 
     As shown in  FIG. 10 , the main control unit  110  according to the second configuration example includes a CPU  121 , a main memory  122 , an HDD  123 , a scanner-system image processing unit (an input image processing unit)  124 , a page memory  125 , and a printer-system image processing unit (an output image processing unit)  126 . The main memory  122 , the HDD  123 , the page memory  125 , and the printer-system image processing unit (the output image processing unit)  126  can be realized as those same as the main memory  22 , the HDD  23 , the page memory  25 , and the output image processing unit  26  explained in the first configuration shown in  FIG. 2 . Therefore, detailed explanation is omitted concerning the main memory  122 , the HDD  123 , the page memory  125 , and the output image processing unit  126 . 
     The CPU  121  manages control of the entire digital multifunction peripheral  101 . The CPU  121  realizes various functions by executing programs stored in a not-shown program memory. Like the CPU  21  according to the first configuration example, the CPU  121  performs control for realizing a copy function, a facsimile function, and a network scan function. The CPU  121  also has a function of setting a value corresponding to an operation mode of the digital multifunction peripheral  101  as a reference value for detecting an area on the outside of an original document in the outside-of-document erasing processing. 
     The input image processing unit  124  processes an input image. The input image processing unit  124  shown in  FIG. 10  functions as a scanner-system image processing unit that processes, as an input image, an image scanned by the scanner  111 . Various kinds of image processing by the input image processing unit  124  may be realized by the CPU  121  executing programs for image processing. An image input to the input image processing unit  124  is not limited to image data input from the scanner  111 . For example, the input image processing unit  124  may input, as an input image, image data received by the NW unit  114  through a network or image data received by the FAX unit  113  through facsimile communication. 
     The input image processing unit  124  includes various image processing modules  132   a ,  132   b , and  132   c  and an outside-of-document erasing unit  133 . The input image processing unit  124  according to the second configuration example shown in  FIGS. 10 and 11  is different from the input image processing unit  24  according to the first configuration example shown in  FIG. 2  in order for processing image data supplied from the scanner. 
     The image processing modules  132   a ,  132   b , and  132   c  are image converting units that convert image data according to an operation mode. The image processing module  132   a ,  132   b , or  132   c  is selected according to an operation mode of the digital multifunction peripheral  101 . The image processing module  132   a ,  132   b , or  132   c  selected according to the operation mode subjects image data scanned by the scanner  111  to image processing and supplies the image data to the outside-of-document erasing unit  133 . 
     Contents of the image processing executed by the image processing modules  132   a ,  132   b , and  132   c  may be the same as the contents of the image processing executed by the image processing modules  32   a ,  32   b , and  32   c  explained in the first configuration example. Therefore, detailed explanation is omitted concerning the contents of the image processing in the image processing modules  132   a ,  132   b , and  132   c.    
     The outside-of-document erasing unit  133  erases an area on the outside of an original document from image data processed by the image processing modules  132   a ,  132   b , and  132   c  (converts the area into white). The outside-of-document erasing unit  133  converts the image data into binary monochrome image data, detects the area on the outside of the original document from the binary monochrome image data, and erases the area on the outside of the original document from the image data. 
     The outside-of-document erasing processing in the outside-of-document erasing unit  133  is explained in detail below. 
       FIG. 11  is a diagram of a configuration of the outside-of-document erasing unit  133  according to the second configuration example. 
     As shown in  FIG. 11 , the outside-of-document erasing unit  133  according to the second configuration example includes a monochrome conversion unit  141 , an outside-of-document detecting unit  142 , and an erasing unit  143 . The outside-of-document detecting unit  142  and the erasing unit  143  in the outside-of-document erasing unit  133  shown in  FIG. 11  can be realized as those same as the outside-of-document detecting unit  42  and the erasing unit  43  shown in  FIG. 5 . Therefore, detailed explanation is omitted concerning the outside-of-document detecting unit  142  and the erasing unit  143  shown in  FIG. 11 . 
     The monochrome conversion unit  141  includes a monochromization module group  151  and a binarization module  152 . In an example shown in  FIG. 11 , the monochromization module group  151  includes a first conversion module  161   a  and a second conversion module  161   b  as modules for monochromizing image data. 
     In the example shown in  FIG. 11 , the image processing module for copying  132   a  outputs, as color image data for printing, color image data of a complementary color system formed by signals of C (cyan), M (magenta), and Y (yellow). The image processing module for NW  132   b  outputs, as color image data as a scan result, color image data of a primary color system formed by signals of R (red), G (green), and B (blue). The image processing module for NW  132   b  may output color image data formed by signals of Y, Cb, and Cn as the color image data as a scan result. Further, the image processing module for NW  132   b  may output color image data of a data format (a data format such as JPEG) designated by the user as the color image data as a scan result. The image processing module for FAX  132   c  outputs monochrome image data formed by a signal of BK (monochrome) as image data for facsimile transmission. 
     The monochromization module group  151  shown in  FIG. 11  includes conversion modules for monochrome conversion corresponding to the image processing modules  132   a ,  132   b , and  132   c . The first conversion module  161   a  is a processing module for monochrome conversion corresponding to the image processing module for copying  132   a . The second conversion module  161   b  is a processing module for monochrome conversion corresponding to the image processing module for NW  132   b.    
     As shown in  FIG. 11 , when the image processing module for FAX  132   c  outputs monochrome image data, a module for monochrome conversion corresponding to the image processing module for FAX  132   c  is unnecessary. However, a processing module that corrects the monochrome image data from the image processing module for FAX  132   c  before the monochrome image data is supplied to the binarization module may be provided in the monochromization module group  151 . 
     The first conversion module  161   a  corresponding to the image processing module for copying  132   a  supplies image data obtained by monochromizing color image data given from the image processing module for copying  132   a  to the binarization module. When the image processing module for copying  132   a  outputs color image data including color pixels formed by signals of C, M, Y, the first conversion module  161   a  converts the color pixels formed by values of C, M, and Y into monochrome pixels. In this case, a method same as the processing for monochromizing the color pixels formed by the values of R, G, and B can be applied to the first conversion module  161   a . The first conversion module  161   a  converts the color pixels formed by the values of C, M, and Y into a monochrome pixel value (BK) according to “BK=α×C+β×M+γ×Y” using α, β, and γ that satisfy “0≦α, β, γ≦ 1 , α+β+γ”. 
     For example, in the first conversion module  161   a , it is conceivable to calculate the monochrome pixel value (BK) from a color pixel value according to BK=(C+M+Y)/3. In this case, each of the coefficients α, β, and γ is set as “0.333 . . . ”. The CPU  121  sets the coefficients α, β, and γ in the first conversion module  161   a . The coefficients α, β, and γ are desirably values that make it easy to separate a black image in an original document image and a black image on the outside of the original document image. For example, the CPU  121  determines values of the coefficients α, β, and γ on the basis of original document modes (e.g., a character mode, a photograph mode, and a character and photograph mode). 
     The second conversion module  161   b  corresponding to the image processing module for NW  132   b  supplies image data obtained by monochromizing color image data obtained as a scan result to the binarization module  152 . The second conversion module  161   b  converts color image data given as a scan result from the image processing module for NW  132   b  into monochrome image data. For example, the second conversion module  161   b  converts color pixels formed by value of R, G, and B or values of Y, Cb, and Cn into monochrome pixels. The monochromization processing explained above can also be applied to the second conversion module  161   b.    
     As image processing for facsimile transmission, the image processing module for FAX  132   c  converts input image data into monochrome image data for facsimile transmission. Since image data output from the image processing module for FAX  132   c  is monochrome image data, the monochromization processing is unnecessary. Therefore, the image processing module for FAX  132   c  directly supplies monochrome image data as an image processing result to the binarization module  152  through the monochromization module group  151 . 
     The binarization module  152  binarizes the monochrome image data on the basis of a reference value given from the CPU  121 . Like the binarization module  52  explained in the first configuration example, the binarization module  152  binarizes pixels forming the monochrome image data according to a binarization threshold (the reference value given from the CPU  121 ) for separating a black image on the outside of an original image and images in the other areas. 
     In the second configuration example, the monochrome image data supplied to the binarization module  152  is obtained by different various kinds of processing corresponding to the operation modes. Therefore, the CPU  121  determines a binarization threshold as a reference value for detecting the outside of the original document according to an operation mode. The CPU  121  determines a binarization threshold with which areas erased by the outside-of-document erasing processing are the same as much as possible irrespective of an operation mode. In other words, the CPU  121  determines a binarization threshold corresponding to processing contents until an input image (a scan image) reaches the binarization module  152  (processing contents specified by an operation mode) such that the same area is erased as the outside of the original document irrespective of an operation mode. After determining such a binarization threshold, the CPU  121  sets the binarization threshold in the binarization module  152 . 
     For example, when the digital multifunction peripheral  101  is in the copy mode, the CPU  121  supplies a binarization threshold for the copy mode to the binarization module  152 . In the copy mode, image data scanned by the scanner  111  is subjected to image processing by the image processing module for copying  132   a  and monochromized by the first conversion module  161   a . In other words, when the digital multifunction peripheral  101  is in the copy mode, the CPU  121  sets, in the binarization module  152 , a binarization threshold for the copy mode corresponding to processing contents of the image processing module for copying  132   a  and the first conversion module  161   a.    
     When the digital multifunction peripheral  101  is in the network scan mode, the CPU  121  supplies a binarization threshold for the network scan mode to the binarization module  152 . In the network scan mode, image data scanned by the scanner  111  is subjected to image processing by the image processing module for NW  132   b  and monochromized by the second conversion module  161   b . When the digital multifunction peripheral  101  is in the network scan mode, the CPU  121  sets, in the binarization module  152 , a binarization threshold for the network scan mode corresponding to processing contents of the image processing module for NW  132   b  and the second conversion module  161   b.    
     When the digital multifunction peripheral  101  is in the facsimile mode, the CPU  121  supplies a binarization threshold for the facsimile mode to the binarization module  152 . In the facsimile mode, image data scanned by the scanner  111  is monochromized by the image processing module for FAX  132   c  as monochrome image data for facsimile transmission. In other words, when the digital multifunction peripheral  101  is in the facsimile mode, the CPU  121  sets, in the binarization module  152 , a binarization threshold for the facsimile mode corresponding to processing contents of the image processing module for FAX  132   c.    
     The binarization threshold for the copy mode, the binarization threshold for the network scan mode, and the binarization threshold for the facsimile mode are set such that an area erased by the outside-of-document erasing processing is the same in all the operation modes, i.e., the copy mode, the network scan mode, and the facsimile mode. The binarization thresholds for the respective operation modes are, for example, values set in advance. The binarization thresholds for the respective operation modes may be set according to original document modes (a character mode, a photograph mode, and a character and photograph mode). Further, the binarization thresholds for the respective operation modes may be set for each of plural adjustment levels. 
       FIG. 12  is a diagram of a setting example of the binarization thresholds for the respective operation modes in the second configuration example. 
     In an example shown in  FIG. 12 , the binarization thresholds for the respective operation modes for each of plural adjustment levels. The adjustment level indicates intensity (an adjustment level) for detecting an area on the outside of an original document from image data. In the example shown in  FIG. 12 , it is assumed that a density value of monochrome pixels is represented by 256 gradations. Setting data of the binarization thresholds shown in  FIG. 12  are stored in, for example, the HDD  23  or a not-shown nonvolatile memory. 
     As shown in  FIG. 12 , the binarization thresholds for the respective operation modes are set to different values even at the same adjustment level. This is because, as explained above, the same area is detected as an area on the outside of an original document from image data obtained by different processing for each of the operation modes. For example, in the example shown in  FIG. 12 , at an adjustment level “0” (a default value peculiar to the digital multifunction peripheral  101 ), the binarization threshold for the copy mode is larger than the binarization threshold for the network scan mode and is smaller than the binarization threshold for the facsimile mode. The binarization module  152  generates, according to the binarization threshold for each of the operation modes shown in  FIG. 12 , binary monochrome image data with which the same area is detected as an area on the outside of an original document at the respective adjustment levels irrespective of an operation mode. 
     A flow of processing in the digital multifunction peripheral  101  according to the second configuration example is explained. 
       FIG. 13  is a flowchart for explaining a flow of processing including processing for scanning an original document image in the digital multifunction peripheral  101  according to the second configuration example. 
     In the digital multifunction peripheral  101 , when the user performs copying, network scan, or facsimile transmission, the user sets an original document in the scanner  111  and designates an operation mode using the operation unit  115 . In designating an operation mode, the user can designate whether the outside-of-document erasing processing should be set valid or invalid. The CPU  121  sets the operation mode according to the designation by the user (Act  31 ). After designating the operation mode, the user enters a start key for instructing the start of scanning of the original document provided in the operation unit  115 . When the CPU  21  detects the enter of the start key (Act  32  YES), the CPU  21  starts the scanning of the original document (Act  33 ). 
     When the operation mode of the digital multifunction peripheral  101  is the copy mode (Act  34 , YES), the CPU  121  supplies image data scanned by the scanner  111  to the image processing module for copying  132   a . The image processing module for copying  132   a  applies image processing for printing (for copying) (e.g., color conversion to C, M, and Y signals) to the image data supplied from the scanner  111  (Act  35 ). As a result, the image processing module for copying  132   a  generates image data for printing from the image data scanned by the scanner  111 . 
     On the other hand, the CPU  121  determines whether the outside-of-document erasing processing is valid (Act  36 ). When the outside-of-document erasing processing is valid (Act  36 , YES), the CPU  121  determines on the basis of a detection signal of the detector  11   c  whether the document cover  11   b  is in the open state (Act  37 ). When it is determined that the document cover  11   b  is in the open state (Act  37 , YES), the CPU  121  determines that the outside-of-document erasing processing is executed. 
     In executing the outside-of-document erasing processing, the CPU  121  performs setting for the outside-of-document erasing unit  133  (Act  38 ). In the digital multifunction peripheral  101  according to the second configuration example, as explained above, as the setting for the outside-of-document erasing unit  133 , the CPU  121  selects a conversion module from the monochromization module group  151  according to an operation mode and sets a binarization threshold corresponding to the operation mode in the binarization module. When the operation mode is the copy mode, the CPU  121  selects the first conversion module  161   a  from the monochromization module group  151  and sets a binarization threshold for the copy mode in the binarization module  152 . 
     The outside-of-document erasing unit  133  set by the CPU  121  according to the operation mode erases an area on the outside of the original document from the image data for printing supplied from the image processing module for copying  132   a  (Act  39 ). As explained above, the outside-of-document erasing unit  133  monochromizes the image data for printing, detects the area on the outside of the original document from the monochromized image data, and outputs the image data for printing from which the detected area on the outside of the original image is erased. 
     The image data, from which the area on the outside of the original document is erased, output from the outside-of-document erasing unit  113  is stored in the page memory  125  as a processing result of the input image processing unit  124 . The page memory  125  stores the image data (the image data from which the area on the outside of the original document is erased) output by the outside-of-document erasing unit  133  (Act  40 ). 
     When the image data output from the input image processing unit  124  is stored in the page memory  125 , the CPU  121  processes the image data stored in the page memory  125  using a processing unit (e.g., a printer, a network interface, or a facsimile interface) corresponding to the operation mode. When the operation mode is the copy mode (Act  41 , YES), the CPU  121  processes the image data stored in the page memory  125  using the output image processing unit  126  and prints the image data using the printer  112  (Act  42 ). 
     When the operation mode of the digital multifunction peripheral  101  is the network scan mode (Act  43 , YES), the CPU  121  supplies the image data scanned by the scanner  111  to the image processing module for NW  132   b . The image processing module for NW  132   b  applies image processing for network scan (for network transfer) (e.g., resolution conversion or image compression corresponding to user designation) to the image data supplied from the scanner  111  (Act  44 ). As a result, the image processing module for NW  132   b  generates image data for network scan from the image data scanned by the scanner  111 . 
     On the other hand, as explained above, the CPU  121  determines whether the outside-of-document erasing processing should be executed (Acts  36  and  37 ). When it is determined that the outside-of-document erasing processing is executed in the network scan mode, the CPU  121  sets the outside-of-document erasing unit  133  according to the network scan (Act  38 ). For example, as the setting for the network scan, the CPU  121  selects the second conversion module  161   b  from the monochromization module group  151  and sets a binarization threshold for the network scan mode in the binarization module  152 . The outside-of-document erasing unit  133  set for the network scan erases the area on the outside of the original document from the image data for network scan supplied from the image processing module for NW  132   b  (Act  39 ) and stores the image data from which the area on the outside of the original document in the page memory  125  (Act  40 ). 
     When the operation mode is the network scan mode (Act  45 , YES), the CPU  121  transfers the image data (the image data as a scan result from which the area on the outside of the original document is erased) stored in the page memory  125  to a storage destination designated by the user or stores the image data (Act  46 ). For example, when the image data is stored in a user terminal as an external apparatus on a network, the network interface  114  transfers the image data stored in the page memory  125  to the user terminal. 
     When the operation mode of the digital multifunction peripheral  101  is the facsimile mode (Act  47 , YES), the CPU  121  supplies the image data scanned by the scanner  111  to the image processing module for FAX  132   c . The image processing module for FAX  132   c  applies image processing for facsimile (facsimile transmission) (e.g., monochrome conversion) to the image data supplied from the scanner  111  (Act  48 ). As a result, the image processing module for FAX  132   c  generates image data for facsimile from the image data scanned by the scanner  111 . 
     On the other hand, as explained above, the CPU  121  determines whether the outside-of-document erasing processing should be executed (Acts  36  and  37 ). When it is determined that the outside-of-document erasing processing is executed in the facsimile mode, the CPU  121  sets the outside-of-document erasing unit  133  according to the facsimile mode (Act  38 ). For example, as the setting for the facsimile mode, the CPU  121  omits the respective conversion modules of the monochromization module group  151  and sets a binary threshold for the facsimile mode in the binarization module  152 . The outside-of-document erasing unit  133  set for the facsimile mode erases the area on the outside of the original document from the image data for facsimile supplied from the image processing module for FAX  132   c  (Act  39 ) and stores the image data from which the area on the outside of the original document is erased in the page memory  125  (Act  40 ). 
     When the operation mode is the facsimile mode (Act  49 , YES), the CPU  121  transmits by facsimile the image data stored in the page memory  125  (image data for facsimile transmission from which the area on the outside of the original document is erased) to a telephone number designated by the user (Act  50 ). 
     As explained above, in the digital multifunction peripheral according to the second configuration example, the image data scanned by the scanner is processed by the image processing units corresponding to the various operation modes and the area on the outside of the original document is erased from the image data, which is processed by the respective image processing units, by the outside-of-document erasing unit set according to the operation modes. The outside-of-document erasing unit is set according to the operation modes (processing contents of the image processing units corresponding to the operation modes) such that the area erased as the outside of the original document is the same in all the operation modes. As a result, in the digital multifunction peripheral according to the second configuration example, it is possible to prevent fluctuation from occurring in a result of the outside-of-document erasing processing depending on an operation mode. In other words, in the digital multifunction peripheral according to the second configuration example, it is possible to apply the same outside-of-document erasing processing to input image data irrespective of an operation mode. 
     A digital multifunction peripheral and a main control unit according to a third configuration example are explained below. 
       FIG. 14  is a block diagram of a digital multifunction peripheral  201  and a main control unit  210  according to the third configuration example. 
     As shown in  FIG. 14 , the digital multifunction peripheral  201  according to the third configuration example includes the main control unit  210 , a scanner  211 , a printer  212 , a facsimile communication unit (a FAX unit)  213 , a network communication unit (a NW unit)  214 , and an operation unit  215 . The scanner  211 , the printer  212 , the facsimile communication unit (the FAX unit)  213 , the network communication unit (the NW unit)  214 , and the operation unit  215  are the same as the scanner  11 , the printer  12 , the FAX unit  13 , the NW unit  14 , and the operation unit  15  in the digital multifunction peripheral  1  according to the first configuration example shown in  FIGS. 1 and 2 . Therefore, detailed explanation is omitted concerning the scanner  211 , the printer  212 , the FAX unit  213 , the NW unit  214 , and the operation unit  215 . 
     The main control unit  210  according to the third configuration example shown in  FIG. 14  has basic functions same as those of the main control unit  10  shown in  FIG. 2  explained in the first configuration example. However, the main control unit  210  according to the third configuration example and the main control unit  10  according to the first configuration example are different in a flow of processing for input image data. 
     As shown in  FIG. 14 , the main control unit  210  according to the third configuration example includes a CPU  221 , a main memory  222 , an HDD  223 , a scanner-system image processing unit (an input image processing unit)  224 , a page memory  225 , an image processing unit (an output image processing unit)  226  for a printer system, and an outside-of-document erasing unit  231 . The main memory  222 , the HDD  223 , the page memory  225 , and the printer-system image processing unit (the output image processing unit)  226  can be realized as those same as the main memory  22 , the HDD  23 , the page memory  25 , and the output image processing unit  26  explained in the first configuration example shown in  FIG. 2 . Therefore, detailed explanation is omitted concerning the main memory  222 , the HDD  223 , the page memory  225 , and the output image processing unit  226 . 
     The CPU  221  manages control of the entire digital multifunction peripheral  201 . The CPU  221  realizes various functions by executing programs stored in a not-shown program memory. Like the CPU  21  according to the first configuration example, the CPU  221  performs control for realizing a copy function, a facsimile function, and a network scan function. The CPU  221  also has a function of setting, in the outside-of-document erasing unit  231 , a reference value for detecting an area on the outside of an original document from image data read out from the page memory  225 . 
     The input image processing unit  224  processes an input image. The input image processing unit  224  shown in  FIG. 14  functions as a scanner-system image processing unit that processes an image scanned by the scanner  211  as an input image. Various kinds of image processing of the input image processing unit  224  may be realized by the CPU  221  executing programs for the image processing. 
     The input image processing unit  224  includes various image processing modules  232   a ,  232   b , and  232   c . In the input image processing unit  224  according to the third configuration example shown in  FIG. 14 , contents of image processing executed by the image processing modules  232   a ,  232   b , and  232   c  may be the same as the contents of the image processing executed by the image processing modules  32   a ,  32   b , and  32   c  explained in the first configuration example. Therefore, detailed explanation is omitted concerning the contents of the image processing executed by the image processing modules  232   a ,  232   b , and  232   c.    
     The CPU  221  selects any one of the image processing modules  132   a ,  132   b , and  132   c  according to an operation mode of the digital multifunction peripheral  101 . The image processing module  232   a ,  232   b , or  232   c  selected according to the operation modes subjects image data scanned by the scanner  211  to the image processing. 
     The page memory  225  stores image data subjected to the image processing by the image processing modules  232   a ,  232   b , and  232   c . For example, the page memory  225  stores image data output from the image processing module  232   a  as image data for printing, stores image data output from the image processing module  232   b  as image data for network scan, and stores image data output from the image processing module  232   c  as image data for facsimile. The page memory  225  can also store image data received by the NW unit  114  through a network or image data received by the FAX unit  113  through facsimile communication. 
     The outside-of-document erasing unit  231  erases an area on the outside of an original document from image data read out from the page memory  225 . The outside-of-document erasing unit  231  can be realized in a configuration same as that of the outside-of-document erasing unit  133  explained in the second configuration example. The outside-of-document erasing unit  231  processes the image data read out from the page memory  225  using a module designated by the CPU  221 . In the third configuration, the outside-of-document erasing unit  231  does not process image data directly output from a processing unit corresponding to an operation mode. Like the outside-of-document erasing unit  133 , the outside-of-document erasing unit  231  includes the various conversion modules  161   a  and  161   b  corresponding to the respective operation modes as the monochromization module group  151 . Therefore, the CPU  221  designates a conversion module for monochromizing image data read out from the page memory  225 . 
     The CPU  221  sets a binarization threshold for binarizing monochromized image data in a binarization module. The CPU  221  determines, according to the method explained in the second configuration example, a binarization threshold corresponding to image data to be processed. 
     For example, when the image data read out from the page memory  225  is image data for printing (i.e., when the operation mode is the copy mode), the CPU  221  designates the first conversion module  161   a  as a monochromization module in the outside-of-document erasing unit  231  and sets a binarization threshold for the copy mode in the binarization module  152 . When the image data read out from the page memory  225  is image data for network scan (i.e., when the operation mode is the network scan mode), the CPU  221  designates the second conversion module  161   b  as the monochromization module in the outside-of-document erasing unit  231  and sets a binarization threshold for the network scan mode in the binarization module  152 . When the image data read out from the page memory  225  is image data for facsimile (i.e., when the operation mode is the facsimile mode), the CPU  221  omits the monochromization module in the outside-of-document erasing unit  231  and sets a binarization threshold for the facsimile mode in the binarization module  152 . 
     A flow of processing in the digital multifunction peripheral  201  according to the third configuration example is explained below. 
       FIG. 15  is a flowchart for explaining a flow of processing including processing for scanning an original document image in the digital multifunction peripheral  201  according to the third configuration example. 
     When copying, network scan, or facsimile is performed in the digital multifunction peripheral  201 , a user sets an original document in the scanner  211  and designates an operation mode using the operation unit  215 . In designating an operation mode, the user can also designate whether the outside-of-document erasing processing should be set valid or invalid. The CPU  221  sets the operation mode according to the designation by the user (Act  61 ). In setting the operation mode, the CPU  221  also sets whether the outside-of-document erasing processing is valid or invalid. 
     After designating the operation mode, the user enters a start key for instructing the start of scanning of the original document provided in the operation unit  215 . When the CPU  221  detects the enter of the start key (Act  62 , YES), the CPU  221  starts the scanning of the original document (Act  63 ). When the operation mode of the digital multifunction peripheral  201  is the copy mode (Act  64 , YES), the CPU  221  supplies image data scanned by the scanner  211  to the image processing module for copying  232   a . The image processing module for coping  232   a  applies image processing for printing (for copying) (e.g., color conversion to C, M, and Y signals) to the image data supplied from the scanner  211  (Act  65 ). As a result, the image processing module for copying  232   a  generates image data for printing from the image data (a scan image) scanned by the scanner  211 . 
     The page memory  225  once stores the image data for printing, which is generated from the scan image by the image processing module for copying  232   a , as a processing result of the input image processing unit  224  (Act  66 ). The page memory  225  stores the image data for printing from which the area on the outside of the original document is not erased yet. 
     The CPU  221  determines whether the outside-of-document erasing processing is valid (Act  67 ). When the outside-of-document erasing processing is valid (Act  67 , YES), the CPU  221  determines on the basis of a detection signal of the detector  11   c  whether the document cover  11   b  is in the open state (Act  68 ). When it is determined that the document cover  11   b  is in the open state (Act  68 , YES), the CPU  221  determines that the outside-of-document erasing processing is executed. 
     In executing the outside-of-document erasing processing, the CPU  221  performs setting for the outside-of-document erasing unit  233  (Act  69 ). In the digital multifunction peripheral  201  according to the third configuration example, as explained above, as the setting for the outside-of-document erasing unit  233 , the CPU  221  selects a conversion module from the monochromization module group  151  according to an operation mode and sets a binarization threshold corresponding to the operation mode in the binarization module  152 . When the operation mode is the copy mode, the CPU  221  sets the outside-of-document erasing unit  233  for the copy mode. For example, as the setting for the copy mode, the CPU  221  selects the first conversion module  161   a  from the monochromization module group  151  and sets a binarization threshold for the copy mode in the binarization module  152 . 
     The outside-of-document erasing unit  233  set for the copy mode by the CPU  221  erases the area on the outside of the original document from the image data read out from the page memory  225  (the image data for printing generated by the image processing module for copying  232   a ) (Act  70 ). As explained above, the outside-of-document erasing unit  233  monochromizes the image data for printing, detects an area on the outside of the original document from the monochromized image data, and outputs image data for printing from which the detected area on the outside of the original document is erased. When the operation mode is the copy mode (Act  71 , YES), the CPU  221  prints (copies) the image data from which the area on the outside of the original document is erased by the outside-of-document erasing unit  223  on a sheet (Act  72 ). When the operation mode is the copy mode, the outside-of-document erasing unit  223  according to the third configuration example supplies the image data from which the area on the outside of the original document is erased to the output image processing unit  226 . The printer  212  prints the image data, from which the area on the outside of the original document is erased, processed by the output image processing unit  226 . 
     When the operation mode of the digital multifunction peripheral  201  is the network scan mode (Act  73 , YES), the CPU  221  supplies the image data scanned by the scanner  211  to the image processing module for NW  232   b . The image processing module for NW  232   b  applies image processing for network scan (for network transfer) (e.g., resolution conversion or image compression corresponding to user designation) to the image data supplied from the scanner  211  (Act  74 ). As a result, the image processing module for NW  232   b  generates image data for network scan from the image data (a scan image) scanned by the scanner  211 . 
     The page memory  225  once stores the image data for network scan, which is generated from the scan image by the image processing module for NW  232   b , as a processing result of the input image processing unit  224  (Act  66 ). In the network scan mode, the page memory  225  stores the image data for network scan from which the area on the outside of the original document is not erased yet. 
     On the other hand, as explained above, the CPU  221  determines whether the outside-of-document erasing processing should be executed (Acts  67  and  68 ). When it is determined that the outside-of-document erasing processing is executed in the network scan mode, the CPU  221  sets the outside-of-document erasing unit  133  according to network scan (Act  69 ). For example, as the setting for network scan, the CPU  221  selects the second conversion module  161   b  from the monochromization module group  151  and sets a binarization threshold for the network scan mode in the binarization module  152 . The outside-of-document erasing unit  233  set for network scan erases the area on the outside of the original document from the image data read out from the page memory  225  (the image data for network scan generated by the image processing module for NW  232   b ) (Act  70 ). 
     When the operation mode is the network scan mode (Act  75 , YES), the CPU  121  transfers the image data from which the area on the outside of the original document is erased by the outside-of-document erasing unit  223  (the image data as a scan result from which the area on the outside of the original document is erased) to a storage destination designated by the user or stores the image data (Act  76 ). For example, when the image data is stored in a user terminal as an external apparatus on a network, the network interface  214  transfers the image data output from the outside-of-document erasing unit  233  to the user terminal. 
     When the operation mode of the digital multifunction peripheral  201  is the facsimile mode (Act  77 , YES), the CPU  221  supplies the image data scanned by the scanner  211  to the image processing module for FAX  232   c . The image processing module for FAX  232   c  applies image processing for facsimile (facsimile transmission) (e.g., monochrome conversion) to the image data supplied from the scanner  211  (Act  78 ). As a result, the image processing module for FAX  232   c  generates image data for facsimile from the image data scanned by the scanner  211 . 
     The page memory  225  once stores the image data for facsimile, which is generated from the scan image by the image processing module for FAX  232   c , as a processing result of the input image processing unit  224  (Act  66 ). In the facsimile mode, the page memory  225  stores the image data for facsimile from which the area on the outside of the original document is not erased yet. 
     On the other hand, as explained above, the CPU  221  determines whether the outside-of-document erasing processing should be executed (Acts  67  and  68 ). When it is determined that the outside-of-document erasing processing is executed in the facsimile mode, the CPU  221  sets the outside-of-document erasing unit  233  according to the facsimile mode (Act  69 ). For example, as the setting for the facsimile mode, the CPU  221  omits the respective conversion modules of the monochromization module group  151  and sets a binary threshold for the facsimile mode in the binarization module  152 . The outside-of-document erasing unit  233  set for the facsimile mode erases the area on the outside of the original document from the image data read out from the page memory  225  (the image data for facsimile generated by the image processing module for FAX  232   c ) (Act  70 ). 
     When the operation mode is the facsimile mode (Act  79 , YES), the CPU  221  transmits by facsimile the image data from which the area on the outside of the original document is erased by the outside-of-document erasing unit  223  (image data for facsimile transmission from which the area on the outside of the original document is erased) to a telephone number designated by the user (Act  80 ). 
     As explained above, in the digital multifunction peripheral according to the third configuration example, the image data scanned by the scanner is processed by the image processing units corresponding to the various operation modes and stored in the page memory and, when the image data stored in the page memory is read out, the area on the outside of the original document is erased from the image data by the outside-of-document erasing unit set according to an operation mode. The outside-of-document erasing unit is set according to the operation modes (contents of image processing carried out before the document data is stored in the page memory) such that the area erased as the outside of the original document is the same in all the operation modes. As a result, in the digital multifunction peripheral according to the third configuration example, it is possible to prevent fluctuation from occurring in a result of the outside-of-document erasing processing depending on an operation mode. In other words, in the digital multifunction peripheral according to the third configuration example, it is possible to apply the same outside-of-document erasing processing to input image data irrespective of an operation mode. Further, in the digital multifunction peripheral according to the third configuration example, since the outside-of-document erasing processing is applied to the image data read out from the page memory, it is possible to easily apply the outside-of-document erasing processing to image data supplied from apparatuses other than the scanner. 
     Setting of intensity for determining an area on the outside of an original document is explained below. 
     A processing procedure for setting intensity (hereinafter also referred to as adjustment level) for determining an area on the outside of an original document on the basis of operation by the user is explained. Setting of the adjustment level explained below can be applied to each of the digital multifunction peripherals according to the first to third configuration examples. 
     As explained above, in each of the digital multifunction peripherals according to the first to third configuration examples, one adjustment level is set and the same result of the outside-of-document erasing processing (image data from which the same area is erased as an area on the outside of an original document) is obtained in the various operation modes. This means that an adjustment level designated by the user is common to the operation modes. In other words, the user designate one adjustment level common to the operation modes without designating an adjustment level for each of the operation modes. 
       FIG. 16  is an external view for explaining an overall configuration of an operation panel P serving as the operation units  15 ,  115 , and  215 . 
     As shown in  FIG. 16 , the operation panel P includes a display section P 1 , a function selection key P 2 , a setting key P 3 , a start key P 4 , a reset key P 5 , a stop key P 6 , and a ten key P 7 . 
     The display section P 1  includes a liquid crystal display device incorporating a touch panel. The display section P 1  displays operation guidance for the user and displays various operation screens including icons that can be operated through the touch panel. For example, in a standby state of the digital multifunction peripheral, the display section P 1  displays a basic menu screen shown in  FIG. 16 . The basic menu screen shown in  FIG. 16  is a basic menu screen in the copy mode. 
     The display section P 1  also has a function of displaying image data. For example, the display section P 1  can display a preview image with which the user checks an image. For example, the display section P 1  can display, as the preview image, image data (a scan image) scanned by the scanner of the digital multifunction peripheral or an image after being subjected to image processing. 
     The function selection key P 2  is a hard key for selecting various functions. As the function selecting key P 2 , for example, a scan mode selection key for selecting the scan mode, a copy mode selection key for selecting the copy mode, a facsimile mode selection key for selecting the facsimile mode, and the like are provided. 
     The setting key P 3  is a key for performing various kinds of setting in the digital multifunction peripheral. When the setting key P 3  is entered, the digital multifunction peripheral shifts to a setting processing mode. Items to be set by the setting key P 3  are mainly items concerning default setting values. Contents set after the enter of the setting key P 3  are stored as default setting values and reflected on the processing in the digital multifunction peripheral. For example, a default value of intensity (an adjustment level) for determining an area on the outside of an original document is set in a setting screen displayed on the display section P 1  when the setting key P 3  is entered. 
     The start key P 4  is a hard key for instructing the start of processing (e.g., scan start). For example, in the copy mode, copying (scanning) is started according to the enter of the start key P 4 . The reset key P 5  is a hard key for instructing reset of setting contents and the like. For example, setting and the like input through the touch panel of the display section P 1  are reset according to the reset key. The stop key P 6  is a hard key for instructing suspension of an operation being executed by the digital multifunction peripheral. For example, when the stop key P 6  is entered during a copy operation of the digital multifunction peripheral, the copy operation is suspended. The ten key P 7  is a hard key for inputting numbers and the like. The ten key P 7  is used for inputting information such as the number of copies and a department code. 
     In the operation panel P shown in  FIG. 16 , besides the various keys explained above, a help (HELP) key for instructing display of a user guide, a setting and registration key for instructing execution of setting or registration, a template key for selecting a template as data registered in advance, an interrupt key for requesting interrupt of an operation, a state check key for checking a state of the digital multifunction peripheral, a key for performing security setting and the like, a power save key for switching a power save operation mode for reducing power consumption and a normal operation mode, an on-hook and pause key for setting an on-hook state as a telephone function, a clear key for clearing numbers and the like input by the ten key and the like, an alarm indicator for informing abnormality in the digital multifunction peripheral. 
     Setting of an adjustment level performed by using the operation panel P is explained below. 
     When the setting key P 3  is entered in the operation panel P, the display section P 1  displays a default setting screen for setting default values of the various functions. The default setting screen may be a screen for setting default values set for each of users or may be a screen for setting default values common to all the users. In both the cases, intensity (an adjustment level) for determining an area on the outside of an original document is not set for each of the operation modes but are set as a value common to all the operation modes. 
     In each of the digital multifunction peripherals according to the first to third configuration examples, image data from which the same area on the outside of an original document is erased is obtained as a result of the outside-of-document erasing processing in all the operation modes. In other words, when a default value of intensity (an adjustment level) for determining an area on the outside of an original document is set, the user set one adjustment level for the digital multifunction peripheral. Therefore, default setting concerning intensity for determining an area on the outside of an original document is not instructed by the user on a setting screen for the operation modes (e.g., the setting screen to which the digital multifunction peripheral shifts from the function selection key P 2 ) but is instructed by the user on a setting screen to which the digital multifunction peripheral shifts from the setting key P 3 . 
     For example, a default setting screen displayed according to the enter of the setting key P 3  includes an icon for default setting concerning the outside-of-document erasing processing. When the icon for outside-of-document erasing setting is selected, the display section P 1  displays a setting screen on which the user designates an adjustment level as intensity for determining an area on the outside of an original document (a setting screen for an adjustment level). 
       FIGS. 17 and 18  are diagrams of display examples of the setting screen for an adjustment level. 
     The display example shown in  FIG. 17  is an example in which the setting screen on which the user designates intensity for determining an area on the outside of an original document is displayed on the display section P 1 . In the setting screen shown in  FIG. 17 , the user can designate, as intensity (an adjustment level) for determining an area on the outside of an original document, a desired adjustment level from five levels (“+1” to “+5”) higher than a predetermined reference level (“0”) and five levels (“−1” to “−5”) lower than the reference level. Every time the user touches an icon K 1  arranged on a left end side in the setting screen shown in  FIG. 17 , the adjustment level is changed to a lower level step by step. Every time the user touches an icon K 2  arranged on a right end side in the setting screen shown in  FIG. 17 , the adjustment level is changed to a higher level step by step. In other words, the user can visually and intuitively adjust the adjustment level easily according to the number of times the user touches the icons K 1  and K 2  arranged at both the ends. 
     The display example shown in  FIG. 18  is an example in which a setting screen for the outside-of-document determination level shown in  FIG. 17  is displayed in an area on a lower side of the display section P 1  and a preview screen for image data is displayed in an area on an upper side of the display section P 1 . In the display example shown in  FIG. 18 , image data from which an area on the outside of an original document is not erased yet and the image data from which the area on the outside of the original document is erased are displayed on the preview screen. In the display example shown in  FIG. 18 , the image data displayed on the preview screen may be image data stored in the HDD or the like in advance or may be image data obtained by scanning an original set by the user with the scanner. Since the display example shown in  FIG. 18  is the setting screen for adjusting default setting for outside-of-document erasing, an area to be erased as the outside of the original document may be highlighted on the preview screen. 
     In the display example shown in  FIG. 18 , every time the adjustment level is changed, each of the outside-of-document erasing units  31 ,  133 , and  231  performs the outside-of-document erasing processing at the changed adjustment level. The image data obtained by such outside-of-document erasing processing is displayed on the preview screen as an image subjected to the outside-of-document erasing processing at an adjustment level designated by the user. In the display example shown in  FIG. 18 , every time the user changes the adjustment level, an image as a result of performing the outside-of-document erasing processing at the changed adjustment level is displayed. With the preview screen explained above, the user can visually and specifically recognize a state of an area to be erased by processing carried out at the designated adjustment level. 
     Each of the digital multifunction peripherals according to the first to third configuration examples may display the preview screen on the display section P 1  not only during the default setting but also when processing including the outside-of-document erasing processing is executed. The user selects whether such a preview screen should be displayed. 
     For example, when a user who desires to check a state of the outside-of-document erasing processing on the preview screen executes the various kinds of processing, the user turns on a preview button provided in the operation panel P. When the preview button is ON, the display section P 1  of the operation panel P displays image data after the outside-of-document erasing processing on the preview screen before the image data is actually processed. For example, when the preview button is ON in the copy mode, the display section P 1  displays image data after the outside-of-document erasing processing on the preview screen before printing is executed. When an image displayed on such a preview screen is satisfactory, the user instructs execution of the processing by entering a not-shown execution start key. When the image displayed on the preview screen is dissatisfactory, the user stops the processing indicated by the image by entering a not-shown processing stop key. In this case, the digital multifunction peripheral may perform rescanning of the original document. 
     Whether the preview screen is set valid may be set as default concerning the outside-of-document erasing processing. For the setting, the user only has to designate presence or absence of preview check during execution of processing on the setting screen for the outside-of-document erasing processing. When the preview check is set valid in the default setting, in the processing including the outside-of-document erasing processing, the display section P 1  displays image data after the outside-of-document erasing processing on the preview screen before processing (e.g., printing) is performed by using the image data after the outside-of-document erasing processing. As a result, the user can check image data obtained by the outside-of-document erasing processing before executing the various kinds of processing using an input image. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.