Abstract:
An image data processing apparatus includes an execution device, a use determination device, an identification device, an execution determination device, and a control device. The execution device executes a predetermined data processing of image data. The use determination device determines at least one used amount in at least one specified portion which is used when the data processing is executed. The identification device identifies an attribute of the image data, The execution determination device determines whether or not to execute the data processing of the image data based on the attribute of the image data identified by the identification device and the at least one used amount determined by the use determination device. The control device makes the execution device execute the data processing of the image data when it is determined by the execution determination device to execute the data processing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Japanese Patent Application No. 2006-98210 filed Mar. 31, 2006 in the Japanese Patent Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    The present invention relates to an image processing apparatus that performs a predetermined image data processing on a plurality of types of image data having different attributes. 
         [0003]    A typical known multifunction machine has a variety of functions, such as a copier function, a facsimile function, and a printer function. Such a multifunction machine is capable of performing copying of a document, performing transmission/reception of facsimile through a public telephone network, and performing printing in response to a command input from a connected personal computer (hereinafter referred to as a “PC”). 
       SUMMARY 
       [0004]    In the above multifunction machine, a variety of data, including document image data read from a document to perform the copier function, facsimile reception image data received by the facsimile function, and PC image data received from the PC, is temporarily stored in a memory, such as a DRAM, for managing the variety of data, The stored variety of data is read from the memory and subsequently is printed or outputted to a device, such as the PC, in accordance with a setting of the multifunction machine. 
         [0005]    However, the above multifunction machine involves the following problems. Specifically, since it is required to manage a plurality of types of image data corresponding to a plurality of functions in the multifunction machine, data amount of inputted image data sometimes exceeds a capacity of the memory. In this case, the image data cannot be stored. 
         [0006]    Also, although printing of image data temporarily stored in the memory is usually started promptly, a sheet discharge tray sometimes become full of printed sheets. Then, printing of the image data may become unable. Once storage or printing of image data becomes unable as above, further data processing such as storage or printing of inputted data becomes completely nonexecutable, regardless of the importance of the image data. 
         [0007]    Accordingly, it is desirable to provide an image data processing apparatus in which data processing is securely performed with respect to image data having a specified attribute. 
         [0008]    The present invention provides an image data processing apparatus which includes an execution device, a use determination device, an identification device, an execution determination device, and a control device. The execution device executes a predetermined data processing of image data. The use determination device determines at least one used amount in at least one specified portion which is used when the data processing is executed. The identification device identifies an attribute of the image data. The execution determination device determines whether or not to execute the data processing of the image data based on the attribute of the image data identified by the identification device and the at least one used amount determined by the use determination device. The control device makes the execution device execute the data processing of the image data when it is determined by the execution determination device to execute the data processing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    A preferred embodiment of the present invention will be described hereinafter with reference to the drawings, in which: 
           [0010]      FIG. 1  is a perspective view showing an appearance of a multifunction apparatus in an embodiment of the present invention; 
           [0011]      FIG. 2  is a cross-sectional view showing a schematic structure of a printer unit of the multifunction apparatus; 
           [0012]      FIG. 3  is a block diagram showing a schematic configuration of the multifunction apparatus; 
           [0013]      FIG. 4  is a flowchart showing an image forming process in the present embodiment; 
           [0014]      FIG. 5  an explanatory view showing a relationship between attributes of image data and thresholds of a loaded ratio; 
           [0015]      FIG. 6  is a flowchart showing a loaded ratio prediction process in the present embodiment; and 
           [0016]      FIG. 7  is a flowchart showing a sheet discharge prohibition process in the present embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    As shown in  FIG. 1 , a multifunction apparatus  1  in an embodiment of the present invention includes a printer unit  2  located in a lower portion of the multifunction apparatus  1  and a scanner unit  4  located in an upper portion of the multifunction apparatus  1 . 
         [0018]    The multifunction apparatus  1  is capable of performing a scanner function, a printer function, a copier function, and a facsimile (hereinafter also referred to as a “FAX”) function for reading an image on a document as image data. In the scanner function, an image on a document is read as image data. In the printer function, an image based on image data is printed on a sheet. The copier function is performed by a combination of the scanner function and the printer function. In the FAX function, transmission/reception of image data is performed through a public telephone network  100 , and received image data is temporarily stored in a memory (e.g., a buffer  12  shown in  FIG. 13 ) and is printed later on a sheet. 
         [0019]    An operation panel  6  is disposed in a front upper portion of the multifunction apparatus  1 . The operation panel  6  includes an LCD (liquid crystal display) portion  6   a  for displaying an operating state and the like of the multifunction apparatus  1 , and a variety of operation buttons  6   b  for inputting a variety of commands. 
         [0020]    A notification unit  8  for outputting an alarm sound and an audio sound is also disposed in the front upper portion of the multifunction apparatus  1 . The notification unit  8  includes a speaker, an amplifier, and others. 
         [0021]    A document platform cover  25  is disposed in the front upper portion of the multifunction apparatus  1 . A hinge portion  29  is disposed in a left end portion of the multifunction apparatus  1  seen from a front direction. The document platform cover  25  is upwardly rotatable around the hinge portion  29 . 
         [0022]    Although the printer unit  2  shown in  FIG. 1  has a substantially rectangular parallelepiped configuration, the printer unit  2  also includes a sheet feed cassette  32  shown in  FIG. 2 . 
         [0023]    The scanner unit  4  of a flat-bed type is configured to read an image from a document placed on a platen glass (not shown) by means of a line-type CCD unit. An ADF (Auto Document Feeder) mechanism  26  for sequentially reading images from a plurality of sheets of a document is provided in an upper left end portion of the document platform cover  25 , The ADF mechanism  26  is configured to take in the document sheet by sheet from a document feed tray  28 , have the CCD unit perform reading of the images on the document line by line, and discharge the document after the reading of the images onto a document discharge tray  27 . Accordingly, the scanner unit  4  is capable of reading images on the plurality of sheets of the document loaded on the document feed tray  28  sequentially sheet by sheet. 
         [0024]    As shown in  FIG. 2 , the printer unit  2  includes a printer engine  30 , the sheet feed cassette  32 , a sheet feed roller  36 , a plurality of conveyance rollers  40 , and a sheet guide  42 . The sheet feed cassette  32  contains a plurality of sheets of recording paper  34  as a recording medium in a stacked manner. The sheet feed roller  36  feeds the recording paper  34  contained in the sheet feed cassette  32  sheet by sheet toward the printer engine  30 . The conveyance rollers  40  convey the recording paper  34  fed through the sheet feed roller  36  toward the printer engine  30  and discharge the recording paper  34  after image formation into a sheet discharge tray  38 . 
         [0025]    The sheet feed cassette  32  is mounted by inserting the sheet feed cassette  32  into the multifunction apparatus  1  from outside in a lower end portion of a right side of the multifunction apparatus  1  seen from a front side. 
         [0026]    The sheet discharge tray  38  is provided between the scanner unit  4  and the printer unit  2 , that is, above the printer unit  2 . The sheet discharge tray  38  includes a surface on which the sheets of the recording paper  34  are stacked and an opposed. surface (hereinafter also referred to as an “upper tray surface 38a”). A height sensor  20  including, for example, an infrared light emitting diode and a photodiode as a position detecting element is provided in the upper tray surface  38   a . The height sensor  20  detects a distance between an upper surface of the stacked recording paper  34  and the upper tray surface  38   a  based on a light reception timing of a reflected light reflected by the upper surface of the stacked recording paper  34  in the sheet discharge tray  38 . 
         [0027]    The printer engine  30  includes a toner cartridge  46 , a laser emitter  48 , a transfer roller  50 , and a fixing device  56 . The toner cartridge  46  houses a photosensitive drum  44 . The laser emitter  48  emits a laser beam to the photosensitive drum  44  thereby to form an electrostatic latent image on the photosensitive drum  44 . The transfer roller  50  presses the recording paper  34  onto the photosensitive drum  44  with toner adhered to the electrostatic latent image formed by the laser emitter  48  thereby to form a toner image on the recording paper  34 . The fixing device  56  fixes an image on the recording paper  34  by pressing the recording paper  34  carrying the formed toner image with a heating roller  52  and a pressure roller  54 . 
         [0028]    According to the printer engine  30  in the present embodiment, which is for use in a known laser printer, an image corresponding to image data inputted in the laser emitter  48  is formed on the recording paper  34 . 
         [0029]    An electric configuration of the multifunction apparatus  1  of the present embodiment will now be described with reference to  FIG. 3 . 
         [0030]    As shown in  FIG. 3 , the multifunction apparatus  1  in the present embodiment includes a control unit  10 , the buffer  12 , a database  14 , a PC interface unit (hereinafter referred to as a “PC-I/F unit”)  16 , a line control unit  18 , etc. that are interconnected through a bus line  22 , in addition to the printer unit  2 , the scanner unit  4 , the operation panel  6 , the notification unit  8 , and the height sensor  20  as described above. 
         [0031]    The buffer  12  temporarily stores image data received through the PC-I/F unit  16  and the line control unit  18 , and image data read by the scanner unit  4 . 
         [0032]    The database  14  constituted by a rewritable nonvolatile memory (e.g., an EEPROM) stores control parameters required for performing a variety of processings by the control unit  10  and a variety of information registered by a user, such as a telephone directory including a name, a company name, a telephone number, a FAX number, etc. 
         [0033]    The PC-I/E unit  16  is an interface for connecting the multifunction apparatus  1  to a PC  90  through a communication cable. 
         [0034]    The line control unit  18  performs a line control, including transmission of a calling signal in accordance with a command from the operation button  6 a and reception of a calling signal. At the time of FAX transmission, the line control unit  18  converts image data read by the scanner unit  4  into a modulated signal corresponding to a frequency band of the public line network and transmits the modulated signal. At the time of FAX reception, the control unit  18  demodulates a modulated signal transmitted through the public line network and converts the demodulated signal into image data. 
         [0035]    The line control unit  18 , to which a decoding unit (not shown) and an encoding unit (not shown) are connected, encodes the image data before conversion into the modulated signal at the time of FAX transmission, and decodes the demodulated image data at the time of FAX reception. 
         [0036]    The control unit  10  is constituted by a known microcomputer mainly including a CPU, a ROM, a RAM, and the like. The control unit  10  controls these components in accordance with a command inputted by a user through the operation buttons  6   b  of the operation panel  6  and a command inputted from an external device, such as a FAX machine, through the external PC  90  or a public telephone network  100 . Thus, the multifunction apparatus  1  of the present embodiment may function as a printer, a scanner, a copier, and a FAX machine. 
         [0037]    Specifically, when the control unit  10  receives a print request from the PC  90 , the control unit  10  receives image data subsequently transmitted from the PC  90 , and temporarily stores the received image data in the buffer  12 . When reception of the image data is completed, the control unit  10  controls the printer unit  2  so as to form an image, based on the image data stored in the buffer  12 , on the recording paper  34 . 
         [0038]    When a read request of an image on a document is inputted by the user through the PC  90  or the operation panel  6 , the control unit  10  controls the scanner unit  4  so as to read the image and stores read image data in the buffer  12 . When reading of the image on the document is completed, the control unit  10  transmits the image data stored in the buffer  12  to the PC  90  based on a predetermined operation mode, and stores the image data in a memory installed in the PC  90  or in the database  14 . According to the procedure described above, the multifunction apparatus  1  of the present embodiment may operate as a printer or a scanner. 
         [0039]    When a copy request is inputted by the user through the operation panel  6 , the control unit  10  controls the scanner unit  4  in accordance with an operation mode currently set regarding copying so as to read an image on a document placed by the user and stores read image data in the buffer  12 . When reading of the image on the document is completed, the control unit  10  controls the printer unit  2  so as to form (i.e., copy) an image, based on the image data stored in the buffer  12 , on the recording paper  34 . 
         [0040]    When the control unit  10  receives a document reception request from an external device, for example, a FAX machine, through the line control unit  18 , the control unit  10  receives image data subsequently transmitted from the FAX machine, and temporarily stores the received image data in the buffer  12 . When reception of the image data is completed, the control unit  10  controls the printer unit  2  so as to form (reproduce) an image, based on the image data stored in the buffer  12 , on the recording paper  34 . 
         [0041]    When a FAX command is inputted by the user through the operation panel  6 , the control unit  10  controls the scanner unit  4  in accordance with an operation mode currently set regarding facsimile so as to read an image on a document placed by the user and stores read image data in the buffer  12 . When reading of the image on the document is completed, the control unit  10  transmits the image data stored in the buffer  12  to a transmission destination specified through the line control unit  184   
         [0042]    When a command for setting a variety of operation modes (a variety of detailed settings regarding the copier function, the FAX function, the scanner function, and the printer function) of the multifunction apparatus  1  is inputted by the user through the operation panel  6 , the control unit  10  displays a screen for operation mode setting on the LCD portion in accordance with the command. Then, the control unit  10  reads a further command input by the user following instructions on the screen, and appropriately stores read parameters in a storage area, such as the RAM, the database  14 , or the like, thereby to set an operation mode of the multifunction apparatus  1 . 
         [0043]    As described above, when the control unit  10  receives a print request from the PC  90 , a document reception request from an external FAX machine, or a copy command by the user, the control unit  10  performs a process of forming an image on the recording paper  34  in accordance with received image data or image data read from the document and of discharging the recording paper  34  carrying the formed image into the sheet discharge tray  38 . 
         [0044]    Particularly, in the present embodiment, the control unit  10  performs an image forming process including monitoring a loaded ratio (actual loaded height/fully loaded height) of the recording paper  34  in the sheet discharge tray  38 . The image forming process also includes preventing the sheet discharge tray  38  from being fully loaded by forming an image having a specified attribute (for example, image data in accordance with a copy command) on the recording paper  34  and thus preventing image formation of image data having a different attribute (for example, image data received from the FAX machine) on the recording paper  34  from becoming unable. 
         [0045]    The image forming process performed by the control unit  10  of the present embodiment will be described below with reference to  FIG. 4 . 
         [0046]    The image forming process in the present embodiment is started by an input of a print request from the PC  90 , a document reception request from an external FAX machine, or a copy command by the user. In S 200 , based on information included in the received request or the command inputted through the operation panel  6 , an attribute of image data to be received from a request source or read from the document are identified. The attribute of image data is, for example, “Copy”, “PC Print”, “FAX”, “Administrator&#39;s PC Print”, or “FAX from a Predetermined Sender”, as shown in  FIG. 5 . 
         [0047]    The control unit  10  identifies the attribute of image data based on information, such as a login name of the PC  90 , a document type, a document name, a date, and a time, which is included in the print request from the PC  90 , a telephone number of the FAX machine included in the document reception request from the FAX machine, or the command inputted through the operation panel  6 . 
         [0048]    In S 210 , it is determined whether or not a prohibition flag corresponding to the identified attribute of image data is set, The prohibition flag is set when image formation based on image data having a specified attribute, and thus discharge of the recording paper  34  to the sheet discharge tray  38  is prohibited. The prohibition flag is reset when such image formation is permitted. When it is determined that a prohibition flag corresponding to the identified attribute of image data is not set (S 210 : NO), it is determined that image formation based on image data having the identified attribute is permitted. Then, the present process proceeds to S 220 . 
         [0049]    In S 220 , in a case where a print request or a document reception request is received in S 200 , image data received subsequent to the request is stored in the buffer  12 . In a case where a copy command is received in S 200 , image data read from a document by controlling the scanner unit  4  is stored in the buffer  12 . Then, the present process proceeds to S 230 . 
         [0050]    In S 230 , a distance detected by the height sensor  20  (i.e., the distance between the upper surface of the stacked recording paper  34  and the upper tray surface  38   a ) is read, and calculation of a loaded ratio of the sheet discharge tray  38  is performed based on the read distance. 
         [0051]    In S 240 , it is determined whether or not the calculated loaded ratio is smaller than a predetermined threshold. The predetermined threshold is a value set for each attribute of image data as shown in  FIG. 5 . The predetermined threshold is a maximum value of the loaded ratio (THRESHOLD OF LOADED RATIO in  FIG. 5 ) of the sheet discharge tray  38 , up to which discharge of the recording paper  34  to the sheet discharge tray  38  is permissible, Each threshold is previously registered by the user or an apparatus administrator. 
         [0052]    When it is determined in S 240  that the loaded ratio is smaller than the threshold (S 240 : YES), the present process proceeds to S 250 . In S 250 , it is determined whether or not a prediction flag is set, The prediction flag indicates whether or not to perform a prediction process to predict whether or not the loaded ratio of the recording paper  34  will exceed the threshold if image formation is performed on the recording paper  34  based on the input image data. The prediction flag is set or reset by the user or the apparatus administrator through the operation panel  6 . 
         [0053]    When it is determined in S 250  that a prediction flag is set (S 250 : YES), the present process proceeds to S 310 . In S 310 , a later-described loaded ratio prediction process is performed. When the loaded ratio prediction process has been completed, the present image forming process is terminated. 
         [0054]    When it is determined in S 250  that a prediction flag is not set (S 250 : NO), the present process proceeds to S 260 . In S 260 , image formation on the recording paper  34  is performed by controlling the printer unit  2 . Specifically, in S 260 , an image for one page is formed on the recording paper  34 . 
         [0055]    Subsequently, in S 270 , the recording paper  34  carrying the image is discharged to the sheet discharge tray  38 . In S 280 , a loaded ratio is calculated based on a value detected by the height sensor  20 . In S 290 , it is determined whether or not the calculated loaded ratio is smaller than the predetermined threshold. When it is determined that the calculated loaded ratio is smaller than the predetermined threshold (S 290 : YES), the present process proceeds to S 300 . 
         [0056]    In S 300 , it is determined whether or not image formation for all pages based on the image data has been completed. When it is determined that image formation for all pages has not been completed (S 300 : NO), the present process returns to S 260 . Then, processings from S 260  are performed, i.e., image formation for the next page is performed. When it is determined that image formation for all pages has been completed (S 300 : YES), the present process is terminated. 
         [0057]    When it is determined in S 210 , that a prohibition flag corresponding to the identified attribute of image data is set (S 210 : YES), the present process proceeds to S 330 , In S 330 , reception of image data is refused in a case where a print request or a document reception request is received in S 200 . Then, the present process proceeds to S 320 , and a later-described sheet discharge prohibition process is performed. In a case where a copy request is received in S 200 , the present process directly proceeds to S 320 , and the sheet discharge prohibition process is performed. 
         [0058]    When it is determined in S 240  that the loaded ratio is equal to or larger than the threshold (S 240 : NO), or when it is determined in S 290  that the loaded ratio is equal to or larger than the threshold (S 290 : NO), the present process proceeds to S 320 . When a sheet discharge prohibition process in S 320  is completed, the present process is terminated. 
         [0059]    A loaded ratio prediction process performed in S 310  will be described below with reference to  FIG. 6 . 
         [0060]    When the loaded ratio prediction process is started, a number of sheets of the recording paper  34  that can be discharged to the sheet discharge tray  38  is calculated. Specifically, in S 410 , a difference between the loaded ratio calculated in S 220  and the threshold is calculated. In S 420 , the number of sheets of the recording paper  34  that can be discharged (hereinafter also referred to as a “number of dischargeable sheets”) is calculated based on the difference between the loaded ratio and the threshold, and a predetermined thickness of a sheet of the recording paper  34 . 
         [0061]    In S 430 , it is determined whether or not a number of pages of inputted image data is smaller than the number of dischargeable sheets. When it is determined that the number of pages of image data is smaller than the number of dischargeable sheets (S 430 : YES), the present process proceeds to S 440 . In S 440 , images for all pages corresponding to entire image data are formed on the recording paper  84  by controlling the printer unit  2 , and the recording paper  34  is discharged to the sheet discharge tray  38 . Then, the present process is terminated. 
         [0062]    When it is determined in S 430  that the number of pages of image data is equal to or larger than the number of dischargeable sheets (S 430 : NO), the present process proceeds to S 450 . In S 450 , it is determined whether or not a start flag is set. The start flag indicates whether or not to start image formation in a case where the loaded ratio of the recording paper  34  will exceed the threshold if image formation for all pages is performed. The start flag is set or reset by the user or the apparatus administrator through the operation panel  6 . 
         [0063]    When it is determined in S 450  that the start flag is not set (S 450 : NO), the present process proceeds to S 460 . In S 460 , the later-described sheet discharge prohibition process is performed. When the sheet discharge prohibition process is completed, the present process is terminated. 
         [0064]    When it is determined in S 450  that the start flag is set (S 450 : YES), the present process proceeds to S 470 . In S 470 , a message indicating that the loaded ratio of the sheet discharge tray  38  will exceed the threshold if image formation is performed is displayed on the LCD portion  6   a . An example of the message is “Remove the recording paper to avoid full loading of the sheet discharge tray.” Also in S 470 , an alarm sound is generated from the notification unit  8 . 
         [0065]    Then, the present process proceeds to S 260  in the image forming process, and image formation is started, Since the loaded ratio of the sheet discharge tray  38  has not exceeded the threshold at the current moment, image formation continues to be performed until the loaded ratio has exceeded the threshold, while display of the message and the alarm sound give a warning that the loaded ratio will exceed the threshold. 
         [0066]    The sheet discharge prohibition process to be performed in S 320  and S 460  will be described below with reference to  FIG. 7 , 
         [0067]    When the sheet discharge prohibition process is started, a message (for example, “Remove the recording paper from the sheet discharge tray.”) requesting to remove the recording paper  34  is displayed on the LCD portion  6   a  and an alarm sound is generated by the notification unit  8  in S 510 . Then, the present process proceeds to S 520 . In S 520 , a loaded ratio is calculated based on a value detected by the height sensor  20 . 
         [0068]    Subsequently in S  530 , it is determined whether or not the calculated loaded value is smaller than a predetermined threshold. When it is determined that the calculated loaded value is smaller than the threshold (S 530 : YES), the present process proceeds to S 560 . In S 560 , a prohibition flag corresponding to the attribute of image data is reset. Specifically, when the user removes the recording paper  34 , for example, after seeing the above message, the loaded ratio becomes smaller than the threshold. In this case, the prohibition flag is reset thereby to permit image formation based on image data having the attribute. 
         [0069]    When it is determined that the calculated loaded value is equal to or larger than the threshold (S 530 : NO), the present process proceeds to S 540 . In S 540 , it is determined whether or not a predetermined time has elapsed since the message is displayed on the LCD portion  6 . 
         [0070]    When it is determined that the predetermined time has not elapsed (S 540 : NO), the present process returns to S 510 . The processings from S 510  to S 540  are repeatedly performed until the recording paper  34  is removed from the sheet discharge tray  38  or the predetermined time has elapsed. When it is determined that the predetermined time has elapsed (S 540 : YES), the present process proceeds to S 550 . In S 550 , the prohibition flag is set, and then the present process is terminated. That is, image formation based on the inputted image data is not performed since the loaded ratio of the sheet discharge tray  38  does not change. Also, by setting the prohibition flag, image formation is not performed even if image data having the same attribute is inputted. 
         [0071]    In the multifunction apparatus  1  of the present embodiment as described above, when a print request from the PC  90 , a document reception request from an external FAX machine, or a copy command by the user is inputted, an attribute of image data subsequently received or read by the scanner unit  4  is identified. Also, a loaded ratio of the recording paper  34  in the sheet discharge tray  38  is calculated based on a value detected by the height sensor  20 , When the loaded ratio of the sheet discharge tray  38  is equal to or larger than a predetermined threshold corresponding to the attribute of the image data, image formation based on the image data is not started. 
         [0072]    According to the multifunction apparatus  1  of the present embodiment, when the loaded ratio of the sheet discharge tray  38  is, for example, equal to or larger than the threshold (two-thirds) predetermined with respect to “copy” and “PC print”, image formation based on image data having these attributes is not performed. In contrast, only image formation may be performed based on image data having a specified attribute (“FAX”, “Administrator&#39;s PC Print”, and “FAX Received from a Predetermined Transmission Source”) having the threshold of two-thirds or larger. Accordingly, image formation based on image data having a specified attribute may securely be performed. 
         [0073]    Particularly, in the present embodiment, the threshold for FAX, regarding which it is necessary to request retransmission to a transmission source when image formation cannot be performed, is set at a value larger than the thresholds for other functions, such as “copy” and “PC print”. Accordingly, image formation based on image data received from the FAX machine may securely be performed. 
         [0074]    According to the multifunction apparatus  1  of the present embodiment, when the prediction flag is set, the number of dischargeable sheets of the recording paper  34  is calculated based on the difference between the loaded ratio and the threshold, and the predetermined thickness of a sheet of the recording paper  34 . Then, it is determined whether or not the number of pages of inputted image data is smaller than the number of dischargeable sheets. By such a determination using the number of dischargeable sheets and the number of pages of the image data, it is predicted whether or not the loaded ratio of the sheet discharge tray  38  will exceed the threshold if image formation of all the pages based on the inputted image data is performed. Subsequently, it is determined whether or not to perform image formation based on the image data in accordance with whether or not the loaded ratio will exceed the threshold. 
         [0075]    Accordingly, in a case where the loaded ratio of the sheet discharge tray  38  will exceed the threshold for “PC print”, i.e., two-thirds, if image formation of the image data received from the PC  90  is performed, image formation based on the image data may be prevented. It may, therefore, be possible to securely perform image formation based on image data received from the FAX machine or image data received from the administrator&#39;s PC  90  with a predetermined threshold larger than the threshold for the image data received from the PC  90 . 
         [0076]    According to the multifunction apparatus  1  of the present embodiment, when the attribute of image data identified based on the inputted request or command is identical with the attribute of image data, regarding which it is previously determined that image formation should not be performed, reception or reading of the image data is prohibited, and thus the image data is not stored in the buffer  12 . Accordingly, wasteful use of the buffer  12  for temporarily storing received image data or read image data may be prevented. When the loaded ratio is smaller than a threshold for an attribute, prohibition of reception or reading of image data of the attribute is cancelled. Therefore, when the recording paper  34  is removed from the sheet discharge tray  38 , and thereby the loaded ratio is reduced, image data having an attribute for which the loaded ratio is smaller than the threshold may be received again. 
         [0077]    According to the multifunction apparatus  1  of the present embodiment, when image formation should not be performed or when image formation for all the pages cannot be performed, a message requesting removal of the recording paper  34  is displayed on the LCD portion  6   a  and an alarm sound is generated from the notification unit  8 . This may facilitate the user to recognize the current state. 
         [0078]    While only one embodiment of the present invention has been described above, it will be understood that the present invention may be embodied in various forms without departing from the spirit and scope of the present invention. 
         [0079]    For example, when the prediction flag is set, it is predicted whether or not the loaded ratio of the sheet discharge tray  38  after image formation will exceed the threshold if image formation based on the inputted image data is performed, in the above embodiment. Then, it is determined whether or not to perform image formation based on the image data in accordance with the prediction of whether or not the loaded ratio after image formation will exceed the threshold. However, it may always be determined whether or not to perform image formation based on the image data in accordance with whether or not the loaded ratio after image formation will exceed the threshold. In this case, determination between an actual loaded ratio of the sheet discharge tray  38  before image formation and the threshold may be omitted. 
         [0080]    In the above embodiment, the number of dischargeable sheets of the recording paper  34  is calculated based on the difference between the loaded ratio and the threshold, and the predetermined thickness of a sheet of the recording paper  34 . However, it may be possible to calculate an occupying ratio of the recording paper  34  to be discharged in the sheet discharge tray  38 , and calculate a loaded ratio after image formation based on the calculated occupying ratio and a loaded ratio before image formation (i.e., an actual loaded ratio of the sheet discharge tray  38 ). In this case, it may be determined whether or not the calculated loaded ratio after image formation exceeds the threshold. 
         [0081]    In the above embodiment, a loaded ratio of the recording paper  34  in the sheet discharge tray  38  is calculated, and by preventing image formation based on image data having a specified attribute, image formation based on image data having a different attribute is securely performed. However, a configuration may be possible in which a data occupying ratio in the buffer  12  or a memory capable of storing image data is detected. 
         [0082]    For example, in a process based on a data occupying ratio in the buffer  12 , when the control unit  10  receives a print request from the PC  90 , a document reception request from an external FAX machine, or a copy command by the user, the control unit  10  identifies the attribute of image data and also detects a data occupying ratio in the buffer  12  at the moment. Subsequently, a comparison is made between the detected data occupying ratio in the buffer  12  and a maximum value of the data occupying ratio in the buffer  12 , which is predetermined for each attribute of image data and up to which storage of image data into the buffer  12  is permissible. Then, it may be determined whether or not to store the image data into the buffer  12 . According to the configuration as above, it may be possible to preferentially store image data having a specified attribute, such as “FAX”, into the buffer  12  depending on the data occupying ratio in the buffer  12 . 
         [0083]    It may be possible to perform both the following processes. Specifically, one process is to prohibit image formation based on image data having a specified attribute depending on the loaded ratio of the sheet discharge tray  38  and thus to prohibit discharge to the sheet discharge tray  38 . The other process is to prohibit storage of image data having a specified attribute into the buffer  12  depending on the data occupying ratio in the buffer  12 . 
         [0084]    It may also be possible to provide a plurality of memories capable of storing image data or a plurality of sheet discharge trays  38  such that image data or the recording paper  34  is stored or stacked in turn. In this case, it may be possible to prohibit storage into the memories or image formation on the recording paper  34  of image data having a specified attribute depending on whether or not a specified memory or a specified sheet discharge tray  38  is in use. Then, processing such as storage in the memory or image formation of image data having a different attribute, for example “FAX”, from the specified attribute may securely be performed. 
         [0085]    Attributes of image data and thresholds of the loaded ratio are not limited to the attributes and values used in the above embodiment, but a variety of attributes and values may be appropriately employed. 
         [0086]    For example, “PC Print” or “FAX from a Specified User” may be employed in addition to “PC Print from Administrator&#39;s PC” or “FAX from a Specified FAX Machine”. Specifically, when a user of the PC  90  issues a print request during a login using the user&#39;s ID, user identification information, such as the login name is included in the print request. When a user of a FAX machine issues a document transmission request while inputting user identification information, such as the user&#39;s ID, the user identification information is included in the document transmission request. 
         [0087]    Accordingly, when the above request is transmitted, the control unit  10  may identify not only the specified apparatus but also the user of the apparatus from the received request. Thus, “PC Print” or “FAX from a Specified User” may be employed as an attribute of image data. 
         [0088]    In the above embodiment, a loaded height of the recording paper is detected thereby to perform determination based on a loaded ratio as a ratio of an actual loaded height to a fully loaded height and a threshold in the loaded ratio. However, it may be possible, for example, to detect a number of sheets of the recording paper thereby to perform determination based on the number of sheets and a threshold in the number of sheets. It may also be possible to detect a weight of the recording paper thereby to perform determination based on the weight and a threshold in the weight.