Patent Publication Number: US-2007109582-A1

Title: Image data storage device, photocopier, image forming system, and image data storage method

Description:
CROSS REFERENCE  
      This Nonprovisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2005-328954 filed in Japan on Nov. 14, 2005, the entire contents of which are hereby incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      The present invention relates to an image data storage device, a photocopier, an image forming system, and an image data storage method in which inputted image data is stored, and in particular relates to an image data storage device, a photocopier, an image forming system, and an image data storage method which compress and store inputted image data.  
      An image data storage device is provided in the interior of an image forming device which prints image data upon paper, or of a display device which displays image data. Such an image data storage device has an image data recording unit for recording image data. Recently, in such an image data recording unit, it is often the case that the image data is recorded in a compressed state. The reason for this is that, by compressing the image data, the storage capacity which is needed for storing the image data becomes smaller.  
      However, if the image data is recorded in the compressed state, sometimes a delay has been created in processing when performing rotation processing of this image data. The reason for this is that, in order to rotate image data which is recorded, it is necessary to decompress all of the compressed image data, and the start of rotation processing is delayed by just the time spent waiting for the decompression processing to be completed.  
      As a countermeasure against this type of processing delay, in Japanese Laid-Open Patent Publication H08-224916 and Japanese Laid-Open Patent Publication H08-317225, there is disclosed a technique for separating image data which is to be compressed into a plurality of square blocks of image data, and compressing, decompressing, and rotating each of these square blocks of image data individually. It is possible to start the rotation processing even without waiting for the decompression processing to be completed, since, according to this technique, it is possible to start rotation processing of the image data at the time point that at least a single square block of image data has been decompressed.  
      However, with the technique described in Japanese Laid-Open Patent Publication H08-224916 and Japanese Laid-Open Patent Publication H08-317225, since, before reading out the first square block of image data, it is necessary to decompress the compressed image data before reading it out, accordingly the start of reading out the image data is still delayed, just as used previously to be the case. It is very important to prevent such delay in starting the reading out of the image data, since any delay in starting the reading out of the image data is experienced in sequence with delay in output processing for the image data.  
      The object of the present invention is to provide an image data storage device, a photocopier, an image forming system, and an image data storage method which, while being prepared to read out image data rapidly, also compress and store the image data.  
     SUMMARY OF THE INVENTION  
      The image data storage device according to the present invention stores image data which has been inputted. And-this image data storage device includes an image data input unit, an image data recording unit, a compression processing unit, a region decision unit, and a compression control unit. The image data input unit receives input of image data. The image data recording unit records image data inputted by the image input unit. The compression processing unit compresses image data to be recorded in the image data recording unit. The region decision unit decides whether or not image data which has been inputted by the image input unit is image data related to an edge portion region of an image. And the compression control unit controls the compression processing unit so that compression processing is canceled for image data which has been decided, by the region decision unit, to be image data related to an edge portion region of an image.  
      In the image data which is recorded in the image data recording unit, the image data which relates to edge portion regions of the image is recorded in a non-compressed state. The reason is that normally, when outputting the image data, it is read out from image data which relates to an edge portion region of the image.  
      By storing the image data at the position where reading out is started in a non-compressed state, it becomes unnecessary to decompress this image data before reading it out. Accordingly, there is no delay in starting to read out the image data. On the other hand, since the major portion of the image data is compressed, accordingly the capacity required by the image data which is to be stored by this image data storage device is kept small. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a block diagram showing the general structure of a photocopier according to a first embodiment of the present invention;  
       FIG. 2  is a block diagram showing the general structure of an image data storage unit;  
       FIG. 3  is a block diagram showing the general structure of an image data recording unit;  
       FIGS. 4A and 4B  are figures showing an example of arrangement of compressed regions and non-compressed regions in image data;  
       FIG. 5  is a flow chart showing the sequence of processing performed by a CPU during storage of image data;  
       FIG. 6  is a flow chart showing the sequence of processing performed by the CPU in a compression processing step;  
       FIG. 7  is a figure showing an example of a position for starting readout of the image data;  
       FIG. 8  is a figure schematically showing a sequence for reading out the image data;  
       FIG. 9  is a flow chart showing the sequence of processing performed by a first processor during an image forming step;  
       FIG. 10  is a flow chart showing the sequence of processing performed by a second processor during this image forming step;  
       FIGS. 11A and 11B  are figures showing examples of arrangement of compressed regions and non-compressed regions in the image data, in second and third embodiments of the present invention;  
       FIG. 12  is a figure showing an alternative example of arrangement of compressed regions and non-compressed regions in the image data;  
       FIG. 13  is a figure showing the general structure of an image forming system according to an embodiment of the present invention;  
       FIG. 14  is a block diagram showing the general structure of a photocopier according to another embodiment of the present invention; and  
       FIG. 15  is a figure showing the structure of an image data recording unit according to another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      A photocopier, which incorporates an image data storage device according to the present invention, will now be explained using  FIG. 1 . This photocopier  1  has a ROM  11 , a RAM  15 , an image reading unit  12 , an actuation unit  16 , an interface unit  13 , an image forming unit  14 , a power supply unit  17 , a display device  18 , and an image data storage unit  20 .  
      A plurality of programs which are required for the operation of the photocopier  1  are recorded in the ROM  11 . The RAM  15  is a volatile memory for storing temporary data. By reading an image of a original which has been set in a reading position, the image reading unit  12  generates image data according to the image of the original. The interface unit  13  is endowed with the function of receiving image data which is transmitted from a personal computer. Based upon image data generated by the image reading unit  12  or upon image data received from the interface unit  13 , the image forming unit  14  performs image forming processing upon paper by a electronic photographic method. The actuation unit  16  receives input of job commands by the user, or input for setting details of the image forming processing. The power supply unit  17  supplies electrical power of set amounts to the various portions of the photocopier  1 . And, according to a request from the user, the display device  18  displays a preview image according to image data stored in the image data storage unit  20 . In this embodiment, the image forming unit  14  and the display device  18  each corresponds to the “image data output unit” of the Claims.  
      As shown in  FIG. 2 , the image data storage unit  20  includes an image processing unit  21 , an image data input and output unit  22 , a region decision unit  24 , a compression processing unit  23 , a compression/decompression control unit  25 , an image data recording unit  26 , and a CPU  27 .  
      The image processing unit  21  performs image processing upon the image data which has been inputted via the image data input and output unit  22 . This image processing unit  21  includes a main image processing board  30  and an auxiliary image processing board  40 . The main image processing board  30  includes a multi-value image processing unit  31 , a memory  33 , a laser controller  34 , and a processor  32 . The multi-value image processing unit  31  performs processing upon image data which has arrived such as shading compensation, density compensation, region separation, filter processing, MTF compensation, resolution conversion, electronic zooming (processing for change of scale), gamma compensation, and the like. The memory  33  records image data which has been image processed and control information related to the order of image processing. The laser controller  34  transfers image data upon which image processing has been performed to the image forming unit  14 . And the processor  32  controls the various portions of this image processing unit in an integrated manner.  
      The auxiliary image processing board  40  is connected to the main image processing board  30  via a connector. This auxiliary image processing board  40  includes a binary image processing unit  41 , a memory  42 , and an interface unit  43 . The binary image processing unit  41  performs binary image processing based upon signals from the processor  32  upon the main image processing board  30 . The memory  42  records binary image data which has been subjected to image processing, and various types of control information related to the image processing. And the interface unit  43  includes a gate array which controls the memories  33  and  42 , a gate array which controls a hard disk, a SCSI which is an external interface, and a gate array which controls the SCSI.  
      The image data input and output unit  22  receives image data which has been generated by the image reading unit  12 , or image data which has been inputted from an external personal computer via the interface unit  13 . In this embodiment, the image data input and output unit corresponds to the “image data input unit” of the Claims.  
      The region decision unit  24  decides, for image data which is sent to the compression processing unit  23  from the image processing unit  21 , to which region this image data relates. In particular, the region decision unit  24  decides, for image data which is sent to the compression processing unit  23  from the image processing unit  21 , whether it is image data related to an edge portion region of the image, or image data related to a region of the image other than an edge portion. The compression processing unit  23  compresses image data which has been processed by the image processing unit  21 . At this time, the compression processing by the compression processing unit  23  is executed based upon a control signal from the compression/decompression control unit  25 .  
      The compression/decompression control unit  25  outputs a control signal to the compression procession unit  23  so that compression processing is not performed upon image data for which it has been decided, by the region decision unit  24 , that it is image data related to an edge portion region of the image. In this embodiment of the present invention, the control unit  25  corresponds to the “compression control unit” of the Claims.  
      As shown in  FIG. 3 , the image data recording unit  26  includes a first buffer memory  51 , a second buffer memory  52 , a third buffer memory  56 , an address table  54 , a non-compressed data recording unit  53 , and a compressed data recording unit  55 .  
      The first buffer memory  51  and the second buffer memory  52  temporarily store image data which is outputted via the image data input and output unit  22 . The third buffer memory  56  temporarily records image data which is to be compressed by the compression processing unit  23 . The relationship between the image data and the recording region in which that image data is recorded in the third buffer memory  56 .  
      The non-compressed data recording unit  53  is a non-volatile memory which records that image data, among the image data which has been received by the image data input and output unit  22 , which has not been compressed by the compression processing unit  23 . And the compressed data recording unit  55  is a hard disk which records that image data, among the image data which has been received by the image data input and output unit  22 , which has been compressed by the compression unit  23 . In this embodiment, the image data in the non-compressed state is recorded in a high speed memory (for example, S-RAM), which can read and write this non-compressed data at higher speed, than the compressed data recording unit  55  can read and write the image data which is in the compressed state.  
      Now, the arrangement of image data which is recorded in the compressed state and of image data which is recorded in the non-compressed state will be explained with reference to  FIG. 4A . In  FIG. 4A , the image data  60  is image data related to an image of a original of A4 size. In this image data  60 , a block of non-compressed image data  61  is allocated to the upper side edge portion of the original image, a block of non-compressed image data  62  is allocated to the left side edge portion of the original image, a block of non-compressed image data  64  is allocated to the lower side edge portion of the original image, and a block of non-compressed image data  63  is allocated to the right side edge portion of the original image. These blocks  61  through  64  of non-compressed image data are allocated so as to surround the compressed image data  65 . This compressed image data  65  consists of a plurality of square blocks of image data. In this embodiment, the compressed image data  65  consists of  40  square blocks of image data, arranged in an array 8 horizontally by 5 vertically.  
      As shown in  FIG. 4B , the non-compressed image data blocks  61  through  64  and the compressed image data  65  are separated when recording the image data  60  in the image data recording unit  26 , and are each stored in separate places. The non-compressed image data blocks  61  through  64  are not subjected to compression processing, but are simply recorded in the non-compressed data recording unit  53 . On the other hand, the compressed image data  65  is recorded in the compressed data recording unit  55 , after each of its square blocks of image data has been subjected to compression processing. The addresses of the non-compressed image data blocks  61  through  64  and of each of the square blocks of image data in the compressed image data  65  are recorded in the address table  54 .  
      The CPU  27  controls the operation of the various sections of this image data storage unit  20  in an integrated manner.  FIG. 5  is a flow chart showing the sequence of processing performed by the CPU  27  during storage of image data. First, the CPU  27  receives image data via the image data input and output unit  22  (S 1 ). Next, image processing is performed by the image processing unit  21  upon the image data which has been received by the CPU  27  (S 2 ). The image data upon which image processing has been performed in the step S 2  is sent to the compression processing unit  23 .  
      Next, the CPU  27  performs region decision processing upon the image data which is sent to the compression processing unit  23  from the image processing unit  21  (S 3 ). This region decision processing in the step S 3  is processing for deciding whether or not the image data which is the subject of region decision is image data related to an edge portion region of the image. Here, the CPU  27  decides whether or not the image data which is the subject of region decision is image data related to any one of the blocks of non-compressed image data  61  through  64 .  
      In this region decision processing of the step S 3 , if the image data which is the subject of region decision is image data related to an edge portion region of the image, then the CPU  27  calculates the address of the region in which this image data is recorded and records it in the address table  54  (S 4 ). And next, the CPU  27  records, in the storage region of the non-compressed data recording unit  53  which is specified by the address which has been recorded in the address table  54 , image data corresponding to that address (S 5 ).  
      On the other hand if, in the region decision processing of the step S 3 , the image data which is the subject of region decision is not image data related to an edge portion region of the image, then the CPU  27  performs compression processing upon that image data (S 6 ).  
       FIG. 6  is a flow chart showing the-sequence of processing performed by the CPU in the compression processing step of S 6 . When the compression processing step of S 6  starts, the CPU  27  records the image data which is to be compressed in the third buffer memory  56  (S 11 ). Next, the CPU  27  waits until one square block of image data is recorded in the third buffer memory  56  (S 12 ).  
      In the wait step S 12 , when one square block of image data has been recorded in the third buffer memory  56 , the CPU  27  performs compression processing in the compression processing unit  23  upon this square block of image data which has been recorded (S 13 ).  
      Next, the CPU  27  decides whether or not the compression processing has been completed for all of the square blocks of image data (S 14 ), and if some square blocks of image data still remain to be processed, then the flow of control is transferred back to the step S 11  again. On the other hand, if compression processing has now been completed for all of the square blocks of image data, then the CPU  27  terminates this compression processing step S 6 .  
      Next, the CPU  27  records the address of the region in which each square block of image data is to be recorded in the address table  54  (S 7 ). And next, the CPU  27  records, in the storage region of the compressed data recording unit  55  which is specified by the address recorded in the address table  54 , the image data which corresponds to that address (S 8 ).  
      Next, the CPU  27  decides whether or not all of the image data which is to be recorded has been recorded in the image data recording unit  26  (S 9 ), and, if some image data still is present that must be recorded, then the flow of control is transferred back to the step S 3  again for further region decision processing.  
      By the steps S 1  through S 9  and S 11  through S 14  described above, image data related to the image of one original page is stored in the image data storage unit  26  in a compressed state. It should be understood that, although portions which are stored in a non-compressed state are included in the image data stored in the image data storage unit  26 , these portions which are stored in a non-compressed state amount to 5% to 15% of the total amount of image data. Due to this, even though there are some blocks of image data which are stored in a non-compressed state, the capacity for storing image data in the image data storage unit  26  is made sufficiently compact.  
      Next, the processing for reading out image data stored in the image data storage unit  26  will be explained. When reading out image data, the read out starting position is different according to the rotation processing which is applied to this image data.  FIG. 7  shows an example of a position for starting readout of image data. The arrow sign  71  relates to the case of rotation processing through 0°; in other words, it shows the starting position and the read out direction when no rotation processing is to be performed. The arrow sign  72  shows the starting position and the read out direction when rotation processing through 90° is to be performed. The arrow sign  73  shows the starting position and the read out direction when rotation processing through 180° is to be performed. And the arrow sign  74  shows the starting position and the read out direction when rotation processing through 270° is to be performed.  
      In this embodiment, when starting to read out from any one of the above described four read out starting positions, image data which has been stored in a non-compressed state is initially read out. Due to this, it is possible to start reading out the image data before performing decompression processing upon that portion of the image data which has been compressed.  
      The processing for reading out the image data will now be explained using  FIG. 8 . Here, there is shown an example in which, according to an image forming command from the user, reading out is started as shown by the arrow sign  71  in  FIG. 7 . The image data is sent from the non-compressed data recording unit  53  and the compressed data recording unit  55  to the first buffer memory  51  or the second buffer memory  52 , and is temporarily stored in the first buffer memory  51  or the second buffer memory  52 . And the image data is supplied to the image forming unit  14  from the first buffer memory  51  and the second buffer memory  52 .  
      When storing the image data in the first buffer memory  51  or the second buffer memory  52 , the image data is separated into a plurality of band-shaped processing blocks  80  through  89 , and storage of the image data is performed for each of these processing blocks  80  through  89 . Initially, the image data in the non-compressed state related to the processing block  80  is stored in the first buffer memory  51 . Since this image data related to the processing block  80  is recorded in high speed memory, the storage processing for this processing block  80  is performed rapidly. At the same time, with regard to the image data related to the processing block  81 , decompression processing of the compressed image data is performed, and, after this decompression processing has been completed, the image data relating to this processing block  81  is stored in the second buffer memory  52 . The decompression processing and storage processing for the image data related to the processing blocks  82  through  89  is started sequentially at the time points that space can become available in the first buffer memory  51  or the second buffer memory  52 .  
      The image data for each of the processing blocks  80  through  89  which has been stored in the first buffer memory  51  or the second buffer memory  52  is supplied to the image forming unit  14  for each processing block  80  through  89  at a time. And the image forming unit  14  is able to start image forming processing at the time point that the image data related to the first processing block  80  has been supplied. Due to this, the image forming processing is started rapidly after the user issues an image forming command.  
       FIG. 9  is a flow chart showing the sequence of processing performed by the first processor  25 A during this image forming processing. The first processor  25 A performs the task of controlling the processing for reading out the image data and outputting it to the image data input and output unit  22 . During image forming processing, setting information is supplied from the CPU  27  to the first processor  25 A and the second processor  25 B, including information related to the amount of image data, corresponding to the size of paper upon which printing is to be performed. The first processor  25 A first sets the sequence for the read out processing of the image data (S 21 ). In this setting step S 21 , the first processor  25 A sets the starting address and the reading out sequence for the image data, according to the setting for angle of rotation included in the image forming command from the user.  
      Next, the first processor  25 A calculates the position of the image data for read out processing (S 22 ). After this calculation step S 22 , the first processor  25 A decides whether the position of the image data for read out processing corresponds to one of the non-compressed image data blocks  61  through  64 , or to the compressed image data  65  (S 23 ).  
      If, in the decision step S 23 , it is decided that the image data for read out processing belongs to the blocks of non-compressed image data  61  through  64 , then the first processor  25 A performs region decision processing upon the image data for read out processing (S 24 ). In concrete terms, in this case, the first processor  25 A decides to which of the blocks the image data for read out processing belongs to: the block of non-compressed image data  61 , the block of non-compressed image data  62 , the block of non-compressed image data  63 , or the block of non-compressed image data  64 . Next, the first processor  25 A refers to the address table  54 , and reads out the image data by the non-compressed data recording unit  53  (S 26 ).  
      If, on the other hand, in the decision step S 23 , it is decided that the image data for read out processing belongs to the compressed image data  65 , then the first processor  25 A refers to the address table  54 , and reads out the image data, after it has been decompressed, from the first buffer memory  51  or the second buffer memory  52  (S 25 ).  
      It should be understood that the image data which has been read out in the image data reading out step of S 26  or S 25  is sent to the image forming unit  14  via the image data input and output unit  22 . After the image data read out step of S 26  or S 25 , the first processor  25 A decides whether or not the reading out of image data has been completed (S 27 ); and, if it has not been completed, then the flow of control is transferred back to the calculation step S 22  again.  
       FIG. 10  is a flow chart showing the sequence of processing performed by the second processor  25 B during image forming processing. This second processor  25 B performs the task of controlling the decompression processing of the image data belonging to the processing block which is read out next by the first processor  25 A.  
      First, the second processor  25 B decides whether or not any compressed data is included in the image data belonging to the processing block which is read out next by the first processor  25 A (S 30 ). If, in this decision step S 30 , it is decided that compressed image data is indeed included in the image data belonging to the processing block which is read out next by the first processor  25 A, then the second processor  25 B acquires information for the processing block upon which decompression processing must be performed (S 31 ). In this step S 31 , the second processor  25 B specifies the square blocks of image data included in the processing block upon which decompression processing must be performed, based upon the rotational angle setting for the image.  
      Next, the second processor  25 B performs decompression processing upon the plurality of square blocks of image data which are included in the relevant processing block (S 32 ). And the second processor  25 B stores the square image data, after it has been decompressed, in the first buffer memory  51  or the second buffer memory  52 . It should be understood that, if both the first buffer memory  51  or the second buffer memory  52  are in the full state, then the second processor  25 B waits until spare room becomes available in either the first buffer memory  51  or the second buffer memory  52 .  
      Thereafter, the second processor  25 B waits until the decompression processing of the image data for the relevant processing block has been completed (S 33 ), and, when it is completed, the second processor  25 B terminates the decompression processing of the image data belonging to the relevant processing block.  
      In this first embodiment of the present invention, by the two processors  25 A and  25 B which have received the image forming information from the CPU  27  performing processing in parallel, the reading out processing of the image data and the decompression processing of the image data are performed at the same time. Due to this, after an image forming command has been issued, along with the reading out of the image data being started immediately, also the decompression processing for the image data to be read out next is performed. Because of this, it is possible to supply the compressed image data rapidly to the image forming unit  14 . Furthermore, even if the image forming processing is accompanied by rotation processing, it is unlikely that any delay will occur in the starting of image forming processing for the compressed image data.  
       FIG. 11A  shows the arrangement of non-compressed image data and compressed image data in the image data, according to a second embodiment of the present invention. This second embodiment differs from the first embodiment described above, in that the image data related to the right side edge portion region is compressed. Due to this, one further column of square blocks of image data is appended, so that the proportion of compressed regions in the image data can be increased, as compared with the first embodiment described above.  
      And  FIG. 11B  shows the arrangement of non-compressed image data and compressed image data in the image data, according to a third embodiment of the present invention. This third embodiment differs from the first embodiment described above, in that the image data related to the upper side edge portion region and also the right side edge portion region is compressed. Since, due to this, both the number of rows and the number of columns of square blocks of image data are increased, accordingly the proportion of compressed regions in the image data can be further increased, as compared with the first and second embodiments described above.  
      It should be understood that although, in the first through third embodiments described above, the compressed image data  65  consisted of a plurality of square blocks of image data, it would also be acceptable, as shown in  FIG. 12 , for the compressed image data  65  to consist of a plurality of band shaped rectangular blocks of image data.  
      Furthermore although, in the first through the third embodiment described above, a structure was shown in which the image reading unit  12 , the image forming unit  14 , and the image data storage unit  20  were provided within a single unitary device, it would also be acceptable for the image reading unit  12 , the image forming unit  14 , and the image data storage unit  20  to be separate devices. For example, as shown in  FIG. 13 , an image forming system  1 ′ might be constructed by connecting together an image reading unit  12 ′, an image forming unit  14 ′, and an image data storage unit  20 ′.  
       FIG. 14  is a block diagram showing the general structure of a photocopier  1 ′ according to a fourth embodiment of the present invention. The overall structure of this photocopier  1 ′ is the same as that of the photocopier  1 , described above. However, in addition to the structure of the photocopier  1 , this photocopier  1 ′ further includes a network adapter  28  and an external recording device  29 . The network adapter  28  is connected to a network such as a LAN circuit or the like. This network adapter  28  controls communication between the photocopier  1 ′ and external devices which is performed via the network. A removable disk is fitted to the external recording device  29 . In this embodiment this external recording device is an opto-magnetic disk drive, into which an opto-magnetic disk is loaded.  
       FIG. 15  is a figure showing the structure of an image data recording unit  26 ′ in the photocopier  1 ′. The overall structure of this image data recording unit  26 ′ is the same as that of the image data recording unit  26 , described above. However, a storage region  55 A for storing the image data blocks  61  through  64  is provided within the compressed data recording unit  55 .  
      In this fourth embodiment, based upon a command from the user, the CPU  27  stores the non-compressed blocks of image data  61  through  64  in the storage region  55 A. When storing the non-compressed blocks of image data  61  through  64  in the storage region  55 A, these non-compressed blocks of image data  61  through  64  are compressed by the compression/decompression control unit  25  controlling the compression processing unit  23 . It should be understood that, in this fourth embodiment, the CPU  27  corresponds to the “storage unit” of the Claims.  
      By compressing the image data blocks  61  through  64  when storing them in this manner, it becomes easy to perform long term storage or transfer of the image data blocks  61  through  64 . In this embodiment, based upon a command from the user, the compressed image data blocks  61  through  64  may be transferred from the storage region  55 A to the external recording device  29 , so as to be written upon the opto-magnetic disk which is loaded into the external recording device  29 . Furthermore, based upon a command from the user, the compressed image data blocks  61  through  64  may be transferred from the storage region  55 A to the network adapter  28 . Thereafter, these compressed image data blocks  61  through  64  are transferred to an external device which is connected via the network.  
      With this photocopier  1 ′, file names such as “****A” are allocated to the image data blocks  61  through  64 , while file names such as “****B” are allocated to the compressed image data  65 . In this manner, identifiers are appended to the tail ends of the file names in the photocopier  1 ′, for identifying whether the files are the image data blocks  61  through  64  or the compressed image data  65 .  
      As a result, if image data in the compressed state has been received from externally by the photocopier  1 ′, it is possible to determine whether or not it is necessary to decompress this image data in advance. If, for example, a file with a file name of “****A” has been received from externally by the photocopier  1 ′, then, before image forming processing is performed, decompression processing upon this file which has been received is completed, and it is stored in the non-compressed data recording unit  53 . Due to this, in this fourth embodiment as well, just as with the first through the third embodiments described above, no delay due to performing decompression processing upon the blocks of image data  61  through  64  occurs when starting the image forming process.  
      Finally, in the above described explanation of an embodiment of the present invention, all of the features are shown by way of example, and should not be considered as being limitative of the present invention. The scope of the present invention is not to be defined by any of the features of the embodiment described above, but only be the scope of the appended Claims. Moreover, equivalents to elements in the Claims, and variations within their legitimate and proper scope, are also to be considered as being included within the scope of the present invention.