Abstract:
An image processing apparatus includes an image composition unit configured to generate a composite image by compositing first and second images, a specification unit configured to specify a generation process of the first and second images, and a selection unit configured to select a compression parameter to compress the composite image based on the combination of the generation process of the first and second images specified by the specification unit. In addition, an image compression unit is configured to compress the composite image using the compression parameter selected by the selection unit. The image composition unit generates the composite image by compositing the first image regarded as a semitransparent image and the second image.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a compression technique for compressing a composite image. 
   BACKGROUND OF THE INVENTION 
   In recent years, cases that multi-functional peripherals are equipped in offices and copy shops are increasing. A multi-functional peripheral (MFP) is an image processing apparatus which has various functions from a scan function (to be referred to as “SCAN” hereinafter) to a print function (to be referred to as “PDL” hereinafter) and a transmission function (to be referred to as “SEND” hereinafter). The MFP normally adopts a unique compression (decompression) method so as to efficiently process image data and to reduce the image memory size. 
   More specifically, image data in “SCAN”, “PDL”, and “SEND” (scanned image data, PDL image data, and SEND image data) are compressed (decompressed) at their optimal compression parameters. For example, since the scanned image data includes many noise components of a scanner and image deterioration is not conspicuous even when a high compression ratio is selected, it is compressed using compression parameter for the high compression ratio so as to reduce the image memory size. On the other hand, since the PDL image data includes nearly no noise components unlike scanned image data, and image deterioration becomes considerably conspicuous if it is compressed by selecting the same high compression ratio as for scanned image data, it is compressed using compression parameter for a low compression ratio. 
   Furthermore, the MFP comprises an image composition function, and can generate a composite image when the user superposes a form image (scanned image data or PDL image data) stored in a storage unit in the MFP and newly input scanned image data or PDL image data. 
   Japanese Patent Laid-Open No. 6-214923 (US Patent Laid-Open No. 2002-0012453-A1) discloses a transmission technique which generates a composite image by compositing PDL image data and scanned image data using the image composition function of the MFP, compressing the composite image, and transmitting the compressed composite image to a host computer connected on the network. 
   However, the above patent reference  1  describes that the generated composite image is compressed and is then transmitted, but it does not describe about any selection procedure of a compression parameter upon compressing the composite image. 
   On the other hand, upon compressing composite image obtained by compositing scanned image data and PDL image data, for example, when compression parameter for a high compression ratio is selected in image compression, severe image deterioration occurs in the PDL image data portion of the composite image. Hence, upon compressing the composite image, it is an important issue to select an optimal compression parameter(compression ratio) in correspondence with image data to be composited in terms of image deterioration. 
   SUMMARY OF THE INVENTION 
   The present invention has been made in consideration of the above situation, and has as its object to avoid image deterioration caused by image compression by selecting an appropriate compression parameter(compression ratio) upon compressing a composite image generated by compositing a plurality of image data. 
   In order to achieve the above object, an image processing apparatus according to the present invention comprises the following arrangement. That is, an image processing apparatus, comprising: 
   image composition unit configured to generate a composite image by compositing first and second images; 
   checking unit configured to check for each image if each of the first and second images to be composited is a scanned image which is generated by scanning an image by a scanner, or a PDL image which is generated via an application and is described in a page description language; 
   selection unit configured to select a compression parameter(compression ratio) used to compress the composite image on the basis of a combination of the first and second images to be composited checked by the checking unit; and 
   image compression unit configured to compress the composite image using the compression parameter selected by the selection unit. 
   According to the present invention, upon compressing a composite image generated by compositing a plurality of image data, image deterioration caused by image compression can be avoided by selecting an appropriate compression parameter. 
   Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. 

   
     BRIEF 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 description, serve to explain the principles of the invention. 
       FIG. 1  is a diagram showing the overall arrangement of an image processing system which comprises an image processing apparatus (MFP) according to an embodiment of the present invention; 
       FIG. 2  is a diagram for explaining an overview of an image composition function of the MFP; 
       FIG. 3  shows an example of a user interface window of the MFP in the image composition process; 
       FIG. 4  shows an example of a user interface window of the MFP in the image composition process; 
       FIG. 5  is a block diagram showing the arrangement of functional blocks of the image processing apparatus (MFP) according to the embodiment of the present invention; 
       FIG. 6  is a functional block diagram showing details of an image compression unit; 
       FIG. 7  is a diagram for explaining an overview of an image compression process in the MFP according to the first embodiment of the present invention; 
       FIG. 8  is a flowchart showing the flow of the image compression process in the MFP according to the first embodiment of the present invention; 
       FIG. 9  is a diagram for explaining an overview of an image composition process and image compression process in the MFP according to the second embodiment of the present invention; 
       FIG. 10  is a flowchart showing the flow of the image composition process and image compression process in the MFP according to the second embodiment of the present invention; 
       FIG. 11  is a diagram for explaining an overview of an image composition process and image compression process in the MFP according to the third embodiment of the present invention; and 
       FIG. 12  is a flowchart showing the flow of the image composition process and image compression process in the MFP according to the third embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings. 
   First Embodiment 
   &lt;Arrangement of Image Processing System Which Can Use Image Composition Function&gt; 
     FIG. 1  is a diagram showing the overall arrangement of an image processing system which comprises an image processing apparatus (MFP  101 ) according to an embodiment of the present invention. Referring to  FIG. 1 , reference numeral  101  denotes an MFP which comprises an image composition function. Reference numerals  102  and  103  denote host computers ( 102 : host computer A,  103 : host computer B) which are connected to the MFP  101  via a network  109  to be able to communicate with each other. With this arrangement, the operation executed when the user uses the image composition function of the MFP  101  will be briefly described below. 
   Initially, the user registers image data  105  (PDL image data) from the host computer A or B ( 102 ,  103 ) in a storage device  108  in the MFP  101  as a “form image”. The user then places an original  104  on a document table of the MFP  101  and scans the original  104  by operating a control panel to obtain an “original image” (scanned image data). Assume that the image data  105  registered in the storage device  108  is used as the form image upon image composition. 
   Note that the “form image” is image data which is registered in the MFP  101  in advance of those which are to be composited by the MFP  101 , and the “original image” is image data input to the MFP  101  to be composited to the “form image”. Also, the “PDL image data” is image data which is generated via an application installed in the host computer A or B ( 102 ,  103 ) and is described in a page description language (PDL), and the “scanned image data” is image data generated by scanning an image by “SCAN” of the MFP  101 . 
   When the user makes settings required to output a composite image, an image composition process of the form image and original image is executed in the MFP  101  to generate a composite image  107 , which is then printed out. 
   In the image processing system, as an output mode of the composite image  107 , those other than the print output can be implemented. For example, the composite image  107  can be sent (by “SEND”) to the host computer A ( 102 ) or host computer B ( 103 ) via the network  109 . Also, the composite image  107  can be output to and stored in the storage device  108  in the MFP  101 . 
   Also, in the MFP  101 , the original image  104  to be composited to the form image  105  can be input by methods other than “SCAN”. For example, image data  106  (PDL image data) which is received from the host computer A or B ( 102 ,  103 ) via the network  109  can be used as a original image, which is composited to the form image  105 . 
   Furthermore, the MFP  101  registers the form image  105  via the host computer A or B ( 102 ,  103 ). However, the present invention is not particularly limited to this. For example, image data obtained by “SCAN” (scanned image data) can be registered in the storage device  108  as a form image. 
   &lt;Overview of Image Composition Function of MFP&gt; 
   The image composition function of the MFP  101  will be described below using  FIGS. 2 to 4 .  FIG. 2  is a diagram for explaining an overview of an image composition process by the image composition function of the MFP  101 , and  FIGS. 3 and 4  show examples of user interface windows of the MFP  101  in the image composition process. 
   Referring to  FIG. 2 , reference numeral  2104  denotes a form image; and  2105 , an original image. Upon compositing the original image  2105  to the form image  2104  and outputting a composite image, the user selects a form image via the user interface window used to select a form image shown in  FIG. 3 . When the original image  2105  used in the image composition process is scanned by “SCAN”, the user interface ( FIG. 3 ) is displayed on the control panel of the MFP  101 . When the original image  2105  used in the image composition process is sent to the MFP  101  via the host computer A or B ( 102 ,  103 ), the user interface is displayed on a monitor of the host computer A or B ( 102 ,  103 ). 
   The user interface window displays a list ( 300 ) of image data registered in the storage device  108 . The user selects desired image data ( 301 ) from the list ( 300 ), and presses a button  302  to determine that the selected image data is used as the form image  2104 . Also, upon registering image data in the storage device  108 , the user designates image data to be registered as a form image, thus registering the image data as the form image  2104  in advance. 
   The determined form image  2104  undergoes a semitransparent process (density conversion or luminance conversion) ( 202 ) at a set semitransparent composition ratio to generate a post-semitransparent processing form image  203 .  FIG. 4  shows a user interface for setting the semitransparent composition ratio used in the semitransparent process, and a sub window  401  is displayed after the form image is determined upon depression of the button  302 . As shown in the sub window  401  of  FIG. 4 , the user sets the semitransparent composition ratio using a slider bar  402 . 
   The post-semitransparent processing form image  203  and original image  2105  are composited ( 205 ) to generate a composite image  107 . The generated composite image  107  is compressed ( 207 ), and is stored in the storage device  108 . Note that details of image compression will be described later. 
   &lt;Type of Image Composition&gt; 
   The MFP  101  can execute various composition methods. For example, the MFP  101  can execute multiply composition and add composition. Note that the multiply composition is a composition method which is given by:
 
Output=Input×Input/255   (1)
 
and is effective in image composition with the post-semitransparent processing form image  203 .
 
   Also, the add composition is a composition method which composites images by superposing the original image on the form image. 
   &lt;Arrangement of Functional Blocks of MFP  101 &gt; 
   The arrangement of functional blocks of the MFP  101  will be described below.  FIG. 5  is a block diagram showing the arrangement of functional blocks of the image processing apparatus (MFP  101 ) according to the embodiment of the present invention. 
   Note that the operations of respective blocks when PDL image data is registered as the form image  2104 , and the original image  2105  obtained by “SCAN” is to be composited to the form image  2104  as an example of image composition will be described. 
   The PDL image data is received via a network I/F unit  504 , and undergoes an appropriate image process by a PDL image processor  503 . After that, the PDL image data is compressed by an image compression unit  506 , and is then registered as the form image  2104  in a storage unit  507 . After the form image  2104  is selected and the semitransparent composition ratio is set via a control panel unit  510 , a UI analysis unit  511  analyzes the setting information. 
   Upon analyzing the setting information, the form image registered in the storage unit  507  is read out as compressed image data and is decompressed by the image compression unit  506 , and a semitransparent image generator  512  then generates the post-semitransparent processing form image  203  according to the set semitransparent composition ratio. 
   After that, the post-semitransparent processing form image  203  is sent to an image composition unit  505 . On the other hand, the original image  2105  obtained by “SCAN” undergoes an appropriate image process by a scanned image processor  502  via a scanner I/F unit  501 , is then input to the image composition unit  505 , and is composited to the post-semitransparent processing form image  203  generated in advance. 
   After the image composition, the composite image is compressed by the image compression unit  506 , and is stored in the storage unit  507 . The MFP  101  can temporarily save the compressed composite image in the storage unit  507  in that state. Furthermore, the saved composite image is decompressed by the image compression unit  506 , undergoes an image process by a printer image processor  508 , and is then printed out. Also, the decompressed image undergoes an image process by a transmission image processor  509 , and is then transmitted. 
   &lt;Arrangement of Image Compression Unit  506 &gt; 
     FIG. 6  is a functional block diagram showing details of the image compression unit  506 . Reference numerals  601  to  603  respectively denote a device-specific compression unit, a device-specific expansion unit, and a compression unit upon transmission. The device-specific compression unit  601  is compression means used when image data is saved in the storage unit  507  in the MFP  101 , and uses a compression method unique to the MFP  101  on the ground of efficient use of memory resources in place of a general-purpose compression method. More specifically, the compression unit  601  segments an image into tiles, and can perform image compression for respective tiles using an appropriate compression parameter(compression ratio). 
   The device-specific expansion unit  602  is expansion means which expands an image compressed by the device-specific compression unit  601 . The compression unit  603  upon transmission adopts JPEG compression well known as a color encoding method, and an image compressed by the unit  603  can be browsed by a viewer of an arbitrary host computer. The detailed arrangement of the device-specific compression unit  601  and expansion unit  602  will be described below. 
   The device-specific compression unit  601  comprises a compression block line buffer, encoder, and attribute flag encoder. The compression block line buffer segments an image into tiles (each tile size=M×N pixels). Then, the encoder can encode each tile (M×N pixels) separately by discrete cosine transformation encoding (JPEG) as an encoding method of color information and runlength encoding as encoding of attribute flag data information. Note that M and N must be integer multiples of a window size for discrete cosine transformation encoding. In the JPEG encoding method used in this embodiment, since the window size for compression is 8×8 pixels, for example, if M=N=32, a 32×32 pixel tile is further segmented into 16 8×8 pixel windows, and JPEG compression is applied for respective 8×8 pixels (the following description will be given under the assumption of M=N=32, but the present invention is not limited to such specific values). 
   The encoder quantizes 16 8×8 pixel windows included in a tile image of 32×32 pixels by applying known DCT transformation. Quantization coefficients (to be referred to as a quantization matrix hereinafter) used in this case can be selectively set for each tile (note that the aforementioned compression parameter indicates the quantization matrix in this embodiment). A switching signal is input to an attribute flag encoder. 
   In the attribute flag encoder, a determination unit executes a determination process with reference to attribute flag data of 32×32 pixels corresponding to the above image data, generates a selection signal of quantization coefficients, and outputs it to the encoder. The attribute flag data is appended to each pixel. However, since the encoding method in an M×N pixel tile is constant as in this embodiment, the determination unit must analyze attribute flag data in the tile to determine a representative attribute of the tile. 
   The device-specific decompression unit  602  will be described below. The device-specific decompression unit  602  comprises an attribute flag decoder, decoder, line buffer, and determination unit. When data for M×N pixels of the compressed and stored attribute flag data are read out, the attribute flag decoder decodes them. The decoder executes a decoding process of image data while switching a decoding parameter of the image data (a dequantization matrix in this embodiment) in accordance with the decoding result of the attribute flag data, and outputs the decoding result to the line buffer. At this time, attribute flag data are decoded, the determination unit executes analysis and determination process of the decoded attribute flag data in the M×N pixels, and the decoder sets a dequantization matrix required to decode the corresponding image data of M×N pixels upon decoding. 
   Since the attribute flag data are compressed by a lossless compression method such as runlength encoding free from any deterioration of data, the determination result for an identical tile upon encoding becomes equal to that upon decoding. Therefore, even when respective tiles are quantized using different quantization coefficients, dequantization coefficients suited to these tiles are set upon decoding. Hence, correct decoded image data can be obtained. 
   &lt;Details of Image Compression Process of Composite Image&gt; 
   The operations of the respective blocks in  FIG. 5  in the image compression process of the composite image will be described below using  FIGS. 7 and 8 .  FIG. 7  is a diagram for explaining an overview of an image compression process in the MFP  101 , and  FIG. 8  is a flowchart showing the flow of the image compression process in the MFP  101 . 
   In step S 801 , the image composition unit  505  performs image composition ( 205 ) using the post-semitransparent processing form image  203  generated by applying the semitransparent process ( 202 ) to the form image  2104 , and the original image  2105 . Upon image composition, the image composition unit  505  acquires combination information  701  used to determine if the post-semitransparent processing form image  203  and original image  2105  are respectively scanned image data or PDL image data. The acquired combination information  701  undergoes information analysis by the UI analysis unit  511  ( 702 ). 
   If both the post-semitransparent processing form image  203  and original image  2105  are PDL image data as a result of information analysis by the UI analysis unit  511  (“Yes” in step S 802 ), the UI analysis unit  511  selects a compression parameter(compression ratio)  704  for PDL image data ( 702 ). The selected compression parameter  704  is read out from the storage unit  507 , and is then set in the image compression unit  506  (step S 806 ). 
   On the other hand, if “No” in step S 802 , the flow advances to step S 803 . If the post-semitransparent processing form image  203  is PDL image data and original image  2105  is scanned image data as a result of information analysis by the UI analysis unit  511  (“Yes” in step S 803 ), the UI analysis unit  511  selects the compression parameter  704  for PDL image data ( 702 ). The selected compression parameter  704  is read out from the storage unit  507 , and is then set in the image compression unit  506  (step S 807 ). 
   If “No” in step S 803 , the flow advances to step S 804 . If the post-semitransparent processing form image  203  is scanned image data and original image  2105  is PDL image data as a result of information analysis by the UI analysis unit  511  (“Yes” in step S 804 ), the UI analysis unit  511  selects the compression parameter  704  for PDL image data ( 702 ). The selected compression parameter  704  is read out from the storage unit  507 , and is then set in the image compression unit  506  (step S 808 ). 
   Finally, if none of the conditions in steps S 802 , S 803 , and S 804  are met (i.e., if neither the post-semitransparent processing form image  203  nor the original image  2105  are PDL image data), it is determined that both the post-semitransparent processing form image and original image are scanned image data, and the UI analysis unit  511  selects a compression parameter  704  for scanned image data ( 702 ). Furthermore, the compression parameter  704  selected by the UI analysis unit  511  is read out from the storage unit  507 , and is set in the image compression unit  506  (step S 809 ). 
   In this way, in consideration of occurrence of image deterioration upon application of the compression parameter(compression ratio) for scanned image data to PDL image data, the MFP according to this embodiment selects the compression parameter for PDL image data in image compression when PDL image data is used as the original image or form image. 
   In step S 810 , the image compression unit  506  compresses the composite image using the compression parameter  704  selected as described above ( 207 ). Furthermore, in step S 811  the compressed composite image is stored in the storage unit  507  ( 208 ). 
   As can be seen from the above description, the MFP according to this embodiment determines a compression parameter (compression ratio for scanned image data, and that for PDL image data) on the basis of the combination information (information associated with a combination of scanned image data and PDL image data) of two different types of image data (form image, original image) which are composited, upon compressing the composite image. Hence, image deterioration of the composite image, which may occur due to image compression, can be prevented. Upon determination of the compression parameter, since the compression parameter for PDL image data is used as far as possible, deterioration of the composite image can be avoided. 
   Second Embodiment 
   In the first embodiment, the compression parameter(compression ratio) is switched on the basis of the combination information  701 . However, the present invention is not limited to this, and the compression parameter may be switched based on a semitransparent composition ratio in the image composition process. A detailed explanation will be given using  FIGS. 9 and 10 . 
     FIG. 9  is a diagram for explaining an overview of an image composition process and image compression process in the MFP according to the second embodiment of the present invention, and  FIG. 10  is a flowchart showing the flow of the image composition process and image compression process. 
   In step S 1001 , the image composition unit  505  composites the post-semitransparent processing form image  203  generated by applying the semitransparent process ( 202 ) to the form image  2104 , and the original image  2105  ( 205 ). In step S 1002 , the UI analysis unit  511  compares semitransparent composition ratio information  901  set in image composition with a threshold of a semitransparent composition ratio set in advance by the user ( 902 ). The threshold of the semitransparent composition ratio is a value indicating the importance level of a form image set by the user, and is input via the control panel unit  510 . When the threshold of the semitransparent composition ratio is low, the user does not attach an importance on the form image. 
   If the semitransparent composition ratio set by the user in image composition is smaller than its threshold as a result of comparison by the UI analysis unit  511  (“Yes” in step S 1002 ), it is determined that the user does not attach an importance on the post-semitransparent processing form image  203 , and the flow advances to step S 1004  to select a compression parameter(compression ratio)  903  optimal to the original image  2105  from the storage unit  507  (the compression parameter for scanned image data in this case). Furthermore, in step S 1005  the image compression unit  506  compresses the composite image  206  ( 207 ). After that, the compressed image is stored in the storage unit  507  (step S 1006 ). 
   By contrast, if the semitransparent composition ratio set by the user in image composition is larger than its threshold as a result of comparison by the UI analysis unit  511  (“No” in step S 1002 ), it is determined that the user attaches an importance on the post-semitransparent processing form image  203 , and the flow advances to step S 1003 . In step S 1003 , a compression parameter  903  is selected in the same steps (steps S 802  to S 809 ) as in the first embodiment. In step S 1005 , the image compression unit  506  compresses the composite image  206  ( 207 ). After that, the compressed composite image  206  is stored in the storage unit  507  (step S 1006 ). 
   As can be seen from the above description, the MFP according to this embodiment switches the compression parameter (compression parameter for scanned image data, that for PDL image data) using the semitransparent composition ratio upon image composition. Hence, image compression that reflects the importance level on the form image set by the user can be executed. 
   Third Embodiment 
   In the second embodiment, the compression parameter(compression ratio) is switched using the semitransparent composition ratio upon image composition. However, the present invention is not limited to this, and the compression parameter may be switched on the basis of a composite attribute flag which is generated at the same time upon image composition. A detailed explanation will be given hereinafter using  FIGS. 11 and 12 . 
     FIG. 11  is a diagram for explaining an overview of an image composition process and image compression process in the MFP according to the third embodiment of the present invention, and  FIG. 12  is a flowchart showing the flow of the image composition process and image compression process. 
   &lt;Generation Method of Composite Attribute Flag&gt; 
   A generation method of a composite attribute flag (form attribute flag and original attribute flag) will be described first using  FIG. 11 . Referring to  FIG. 11 , reference numeral  1101  denotes a form attribute flag as an attribute flag of the form image  2104 ; and  1104 , a original attribute flag as an attribute flag of the original image  2105 . Note that the “attribute flag” is attribute data used to identify attributes of respective areas that form an image, i.e., to identify if these areas correspond to a text part, photo part, graphics part, and so forth. The attribute flag is normally used to switch an image process in a print output process (for example, the image process is switched like image process A for the text part, image process B for the photo part, and image process C for the graphics part). However, in the MFP according to this embodiment, the composite attribute flag is generated, and is used to switch a compression parameter upon image compression. 
   Note that a case will be described below wherein the priority order is set so that a text part and thin line part of the form attribute flag  1101  are valid upon generation of the composite attribute flag (the priority order is set via the control panel unit  510 ). 
   The semitransparent image generator  512  extracts a predetermined attribute flag (text part and thin line part in this case) from the generated form attribute flag  1101  ( 1102 ), thus generating a post-form extraction flag  1103 . The image composition unit  505  composites the post-form extraction flag  1103  and the original attribute flag  1104  ( 1105 ). At this time, the post-form extraction flag  1103  has top priority, and the original attribute flag  1104  is used as another attribute flag. As a result, a composite attribute flag  1106  is generated. 
   &lt;Flow of Image Composition and Image Compression Processes&gt; 
   The flow of the image composition and image compression processes will be described below using  FIG. 12 . In step S 1201 , the image composition unit  505  generates the composite image  107  and composite attribute flag  1106 . In step S 1202 , the image compression unit  506  analyzes the composite attribute flag  1106  for respective areas ( 1109 ) to check if the attribute flag of the area of interest is the post-form extraction attribute flag  1103  or original attribute flag  1104 . 
   If it is determined in step S 1202  that the attribute flag of the area of interest is the post-form extraction attribute flag  1103 , the flow advances to step S 1203 . Since the attribute flag of the area of interest is the post-form extraction attribute flag  1103 , it is better to compress the area of interest using a compression parameter for PDL image data as a form image. Therefore, in step S 1203  a compression parameter for PDL image data (compression parameter A ( 1107 ) in the example of  FIG. 11 ) is selected, and is read out from the storage unit  507 . Then, the compression parameter is set in the image compression unit  506 . 
   On the other hand, if it is determined in step S 1202  that the attribute flag of the area of interest is the original attribute flag  1104 , the flow advances to step S 1204 . Since the attribute flag of the area of interest is the original attribute flag  1104 , it is better to compress the area of interest using a compression parameter for scanned image data as a original image. Therefore, in step S 1204  a compression parameter for scanned image data (compression parameter B ( 1108 ) in the example of  FIG. 11 ) is selected, and is read out from the storage unit  507 . Then, the compression parameter is set in the image compression unit  506 . 
   In step S 1205 , the image compression unit  506  compresses the composite image  206  using compression parameters ( 1107  or  1108 ) set for respective areas ( 207 ). Furthermore, in step S 1206  the compressed composite image is stored in the storage unit  507  ( 208 ). 
   As can be seen from the above description, in the MFP according to this embodiment, the compression parameter (compression parameter for scanned image data, that for PDL image data) of the composite image is switched for respective areas on the basis of the composite attribute flag generated upon image composition. Hence, the composite image can be compressed at an appropriate compression parameter. 
   Other Embodiments 
   Note that the present invention may be applied to either a system constituted by a plurality of devices (e.g., a host computer, interface device, reader, printer, and the like), or an apparatus consisting of a single equipment (e.g., a copying machine, facsimile apparatus, or the like). 
   The objects of the present invention are also achieved by supplying a storage medium, which records a program code of a software program that can implement the functions of the above-mentioned embodiments to the system or apparatus, and reading out and executing the program code stored in the storage medium by a computer (or a CPU or MPU) of the system or apparatus. 
   In this case, the program code itself read out from the storage medium implements the functions of the above-mentioned embodiments, and the storage medium which stores the program code constitutes the present invention. 
   As the storage medium for supplying the program code, for example, a floppy® disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape, nonvolatile memory card, ROM, and the like may be used. 
   The functions of the above-mentioned embodiments may be implemented not only by executing the readout program code by the computer but also by some or all of actual processing operations executed by an OS (operating system) running on the computer on the basis of an instruction of the program code. 
   Furthermore, the functions of the above-mentioned embodiments may be implemented by some or all of actual processing operations executed by a CPU or the like arranged in a function extension board or a function extension unit, which is inserted in or connected to the computer, after the program code read out from the storage medium is written in a memory of the extension board or unit. 
   The present invention is not limited to the above embodiments and various changes and modifications can be made within the spirit and scope of the present invention. Therefore to apprise the public of the scope of the present invention, the following claims are made. 
   CLAIM OF PRIORITY 
   This application claims priority from Japanese Patent Application No. 2004-255772 filed on Sep. 2, 2004, which is hereby incorporated by reference herein.