Abstract:
An image processing apparatus, includes: a first extractor, configured to extract compression data items of a plurality of images to extraction image data items; a corrector, configured to correct the extraction image data items, when the images are printed on a print medium; a second extractor, configured to extract one of the compression data items to a sample image data item; an acquirer, configured to acquire, from the sample image data item, a characteristic information item indicative of image characteristic to be corrected by the correction, in a case where at least parts of the images to be printed are to be overlapped when viewed from a first direction; and a calculator, configured to calculate correction amounts each of which is to be applied to an associated one of the extraction image data items based on the characteristic information item.

Description:
CROSS-REFERENCE TO THE RELATED APPLICATIONS 
     Present application claims the benefit of priority under 35 USC 119 to Japanese Patent Application No. 2007-227358 filed Sept. 3, 2007, the entire content of which in incorporated herein by reference. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to an image processing apparatus capable of performing a correcting process when an image is printed on a print medium with respect to extraction image data extracted from compression data of the image, a printer including the same, and at image processing method. 
     2. Description of the Related Art 
     Conventionally, in an image printing process, image processing of decompressing compression data such as JPEG so as to extract original image data and converting into print data according to a specified print layout is performed. A processing time necessary for the image processing is increased by increase in number of pixels configuring an image. As a result, a standby time until the start of the printing is increased. Accordingly, there is a need for shortening the processing time by increasing the efficiency of the processing. 
     As an example of the increase in efficiency of the processing, a technology of shortening a processing time when a compressed image is rotated and output is disclosed in Japanese Patent Publication No. 2006-101014. 
     However, an image may be printed on one page in plural numbers. For example, there is allocation print in which one image is printed on one page at four places or layout print in which one image is printed on one page at a plurality of places according to a layout having a predetermined position and a predetermined size (and a predetermined shape). When one image is printed on one page at the plurality of places, the image to be printed may be individually subjected to a correcting process. For example, if the face of a person included in the image is dark, a brightness correcting process of brightening the face of each of the images to be printed is performed. 
     If the image correcting process is performed, a process of acquiring characteristic information (for example, skin color information, brightness information or the like) of data to be corrected from the image data of an original image and calculating a necessary correction amount is performed. The process of acquiring the characteristic information is generally performed as follows. That is, sample image data sampled from the original image data is generated, a predetermined statistical value computation is performed with respect to the generated sample image data, and the result of computing the statistically value is acquired as the characteristic information. 
     At this time, since the sampling process of generating the sample image data from the original image data includes an image deployment process, a processing time is increased. Accordingly, if the image requiring the correction is printed on one page in plural numbers in a state in which one image has a different correction condition, since the sampling processing tine is required by the plurality off pixels when printing is performed, a standby tire until the start of the printing is increased. Accordingly, if a plurality of images to be corrected are printed on one page, there is a need for shortening the processing time by increasing the efficiency of the processing. 
     SUMMARY 
     According to an aspect of the invention, there is provided an image processing apparatus, includes: a first extractor, configured to extract compression data items of a plurality of images to extraction image data items; a corrector, configured to correct the extraction image data items, when the images are printed on a print medium; a second extractor, configured to extract one of the compression data items to a sample image data item; an acquirer, configured to acquire, from the sample image data item, a characteristic information item indicative of image characteristic to be corrected by the correction, in a case where at least parts of the images to be printed are to be overlapped when viewed from a first direction; and a calculator, configured to calculate correction amounts each of which is to be applied to an associated one of the extraction image data items based on the characteristic information item. 
     When the plurality of images to be corrected overlap with each other in the direction perpendicular to the transportation direction of the print medium, that is, in the print direction, it is possible to simultaneously print the plurality of images when the images are printed on the print medium. At this time, according to the above configuration, the correction amounts of the plurality of images are calculated on the basis of the characteristic information. Accordingly, since the sampling process of acquiring the characteristic information does not need to be repeatedly performed by the number of images in the process of printing the images on the print medium, it is possible to suppress the increase in standby time until the printing is started. 
     In the image processing apparatus, the characteristic information item may be duplicated so that each of duplicated characteristic information items are applied to an associated one of the extraction image data items. 
     Accordingly, it is possible to simultaneously perform the calculating processes of the correction amounts of the plurality of images. Thus, since the correction amounts of the plurality of images can be simultaneously calculated when the printing process is performed, it is possible to further suppress the increase in standby time until the printing is started. 
     In the image processing apparatus, the sample image data item may have lower resolution than the extraction image data items. 
     Accordingly, since the number of pieces of generated sample image data is decreased, the processing load of the sampling process is reduced. In addition, the data amount of the sample image data is reduced, a process of computing the correction amounts can be reduced. As a result, it is possible to suppress the increase in standby time until the printing is started. 
     According to another aspect of the invention, there is provided a printer including: the image processing apparatus; and a printing unit, configured to print the images on the print medium while transporting the print medium in a second direction perpendicular to the first direction 
     According to this printer, since the above image processing apparatuses is included and thus the correction amounts of the plurality of images can be simultaneously calculated when the printing process is performed, it is possible to suppress the increase in standby time until the printing is started. 
     According to still another aspect of the invention, there is provided a method for processing a plurality of images, including: extracting compression data items of a plurality of images to extraction image data items; correcting the extraction image data items, when the images are printed on a print medium; extracting one of the compression data items to a sample image data item; acquiring, from the sample image data item, a characteristic information item indicative of image characteristic to be corrected by the correction, in a case where at least parts of the images to be printed are to be overlapped when viewed from a first direction; and calculating correction amounts each of which is to be applied to an associated one of the extraction image data items based on the characteristic information item. 
     According to this method, the same effects as the image processing apparatus can be obtained. This method may further include the process corresponding to the configuration of the image processing apparatus of the above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiment may be described in detail with reference to the accompanying drawings, in which: 
         FIG. 1  is a view showing the configuration of a printer including an image processing apparatus according to an embodiment of the present invention; 
         FIG. 2  is a flowchart showing a general image correction preprocess and a print data output process; 
         FIG. 3  is a flowchart showing a sample image data generating process of obtaining characteristic information; 
         FIG. 4  is a view showing a process of converting input original image data into sample image data; 
         FIG. 5  is a flowchart showing a process of correcting an image printed on one page; 
         FIG. 6  is a view showing an image printed on one page by a selected print format; and 
         FIG. 7  is a view showing a case where images having different sizes are layout-printed. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention will be described.  FIG. 1  is a printer  10  including an image processing apparatus according to an embodiment of the present invention. The printer  10  receives image data output from an electronic: apparatus such as a digital still camera (DSC) or a recording medium such as an IC card from an input terminal  17  included in the printer  10 , generates predetermined print data, and prints an image on a print medium  20  transported in a predetermined transportation direction (a direction denoted by a white arrow of the drawing). 
     At this time, the printer  10  of the present embodiment is controlled by a controller  51  configured by a CPU or a memory (not shown). That is, the image data received from the input terminal  17  is received via an interface unit  57  and the received image data is subjected to necessary image processing by an image processor  52 . At this time, the image data or data which is being processed is stored and read using a data memory  55 . The image data which is subjected to the processing is subjected to a color converting process or a halftone process by a print data generator  53  such that predetermined print data is generated and stored in an image memory  56 . Thereafter, the stored print data is output to a printer engine  54  which is a printing unit. The printer engine  54  performs the printing process of the image by setting a direction perpendicular to a transportation direction of the print medium  20  as a print direction and ejecting inks of respective colors onto the print medium  20  on the basis of the print data. 
     In such a printing process, if the image data received from the input terminal  17  is compression data (for example, JPEG data), the controller  51  controls the image processor  52  so as to perform a process of extracting the compression data. When the compression data is extracted, a data correcting process is also performed. In the present embodiment, the contents of the correcting process are determined by selecting correction parameters displayed on a display panel  15  provided in the printer  10  using an input unit such as a manipulation button  12  included in the printer  10  by a user of the printer  10 . Accordingly, the controller  51  displays the correction parameters, which are previously stored in the controller  51 , on the display panel  15  so as to be selected by the user before the correcting process. In addition, the displayed correction parameters include, for example, a filter (color/monochrome/sepia), brightness adjustment (brighter/bright/standard/dark/darker) and contrast (standard/strong/stronger). 
     The correction contents may be automatically determined according to types of the received image (for example, a person and a landscape). The types of the image may be acquired from metadata (for example, Exif (registered trademark) data added to the image data. 
     The controller  51  obtains the determined correction contents via the interface unit  57  and calculates the correction amount of the image data on the basis of the obtained correction contents. Thereafter, the controller  51  recognizes that a print start button  13  provided in the printer  10  is pressed by the user via the interface unit  57 , the image processor  52  is controlled such that the image data is corrected by a correction amount. The corrected image data is converted into the print data as described above, the print data is output to the printer engine  54 , and the corrected image is printed on the print medium  20 . 
     The controller  51  also performs a process of deciding the print format such as the sizes or the number and the positions of the images printed on one page or the print direction of the image on the print medium  20 . For example, an allocation printing process in which the positions and the number of the images printed on one page are allocated or a layout printing process in which the images are disposed at predetermined positions with predetermined sizes is performed. The deciding process is performed by selecting a selection item displayed on the display panel  15  provided in the printer  10  using the input unit such as the manipulation button  12  provided in the printer  10  by the user of the printer  10 , 
     Next, the process which is performed in the image processing performed by the printer  10 , that is, the process of extracting the input compression data to original image data and correcting the extracted image, will be described with reference to  FIGS. 2 to 4 . This facilitates the understanding of the effect of the process which is performed when the image printed by correcting one image by a different correction condition exists in plural numbers on one page by the image processing apparatus of the following embodiment. 
       FIG. 2  is a flowchart showing a general image correction preprocessor S 200  and a print data output process S 300 . The process of a step S 100  and steps S 201  to S 204  is performed as the general image correction preprocess S 200  with respect to the input image data and the process of steps S 301  to S 307  is performed as the print data output process S 300 . These processes are performed by executing a predetermined program stored in a memory by the controller  51  under a predetermined operating system and are basically independent of each other. 
     First, the general image correction preprocess S 200  will be described. This process is automatically started when the image data is received from the input terminal  17 . Alternatively, the general image correction preprocess may be stated at a time point when the user selects one of the image data previously stored in the data memory. In this case, the controller  51  displays the stored images on the display panel  15  and uses one image selected by the user using the manipulation button  12  as the received image data. 
     First, in a step S 100 , the received image data is subjected to a sample image data generating process. The processing step S 100  is a process of generating the image data for obtaining characteristic information which becomes the reference of the calculation of the correction amount of the image performed in a step S 204  and is performed by enabling the controller  51  to function as a extraction unit. The details of this process will be described with reference to  FIGS. 3 and 4 . In the present embodiment, the compression data is JPEG type data. The compression data is not limited to the JPEG type data and image data of other compression method such as a graphic interchange format (GIF) may be used. 
     In the sample image data generating process S 100 , first, a process of acquiring the compression data of the image is performed (step S 101 ). In the present embodiment, the controller  51  records and acquires JPEG type compression data in the data memory  55  via the interface unit  57 . Next, the sample image data of one line is extracted (step S 102 ) and the sample image data of one line is stored (step S 103 ). Next, it is determined whether the process of storing the sample image data of all lines is finished (step S 105 ) and, if so not (step S 105 : NO), the process returns to the step S 102  and the same process is repeated with respect to a next line, If all lines are finished (step S 105 ; YES), the process progresses to the step S 201  of  FIG. 2 . 
     The process of the step S 102 , the step S 103  and the step S 105  will be described in detail with reference to  FIG. 4 .  FIG. 4  shows a process of converting JPEG data of Quad-VGA in which the received original image data has 960×1280 pixels into sample image data of QVGA (Quarter-VGA) having 240×320 pixels. 
     First, one line of the JPEG data, that is, a block line of one column in which 8×8 pixels forms one block, is decoded. In more detail, Huffman decompression, inverse quantization and inverse DCT processes are sequentially performed. At this time, the decode process, for example, a predetermined thinning process such as the drop of the coefficient of a predetermined frequency component at the inverse DCT process is performed. In the present embodiment, the vertical and horizontal thinning rates of the extracted image are set to 1/4. Accordingly, by repeating the process of a total of 120 lines in which one line includes eight pixels, the image is converted into the image of 240×320 pixels which is 1/4 of the pixel number of the original image data. 
     Originally, as described above, since the sample image data becomes the reference image for obtaining the characteristic information for calculating the correction amount, it is preferable that the thinning rate is set to a value which can accurately obtaining the characteristic information. For example, a plurality of thinning rates (for example, 1/2, 1/4, and 1/8) may be previously set and a proper thinning rate may be selected according to the pixel number of the original image. If the proper thinning rate cannot be set by the pixel number ratio of the original image to the sample image, the pixel number may be corrected by a pixel interpolation process. 
     By thinning the original image data so as to generate the low-resolution sample image data with a small pixel number, it is possible to reduce the load of the statistical value computing process. In addition, if the pixel number of the original image is small, the thinning rate may be set to 1/1 (that is, the thinning process is not performed) such that the sample image data having the same pixel number as the original image is generated. 
     Returning to  FIG. 2 , the statistical value computing process is performed in a step S 201 . The controller  51  performs this process by functioning as an acquiring unit. By this process, data necessary for calculating the correction amount is computed from the sample image data. In more detail, for example, a color or brightness histogram is computed, a pixel region having a skin color is computed, or an edge position is calculated. The total result is the characteristic information representing the characteristics of the image. 
     Next, in a step S 202 , a process of storing the statistical value computing result is performed. The controller  51  performs this process by storing the statistical value computing result, that is, the characteristic information, in a predetermined region of the data memory  55 . Here, the controller  51  and the data memory  55  function as a storage unit and perform the process of the step S 202 . 
     Next, in a step S 203 , the correction contents of the image are acquired. As described above, the correction contents of the image selected and input by the user of the printer  10  are acquired. In a step S 204 , a process of calculating the correction amount of the extraction image data using the store statistical value computing result is performed. For example, if, in the correction contents selected by the user, the brightness level is “bright” and the extraction image data is the data format represented by YCbCr, the correction amount of the brightness data Y corresponding to “bright” is calculated as the correction amount of the extraction image data. The controller  51  performs the process of the step S 203  and the sap S 204  by functioning as a calculating unit. 
     The above-described processes, that is, the processes from the step S 100  to the step S 204 , are performed as the general image correction preprocess S 200  with respect to the received image data. 
     Next, the print data output process S 300  will be described. This process is simultaneously started with the general image correction preprocess S 200 . First, in a step S 301 , it is determined whether or not printing is performed. The controller  51  repeats the determination until the print start button  13  ( FIG. 1 ) is pressed (step S 301 : NO). If it is determined that the print start button  13  is pressed (step S 301 : YES), the process progresses to a next step S 302 , which extracts the compression data of the image to be printed to the original image data by one line. In addition, the extraction image data is extracted to the pixel data having 960×1280 pixels as described in  FIG. 4 . 
     Subsequently, in a step S 303 , the extraction image data of one line is corrected on the basis of the correction amount. The controller  51  controls the image processor  52  on the basis of the correction amount calculated in the step S 204  so as to correct the extraction image data. For example, as described above, if, in the correction contents selected by the user, the brightness level is “bright” and the extraction image data is the data format represented by YCbCr, the data is corrected by the correction amount of the brightness data Y calculated in the step S 204 . Accordingly, the controller  51  controls the step S 303  to be started after the process of the step S 204  of the general image correction preprocess S 200  is performed. Thus, if the process of the step S 204  is delayed, the process of the step S 303  is delayed. 
     Next, correction image data of one line is stored in a step S 304  and it is determined whether or not the data of one band is stored in a step S 305 . If the corrected extraction image data of one band is not stored (NO), the process progresses to a step S 307 . In contrast, if the corrected extraction image data of one band is stored (YES), a process of converting into print data of one band is performed in a step S 306 . 
     As described with reference to  FIG. 1 , the print data generator  53  performs the converting process such as the color converting process or the halftone process with respect to the corrected extraction image data, converts the extraction image data into predetermined print data, and stores the print data in the image memory  56 . In the present embodiment, the print data is output to the printer engine  54  in the band units having a predetermined data width in the transportation direction of the print medium and a printing process is performed. Accordingly, the stored print data of one band is output to the printer engine  54  by the process of the step S 306 . At this time point, the printing is actually started. Since the method of outputting the print data of the band units to the printer engine  54  is known and is not important in the present embodiment, the description thereof will be omitted. 
     Subsequently, in a step S 307 , it is determined whether or not all lines are finished. If there is an unprocessed line (step S 307 : NO), the process returns to the step S 302  and the process is repeated and, if the extracting and correcting processes of the compression data of all lines are finished (step S 307 : YES), the process of the print data output process S 300  is finished. 
     As described above, the general image correction preprocess S 200  and the print data output process S 300  are performed with respect to the received image data. Then, if the image printed by correcting one image by a different correction condition exists in plural numbers on one page, the process performed by the image processing apparatus of the present embodiment will be described using the flowchart of  FIG. 5 . 
     If the process of  FIG. 5  is started, first, in a step S 501 , a process of acquiring the print format is performed. Subsequently, in a step S 502 , the print position and the size of the image are acquired. In the present embodiment, the print format selected by the user of the printer  10  is described by a page description language (PDL). Accordingly, the controller  51  acquires the position and the size of the image data from the PDL data. Subsequently, in a step S 503 , a process of extracting juxtapositional images having an image region overlapping when viewed from a direction perpendicular to the transportation direction of the print medium is performed. Then, in a step S 504 , a process of acquiring the number of extracted juxtapositional images is performed. Here, the processes from the step S 501  to the step S 504  will be described in detail with reference to  FIG. 6 . 
       FIG. 6  is a view showing the shape of the image printed on one page by correcting one image by the different correction condition. As shown, the allocation printing, in which a total of four images IMD 1  to IMD 4  including two same images juxtaposed in the transportation direction (the vertical direction of the drawing) of the print medium and two same images juxtaposed in the direction (the horizontal direction of the drawing) perpendicular to the transportation direction of the print medium are printed, is performed. 
     At this time, as shown in  FIG. 6 , the PDL data includes data representing the position represented by a coordinate (Xn, Yn) (n=1 to 4) in which one corner of the print medium  20  is an original point (0, 0) and a range W of the print direction and a range H of the transportation direction of the print medium  20 . The controller  51  acquires the coordinates (X 1 , Y 1 ), (X 2 , Y 2 ), (X 3 , Y 3 ) and (X 4 , Y 4 ) and the values of the range W and the range H from the PDL data as the data representing the positions and the sizes of the four pieces of image data (step S 502 ). 
     Next, the controller  51  extracts the juxtapositional images of which at least portions of the image regions overlap with each other in the print direction among the four images IMD 1  to ID 4  from the four acquired coordinates and the value of the range H. In the present embodiment, the images IMD 1  and IMD 2  or the images IMD 3  and IMD 4  are extracted as the juxtapositional images (step S 503 ). A maximum number of extracted juxtapositional images is acquired as the number of juxtapositional images. Accordingly, in the present embodiment, “2” is acquired (step S 504 ). 
     Returning to  FIG. 5 , in a next step S 505 , it is determined whether or not a plurality of juxtapositional images exist. If the plurality of juxtapositional images do not exist (NO), the general image correction preprocess (step S 200 ) of the flowchart of  FIG. 2  is performed. 
     In contrast, if the plurality of juxtapositional images exist (YES), the sample image data generating process (step S 100 ) of the flowchart of  FIG. 3  is performed so as to generate the sample image data and then the processes from the step S 506  to the step S 509  are performed. By the processes from the step S 506  to the step S 509 , it is possible to suppress the increase in the image processing time even when the image corrected by the different correction condition with respect to one image is printed on one page in plural numbers. 
     First, the statistical value computing process is performed in the step S 506 . This process is equal to the step S 201  ( FIG. 2 ). Next, in a step S 507 , a process of duplicating and storing the statistical value computing result by the number of juxtapositional images is performed. The statistical value computing result is stored without duplication in the step S 202  ( FIG. 2 ). However, in this process, since the number of juxtapositional images is two, one juxtapositional image is duplicated and a total of two statistical value computing results is stored in a predetermined storage region of the data memory  55 . 
     Next, in a step S 508 , a process of acquiring the correction contents of the images is performed. In the present embodiment, it is assumed that the user of the printer  10  inputs the brightness of the images as the correction contents using the manipulation button  12  of the printer  10 . The correction contents are input such that the brightness of the image IMD 1  is corrected to “brighter”, the brightness of the image IMD 2  is corrected to “bright”, the brightness of the image IMD 3  is corrected to “standard”, and the brightness of the image IMD 4  is corrected to “darker” and the controller  51  acquires the correction contents of the images. 
     Subsequently, in a step S 509 , the correction amounts of the images of the extraction image data are calculated using the plurality of stored statistical value computing results. At this time, since the statistical value computing results are duplicated by the number of juxtapositional images, the process of calculating the correction amounts of the juxtapositional images may be simultaneously performed. Since the sample image generating process of the step S 100  shown in  FIG. 3  does not need to be performed plural times (two times), it is possible to suppress the increase in the processing time and reduce the processing load. 
     In the present embodiment, first, the process of calculating the correction amounts of the image IMD 1  and the image IMD 2  which are juxtapositional images is performed. In more detail, the process of calculating the correction amount of the image IMD 1  of which the brightness is corrected to “brighter” and the process of calculating the correction amount of the image IMD 2  of which the brightness is corrected to “bright” are simultaneously performed. Next, the process of calculating the correction amounts of the image IMD 3  and the image IMD 4  is performed. At this time, since the process of calculating the correction amounts of all the lines is finished with reference to the image IMD 1  and the image IMD 2 , two duplicated statistical value computing results can be used. That is, the process of calculating the correction amount of the image IMD 3  of which the brightness is corrected to “standard” and the process of calculating the correction amount of the image IMD 4  of which the brightness is corrected to “darker” are simultaneously performed. 
     When the correction amounts of the juxtapositional images are simultaneously calculated, the extraction image data can be simultaneously corrected with respect to the lines included in the band data of the juxtapositional images in the print data output process of the step S 300 . Accordingly, in the print data output process of the step S 300  of  FIG. 5 , the image data correcting process of each line of  FIG. 2  is simultaneously with respect to the juxtapositional images. Thereafter, the extraction image data of the juxtapositional images corrected based on the calculated correction amounts is converted into the print data (band data) in the band units and is printed. 
     As a result, as shown in  FIG. 6 , in the process of outputting the band data for printing the image, since the correction image data of the image IMD 1  and the correction image data of the image IMD 2  are substantially simultaneously prepared, the time until the band data is output is substantially equal to the time until the band data is output when the number of images is one even when the number of juxtapositional images to be corrected is increased. Accordingly, it is possible to suppress the time until the printing is started. 
     As described above, according to the present embodiment, when the image to be corrected exists in plural numbers in the direction perpendicular to the transportation direction of the print medium at the time of the printing process, the correction amounts of the images to be printed can be simultaneously calculated on the basis of the characteristic information duplicated and stored by the same number as the number of the existing images. Accordingly, in the process of printing the image on the print medium, the sampling process of acquiring the characteristic information does not need to be repeatedly performed and thus the standby time until the printing is started can be suppressed from being increased. 
     Although the embodiment of the invention is 
     described, the present invention is not limited to the above-described embodiment and may be variously modified without departing from the scope of the present invention. Hereinafter, modified examples will be described. 
     MODIFIED EXAMPLE 
     Although the statistical value computing results are duplicated and stored by the maximum number of juxtapositional images existing on one pager the statistical value computing results may not be stored by the maximum number of juxtapositional images. The present modified example will be described with reference to  FIG. 7 . 
       FIG. 7  is a view showing the case where the layout print having layouts of various application photographs such as passports or driver&#39;s licenses is performed. These layouts are previously stored in the memory of the controller  51  of  FIG. 1  and a layout displayed on the display panel  15  is decided by the selection of the user. The plurality of images shown in  FIG. 7  are subjected to the different correcting processes with respect to the extraction image data because the sizes thereof are different. The correction contents are set as a default value according to the size of a screen. 
     At this time, although three juxtapositional images are extracted, two statistical value computing results are duplicated and a total of three statistical value computing result are always stored in the above-described embodiment, in the present modified example, the three statistical value computing results may not be always stored in order to reduce the stored data amounts. The process of the present modified example will be described. 
     As shown in  FIG. 7 , if the printing process is performed, an image IMD 11 , an image IMD 12  and an image IMD 13  are printed when the band data is in a range H 1 . Accordingly, in the process of calculating the correction amounts, since the process of correcting three pieces of extraction image data needs to be simultaneously performed, the correction amounts of the images are calculated using the three statistical value computing results together. As shown, if the band data is shifted to a range H 2  in the transportation direction of the print medium, since the process of correcting the extraction image data of all the lines is finished with respect to the image IMD 13 , the processes of correcting the two pieces of extraction image data (image IMD 11  and the image IMD 12 ) are simultaneously performed. Accordingly, at this time, the correction amounts of the images are calculated using the two statistical value computing results together. As a result, it is possible to reduce the storage data capacity by erasing one statistical value computing result. If the band data is shifted to the range H 3 , since the process of correcting the extraction image data of all the lines is finished with respect to the image IMD 12 , the process of correcting one extraction image data (image IMD 11 ) is performed. Accordingly, at this time, the process of correcting the image IMD 11  is performed using one statistical value computing result. As a result, it is possible to reduce the storage data capacity by erasing one statistical value computing result. 
     In contrast, if the band data is shifted to a range H 4  to a range H 5 , since the process of correcting two pieces of extraction image data (the image IMD 16  and the image IMD 15 ) is simultaneously performed, one statistical value computing result is duplicated and the correction amounts of two images IMD 16  and IMD 15  are calculated using the duplicated statistical value computing result. It the band data is shifted from the range H 5  to a range H 6 , since the process of correcting three pieces of extraction image data (the image IMD 16 , the image IMD 15  and the image IMD 14 ) is simultaneously performed, one statistical value computing result is duplicated and the correction amounts of the three images IMD 16 , IMD 15  and IMD 14  are calculated using the three statistical value computing results, 
     According to the present modified example, since the number of stored statistical value computing results is increased/decreased according to the range of the output band data, the statistical value computing result may not be always stored by the maximum number of juxtapositional images. As a result, it is possible to reduce the storage data capacity. 
     Although the statistical value computing result is stored by the maximum number of juxtapositional images and the correction amounts of the juxtapositional images are simultaneously calculated using the stored statistical value computing results, the present invention is not limited to this. For example, one statistical value computing result may be stored regardless of the number of juxtapositional images. In this case, since one statistical value computing result is repeatedly used by the number of juxtapositional images, for examples the method o f accessing the statistical value computing result is performed in serial and a time consumed for the process of calculating the correction amounts is required, but the sample image data generating process of the step S 100  shown in  FIG. 3  is performed one time. The storage capacity of the statistical value computing result may be decreased. Accordingly, although the processing time is increased in the above-described embodiment, the number of times of the sample image data process is increased. Accordingly, even when a plurality of correction images are printed, it is possible to suppress the increase in whole processing time. 
     Although the print data is output in the band units in the above-described embodiment, the present invention is not limited to this. For example, the print data may be output in the units of one page. In this case, since the process of calculating the correction amounts of the juxtapositional images can be simultaneously performed with respect to the images printed on one page, it is possible to suppress the increase in time until the print data of one page is output although the number of images to be printed is increased. 
     Although the image processing apparatus is mounted in the printer in the above-described, the image processing apparatus is not mounted in the printer and may be mounted in a separate apparatus. For example, in  FIG. 1 , the controller  51 , the image processor  52 , the data memory  55  and the interface unit  57  functioning as the image processing apparatus may be mounted in an apparatus having a computer function such as a personal computer. In this case, it is preferable that the apparatus in which the image processing apparatus is mounted includes a unit for inputting the compression data of the image.