Abstract:
A character-recognition device and method for imaging a character string, generating a grayscale image that corresponds to the character string, cutting out, from the grayscale image, individual characters in the character string, obtaining a coincidence of a character image that is being focused on for each of model images of a plurality of kinds of characters by sequentially focusing on cut-out character images to match the cut-out character images against the model images, and recognizing characters corresponding to the cut-out character images based on each coincidence.

Description:
TECHNICAL FIELD 
     One or more embodiments of the present invention relate to character-recognition processing performed using image processing, particularly to a technology for recognizing a composite character including a pair of character elements arrayed in a width direction. 
     BACKGROUND ART 
     In the character-recognition processing, generally individual characters are cut out from a grayscale image generated by imaging a character string, and matching processing (model matching) is performed to each cut-out character using various character models to recognize a content of the character string. In the character cutting out processing, binarized data or grayscale data of the processing target image is projected to x- and y-axis directions, a portion corresponding to the character is extracted from a projection pattern generated on each axis, thereby specifying a region (hereinafter referred to as a “character region”) corresponding to the individual characters. 
     In order to ensure accuracy of the matching processing, it is necessary to specify the character region in each recognition target character. However, in a composite character having a configuration in which independent character elements are arrayed in a width direction corresponding to the character string, sometimes the character elements are individually cut out to perform false matching processing. 
     Therefore, Patent Document 1 describes that, in the case that a character candidate having high reliability for a left-hand side of a previously-learned Chinese character is extracted, the false cutout is determined to be performed, and a character candidate suitable for the left-hand side of the Chinese character and a next character candidate are newly cut out as one character (see Paragraph No. 0033 and the like). 
     In the description of Patent Document 2, after the cutout of the character, tentative matching processing is performed to calculate matching reliability, a standard character length of a full-width character is decided based on the character candidate satisfying a condition that the matching reliability is greater than or equal to a predetermined reference value, all the characters of the recognition targets are cut out based on the recognized standard character length to perform final matching processing (see claim  1  and the like). Additionally, in the case that the character (for example, the Chinese characters “           ” produced by a combination of “         ” and “         ”) produced by a combination of two component characters is extracted in the tentative matching processing, the character is not used to decide the standard character length (see Paragraph Nos. 0015 to 0022, 0061 to 0068, 0089, and the like).
     Patent Document 1: Japanese Unexamined Patent Publication No. 1997-282417 
     Patent Document 2: Japanese Unexamined Patent Publication No. 2010-44485 
     SUMMARY OF THE INVENTION 
     Patent Document 2 suggests that it is unclear whether the combination of a pair of character elements (such as “           ” and “         ” of the Chinese characters) expresses one character or two characters. In the composite character produced by the combination of the character elements each of which can be solely recognized as the character, there is a high risk of overlooking the false recognition because coincidence increases in the case that each character element is individually recognized.
     However, Patent Document 1 only proposes a thought that failure in cutting out the character is recognized to perform the cutout processing again based on a feature of one of the character elements. 
     According to the description of Patent Document 2, when a width of the combination of the two character elements comes close to a standard character width, the combination is cut out as one character. However, there is a possibility of generating the false recognition when the character-recognition method described in Patent Document 2 is applied to a character string of European characters for example, which has a large variation in character size. The character-recognition method described in Patent Document 2 is not used in the case that the composite character is solely the recognition target. 
     One or more embodiments of the invention accurately recognizes the composite character without being influenced by the coincidence obtained by performing matching solely for the individual character element or the variation in size of the individual character element. 
     One or more embodiments of the invention is directed to a character-recognition method for cutting out individual characters in a character string from a grayscale image generated by imaging the character string, obtaining a coincidence of a character image being focused for each of model images of a plurality of kinds of characters by sequentially focusing on cut-out character images to match the cut-out character images against the model images, and recognizing characters corresponding to the cut-out character images based on each coincidence. 
     One or more embodiments of the invention is directed to a composite character model image constructed with a pair of character elements arrayed along a width direction registered while predetermined identification information is provided to the composite character model image. 
     In matching processing using the model image including the identification information, composite matching in which an image of a range including the character image being focused and an adjacent unprocessed character image is matched against the model image including the identification information is performed. A combination of the two character images included in the composite matching target range is recognized as a character corresponding to the matched model image including the identification information when the coincidence obtained by the composite matching is larger than a predetermined reference value. 
     For example, in the case that a horizontal character string is the recognition target, the composite character model image is registered with respect to a character having a configuration in which a pair of character elements is horizontally arrayed. In the character-recognition processing, after the characters are cut out, the matching processing against the model images of various characters is performed sequentially focusing on the cut-out characters along the character string. In this case, the image of the range including the character image being focused and the adjacent unprocessed character image is set to the matching target in the composite matching. 
     The coincidence is supposed to decrease when the combination of the character images in the composite matching target range does not correspond to the composite character, and the high coincidence is considered to be obtained when the combination of the two character images corresponds to the composite character. 
     Therefore, even if each character element of the composite character is independently matched against the model image to obtain the high coincidence for a model image of a character having a similar shape, because the composite matching result is preferentially used, the false recognition of the composite character can be prevented. 
     According to one or more embodiments of the invention, in the character-recognition method, in the matching processing against the model image including the identification information, single matching in which only the character image being focused is matched against the model image including the identification information is performed, and the composite matching is performed at least when the coincidence obtained by the single matching is lower than the reference value. Only the character image being focused is recognized as the character indicated by the model image including the identification information when the coincidence obtained by the single matching is larger than the reference value, and the combination of the two character images included in the composite matching target range is recognized as the character indicated by the model image including the identification information when the coincidence obtained by the composite matching is larger than the reference value. 
     Accordingly, in the case that each character element of the composite character is cut out as one character image, the coincidence of the single matching increases, and the recognition result is used based on the single matching, so that the composite character can correctly be recognized. In the case that each character element of the composite character is cut out as the individual character image, the recognition result is used based on the composite matching, so that each character element can be prevented from being recognized as the independent character. 
     A character-recognition device according to one or more embodiments of the invention includes: an image input unit configured to input as a recognition target a grayscale image generated by imaging a character string; a model storage unit in which model images of a plurality of kinds of characters are registered; a character cutout unit configured to cut out individual characters in the character string from the grayscale image input by the image input unit; a recognition unit configured to obtain a coincidence of a character image being focused for each of the plurality of model images registered in the registration unit by sequentially focusing on cut-out character images to match the cut-out character images against the model images, and recognize characters corresponding to the cut-out character images based on each coincidence; and an output unit configured to output as a recognition result a character string in which the characters recognized with respect to the cut-out character images by the recognition unit are arrayed. 
     In order to realize the above recognition method, the character-recognition device further includes a registration processing unit configured to register to the model storage unit a composite character model image constructed with a pair of character elements arrayed along a width direction while predetermined identification information is provided to the composite character model image. The recognition unit includes a function of, in matching processing against the model image including the identification information, performing composite matching in which an image of a range including the character image being focused and an adjacent unprocessed character image is matched against the model image including the identification information, and the recognition unit is configured to recognize a combination of the two character images included in the composite matching target range as a character corresponding to the matched model image including the identification information when the coincidence obtained by the composite matching is larger than a predetermined reference value. 
     According to one or more embodiments of the invention, in the character-recognition device, the registration processing unit is configured to display a candidate character image to be registered in the model storage unit or the already-registered model image, and receive operation to select a target image to be registered as the composite character model image. The registration processing unit is configured to switch the display of the selected image to identification display with a predetermined identification mark and register the selected image in the model storage unit while providing the identification information to the selected image. 
     Accordingly, the user can assign the composite character necessary for the recognition and register the composite character as the composite character model image. 
     One or more embodiments of the invention further provides a program configured to operate a computer as the character-recognition device is provided. 
     According to one or more embodiments of the invention, the composite character constructed with the pair of character elements arrayed along the width direction can accurately be recognized without being influenced by the coincidence obtained by independently matching each character element against the model image or the size of the character element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating a configuration of a character-recognition device according to one or more embodiments. 
       FIGS.  2 ( 1 ) and  2 ( 2 ) are diagrams illustrating a screen displayed in character-recognition processing together with a change of display according to the processing according to one or more embodiments. 
         FIG. 3  is a flowchart illustrating a procedure of the character-recognition processing according to one or more embodiments. 
         FIG. 4  is a diagram illustrating concepts of lines set for projection processing to a direction along a character string according to one or more embodiments. 
         FIG. 5  is a diagram illustrating a method for setting a reference straight line with respect to a projection pattern according to one or more embodiments. 
         FIG. 6  is a flowchart illustrating a detailed procedure of the projection processing (Step S 5  in  FIG. 3 ) to the direction along the character string according to one or more embodiments. 
         FIG. 7  is a diagram illustrating an example in which the composite character is erroneously recognized according to one or more embodiments. 
         FIG. 8  is a diagram illustrating an example of a screen used to register a composite character model according to one or more embodiments. 
         FIG. 9  is a flowchart illustrating a procedure of matching processing according to one or more embodiments. 
         FIG. 10  is a flowchart illustrating a procedure subsequent to that in  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION 
     In embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one with ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid obscuring the invention.  FIG. 1  illustrates a configuration example of a character-recognition processing device according to one or more embodiments of the present invention. 
     The character-recognition processing device images a character string, reads a character in a generated image, and outputs a read result. The character-recognition processing device includes main body  1  provided with controller  10 , camera  2  capturing the image, display  3 , and operating unit  4 . For example, display  3  is constructed with a liquid crystal monitor, and operating unit  4  includes a mouse and a keyboard. 
     Main body  1  is a general-purpose computer device (personal computer), and includes controller  10  provided with a CPU, main storage  11 , image memory  12 , imaging interface  13 , display interface  14 , input interface  15 , external interface  16 , and external disk read unit  17 . 
     For example, main storage  11  is a hard disk, and image memory  12  is a RAM board. A dedicated program read from external disk  18  by external disk read unit  17  and a font data used in character-recognition processing are registered in main controller  11 . The image output from camera  2  is taken in imaging interface  13 , and subjected to digital conversion. Then converted image data is stored in image memory  12 . 
     The program stored in main storage  11  sets to controller  10  a function of cutting out the character from the image stored in image memory  12  one by one and a function of recognizing a content of the cutout character. A function as a graphical user interface presented to a user through the pieces of processing is also set to controller  10 . By the graphical user interface function, controller  10  displays a screen including a processing target image on display  3  through display interface  14 , and receives operation of operating unit  4  through input interface  15 . 
     According to one or more embodiments of the invention, in the character-recognition processing device, the operation to issue an instruction to read the character is received on the screen in which the processing target image is displayed, the character in the image is recognized by processing in  FIG. 3 , and a recognition result is displayed on the screen. The recognition result may be output to an external device through external interface  16 . 
     FIGS.  2 ( 1 ) and  2 ( 2 ) illustrate an example of the screen displayed on display  3  for the purpose of the character-recognition processing. 
     Screen  30  in FIGS.  2 ( 1 ) and  2 ( 2 ) includes display field  31  for the character string of the recognition target image, display field  32  for an analysis result, read button  33 , and model registration button  34 . In FIGS.  2 ( 1 ) and  2 ( 2 ), it is assumed that shading is generated in a right end portion of the image, and the shade is expressed by a hatched line. 
     FIG.  2 ( 1 ) illustrates the screen before start of read processing. Rectangular frame  35  indicating a processing target region set by the user is displayed in the image of image display field  31 . The user decides a position and a size of rectangular frame  35  by mouse operation and the like to set the processing target region, and operates read button  33 . By this operation, controller  10  recognizes a region corresponding to rectangular frame  35  as the processing target region, performs character-recognition processing (including character cutout processing and matching processing) to the image in the region, and changes the screen as illustrated in FIG.  2 ( 2 ). 
     After the character-recognition processing, in image display field  31  of screen  30 , each character is surrounded by frame  36  indicating a character region specified by the character cutout processing. The character read from the image in each frame  36  is displayed at the upper left of frame  36 . The character string derived from the recognition results of respective character regions is displayed as a read result in a margin on the right of image display field  31 . A name (F1) of a font most suitable for the character string is displayed below the character string. 
     Projection pattern P generated by projection processing for cutting out the character is displayed in blank display field  32  for the analysis result together with straight line M (hereinafter referred to as a “reference straight line M”) set as a cutout reference. 
     The character-recognition processing will be described in detail on the assumption that the recognition target is the horizontal character string in which the characters are darker than a background. 
       FIG. 3  illustrates a schematic procedure of the character-recognition processing performed by controller  10 . 
     The processing target region is set on the screen in FIGS.  2 ( 1 ) and  2 ( 2 ), and the character-recognition processing is started in response to the operation of read button  33 . Initially, controller  10  acquires the image in the processing target region based on positional information on rectangular frame  35  (Step S 1 ). 
     In FIGS.  2 ( 1 ) and  2 ( 2 ), the range including the character string of single row is assigned by way of example. However, actually the range including the character strings of a plurality of rows are sometimes assigned. In consideration of this point, in step S 2 , the projection processing is performed to a y-axis, and the character strings of a plurality of rows are segmented into each row by the generated projection pattern (Step S 2 ). 
     The segmented character strings are sequentially set to the processing target to perform pieces of processing from Step S 4 . 
     In Step S 4 , upper limit y 1  and lower limit y 2  of a processing range on the y-axis are set based on the result of the character string segmenting processing (y-coordinates slightly outside the range determined to be the character string are set to y 1  and y 2 ). In Step S 5 , the projection processing is performed to an x-axis with respect to the image in the range from y 1  to y 2 . 
     When the projection pattern along an x-axis direction is generated by the above processing, a local maximum and a local minimum are extracted from the projection pattern in Step S 6 , and a straight line approximate to a local maximum distribution and a straight line approximate to a local minimum distribution are derived in Step S 7 . In Step S 8 , based on the two approximate straight lines, reference straight line M is set in order to specify a cutout target range. 
     In Step S 9 , each value in the projection pattern is matched against reference straight line M to specify the cutout target range. In each cutout target range, based on the x-coordinates on the right and left edges of the cutout target range and coordinates y 1  and y 2  indicating processing target range on the y-axis, the character region is extracted (Step S 10 ), and matching processing is performed using character models (character image models) included various pieces of font data (Step S 11 ). 
     Then, the flow returns to Step S 3 , and the pieces of processing in Steps S 4  to S 11  are performed to an unprocessed character string when the unprocessed character string exists (“NO” in Step S 3 ). When all the character strings are processed (“Yes” in Step S 3 ), the flow goes to Step S 12  to output the recognition result. The processing instructed by the user is ended when the recognition result is output. 
     In the projection processing performed to the y-axis (Step S 2 ) in the above pieces of processing, a minimum density is projected for every line along the x-axis in the processing target region. Therefore, the density of the character image is projected from the line including any character image, and the density of the background is projected only from the line not including the character image, so that the range including the whole character string can accurately be extracted in a y-axis direction. 
     In the projection processing performed to the x-axis along the character string (Step S 5 ), each of a plurality of lines having different gradients are set at a projection target position, the minimum density of each line is extracted, and a maximum value in the extracted minimum density is used as a projection value.  FIG. 4  illustrates a line setting method. In  FIG. 4 , xi is an x-coordinate of the projection target position, and y 1  and y 2  are an upper limit and a lower limit (obtained in Step S 4 ) of the processing range on the y-axis. 
     Concepts of the projection lines set to coordinate xi will be described with reference to  FIG. 4 . Each line generated by rotating line L 0 , which passes through coordinate xi and is parallel to the y-axis, about a midpoint between a point (xi, y 1 ) and a point (xi, y 2 ) within a predetermined angle α on either side is the projection line with respect to coordinate xi. In an algorithm performed by controller  10 , maximum value Dα of distance d is set instead of angle α because the gradient of the line is changed using distance d from coordinate xi at positions y 1  and y 2  of the processing target range in the y-axis direction. 
     In the case that only the line L 0  along the y-axis is set to the projection direction like in usual projection processing, as illustrated in  FIG. 4 , sometimes a gap between the characters is narrow, the adjacent character projects partially in the narrow gap, and the projecting portion gets on line L 0 . Accordingly, the density of the character is projected to coordinate xi in  FIG. 4 , when the minimum density in line L 0  along the y-axis is projected to coordinate xi based on the same technique as in the projection processing performed to the y-axis. 
     Therefore, according to one or more embodiments of the invention, the lines having various gradients are set, the minimum density is extracted in each line, and the maximum value in the extracted density is used as the projection value with respect to coordinate xi. In the image in which the background is brighter than the character, because the minimum density extracted on the line passing only through the gap is the maximum like in line L 2  in  FIG. 4 , the minimum density being the maximum is projected to coordinate xi. Therefore, the density of the gap between the characters is reflected to generate the projection pattern in which a portion corresponding to the character constitutes a valley while a portion corresponding to the gap constitutes a peak. 
       FIG. 5  illustrates an example (a horizontal axis indicates the x-coordinate and a vertical axis indicates the density) of projection pattern P generated by the projection processing together with a method for setting reference straight line M with respect to a projection pattern. 
     M 1  and M 2  in  FIG. 5  are the approximate straight lines obtained in Step S 7  of  FIG. 3 . As described above, straight line M 1  approximate to the change of the local maximum and straight line M 2  approximate to the change of the local minimum in the projection pattern are obtained in Step S 7 . In Step S 8 , for example, the x-coordinate is moved one by one to combine the points being focused corresponding to the x-coordinates of straight lines M 1  and M 2 , a midpoint between these points is obtained by an average value of the densities at the points, a third straight line approximate to the distribution of the midpoints is set, and the third approximate straight line is used as reference straight line M. 
     The method for setting reference straight line M is not limited to the above method. For example, with respect only to coordinates x 1  and x 2  at both ends of the processing target region, after a midpoint between a corresponding point on straight line M 1  and a corresponding point on straight line M 2  is obtained, the midpoints may be connected to each other to set reference straight line M. Alternatively, based on the patterns of the local maximum and local minimum distributions, a height and the gradient of straight line M may be decided without setting straight lines M 1  and M 2 . 
     Because the projection pattern in  FIG. 5  is identical to that of field  32  in FIG.  2 ( 2 ), the description is made with reference to FIG.  2 ( 2 ). According to one or more embodiments of the invention, because the shading is generated at the end edge on the right in the recognition target image, the peak in projection pattern P decreases toward the right from the left, and a difference in density between the peak and the valley expressing the character also decreases. However, reference curve M also inclines toward the lower right from the upper left according to the density change, and reference straight line M is located at the position where the peak reflecting the gap and the valley reflecting the character can be segmented even in the area where the shading is generated. Therefore, based on reference straight line M, the range corresponding to individual characters can be cut out with no influence of the density change caused by the shading. 
       FIG. 6  illustrates a detailed procedure of the projection processing (corresponding to Step S 5  in  FIG. 3 ) with respect to the x-axis. The procedure of the projection processing will be described with reference to  FIG. 6  together with  FIGS. 4 and 5 . 
     In  FIG. 6 , similarly to the example in  FIG. 4 , it is assumed that xi is the coordinate at the projection target position on the x-axis. X-coordinate x 1  at the left end edge of the processing target region is set to xi as an initial value (Step S 101 ). Until xi becomes x-coordinate x 2  at the right end edge of the processing target region, the following processing is performed while xi is moved pixel by pixel (Steps ST 110  and ST 111 ). 
     In Step S 102 , initial value of −Dα is set to displacement amount d while the initial value of 0 is set to maximum value MAX of the minimum density. Assuming that Dα is a positive value, the initial value of displacement amount d is a negative value. 
     A line connecting coordinate (xi+d, y 1 ) and coordinate (xi−d, y 2 ) is set in Step S 103 . According to the initial values of coordinate xi and displacement amount d set in Steps S 101  and S 102 , the initially-set line is line L 1  in  FIG. 4 . On the other hand, line L 2  in  FIG. 4  is set for d=Dα. 
     Displacement amount d is incremented by one until displacement amount d becomes Dα (Steps S 107  and  108 ), and the processing in Step S 103  is performed to displacement amount d in each time, whereby the line having the different gradient is set in each time within the range from line L 1  to line L 2 . Minimum density Imin in the set line is extracted in Step S 104 . In the case that Imin exceeds maximum value MAX, maximum value MAX is rewritten by Imin (Steps S 105  and S 106 ). In the case that Imin is less than or equal to maximum value MAX (“NO” in ST 105 ), maximum value MAX is maintained at a present value. 
     Thus, the plurality of lines having the different gradients are set to one point xi of the projection target, the minimum density is obtained in each line, and maximum value MAX is extracted in the minimum densities. When the processing is completed to all the lines (“Yes” in Step S 108 ), maximum value MAX at that time is set to projection value of coordinate xi (Step S 109 ). 
     The processing is performed to coordinate xi of each time, and xi is set to x 2  of an end point to end the setting of the projection value, whereby an affirmative determination is made in Step S 111  to end the projection processing. 
     On the other hand, in the case that the image in which the character is brighter than the background is set to the processing target, the maximum density is extracted in each line, and the minimum value in the extracted densities is selected as the projection value. The projection pattern in which the portion corresponding to the character constitutes the peak while the portion corresponding to the gap constitutes the valley is generated. Similarly to the technique in  FIG. 5 , two approximate straight lines M 1  and M 2  are set to the projection pattern, and reference straight line M is set at an intermediate position between straight lines M 1  and M 2 . At the same time, the cutout target range is set to a range where the density is higher than that of reference straight line M in the projection pattern. 
     A character-recognition processing program registered in main storage  11  in  FIG. 1  is set so as to perform the processing to the image in which the character is darker than the background. Alternatively, a program to perform the processing to the image in which the character is brighter than the background may be also incorporated, and which one of the programs may be used to perform the character-recognition processing according to the user selection. 
     According to one or more embodiments of the invention, reference curve M is set around the middle of the range of the local maximum distribution and the range of the local minimum distribution. Alternatively, the height of reference straight line M may be adjusted by a previously-set offset value. 
     According to one or more embodiments of the invention, on the screen in FIGS.  2 ( 1 ) and  2 ( 2 ), the user can also perform drag operation of the reference straight line in field  32  to change the height or the gradient of reference straight line M. Therefore, for failure in performing the processing of automatically cutting out the character, after changing reference straight line M based on a relationship between the peak and the valley of the projection pattern in field  32 , the user can obtain the correct recognition result by operating read button  33  again. 
     As described above, according to one or more embodiments of the invention, when the narrowest gap exists between the characters, the gap and the characters can accurately be segmented from each other. However, in the case that the composite character including the two character elements horizontally arrayed with the gap is recognized, each character element is individually cut out, and the matching processing is performed in each character element. Additionally, as illustrated in  FIG. 7 , in a case where both the right and left character elements can independently be recognized as characters, because of a false recognition with a high coincidence in the matching processing, it is difficult to overlook the false recognition. 
     Therefore, according to one or more embodiments of the invention, an identification flag is set to the character model of the composite character including the character elements horizontally arrayed with the gap, the character model for the composite character is distinguished from the general character model using the identification flag, and the processing having a different content is performed depending on the type of the model in the matching processing. 
       FIG. 8  illustrates an example of the screen used to set a model for the composite character (hereinafter referred to as a “composite character model”). According to one or more embodiments of the invention, using the character models of various pieces of font data stored in main storage  11 , controller  10  produces a list of character models registered as a special character, and displays setting screen  40  in  FIG. 8  on display  3 . Window  41  in which a list of special characters is displayed is arranged in a central portion of setting screen  40 , and registration button  42  and the like are provided in the margin. 
     When the user performs click operation on a certain character in the list, vertical bar VP having a high-brightness color is displayed in the central portion in a horizontal width direction of the character. Vertical bar VP is a mark indicating that the character is selected as a candidate of a composite character model. However, a composite character flag is not set at this stage. Vertical bar VP disappears when the user performs the click operation again. 
     Using the workings, the user selects the character model that needs to be registered as the composite character model from the characters displayed in window  41 , and the user operates registration button  42  after confirming a selection status based on the display of vertical bar VP. In response to the operation of registration button  42 , a flag (hereinafter referred to as the “composite character flag”) indicating the composite character is set to the selected character model. Message  43  indicating that the registration is completed is displayed in the lower portion of the screen. 
     Vertical bar VP is merely a mark, and is only to be set in the central position in the horizontal width of the selected character model. Accordingly, a mark in another form may be displayed instead of vertical bar VP. 
     The image registered as the composite character model is not limited to the font data. For example, a composite character included in an image of a print of a recognition target may be cut out and registered by the user operation. However, in this case, it is necessary to adjust a scale factor of the composite character model according to the size of the font data in the registration destination. 
     The processing of setting the composite character flag is not limited to one that is performed in response to the user operation. For example, controller  10  may analyze the font data to extract a character model having a horizontally-separated form, and set a composite character flag to the extracted character model. Alternatively, dictionary data of composite character models produced by a developer may properly be installed on main storage  11 . 
       FIGS. 9 and 10  illustrate a detailed procedure of the matching processing (corresponding to Step S 11  in  FIG. 3 ) in which a character model group including a composite character model is used. 
     In the matching processing, the character regions extracted by the pieces of processing up to Step S 10  in  FIG. 3  are focused on one by one along the character string. The initial value of 1 is set to counter k indicating a character region to be focused (Step S 201 ), and image G k  of a kth character region is acquired (Step S 202 ). Hereinafter, image G k  is referred to as character image G k . 
     The initial value of 1 is set to counter j specifying a matching target model (Step S 203 ), and jth character model M j  is read (Step S 204 ). Character model M j  and character image G k  are matched against each other to calculate the coincidence therebetween (Step S 205 ). The calculated coincidence is compared to predetermined reference value R (Step S 206 ). In Step S 205 , the scale factor of character model M j  is changed in a plurality of ways, the matching processing is performed in each scale factor, and the highest coincidence is used. 
     When the coincidence is greater than or equal to R (“Yes” in Step S 206 ), matching result information (such as an identification code of character model M j  used in the matching, the coincidence, and the scale factor of model M j  at the time the coincidence is obtained) indicating the content of the matching is stored (Step S 207 ). When the coincidence is less than R (“NO” in Step S 206 ), the flow goes to Step S 208  without storing the matching result information. 
     At this point, controller  10  checks whether the composite character flag is set to character model M j . When the composite character flag is set (“Yes” in Step S 208 ), the flow goes to Step S 209  to extract an image of a range including character image G k  and image G k+1  (a character image that is located adjacent to character image G k  and on which the character recognition is not performed yet) in (k+1)-th character region. The extracted image is matched against character model M j  to calculate the coincidence therebetween (Step S 210 ), and the coincidence is compared to reference value R (Step S 211 ). In Step S 210 , similarly to Step S 205 , the scale factor of character model M j  is changed in a plurality of ways, the matching processing is performed in each scale factor, and the highest coincidence is used. 
     When the coincidence is greater than or equal to reference value R (“Yes” in Step S 211 ), the matching result information is stored (Step S 212 ). In this case, the performance of composite matching covering the range to the adjacent character image G k+1  is written as the matching result information in addition to the identification code of character model M j , the coincidence, and the scale factor. 
     Character model M j  of the matching target is changed by updating counter j until the matching against all the character models set as the matching target is ended (Steps S 213  and  214 ), and the similar processing is performed to each character model M j . A list of character models in which the coincidence of at least reference value R is obtained with respect to the character region being focused is produced based on the matching result information stored during the processing. 
     Subsequent matching processing will be described with reference to  FIG. 10 . 
     When the processing with a final character model is ended, controller  10  checks whether the information indicating that the coincidence of at least R 0  higher than reference value R is obtained by the matching against the composite character model exists in the stored matching result information (Step S 215 ). When the information concerned is found (“Yes” in Step S 215 ), controller  10  analyzes the matching result information to check whether the information indicates that character image G k  is solely matched against the composite character model (Steps S 216  and S 217 ). When character image G k  is not solely matched against the composite character model, but the range including adjacent character image G i+1  is matched against the composite character model to obtain the coincidence of at least R 0  (“NO” in Step S 217 ), the character indicated by the composite character model is applied to the combination of G k  and G k+1  (Step S 218 ), and 2 is added to counter k (Step S 219 ). 
     When the analyzed matching result information indicates that character image G k  is solely matched against the composite character model to obtain the coincidence of at least R 0  (“Yes” in Step S 217 ), the character indicated by the composite character model is applied only to the character image G k  (Step S 220 ), and 1 is added to counter k (Step S 221 ). 
     When the composite character model in which the coincidence of at least R 0  is obtained does not exist (“NO” in Step S 215 ), the character model in which the highest coincidence is obtained is specified (Step S 222 ). 
     When the specified character model is the composite character model (“Yes” in Step S 223 ), the similar procedure as described above is performed in Steps S 217  to S 221 . In the case that the highest coincidence is obtained when the range including character image G k  and adjacent character image G k+1  is matched against the composite character model, the character indicated by the composite character model is applied to the combination of character images G k  and G k+1  (Step S 218 ). In the case that the highest coincidence is obtained when character image G k  is solely matched with the composite character model, the character indicated by the composite character model is applied to character image G k  (Step S 220 ). 
     When the highest coincidence is obtained for the general character model (“NO” in Step S 223 ), the pieces of processing in Steps S 220  and S 221  are performed. Therefore, the character indicated by the general character model having the highest coincidence is applied to character image G k . 
     As described above, in the case that the coincidence of at least R 0  is obtained by the matching against the composite character model or in the case that the coincidence for the composite character model is higher than that for the general character model, the matching result obtained using the composite character model is preferentially used. In the case that the matching result used indicates that the matching is performed to the range including character image G k  of the processing target and the adjacent unprocessed character image G k+1 , after the character indicated by the composite character model is applied to the combination of character images G k  and G k+1 , 2 is added to counter k in Step S 219 . Character image G k+1  is recognized together with character image G K  by the count processing in Step S 219 . 
     According to the above processing, even if the composite character is cut out while horizontally separated, the high-accuracy matching processing can prevent the false recognition. Particularly, the recognition accuracy can considerably enhanced in recognizing the composite character having the form partially matched with a combination in (DZ) of general characters as illustrated in  FIG. 7 . 
     According to one or more embodiments of the invention, both the single matching intended only for the character image G k  being focused and the composite matching intended for the rangecluding character image G k  and adjacent unprocessed character image G k+1  are performed in the matching processing using the composite character model image. Alternatively, the composite matching may be performed only when the coincidence obtained by the single matching is lower than reference value R 0 . 
     According to one or more embodiments of the invention, the character is cut out by the technique of projecting the minimum density within the projection target line. The similar matching processing can be applied when the character is cut out by general projection processing. 
     While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims. 
     DESCRIPTION OF SYMBOLS 
       1  main body 
       2  camera 
       3  display 
       4  operating unit 
       10  controller 
       11  main storage 
       40  screen