JP2014056321A - Image processor and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the difference in thickness between characters without losing a shape representing a character possessed by the character.SOLUTION: An image processor determines a character thickness value for each of a plurality of character groups within an image, and sets a value between the maximum value and the minimum value of the character thickness values as an object value for both of a thinning correction and a thickening correction. The image processor performs the thinning correction with respect to a thick character group whose character thickness value is larger than the object value in such a manner that a thinning amount is not beyond both of the difference between the character thickness value of the thick character group and the object value, and a thinning limitation amount which is the maximum thinning amount within a range in which the character does not lose a shape representing the character, and performs the thickening correction with respect to a thin character group whose character thickness value is smaller than the object value in such a manner that a thickening amount is not beyond both of the difference between the character thickness value of the thin character group and the object value, and a thickening limitation amount which is the maximum thickening amount within a range in which the character does not lose a shape representing the character.

Description

  The present invention relates to image processing for a part representing a character in an image.

  Patent Document 1 discloses image processing for changing the size and thickness of characters in a raster image. The raster image, which is the object of image processing in this document, is an edited image in which a character string (name of the writer) handwritten in a paper entry frame is read by a scanner, and the read images for four sheets of paper are combined into one. It is. In this edited image, the character is different for each character string and there is no limitation on the type of writing instrument used for the entry. Therefore, the character size and the character thickness of the four character strings are inevitably nonuniform. In view of the orderliness of a plurality of character strings, this document describes a line in which the character size is aligned to a predetermined size that can be accommodated in an entry frame, and the line width of an excessively thin character is gradually increased so as to be within an allowable range. It is described that the width adjustment is performed. When the character is crushed in the line width adjustment, the line width immediately before the crushed is taken as the adjusted line width.

JP 2006-157771 A

  The line width adjustment for thickening thin characters in the prior art described above is performed regardless of the thick characters, and ends when the line width reaches a value within the allowable range. By this line width adjustment, the difference in character thickness between a thick character and a thin character is reduced to some extent.

  However, when a thick character having a line width significantly larger than the lower limit of the allowable range exists in the image to be processed, the unevenness of the character thickness becomes conspicuous in the image after the line width adjustment is completed. If there is no thin character outside the allowable range, even if the character thickness is non-uniform, it remains uncorrected.

  In view of such circumstances, the present invention provides an apparatus useful for uniformizing the thickness of characters in an image in which a plurality of characters having different thicknesses are arranged so that characters having the same thickness are collected. The purpose is that.

  An image processing apparatus that achieves the above-described object is an image processing apparatus that performs image processing on characters, and that extracts a plurality of character groups that are segmented by arrangement in the image from the image, For each of the plurality of character groups, a means for determining a character thickness value representative of the thickness of the characters belonging to the character group, and a maximum value and a minimum value among the character thickness values determined for the plurality of character groups Means for setting a value between values as a target value for both thinning correction for thinning a character and thickening correction for thickening a character, and the character thickness value of the plurality of character groups For a bold character group that is a character group larger than the target value, the maximum amount of thinning within a range in which the character to be corrected when the thinning correction is performed does not lose the shape representing the character. Means for obtaining a certain amount of thinning, and correction when performing the thickening correction on a thin character group of which the character thickness value is smaller than the target value among the plurality of character groups; Means for obtaining a limit thickening amount that is a maximum thickening amount within a range in which the character representing the character does not lose its shape, and the thinning amount of the bold character group The thinning correction is performed so as not to exceed both the target thinning amount and the limit thinning amount, which are the differences between the character thickness value and the target value, and Means for performing the thickening correction so that the amount of weighting does not exceed both the target weighting amount and the limit weighting amount, which are the difference between the character thickness value of the fine character group and the target value.

  According to the present invention, in an image in which a plurality of characters having different thicknesses are arranged so that characters of the same thickness are gathered, the thickness between the characters is lost without losing the shape representing the characters that the character has. Difference can be reduced.

1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure which shows the example of the preparation point of the table of contents page as an image used as the object of an image process. It is a figure which shows typically the change of the image by character size adjustment. It is a figure which shows typically the change of the image by character thickness adjustment. It is a figure which shows the disadvantage of the excessive thinning correction | amendment with respect to a character, and the excessive fattening correction | amendment. It is a figure which shows the relationship between the character thickness value of a some character group, and the some quantity defined based on them. 4 is a flowchart illustrating a procedure for converting a document into data by the image forming apparatus. It is a flowchart of a character thickness adjustment routine. It is a flowchart of a character size adjustment routine. It is a figure which shows an example of the formation procedure of a table of contents page in case a character color differs between character groups. It is a figure which shows the other example of the color adjustment of a table of contents page.

  An example will be given in which image processing for uniformizing the thickness of characters in a raster image is performed in an image forming apparatus. However, similar image processing can be realized in any device that handles image data.

  An image forming apparatus 1 illustrated in FIG. 1 is a composite information device called an MFP (Multi-functional Peripheral). In addition to functions as an image forming apparatus such as copying and network printing, the image forming apparatus 1 has a function of converting a paper document into data by scanning and transmitting it to an external apparatus or storing it in the apparatus itself.

  When an operation for instructing the start of the data conversion operation for the paper document is performed by the user on the operation panel 6 of the image forming apparatus 1, the ADF (Auto Document Feeder) 4 receives the instruction from the main controller 3 and the sheet of the paper document is received. Is conveyed to the image scanner 5. The image scanner 5 reads an image from the conveyed sheet, and outputs image data of the number of pages corresponding to the number of sheets with one page of the image for one side of the sheet. The data processing circuit 10 converts the image data obtained by the image scanner 5 into a file of a predesignated format such as PDF (Portable Document Format), and delivers it to the main controller 3.

  The main controller 3 transfers the data file as a document to a destination corresponding to the operation designated by the user. When an operation to transmit to an external personal computer or another device is designated, the file is transferred to the communication interface 8 that is responsible for network connection with the outside. When an operation to be stored inside the image forming apparatus 1 is designated, a file is stored in a memory area called a box provided in a hard disk drive as the storage 9.

  When a copy operation for adding a table of contents page is designated, the table of contents page created by the data processing circuit 10 is delivered to the main controller 3 as will be described later. In this case, the main controller 3 converts the image data output from the image scanner 5 and the table of contents page from the data processing circuit 10 into image data in a format suitable for printing and supplies the image data to the printer engine 7. The printer engine 7 prints the given image data. Thereby, a copy of the paper document and a printed matter of the table of contents are formed.

  In such an image forming apparatus 1, the data processing circuit 10 includes a table of contents page creation unit 12 and a character correction unit 13 related to an additional function of document data conversion in addition to the file creation unit 11 that creates the above-described file. .

  The table of contents page creation unit 12 creates a table of contents page 51 that is useful for browsing data-formatted documents. Specifically, the table of contents page creation unit 12 extracts a specific character string (including a case of a single character) such as a title and a heading of the description content from a data document, and the extracted character string is a blank page. Paste to. The number of pages of the table of contents page 51 depends on the number and size of character strings to be extracted. When the table of contents page 51 is added to a page that originally exists in the document, it is easy for the viewer to grasp the outline of the description contents when browsing the document.

  The character correction unit 13 is image processing means for improving the appearance of the table of contents page 51. That is, the character correction unit 13 equalizes the size and thickness of characters in the index page 51 that is a raster image. The table of contents page 53 after the characters are corrected by the character correction unit 13 is sent to the file creation unit 11 and incorporated into the document file.

  FIG. 2 shows an example of how to create a table of contents page. In the illustrated example, four paper documents 41, 42, 43, and 44 created separately are collectively scanned and converted into data as one document 50. Character strings g1, g2, g3, and g4 described at the upper end of each of the four pages (pages 1, 6, 12, and 15) are extracted from the document 50 and inserted before the first page of the document 50. A table of contents page 51 to be added is created. In the table of contents page 51, the character strings g1, g2, g3, and g4 are arranged from top to bottom in the page layout order of the extraction source. A hyperlink that links an extraction source page to an area where each of the character strings g1, g2, g3, and g4 is arranged is provided. With this hyperlink, when browsing the document 50, it is possible to control to switch the display to a page corresponding to the selected area in response to the area selecting operation on the displayed table of contents page 51. The viewer can easily display a desired page.

  Note that what character string is to be extracted from the document 50 may be determined in advance. For example, it is possible to discriminate characters by using a known attribute discriminating method for discriminating between a character region and a graphic region, and to extract a string of characters that are larger, thicker, or different in color than the surroundings. When the style related to the character arrangement is determined, the character string described in the predetermined part may be extracted.

  By the way, according to the technique of cutting out a part from the document 50 that is a set of images for each page and pasting it on a blank page, it is possible to obtain a table of contents page 51 that conveys the character information of the cut out part as it is. That is, the character information is not lost or changed.

  On the other hand, when a method of converting character information held in the document 50 into text data using a character recognition technique such as OCR and extracting a character string from the text data, the correct table of contents is detected due to erroneous character recognition. May not be obtained. The character string to be extracted is not extracted or replaced with another character. In particular, if a character to be extracted is larger than a certain size or has a decorative pattern near the character, erroneous recognition of the character is easy to place. Therefore, from the viewpoint of the accuracy of information as a table of contents, a method of pasting a cut-out image is excellent.

  However, unlike a table of contents consisting of text data in which fonts can be arbitrarily set, in the table of contents page 51 pasted with an image as a character string, the thickness and size of the characters are different among a plurality of character strings. There is. An extreme difference impairs the quality of the table of contents page 51 as character information.

  Therefore, the character correction unit 13 is provided in the data processing circuit 10 of the image forming apparatus 1. The character correction unit 13 performs character size adjustment for making the character size uniform and character thickness adjustment for making the character thickness uniform. As shown in FIG. 3, in the character size adjustment, a relatively large character on the table of contents page 51 is reduced and a relatively small character is increased. By adjusting the character size, a table of contents page 52 with reduced character size non-uniformity compared to the table of contents page 51 is obtained. Character thickness adjustment is performed on this table of contents page 52. As shown in FIG. 4, in the character thickness adjustment, a relatively thick character in the table of contents page 52 is thinned and a relatively thin character is thickened. By adjusting the character thickness, the table of contents page 53 in which the unevenness of the character thickness is reduced as compared with the table of contents page 52 is obtained. This table of contents page 53 is added to the document.

  As shown in FIG. 5, which is likely to occur when only one of these corrections is performed by adjusting both the “thinning correction” for thinning the character and “thickening correction” for thickening the character. Therefore, it is possible to make the thickness of the characters uniform. When only the thinning correction is performed as shown in FIG. 5A, the thin line elements among the line elements constituting the character are easily broken or broken. In the figure, in the Chinese character “blue” which is one of the thick characters to be thinned, a part of the lower side (two horizontal line elements) has disappeared. Due to this disappearance, the Chinese character “blue” has become a simple design that is not “blue”. That is, the shape representing “blue” of the Chinese character “blue” is lost. Losing the shape also means losing the meaning of the characters. In addition, when only thickening correction is performed as shown in FIG. 5B, breakage (called crushing) in which the gaps between the line elements disappear is likely to occur. In the drawing, among thin characters that are targets for thickening correction, the alphabet “A” and the Chinese character “blue” are crushed. Due to the collapse, the shape representing “A” and the shape representing “blue” are lost.

  Next, the operation of the character correction unit 13 will be described in more detail with a focus on character thickness adjustment.

  In the character thickness adjustment, a character thickness value is determined for each character group obtained by grouping characters in the table of contents page 52. Each character group is a character string divided by the arrangement in the table of contents page 52. In the present embodiment, since a plurality of character strings g1, g2, g3, and g4 extracted from the document 50 are arranged with a predetermined interval, each of these character strings g1, g2, g3, and g4 is a character group. Become. That is, the character group is specified by the layout information generated by the table of contents page creation unit 12 when the character strings g1, g2, g3, and g4 are pasted without analyzing the images for grouping. In the following, it is assumed that the character groups G1, G2, G3, and G4 shown in FIG. 4 correspond to the character strings g1, g2, g3, and g4 in order.

  The character thickness value is a value representing the thickness of characters belonging to the character group. Since the character group is a set of characters extracted from the same page, the font of the characters is common within the character group, and it is considered that the thickness is not extremely different between characters. However, the width of the line element is usually not uniform in each character. Based on these things, the character thickness value in this embodiment is calculated based on the result of the Opening process repeatedly performed by switching the filter size applied to a character in steps. In the opening process, first, the contraction process (Erosion) is performed, and then the expansion process (Dilation) is performed. When the line element of the character disappears in the contraction process, the character is not restored by the expansion process, and the number of character pixels decreases before and after the process. The character thickness value is determined from the filter size at which 50% or more of the character pixels disappear.

  In FIG. 6, among the character thickness values T1, T2, T3, and T4 of the four character groups G1, G2, G3, and G4, the character thickness value T1 of the character group G1 is the maximum value. The character thickness value T2 of G2 is the minimum value. In other words, the set of character groups having the largest difference in thickness is the set of character group G1 and character group G2. Therefore, the character correction unit 13 determines the difference between the maximum character thickness value T1 and the minimum character thickness value T2 as the necessary correction amount X for making the thickness uniform for the character group G1 and the character group G2. Is calculated. The necessary correction amount X is an indicator of the necessity of character thickness adjustment. When the necessary correction amount X is sufficiently small, the character thickness adjustment is unnecessary.

  If both thinning correction and thickening correction are performed to make the thickness uniform, the target value TX of these corrections inevitably is the character thickness value T1 (maximum value) and the character thickness value T2 ( It is a value between (minimum value). As the target value TX, a median value between the maximum value and the minimum value may be simply set, or the occupancy rates of the maximum value character group and the minimum value character group (the occupied area of the index page 52). You may set the value according to the ratio. When the median value is used, the correction amounts for the thinning correction and the thickening correction are made uniform. Since there is no need to consider the occupation ratio, there is an advantage that the processing is simplified. On the other hand, when setting the value according to the occupation ratio, the target value TX is set to a value close to the character thickness value of the character group having the larger occupation ratio than the median value. On the other hand, the correction amount is set small. As a result, the total amount of correction is reduced, and character deterioration can be minimized.

  When the target value TX is determined, it is determined which of the character groups G1, G2, G3, and G4 is to be thinned or thickened. That is, a thick character group that is a character group having a character thickness value larger than the target value TX is subject to thinning correction, and a thin character group that is a character group having a character thickness value smaller than the target value TX is thickened. Subject to correction. In FIG. 6, character groups G1 and G3 are bold character groups, and character groups G2 and G4 are fine character groups.

  The correction amount of the thinning correction for the bold character groups (character groups G1 and G3) is closest to the target thinning amounts M11 and M13 in terms of calculation accuracy within a range not exceeding the limit thinning amounts L11 and L13. Value. The correction amount of the thickening correction for the fine character groups (character groups G2 and G4) is the closest value in terms of calculation accuracy to the target thickening amounts M22 and M24 within a range not exceeding the limit thickening amounts L22 and L24. Is done. In FIG. 6, since the limit thinning amounts L11 and L13 are larger than the target thinning amounts M11 and M13, the target thinning amounts M11 and M13 are thinning correction amounts. Similarly, since the limit fattening amounts L22 and L24 are larger than the target fattening amounts M22 and M24, the target fattening amounts M22 and M24 are correction amounts for thickening correction.

  The target thinning amounts M11 and M13 are differences between the character thickness values T1 and T3 of the thick character group and the target value TX, and the target thinning amounts M22 and M24 are the character thickness values of the thin character group. This is the difference between T2 and T4 and the target value TX. The limit thinning amounts L11 and L13 are the maximum thinning amounts within a range in which the character to be corrected does not lose the shape representing the character. The limit thinning amounts L22 and L24 are: This is the maximum amount of thinning within a range where the character to be corrected does not lose the shape representing the character.

  For example, the limit thinning amounts L11 and L13 are detected as filter sizes immediately before the number of character pixels rapidly decreases in the above-described opening process. For the limit thickening amounts L22 and L24, the Closing process that performs the erosion process (Erosion) after the dilation process (Dilation) contrary to the Opening process is performed by switching the filter size step by step, and the number of character pixels decreases rapidly. It is detected as the filter size immediately before.

  As a specific example of each correction amount for thinning correction and thickening correction, the necessary correction amount X is 4 dots, and the limit thinning amount L11 of the character group G1 and the limit thickening amount L22 of the character group character G2 are both. It is assumed that there are 3 dots. Further, it is assumed that the occupation ratio of the thick character group G1 is 10% and the occupation ratio of the thin character group G2 is 90% (here, a case where a plurality of character groups are two character groups G1 and G2). ing). When the target value TX is the median value of the necessary correction amount X, the characters in the character group G1 are thinned by 2 dots, and the characters in the character group G2 are thickened by 2 dots. When the target value TX is determined in consideration of the occupation rate, for example, the characters of the character group G1 are thinned by 3 dots and the characters of the character group G2 are 1 dot so that the correction amount of the thin character group G2 having a large occupation rate is reduced. Fatten.

  Even when there are three or more character groups having different thicknesses, thinning correction and thickening correction may be performed based on the same concept. When the target value TX is determined according to the occupancy rate, the target value TX may be determined based on the occupancy rate of the thickest character group and the thinnest character group, or the entire correction amount based on the occupancy rates of all the character groups. You may decide so that total amount may become small. It can be thinned by an erosion process (Erosion), and can be made thick by an expansion process (Dilation).

  FIG. 7 is a flowchart of document data conversion operation by the image forming apparatus 1. The image scanner 5 reads the paper documents 41, 42, 43, and 44 (# 1), and the file creation unit 11 of the data processing circuit 10 creates an image data file as the document 50 converted into data (# 2). The table of contents page creation unit 12 creates a table of contents page 51 (# 3), and the character correction unit 13 performs character size adjustment and character thickness adjustment in order (# 4, # 5).

  The file creation unit 11 adds the table of contents page 53 adjusted by the character correction unit 13 to the image data file (# 6). Then, the data processing circuit 10 outputs an image data file (# 7). The image data file to which the table of contents page 53 is added is transmitted to an external device or stored in the storage 9.

  FIG. 8 is a flowchart of the character thickness adjustment routine.

  The character correction unit 13 specifies a character group in the table of contents page 52, which is a raster image after the character size adjustment, based on the character string extraction information from the table of contents page generation unit 12 (# 61). A character thickness value is determined for each character group (# 62), and a necessary correction amount X that is a difference between the maximum value and the minimum value of the character thickness value is calculated (# 63).

  The necessary correction amount X is compared with a predetermined threshold value to check the necessity of character thickness adjustment (# 64). When the necessary correction amount X is smaller than the threshold value (NO in # 64), the character thickness adjustment is not necessary. In this case, the processing flow returns to the flow of FIG.

  When character thickness adjustment is necessary (YES in # 64), the character correction unit 13 calculates the occupancy ratio of each character group (# 65) and determines a target value TX (# 66). Thereby, the character group is divided into a bold character group and a thin character group. A character group in which the difference between the character thickness value and the target value TX is equal to or greater than a predetermined value and the occupation ratio is less than a predetermined value (for example, 80%) is selected as a correction target (# 67). The reason why the occupation ratio is taken into account is to reduce the total amount of the correction amount and make the change of the character due to the correction less noticeable.

  For a character group selected as a correction target, a limit correction amount (a general term for a limit thinning amount and a limit thickening amount) is calculated. That is, the limit thinning amount is calculated for the thick character group (# 68, # 69), and the limit thinning amount is calculated for the thin character group (# 68, # 70).

  If there is no character group in which the target correction amount (the generic name of the target thinning amount and the target thickening amount) exceeds the limit correction amount (NO in # 71), the target correction amount is set as the correction amount for character thickness adjustment. (# 73). If there is a character group whose target correction amount exceeds the limit correction amount (YES in # 71), the limit correction amount is set as the correction amount for that group, and the target correction amount is set as the correction amount for the other groups (# 72). When the correction amount is determined, the character correction unit 13 performs thickening correction and thinning correction (# 74).

  FIG. 9 is a flowchart of the character size adjustment routine. The character size adjustment is basically performed in the same procedure as the character thickness adjustment. It is desirable that the character size is uniform within the page. Uniformity with the original page is maximized by uniformizing to a large occupancy size in the page, but if the character size with a large occupancy size is large or the amount of characters is large, the number of pages in the table of contents May increase the convenience of browsing. On the contrary, if the character size with a small occupation rate is a small size, the visibility may be impaired. Therefore, the limit enlargement amount is defined from the number of table of contents pages to be created, and the limit reduction amount is defined from the minimum character size that is defined as ensuring visibility.

  The character correction unit 13 specifies the character group in the table of contents page 51 created by the table of contents page generation unit 12 based on the character string extraction information by the table of contents page generation unit 12 (# 41). A character size value is determined for each character group (# 42), and a necessary size correction amount which is a difference between the maximum value and the minimum value of the character size value is calculated (# 43).

  The necessary size correction amount is compared with a predetermined threshold value to check the necessity of character size adjustment (# 44). When the necessary size correction amount is smaller than the threshold value (NO in # 44), the character size adjustment is unnecessary. In this case, the processing flow returns to the flow of FIG.

  When character size adjustment is necessary (YES in # 44), the character correction unit 13 calculates the occupancy ratio of each character group (# 45) and determines a target value (# 46). As a result, the character group is divided into a capital letter group to be reduced and a small letter group to be enlarged. A character group in which the difference between the character size value and the target value is greater than or equal to a predetermined value and the occupation ratio is less than the predetermined value is selected as a correction target (# 47). The reason why the occupation ratio is taken into account is to reduce the total amount of correction.

  For a character group selected as a correction target, a limit size correction amount (a general term for a limit reduction amount and a limit enlargement amount) is calculated. That is, the limit reduction amount is calculated for the uppercase group (# 48, # 49), and the limit enlargement amount is calculated for the lowercase group (# 48, # 50). The limit reduction amount is a maximum reduction amount for reducing characters to a predetermined minimum character size value (for example, 12 pt). The limit enlargement amount is the maximum enlargement amount that allows all character groups in the table of contents page 51 to fit in an area for a predetermined number of pages (for example, the same one page as the original).

  If there is no character group whose target size correction amount (generic name of target reduction amount and target expansion amount) exceeds the limit size correction amount (NO in # 51), the target size correction amount is set as the correction amount for character size adjustment ( # 53). If there is a character group whose target size correction amount exceeds the limit size correction amount (YES in # 51), the limit size correction amount is set as the correction amount for that group, and the target size correction amount is set as the correction amount for the other groups. Set (# 52). When the correction amount is determined, the character correction unit 13 performs enlargement correction and reduction correction (# 54).

  For example, the occupation ratio of a character group with a character size value of 20 pt is 80%, and the occupation ratio of a character group with a character size of 10 pt is 20%. In this case, the total correction amount is reduced by adjusting the character size of 10 pt. Therefore, if the character of 10 pt is enlarged by 10 pt and all characters are 20 pt, the character size is unified. However, in this case, the number of pages to be pasted is two pages, and if the character size is all 18 pt, it will fit on one page. Then, a method of reducing the 20pt character by 2pt to 18pt while minimizing the correction amount of the 20pt character having a large occupancy rate to 18 pages by reducing the 20pt character by 2pt is possible. .

  Conversely, if the occupation rate of 8pt characters is 80% and the occupation rate of 20pt characters is 20%, the character size is unified by reducing the 20pt characters by 12pt to 8pt. However, if it is stipulated that characters of 12pt or more are used from the viewpoint of visibility, 8pt characters are converted to 4pt so that all characters are 12pt or more while minimizing the correction amount of 8pt characters having a large occupation rate. Enlarged to 12pt, reduced 20pt character by 8pt to 12pt.

  FIG. 10 is a diagram showing an example of a table of contents page formation procedure when the character color differs between character groups. It is desirable to unify the color of characters in the table of contents page. Therefore, color correction is performed so as to unify the colors of character groups having a large occupation rate. At this time, it is necessary to consider not only the color between character groups but also the relationship between the base color and the character color of each page of the document 50b from which the character string is extracted. For example, if only the character shape of a white character is cut out and a white character is pasted on a blank paper, it cannot be visually recognized.

  Therefore, the limit color correction amount is defined so that the brightness difference between the character and the background becomes a certain level or more. When creating a table of contents page 51b by extracting a character string from the document 50b, there are a case where only the character shape is cut out and a case where an image including the background is cut out. The former is described below.

  When the background color of the table of contents page 51b is fixed to a general paper color (white) as shown in FIG. 10, for example, when the occupancy of white characters is 80% and the occupancy of black characters is 20% Since it should match the one with a higher occupation rate, it should be all white characters, but then the base paper color is white and cannot be seen. Therefore, the minimum necessary brightness difference between the base color and the character color is defined in advance, and the brightness difference is held at least. In this example, for example, if the minimum required brightness difference between the background and the character is 100 at 256 gradations (8 bits) and the background white is 255, the brightness of the character needs to be 155 or less. In other words, the limit minimum correction amount of white characters (this amount must be corrected at least) is lightness-100. If the character brightness of a black character is 0, it is possible to add up to brightness 155. From the occupancy rate of the character group, it is possible to unify the character color by correcting the brightness by +155 for black characters and by correcting the brightness by -100 for white characters.

  FIG. 11 is a diagram showing another example of the color adjustment of the table of contents page. In the case where the background color of the table of contents page 51c is also subject to adjustment, as in the above example, the white character occupancy rate is assumed to be 80% and the black character occupancy rate is assumed to be 20%. In accordance with the idea of giving priority to white characters having a large occupation rate, all the characters may be white characters (brightness 255). In this case, the background needs to be a low brightness background. If the minimum required brightness difference between the background and the character is defined as 100, the background is filled with the brightness of 155. By this processing, it is possible to unify the character colors while maintaining the color of the character group having a large occupation rate.

  Similar to the character thickness adjustment, if the brightness difference between character groups is equal to or smaller than the threshold value, that is, if the colors are similar, the color adjustment can be made not to be performed. If the occupation ratio is equal to or greater than the threshold value, color adjustment may not be performed for the character group. When not only the brightness but also the hue differs between character groups, basically the hue may be adjusted to match a character group with a large occupation rate. Even in the case of colored characters, the background may be achromatic.

  In the above embodiment, the functional configuration, hardware configuration, operation, and the like of the image forming apparatus 1 and the data processing circuit 10 as the image processing apparatus are not limited to examples, and may be changed as appropriate within the scope of the present invention. Also good. For example, the character correction unit 13 may perform only character thickness adjustment among character size adjustment and character thickness adjustment. Conversely, only character size adjustment can be performed. The character size may be adjusted after adjusting the character thickness.

  In addition to the table of contents page 52, the character thickness can be adjusted for an arbitrary raster image in which characters having different thicknesses are mixed. In that case, the characters can be discriminated by image attribute discrimination technology for discriminating between characters and graphics, and for example, the characters can be grouped based on the size of the interval between the characters. Further, it is possible to perform grouping in which characters having a minimum rectangular size containing the determined characters are grouped into one group.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Data processing circuit (image processing apparatus)
52 Table of Contents Page (Image)
g1, g2, g3, g4 Character string G1, G2, G3, G4 Character group T1, T2, T3, T4 Character thickness value TX Target value L11, L13 Limit thinning amount L22, L24 Limit thickening amount M11, M13 Target thinning amount M22, M24 Target thickening amount

Claims (9)

An image processing apparatus that performs image processing on characters,
Means for extracting from the image a plurality of character groups divided by the arrangement in the image;
For each of the plurality of character groups extracted from the image, means for determining a character thickness value representative of the thickness of the characters belonging to the character group;
A value between a maximum value and a minimum value among the character thickness values determined for the plurality of character groups is set as a target value for both the thinning correction for thinning the character and the thickening correction for thickening the character. Means for setting;
Of the plurality of character groups, for a thick character group whose character thickness value is larger than the target value, the character to be corrected when performing the thinning correction loses the shape representing the character. A means for obtaining a limit thinning amount that is a maximum thinning amount within a non-existing range;
Of the plurality of character groups, with respect to a fine character group whose character thickness value is smaller than the target value, the character to be corrected when performing the thickening correction does not lose the shape representing the character. A means for obtaining a limit fattening amount that is the maximum fatening amount within the range;
For the bold character group, the thinning amount does not exceed both the target thinning amount and the limit thinning amount that are the difference between the character thickness value of the bold character group and the target value. While performing the thinning correction, for the fine character group, the thickening amount is a difference between the character thickness value of the fine character group and the target value, and the target thickening amount and the limit thickening amount. An image processing apparatus comprising: means for performing the fattening correction so as not to exceed both. Means for calculating an occupancy ratio that is a ratio of an occupied area in the image for each of the bold character group and the fine character group;
The thinning amount of the thinning correction for the thick character group and the thickening for the thin character group so that the correction amount of the character group having a small occupation ratio is larger than the correction amount of the character group having a large occupation ratio. The image processing apparatus according to claim 1, further comprising: a unit for setting a correction fattening amount. The image processing apparatus according to claim 2, wherein the thinning amount and the thickening amount setting unit sets the thinning amount and the thickening amount to zero for a character group whose occupation ratio is equal to or greater than a threshold value. The means for performing the thinning correction and the thickening correction performs the maximum thinning correction within a range in which the thinning amount does not exceed both the target thinning amount and the limit thinning amount. The image processing apparatus according to claim 1, wherein the thickening correction is performed to a maximum extent within a range in which the fattening amount does not exceed both the target fattening amount and the limit fattening amount. If the difference between the maximum value and the minimum value of the character thickness values is less than or equal to a threshold value, the thinning correction and the thickening correction are not performed for any of the plurality of character groups. Item 5. The image processing apparatus according to any one of Items 1 to 4. The image processing apparatus according to claim 1, wherein the target value setting unit sets a central value between the maximum value and the minimum value as the target value. For each of the plurality of character groups extracted from the image, means for determining a character size value representative of the size of the characters belonging to the character group;
Means for setting a value between a maximum value and a minimum value among the character size values determined for the plurality of character groups as a target size value for both reduction correction for reducing a character and enlargement correction for increasing a character. When,
Maximum reduction that reduces the character size value of the plurality of character groups to a predetermined minimum character size value when performing the reduction correction for an uppercase character group that is a character group whose character size value is larger than the target size value A means for obtaining a limit reduction amount that is a quantity;
For the uppercase group, the reduction correction is performed so that the reduction amount does not exceed both the target reduction amount and the limit reduction amount that are the difference between the character size value of the uppercase group and the target size value, and A target whose enlargement amount is a difference between a character size value of the lowercase letter group and the target size value with respect to a lowercase letter group that is a character group whose character size value is smaller than the target size value among a plurality of character groups The image processing apparatus according to claim 1, further comprising a unit that performs the enlargement correction so as not to exceed both a fattening amount and a maximum value of the character size value. The image processing apparatus according to claim 7, wherein after the reduction correction and the enlargement correction are performed on the plurality of character groups, the thinning correction and the thickening correction are performed by determining the character thickness value. An image scanner that reads a document image from a document sheet;
Means for extracting a plurality of character groups from a plurality of document images read by the image scanner and forming an edited image in which the plurality of character groups are arranged;
For each of the plurality of character groups in the edited image, means for determining a character thickness value representing the thickness of the characters belonging to the character group;
A value between a maximum value and a minimum value among the character thickness values determined for the plurality of character groups is set as a target value for both the thinning correction for thinning the character and the thickening correction for thickening the character. Means for setting;
Of the plurality of character groups, for a thick character group whose character thickness value is larger than the target value, the character to be corrected when performing the thinning correction loses the shape representing the character. A means for obtaining a limit thinning amount that is a maximum thinning amount within a non-existing range;
Of the plurality of character groups, with respect to a fine character group whose character thickness value is smaller than the target value, the character to be corrected when performing the thickening correction does not lose the shape representing the character. A means for obtaining a limit fattening amount that is the maximum fatening amount within the range;
For the bold character group, the thinning amount does not exceed both the target thinning amount and the limit thinning amount that are the difference between the character thickness value of the bold character group and the target value. While performing the thinning correction, for the fine character group, the thickening amount is a difference between the character thickness value of the fine character group and the target value, and the target thickening amount and the limit thickening amount. An image forming apparatus comprising: means for performing the fattening correction so as not to exceed both.

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