JP2018037778A - Image processing device and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing device and an image processing method that can improve readability of a handwritten character while suppressing change of appearance impression of the handwritten character printed on a sheet.SOLUTION: In an image processing device, an image reading unit reads an image of a manuscript to generate image data indicating the image of the manuscript. An object pixel extraction unit extracts a pixel corresponding to a thin line area indicating a thin line having a line width less than a predetermined line width on the manuscript from the image data as an object pixel 2. A density change unit changes a density value of the object pixel 2 such that density of at least some pixels including the minimum density pixel among the object pixels 2 extracted by the object pixel extraction unit approaches to the maximum density Dmax in the object pixels 2.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image processing apparatus and an image processing method for processing image data representing an image of a document.

  In an image processing apparatus having a copy function such as a copier or a multifunction peripheral, an image of a document is printed on a sheet based on image data indicating the image of the document read by the image reading unit. In such an image processing apparatus, for example, when images of a plurality of originals containing handwritten characters such as a questionnaire sheet are read and printed (collected copy) on a single sheet, the density of the handwritten characters depends on the original. It can be very different. In this case, if the print density is adjusted so that a thin handwritten character is printed dark, the dark handwritten character becomes too dark. Conversely, if the print density is adjusted so that dark handwritten characters are printed lightly, thin handwritten characters will be too thin.

  An image processing apparatus is known that converts a K character of a black character portion in a CMYK color signal into a predetermined black character correction value when performing a printing process based on image data sent from a host computer. (For example, refer to Patent Document 1).

JP 2010-288250 A

  However, in the image processing apparatus, the K signal of the black character portion is converted into a predetermined black character correction value regardless of the density (for example, the maximum density) of the black character portion before conversion, so that it is printed on the sheet. The appearance of handwritten characters may change significantly from the original.

  An object of the present invention is to provide an image processing apparatus and an image processing method capable of improving the readability of handwritten characters while suppressing changes in the appearance of handwritten characters printed on a sheet. is there.

  An image processing apparatus according to one aspect of the present invention includes an image reading unit, a target pixel extracting unit, and a density changing unit. The image reading unit reads an image of a document and generates image data indicating the image of the document. The target pixel extraction unit extracts, from the image data, a pixel corresponding to a specific area that satisfies a predetermined condition on the document as a target pixel. The density changing unit includes the target pixel so that the density of at least some of the target pixels extracted by the target pixel extracting unit, including the pixel with the minimum density, approaches the maximum density of the target pixel. Change the density value.

  An image processing method according to another aspect of the present invention includes a target pixel extraction step and a density change step. In the target pixel extraction step, a specific region that satisfies a predetermined condition is extracted from the image of the document as a target pixel based on image data indicating the image of the document read by the image reading unit. In the density change step, among the pixels included in the target pixel extracted in the target pixel extraction step, the density of at least some of the pixels including the pixel with the minimum density approaches the maximum density in the target pixel. The density value corresponding to the target pixel in the image data is changed.

  ADVANTAGE OF THE INVENTION According to this invention, the image processing apparatus and image processing method which can improve the readability of the said handwritten character are suppressed, suppressing the change of the impression of the handwritten character printed on a sheet | seat.

FIG. 1 is a block diagram showing a configuration of an image processing apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an example of image data before density change in the image processing apparatus according to the embodiment of the present invention. FIG. 3 is a diagram for explaining density change processing executed by the image processing apparatus according to the embodiment of the present invention. FIG. 4 is a diagram showing an example of image data after density change in the image processing apparatus according to the embodiment of the present invention. FIG. 5 is a diagram for explaining another example of the density changing process executed by the image processing apparatus according to the embodiment of the present invention. FIG. 6 is a diagram for explaining still another example of the density changing process executed by the image processing apparatus according to the embodiment of the present invention. FIG. 7 is a flowchart illustrating an example of an image processing procedure executed by the image processing apparatus according to the embodiment of the present invention. FIG. 8 is a diagram illustrating an example of an image of a document read by the image processing apparatus according to the embodiment of the present invention. FIG. 9 is a diagram for explaining a modification of the target pixel extraction process executed by the image processing apparatus according to the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.

[Configuration of image processing apparatus]
As shown in FIG. 1, the image processing apparatus 1 according to the embodiment of the present invention includes an operation display unit 11, an ADF 12, an image reading unit 13, an image forming unit 14, a communication I / F 15, a storage unit 16, and a control unit. 17 and the like. Specifically, the image processing apparatus 1 is a multifunction machine having a printer function, a scanner function, a copy function, a facsimile function, and the like. The present invention is not limited to a multi-function machine, and can be applied to any image processing apparatus that can read an image of a document by an image reading unit, such as a copier, a scanner, a printer, and a facsimile machine.

  The operation display unit 11 includes a display unit such as a liquid crystal display that displays information, and an operation unit such as a touch panel and operation buttons that accept user operations.

  The ADF 12 is an automatic document conveyance device that includes a document setting unit, a conveyance roller, a document pressing unit, and a paper discharge unit, and conveys a document to be read by the image reading unit 13.

  The image reading unit 13 includes a document table, a light source, a mirror, an optical lens, and a CCD (Charge Coupled Device), reads an image of the document, and generates image data indicating the image of the document. The image reading unit 13 can also read a plurality of documents arranged on the document table together and generate one image data indicating images of the plurality of documents.

  The image forming unit 14 can execute a printing process based on image data by an electrophotographic method or an inkjet method, and forms an image on a sheet based on the image data. For example, when the image forming unit 14 is an electrophotographic image forming unit, the image forming unit 14 includes a photosensitive drum, a charger, an exposure device, a developing device, a transfer device, and a fixing device.

  The communication I / F 15 executes communication processing according to a predetermined communication protocol with an external facsimile apparatus or an information processing apparatus such as a personal computer via a communication network such as a telephone line, the Internet, or a LAN. It is a communication interface that can.

  The storage unit 16 is a non-volatile storage unit such as a hard disk or a flash memory. The storage unit 16 stores various control programs for executing image processing (described later) executed by the control unit 17.

  The control unit 17 includes control devices such as a CPU, a ROM, and a RAM. The CPU is a processor that executes various arithmetic processes. The ROM is a non-volatile storage unit in which information such as a control program for causing the CPU to execute various processes is stored in advance. The RAM is a volatile or nonvolatile storage unit used as a temporary storage memory (working area) for various processes executed by the CPU.

  Specifically, the control unit 17 includes a target pixel extraction unit 171 and a density change unit 172. The control unit 17 functions as each of these processing units by executing various processes according to the control program. Moreover, the control part 17 may be provided with the electronic circuit which implement | achieves a part or some processing function of each of these process parts.

  The target pixel extraction unit 171 extracts, as target pixels, pixels corresponding to a specific region that satisfies a predetermined condition on the document from image data indicating an image of the document read by the image reading unit 13. Details of the target pixel extraction processing executed by the target pixel extraction unit 171 will be described later.

  The density changing unit 172 includes the target pixels extracted by the target pixel extracting unit 171 so that the density of at least some of the pixels including the pixels with the minimum density approaches the maximum density of the target pixels. Change the density value. Details of the density changing process executed by the density changing unit 172 will be described later.

  By the way, in the image processing apparatus 1, for example, when images of a plurality of originals containing handwritten characters such as a questionnaire sheet are read and printed (collected copy) on one sheet, the darkness of the handwritten characters depends on the original. It can be very different. In this case, if the print density is adjusted so that a thin handwritten character is printed dark, the dark handwritten character becomes too dark. Conversely, if the print density is adjusted so that dark handwritten characters are printed lightly, thin handwritten characters will be too thin. In order to solve such a problem, for example, it is conceivable to collectively convert the density of the handwritten character portion to a predetermined density. However, in this case, since the density of the handwritten character is converted into a predetermined density regardless of the density (for example, the maximum density) of the handwritten character before conversion, the density of the handwritten character printed on the sheet is reduced. The visual impression may change significantly from the original document. On the other hand, according to the image processing apparatus 1 of the present embodiment, by performing the image processing described below, the handwritten character is suppressed while suppressing a change in the appearance of the handwritten character printed on the sheet. It is possible to improve the readability.

[Image processing method in image processing apparatus]
Hereinafter, an image processing method in the image processing apparatus 1 will be described with reference to FIGS.

  FIG. 2 is a schematic diagram schematically showing image data indicating an image of a document read by the image reading unit 13. When image data indicating an image of a document is generated by the image reading unit 13, the target pixel extraction unit 171 selects a pixel corresponding to a thin line region indicating a thin line less than a predetermined line width from the image data as the target pixel. Extract as 2. The fine line region is an example of the specific region. Other examples of the specific area will be described later. The extraction of the target pixel 2 by the target pixel extraction unit 171 is performed as follows, for example.

  First, the target pixel extraction unit 171 sequentially scans the image data in the horizontal direction (main scanning direction), and detects a portion where there is a density difference of a predetermined value or more between adjacent pixels as an edge. Next, the distance between adjacent edges is calculated, and when the distance between adjacent edges is less than a predetermined line width (for example, less than 1.5 mm), the area between the edges (the thin line area) Are extracted as the target pixel 2. For example, when the density of pixels arranged in the horizontal direction is in the state shown in FIG. 2, pixels corresponding to five thin line regions are extracted as target pixels 2a to 2e. When the horizontal scanning is completed, the target pixel extraction unit 171 scans in the vertical direction (sub-scanning direction) in the same manner, and extracts the target pixel 2. Note that the threshold of the line width (1.5 mm above) for determining whether or not the pixel 2 is the target pixel 2 may be changeable according to a user instruction input through the operation display unit 11, for example. .

  Since the handwritten character written on the document with a pencil or a ballpoint pen is a thin line, the pixel corresponding to such a handwritten character is extracted as the target pixel 2 by the target pixel extraction unit 171. For example, target pixels 2a and 2b shown in FIG. 2 are pixels corresponding to thin handwritten characters such as pencils, and target pixels 2c to 2e are pixels corresponding to dark handwritten characters such as ballpoint pens. On the other hand, since the pixel corresponding to the region where the distance between the edges is equal to or larger than the predetermined line width is not extracted as the target pixel 2, the pixel corresponding to the image whose density tends to change gently like a photograph. Are not extracted as the target pixel 2.

  When the extraction of the target pixel 2 is completed, the density changing process by the density changing unit 172 is subsequently performed. The density changing unit 172 detects the density of the pixel with the highest density among the target pixels 2 as the maximum density Dmax. For example, assuming that the image data shown in FIG. 2 indicates the entire image, the density of the target pixel 2c having the highest density among all the target pixels 2a to 2e is detected as the maximum density Dmax.

  Subsequently, as shown in FIG. 3, the density changing unit 172 changes the density value of the target pixel 2 in the image data so that the density of all the pixels of the target pixel 2 is changed to the maximum density Dmax. Thereby, for example, the image data shown in FIG. 2 is changed to the image data shown in FIG. A hatched area in FIG. 4 corresponds to a changed portion by the density changing unit 172.

  Thus, according to the present embodiment, the density of all the pixels in the target pixel 2 is changed to the maximum density Dmax in the target pixel 2. Therefore, even when the image reading unit 13 reads an image of a document (one or a plurality of sheets) including both a thin handwritten character like a pencil and a dark handwritten character like a ballpoint pen, The density of the portion of the thin handwritten character is changed to the same concentration as that of the dark handwritten character (maximum density), so that it becomes easy to read. Further, since the density of the darkest part in the handwritten character is not changed, the appearance impression of the handwritten character printed on the sheet is not greatly changed from the original document.

  Note that the density conversion processing by the density changing unit 172 is not limited to the above example. Hereinafter, with reference to FIGS. 5 and 6, a modified example of the density conversion processing by the density changing unit 172 will be described.

  FIG. 5 shows a first modification of density conversion processing by the density changing unit 172. In the first modification, the density changing unit 172 has a density of a pixel having a density lower than the target lower limit density Dth in the target pixel 2 when a pixel having a density lower than a predetermined target lower limit density Dth exists in the target pixel 2. The density value of the target pixel 2 is changed so that is changed to the target lower limit density Dth. The target lower limit density Dth is set to a value that makes it difficult to read handwritten characters when the density of handwritten characters is lower than this value, for example. The target lower limit concentration Dth may be changeable according to a user instruction input through the operation display unit 11, for example.

  According to the first modified example, the density of pixels having a density lower than the target lower limit density Dth among the pixels in the target pixel 2 is changed to the target lower limit density Dth. That is, only the density of the handwritten character that is difficult to read is changed with the minimum density change amount. Therefore, since the density of the pixels in the target pixel 2 having the density equal to or higher than the target lower limit density Dth is not changed, it is possible to further suppress the change in the appearance impression of the handwritten characters printed on the sheet. For example, since the shade in a dark handwritten character like a ballpoint pen is maintained, a change in the appearance impression of the handwritten character printed on the sheet can be further suppressed.

FIG. 6 shows a second modification of the density conversion process by the density changing unit 172. In the second modified example, the density changing unit 172 has the density of each pixel in the target pixel 2 that is the maximum density Dmax in the target pixel 2 and the target when a pixel having a density lower than the target lower limit density Dth exists in the target pixel 2. The density value of the target pixel 2 is changed so that the density is proportionally distributed to the lower limit density Dth. Specifically, the density changing unit 172 changes the density value by the following conversion formula. However, Din is a density value before conversion, Dout is a density value after conversion, and Dmin is a minimum density in the target pixel 2 (see FIG. 6).
Dout = ((Dmax−Dth) ÷ (Dmax−Dmin)) × (Din−Dmin) + Dth

  According to the second modification, the density of the pixels in the target pixel 2 is changed to a density that is proportionally distributed between the maximum density Dmax and the target lower limit density Dth in the target pixel 2. That is, the density of the handwritten character that is difficult to read is converted to a density that is easy to read, and the density in the handwritten character is substantially maintained. Therefore, it is possible to further suppress changes in the appearance of handwritten characters printed on the sheet. For example, in addition to the shading in a dark handwritten character like a ballpoint pen, the shading in a thin handwritten character like a pencil is maintained, so the change in the visual impression of the handwritten character printed on the sheet Is further suppressed.

  Next, an example of an image processing procedure executed by the control unit 17 will be described with reference to FIG. Here, steps S1, S2,... Represent the numbers of processing procedures (steps) executed by the control unit 17. The image processing is started, for example, in response to a signal indicating a copy instruction being input through the operation display unit 11.

<Step S1>
First, in step S1, the control unit 17 controls the image reading unit 13 to cause the image reading unit 13 to read an image of a document.

<Step S2>
In step S <b> 2, the control unit 17 extracts, as the target pixel 2, a pixel corresponding to a specific area that satisfies a predetermined condition on the document from image data indicating an image of the document read by the image reading unit 13. . For example, the control unit 17 extracts, as the target pixel 2, a pixel corresponding to a thin line region indicating a thin line less than a predetermined line width (for example, less than 1.5 mm).

<Step S3>
In step S3, the control unit 17 causes the target pixel 2 extracted in step S so that the density of at least some of the pixels including the minimum density pixel approaches the maximum density Dmax in the target pixel. Change the density value of the pixel. For example, the control unit 17 detects the density of the pixel with the highest density among the target pixels 2 as the maximum density Dmax. Then, the control unit 17 changes the density value of the target pixel 2 so that the density of all the pixels of the target pixel 2 is changed to the maximum density Dmax.

<Step S4>
In step S4, the control unit 17 controls the image forming unit 14 to cause the image forming unit 14 to print an image based on the image data after the density value is changed in step S3 on the sheet.

  Note that the processing of Step S2 (target pixel extraction step) is executed by the target pixel extraction unit 171 of the control unit 17. The processing of step S3 (density changing step) is executed by the density changing unit 172 of the control unit 17.

  As described above, according to the present embodiment, among the target pixels 2 extracted from the image of the document, the density of at least some of the pixels including the pixels with the minimum density approaches the maximum density of the target pixels 2. The density value of the target pixel 2 is changed. Therefore, it is possible to improve the readability of the handwritten character while suppressing a change in the appearance of the handwritten character printed on the sheet.

[Modification]
In the present embodiment, the target pixel extraction unit 171 extracts the pixel corresponding to the thin line region indicating the thin line having a line width smaller than the predetermined line width as the target pixel 2, but the present invention is not limited to this. In another embodiment, the target pixel extraction unit 171 may extract, as the target pixel 2, a pixel corresponding to a character area indicating a character (an example of the specific area). For example, the target pixel extraction unit 171 may extract a pixel corresponding to the character area as the target pixel 2 by performing a character recognition process on image data indicating an image of the document.

  In still another embodiment, the target pixel extraction unit 171 may extract a pixel corresponding to a handwritten character region (an example of the specific region) indicating a handwritten character as the target pixel 2. For example, the target pixel extraction unit 171 performs character recognition processing on image data indicating an image of a document, and at the same time, prints characters on the document extracted by the character recognition processing (printed characters output by a word processor or the like, handwriting) Only pixels corresponding to handwritten characters may be extracted as the target pixel 2 from the pixels corresponding to (which may include both characters). For example, the target pixel extraction unit 171 compares the shape of each character on the document recognized by the character recognition process with a plurality of print character shape data stored in advance in the storage unit 16 or the like (for example, the degree of similarity). ), A pixel corresponding to a handwritten character and a pixel corresponding to a printed character may be determined.

  In yet another embodiment, the target pixel extraction unit 171 extracts pixels corresponding to non-common parts (an example of the specific region) of a plurality of document images read together by the image reading unit 13 as the target pixels. May be. For example, when two completed questionnaire sheets are arranged on a platen and the two questionnaire sheets are read together by the image reading unit 13, a read image 3 as shown in FIG. The image data shown is generated. The left half area R1 of the read image 3 includes an image of one questionnaire sheet, and the right half area R2 of the read image 3 includes an image of the other questionnaire sheet. For example, the target pixel extraction unit 171 compares the image data corresponding to the region R1 and the image data corresponding to the region R2 for each pixel, and determines a pixel whose density value difference is a certain value or more as the target pixel 2. (See FIG. 9). Thereby, only handwritten characters can be easily extracted from the images of a plurality of originals read together. This modification is effective when a plurality of originals in which handwritten characters are written together by different people on a sheet on which common characters and lines are printed, such as a questionnaire sheet or a test sheet. The region R1 and the region R2 may be set in advance, or may be automatically selected from a plurality of predefined arrangement patterns (number of regions, size, orientation, position, etc.). Alternatively, it may be set according to a user instruction input through the operation display unit 11.

  In the present embodiment, the case where the copy process is performed based on the image data indicating the image of the document read by the image reading unit 13 has been described, but the present invention is not limited to this. In another embodiment, transmission processing by facsimile or e-mail may be performed based on image data indicating an image of a document read by the image reading unit 13.

DESCRIPTION OF SYMBOLS 1 Image processing apparatus 2, 2a-2e Target pixel 3 Read image 13 Image reading part 17 Control part 171 Target pixel extraction part 172 Density change part

Claims (9)

An image reading unit that reads an image of a document and generates image data indicating the image of the document;
A target pixel extraction unit that extracts, from the image data, pixels corresponding to a specific area that satisfies a predetermined condition on the document as target pixels;
The density for changing the density value of the target pixel so that the density of at least some of the pixels including the pixel with the lowest density among the target pixels extracted by the target pixel extraction unit approaches the maximum density of the target pixel. Change part,
An image processing apparatus comprising: The density changing unit changes the density value of the target pixel so that the density of all the pixels of the target pixel is changed to the maximum density of the target pixel.
The image processing apparatus according to claim 1. The density changing unit changes the density of a pixel having a density lower than the target lower limit density in the target pixel to the target lower limit density when a pixel having a density lower than a predetermined target lower limit density exists in the target pixel. To change the density value of the target pixel,
The image processing apparatus according to claim 1. The density changing unit is configured such that when a pixel having a density lower than a predetermined target lower limit density exists in the target pixel, the density of each pixel in the target pixel is a maximum density of the target pixel and the target lower limit density. Changing the density value of the target pixel so that the density is proportionally distributed between the target pixels.
The image processing apparatus according to claim 1. The specific area is a thin line area showing a thin line less than a predetermined line width,
The image processing apparatus according to claim 1. The specific area is a character area indicating a character;
The image processing apparatus according to claim 1. The specific area is a handwritten character area indicating a handwritten character,
The image processing apparatus according to claim 1. The specific area is a non-common part of images of a plurality of documents read together by the image reading unit.
The image processing apparatus according to claim 1. A target pixel extracting step of extracting, as target pixels, pixels corresponding to a specific region that satisfies a predetermined condition on the document from image data indicating an image of the document read by the image reading unit;
A density for changing the density value of the target pixel so that the density of at least some of the pixels including the pixel of the minimum density among the target pixels extracted in the target pixel extraction step approaches the maximum density of the target pixel. Change steps,
An image processing method including:

Images