KR20150109929A - Method of correcting document image using histogram and apparatus thereof - Google Patents

Abstract

A method for correcting a document image using a histogram according to an embodiment of the present invention includes the steps of: acquiring a document image as a digital format; extracting a histogram on the document image; determining a slope of the document image by analyzing the histogram; and correcting a slop of the document image for the document image to have a target slop based on the determined slop of the document image.

Description

TECHNICAL FIELD The present invention relates to a document image correction method and apparatus using a histogram,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document image correction method and apparatus using a histogram, and more particularly, to a method and apparatus for precisely measuring and correcting a tilt degree of a document image obtained in a digital form using a histogram .

BACKGROUND ART [0002] In recent years, a technique of printing out a digital image obtained by using a video input device such as a scanner has been widely used. In particular, as the use of a digital composite apparatus, which not only stores a copy function but also stores a digital image as image data in a computing device or transmits a digital image as a signal to a remote printing apparatus, The trend is spreading widely.

Generally, a scanner converts light condensed from a document through an optical lens into binarized data to produce a digital image, at which time the optical lens travels along a predetermined path. Thus, if a document is placed out of a specified location, such as a user inadvertently placing the document, the digital image for the document is obtained with a tilted orientation.

In such a case, since the oblique digital image is printed out, the printing ink and paper are wasted, and the user who checks the printed matter needs to re-arrange the document to obtain the digital image and printout it, .

In order to solve the above problem, a technique of detecting the contrast of a document near the boundary of the document and detecting the inclination of the document has been used. However, satisfactory results have not yet been obtained in terms of measurement accuracy and user convenience .

Accordingly, there is a need for a new technique capable of accurately measuring the degree of inclination of a document image acquired through a scanner, and providing convenience to the user in terms of document layout when using copying, scanning, and faxing.

And to provide a method and an apparatus which can accurately measure the temperature.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus for providing convenience to a user in terms of document layout when a user uses copy, scan, and fax for a document image.

The problems of the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a method of correcting a document image using a histogram, the method comprising: obtaining a document image in a digital form; extracting a histogram of the document image; Determining a slope of the document image, and correcting the slope of the document image so that the document image has a desired slope based on the determined slope of the document image.

According to another aspect of the present invention, the method may further include printing and outputting the document image with the tilt corrected.

According to another aspect of the present invention, a plurality of histograms of the document image can be extracted.

According to another aspect of the present invention, the step of determining the slope of the document image includes the steps of: comparing the extracted histogram with a plurality of reference histograms previously stored in the slope unit, comparing the slope of the reference histogram closest to the extracted histogram with the document image As a slope with respect to < / RTI >

According to another aspect of the present invention, extracting a histogram for a document image includes extracting a plurality of Y-axis histograms for the document image by changing an angle projected onto the document image, Determining a slope of the document image based on the extracted plurality of Y-axis histograms.

According to another aspect of the present invention, the step of determining the slope of the document image based on the extracted plurality of Y-axis histograms comprises the steps of: extracting a Y-axis histogram closest to the 0-degree Y- Selecting; And determining a projection angle for the selected Y-axis histogram as a slope of the document image.

According to another aspect of the present invention, the step of comparing the plurality of Y-axis histograms with each other to determine the slope of the document image includes the steps of: selecting the most angled Y-axis histogram among the plurality of extracted Y-axis histograms; And determining a projection angle for the selected Y-axis histogram as a slope of the document image.

According to another aspect of the present invention, extracting a histogram for a document image includes extracting a plurality of X-axis histograms for the document image by changing an angle projected onto the document image, Determining a slope of the document image at a projection angle with respect to the selected X-axis histogram; and determining a slope of the document image at a projection angle with respect to the selected X-axis histogram, . ≪ / RTI >

According to an aspect of the present invention, there is provided an apparatus for correcting a document image using a histogram according to an embodiment of the present invention includes a document image acquisition unit in a digital form, a histogram extraction unit for extracting a histogram of the document image, And a slope correcting unit for correcting the slope of the document image so that the document image has a desired slope based on the slope of the determined document image.

In order to solve the above-mentioned problems, a computer-readable medium storing a set of instructions according to an embodiment of the present invention includes instructions for causing a computing device to cause a computing device to: Allowing the image to be acquired in digital form, extracting a histogram for the document image, analyzing the histogram to determine the slope of the document image, and determining, based on the determined slope of the document image, that the document image has a desired slope And corrects the inclination of the document image so that the document image is corrected.

The details of other embodiments are included in the detailed description and drawings.

The present invention has the effect of accurately measuring the degree of inclination of a document image.

The present invention has the effect of providing convenience to the user in terms of document layout when the user uses copy, scan, and fax for the document image.

The effects according to the present invention are not limited by the contents exemplified above, and more various effects are included in the specification.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view schematically showing an overall configuration of a document image correcting apparatus according to an embodiment of the present invention; Fig.
2 is a flowchart of a document image correction method according to an embodiment of the present invention.
Figures 3a and 3b illustrate exemplary 0 degree reference Y and X axis histograms, in accordance with an embodiment of the invention.
Figures 4A-4E illustrate an example of correcting the slope of a document image, in accordance with an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

Like reference numerals refer to like elements throughout the specification.

It is to be understood that each of the features of the various embodiments of the present invention may be combined or combined with each other partially or entirely and technically various interlocking and driving is possible as will be appreciated by those skilled in the art, It may be possible to cooperate with each other in association.

Various embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

1 is a diagram schematically showing an entire configuration of a document image correcting apparatus 100 according to an embodiment of the present invention.

Referring to FIG. 1, a document image correcting apparatus 100 according to the present invention includes a document image obtaining unit 110, a histogram extracting unit 120, a slope determining unit 130, and a skew correction unit 140. Furthermore, the document image correcting apparatus 100 of the present invention may further include a document output unit 150, a control unit 160, and a memory 170.

The image obtaining unit 110 of the present invention performs a function of obtaining a document image in a digital form. Preferably, the image obtaining unit 110 may be a general-purpose scanner that reads information recorded on a document in a graphic form and transmits the information to a computer. However, the present invention is not limited to this, And may include all video input devices of the present technology capable of performing video input.

Here, the document image refers to a document on which letters, numbers, signs, figures, etc. are described and an image for the document, and preferably refers to an image of a general document in which letters, numbers, do.

The histogram extracting unit 120 of the present invention extracts a histogram of a document image divided into a plurality of pixels. A specific method of extracting the histogram by the histogram extracting unit 120 will be described later.

The tilt determining unit 130 of the present invention analyzes one or more histograms extracted by the histogram extracting unit 120 and determines a slope of the document image.

Here, the inclination is a value indicating the degree of tilting of the image with respect to the horizontal line or the X-axis defined by the means by which the document is to be output (such as a display device or a document output sheet) . ≪ / RTI > The slope can be used to express the degree to which the document image is deviated from the desired position in angle terms.

The inclination correcting unit 140 of the present invention performs a function of correcting the inclination of the document image so that the document image has a desired inclination based on the inclination determined by the inclination determining unit 130. [

Here, the target slope of the document image may be a slope value preset by the user, but may preferably mean a slope of 0 ° numerically.

The document output unit 150 of the present invention may perform a function of printing out a document image whose tilt is corrected by a request from a user. Here, the document output unit 150 may refer to a general-purpose printer capable of printing a digital image on a document sheet.

The control unit 160 of the present invention includes a document image obtaining unit 110, a histogram extracting unit 120, a slope determining unit 130, a slope correcting unit 140, a document output unit 150, And the like. The control unit 160 controls the flow of data between the components of the document image tilt correction apparatus 100 or from the outside so that the document image obtaining unit 110, the histogram extracting unit 120, the tilt determining unit 130, The tilt correction unit 140, the document output unit 150, and the memory 170, respectively.

In the memory 170 of the present invention, a document image acquired by the image acquisition unit 110 may be stored or a histogram image extracted by the histogram extraction unit 120 may be stored. Further, the memory 170 may store a plurality of reference histograms classified on an angle basis, and a Y-axis histogram for the reference document image. The memory 170 may include a random access memory (RAM), a read-only memory (ROM), a magnetic disk device, an optical disk device, a flash memory, But is not limited thereto.

Meanwhile, although the above-described configurations have been shown and described as separate configurations for convenience of explanation, each configuration may be merged, or one configuration may be implemented separately.

2 is a flowchart of a document image correction method according to an embodiment of the present invention.

First, a document image is acquired in digital form (S210).

Various methods well known in the art can be used to obtain an image in digital form to obtain a document image.

Next, a histogram of the document image obtained in digital form is extracted (S220).

Here, the histogram for the document image is preferably extracted as a plurality.

Also, depending on the implementation method, the histogram of the document image may include both a Y-axis histogram obtained along the X-axis direction with respect to the Y-axis coordinate and an X-axis histogram obtained along the Y-axis direction with respect to the X-axis coordinate.

According to the implementation method, it is also possible to extract a plurality of histograms of the document image by dividing the document image into the respective regions. For example, it is possible to divide the document image into four rectangular regions having the same width and height, and to extract the X- and Y-axis histograms within each region.

Also, depending on the implementation method, a plurality of Y-axis histograms for the document image can be extracted by sequentially changing the projected angle on the document image. For example, the Y-axis histogram for each angle can be extracted by sequentially changing the angle between the projection direction and the X-axis from -45 ° to 45 ° while the acquired document image is fixed.

Also, depending on the implementation method, a plurality of X-axis histograms for the document image can be extracted by sequentially changing the projected angle on the document image. For example, the X-axis histogram for each angle can be extracted by sequentially changing the angle between the projection direction and the Y-axis from -45 ° to 45 ° with the acquired document image fixed.

On the other hand, since the degree of inclination of the document image is constant in the entire area of the document image, only a part of the document image can be extracted to extract a histogram of a part of the document image.

Next, the slope of the document image is determined by analyzing the extracted histogram (S230).

In order to determine the slope of the document image, a number of reference histograms stored in memory may be used. Here, the reference histogram refers to a histogram of representative typical document images obtained when the general document image is inclined at a certain angle. Thus, the reference histogram may include a reference histogram from -45 ° to 45 °, such as a 0 ° reference histogram, a 10 ° reference histogram, a 20 ° reference histogram, and the like. In the case of using the reference histogram, the reference histogram having the most similar shape can be selected by comparing the extracted histogram and the plurality of reference histograms classified by the angle unit one by one, and the angle value of the reference histogram can be determined by the slope. Of course, it is also possible to use a reference histogram that is divided into a plurality of regions (for example, a left upper region, a lower left region, a right upper region, a right lower region, and the like)

In addition, when a plurality of Y-axis histograms for a document image are extracted by sequentially changing the projected angles on the document image, a 0 ° reference Y-axis histogram (i.e., an angle of 0 ° with respect to a general document image with a slope of 0 ° , And the projection angle of the Y-axis histogram can be determined by the slope of the document image. In FIG. 3A, an exemplary 0 degree reference Y axis histogram 310 is shown.

In addition, when a plurality of X-axis histograms for a document image are extracted by sequentially changing the projected angles to the document image, a 0 ° reference X-axis histogram (i.e., an angle of 0 ° Axis histogram), and the slope of the document image can be determined using the projection angle of the X-axis histogram. In FIG. 3B, an exemplary 0 degree reference X-axis histogram 320 is shown.

As can be seen in FIGS. 3A and 3B, the 0-degree Y-axis histogram and the X-axis histogram for the general document image have angular shapes. With this feature, in the present invention, it is also possible to use a method of selecting the most angled Y-axis histogram among the plurality of extracted Y-axis histograms and determining the projection angle of the Y-axis histogram as the slope of the document image. Also, a method of selecting the most angled X-axis histogram among the extracted X-axis histograms and determining the slope of the document image based on the projection angle of the X-axis histogram can be used

Here, the reference histogram having the shape most similar to the extracted histogram is selected, or the shapes of the objects in the image are compared to select the X-axis and Y-axis histograms most similar to the 0-degree X-axis and Y-axis histogram A known technique can be employed in the present invention. Further, in order to select the most angular Y-axis histogram, a known technique for analyzing the edge shape of an object can be employed in the present invention.

Next, based on the slope of the document image, the slope of the document image is corrected so that the document image has a desired slope (S240).

Step 240 may mean rotating the document image clockwise by the determined document image slope. For example, if it is determined in step 230 that the document image has been skewed by 10 degrees, then in step 240, the document image may be rotated clockwise by 10 degrees.

Next, the document image with the inclination corrected selectively can be printed out (S250).

Step 250 may be performed by a user's prior request (i.e., a request before step S210 is performed) or a post request (i.e., after step S240 has been performed) and may be implemented using a known print output method .

According to the document image correction method of the present invention, even when a document is arranged so that the user unintentionally tilts from a predetermined position, the document image aligned in both the horizontal and vertical directions can be printed out.

Figures 4A-4E illustrate an example of correcting the slope of a document image, in accordance with an embodiment of the present invention.

As shown in FIG. 4A, the document image 410 may be obtained in digital form. In this embodiment, the document image 410 is a general document image in which characters, numbers, signs, figures and the like are aligned in the horizontal direction, and has a slope of -10 degrees, i.e., -10 degrees with respect to the horizontal line or X axis It is assumed to be obtained by tilting.

Next, as shown in FIGS. 4B to 4D, a plurality of histograms 420, 430, and 440 for the document image 410 obtained in digital form can be extracted. Here, the plurality of histograms 420, 430, and 440 may be obtained by changing the angle of projection onto the document image 410. [ More specifically, the first histogram 420 can be extracted as a result of extracting the Y-axis histogram for the document image 410 at a projection angle of 10 degrees, and the first histogram 420 for the Y The second histogram 430 can be extracted as a result of extracting the axis histogram and the third histogram 440 can be extracted as a result of extracting the Y axis histogram for the document image 410 at a projection angle of -10 degrees.

Next, the obtained plurality of histograms 420, 430, and 440 may be analyzed to determine the slope of the document image 410. More specifically, the histograms of the three histograms 420, 430, and 440 may be selected, and the projection angle of the selected histogram may be determined by the slope of the document image 410. 10 and 0, the first histogram 420 and the second histogram 430 have a gentle shape because the histogram is extracted so as to be offset from the direction in which the characters and the like are aligned. However, when projecting at an angle of -10 degrees, the third histogram 440 has a very angular shape because the histogram is extracted in accordance with the aligned direction of the characters and the like. The third histogram 440 having the most angular shape may be selected and the projection angle of -10 degrees with respect to the third histogram 440 may be determined as the slope with respect to the document image 410.

Next, based on the slope of the determined document image 410, the slope of the document image 410 may be corrected such that the document image 410 has a desired slope, as shown in FIG. 4E. In the present embodiment, the tilt corrected document image 450 is obtained by rotating the document image 410 having the slope of -10 degrees clockwise by -10 degrees, assuming that the desired slope is 0 deg. .

The skew corrected document image 450 may be stored in memory in a file form and may be printed out by a user's pre- or post-request.

According to the present invention, it is possible to accurately measure the degree of inclination of a document image and to correct the inclination of the document image automatically without requiring any user intervention, so that the document image can be printed out or stored. Therefore, since the user does not need to pay much attention to arrange the document image at the predetermined position, the user convenience can be improved when copying, scanning, and faxing the document image.

Each block of the block diagrams attached hereto and combinations of steps of the flowchart diagrams may be performed by computer program instructions. These computer program instructions may be loaded into a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus so that the instructions, which may be executed by a processor of a computer or other programmable data processing apparatus, And means for performing the functions described in each step are created. These computer program instructions may also be stored in a computer usable or computer readable memory capable of directing a computer or other programmable data processing apparatus to implement the functionality in a particular manner so that the computer usable or computer readable memory It is also possible that the instructions stored in the block diagram include each block of the block diagram or instruction means for performing the functions described in each step of the flowchart. Computer program instructions may also be stored on a computer or other programmable data processing equipment so that a series of operating steps may be performed on a computer or other programmable data processing equipment to create a computer- It is also possible that the instructions that perform the processing equipment provide the steps for executing the functions described in each block of the block diagram and at each step of the flowchart.

In this specification, each block may represent a portion of a module, segment, or code that includes one or more executable instructions for executing the specified logical function (s). It should also be noted that in some alternative implementations, the functions mentioned in the blocks may occur out of order. For example, two blocks shown in succession may actually be executed substantially concurrently, or the blocks may sometimes be performed in reverse order according to the corresponding function.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software module may reside in a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, a CD-ROM or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor, which is capable of reading information from, and writing information to, the storage medium. Alternatively, the storage medium may be integral with the processor. The processor and the storage medium may reside within an application specific integrated circuit (ASIC). The ASIC may reside within the user terminal. Alternatively, the processor and the storage medium may reside as discrete components in a user terminal.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the present invention is not limited to the disclosed exemplary embodiments, but various changes and modifications may be made without departing from the spirit and scope of the invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the scope of the present invention but to limit the scope of the technical idea of the present invention. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

100: Document image correction device
110: document image obtaining unit
120: histogram extracting unit
130:
140: tilt correction section
150: Document output section
160:
170: memory
310: Y-axis histogram based on 0 °
320: X-axis histogram based on 0 °
410: Document image
420: first histogram
430: second histogram
440: Third histogram
450: Tilted document image

Claims (10)

Obtaining a document image in a digital form;
Extracting a histogram of the document image;
Analyzing the histogram to determine a slope of the document image; And
And correcting the slope of the document image so that the document image has a desired slope based on the determined slope of the document image. The method according to claim 1,
Further comprising the step of printing and outputting the document image whose tilt has been corrected. The method according to claim 1,
Wherein a plurality of histograms of the document image are extracted. The method according to claim 1,
Wherein determining the slope of the document image comprises:
Comparing the extracted histogram with a plurality of reference histograms previously stored in a slope unit;
And determining a slope of a reference histogram closest to the extracted histogram as a slope with respect to the document image. The method according to claim 1,
Extracting a histogram for the document image includes extracting a plurality of Y-axis histograms for the document image by changing an angle projected onto the document image,
Wherein the step of determining the slope of the document image comprises determining the slope of the document image based on the extracted plurality of Y-axis histograms. 6. The method of claim 5,
Determining a slope of the document image based on the extracted plurality of Y-axis histograms,
Selecting a Y-axis histogram closest to the 0-degree Y-axis histogram among the plurality of extracted Y-axis histograms; And
And determining a projection angle of the selected Y-axis histogram as a slope of the document image. 6. The method of claim 5,
Comparing the plurality of Y-axis histograms with each other to determine a slope of the document image,
Selecting the most angled Y-axis histogram among the plurality of extracted Y-axis histograms; And
And determining a projection angle of the selected Y-axis histogram as a slope of the document image. The method according to claim 1,
Wherein extracting the histogram for the document image includes extracting a plurality of X-axis histograms for the document image by changing an angle projected onto the document image,
Wherein determining the slope of the document image comprises:
Selecting an X-axis histogram closest to the 0-degree reference X-axis histogram among the plurality of extracted X-axis histograms, and
And determining a slope of the document image with a projection angle with respect to the selected X-axis histogram. A document image acquiring unit in a digital form;
A histogram extracting unit for extracting a histogram of the document image;
A slope determining unit for analyzing the histogram to determine a slope of the document image; And
And a tilt correcting section for correcting the tilt of the document image so that the document image has a desired tilt based on the determined slope of the document image. 43. A computer-readable medium for storing a set of instructions,
Wherein the sets of instructions cause the computing device to, when executed by the computing device,
The document image is acquired in a digital form,
Extract a histogram of the document image,
Analyze the histogram to determine the slope of the document image, and
And based on the determined slope of the document image, corrects the slope of the document image such that the document image has a desired slope.

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