JP2000253250A - Picture data ground judging method, device therefor and medium recording picture data ground control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a picture to be clearly by obtaining picture data expressed by multi-gradations with the picture element of a dot matrix form, adding gradations, generating degree distribution, calculating the statistical quantity of the characteristic display of an area divided by prescribed gradation and deciding that an area constituting a ground exists when statistical quantity shows a value sufficient for constituting the ground. SOLUTION: A color scanner 20 starts scanning and generates picture data formed of the picture element of low resolution on the picture of a whole flat bed containing the picture of a document. Thus, pre-scanning is executed. It is decided whether or not an area constituting the ground exists in picture data of the document picture, based on a prescribed method from generated picture data. The color scanner 20 operates the flat bed and starts the real scanning of high resolution. A correction processing is executed on picture data which is read by real scanning by a correction curve, based on a prescribed statistical value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image data base determination method, an image data base determination apparatus, and a medium on which an image data base determination control program is recorded. The present invention relates to an image data base determination method, an image data base determination apparatus, and a medium in which an image data base determination control program is determined based on a predetermined frequency distribution.

[0002]

2. Description of the Related Art When handling images on a computer or the like,
Image data of an input image acquired from an image input device such as a scanner or a digital camera is represented by dot matrix pixels, and each pixel is represented by a gradation value. In such cases,
640 dots horizontally on the CRT screen of the computer,
In many cases, an image is displayed with 480 pixels in the vertical direction. Further, since each pixel has data representing a color or brightness by a gradation value, image processing is performed by changing this data. As this image processing, image processing for removing a background is performed on a document image or the like. Here, the background of the document image refers to a set of pixels representing a paper area of the document paper, and is also referred to as a background or a backside. The removal of the background means to change the gradation of the pixel representing the area of the paper to the maximum. That is, when a document image is printed after this image processing, the pixel having the maximum gradation as described above is not printed, and the pixel portion remains on the paper. Therefore, apparently, the pixels in the portion representing the area of the paper are removed, and it is possible to obtain a printed material with sharpness in the base and the character. In such a case, regardless of the presence or absence of the base, the gradation of a pixel having a gradation equal to or higher than a predetermined threshold is uniformly maximized. As an application example, when document paper having both sides printed is read by a scanner, the document image is used to prevent the image data on the back side from being reflected on the image data on the front side of the document image. Since the show-through appears in an area of the surface where nothing should be printed, the show-through is removed by maximizing the gradation of the pixels in this area.

[0003]

The above-described conventional image processing for removing a background has the following problems.
That is, in the background removal processing, regardless of the presence or absence of the background, image processing is uniformly performed on the entire image on the assumption that there is a background. Therefore, the input image has a base,
When the gradation of the luminance of the background is relatively low, there is a problem that the background cannot be removed. In addition, even if this background removal processing is performed, since the image processing is uniform, it is not possible to perform the optimum background removal processing for each input image, so that the background part remains or an image other than the background and the background is removed. There is a problem that the nails disappear.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and determines the presence or absence of a background in an image based on a predetermined frequency distribution of image data constituting the image. Image data background determination method, image data background determination device, and image data background determination device capable of performing a predetermined image data modification process and attaching a base between an image reproduced by the image data and an image other than the background. It is intended to provide a medium in which a control program is recorded.

[0005]

According to a first aspect of the present invention, there is provided an image data base determination method for determining an area constituting a base in an image based on a predetermined frequency distribution of image data. There is provided an image data obtaining step of obtaining image data in which an image is represented by multi-gradation using pixels in a dot matrix, and a gradation distribution is calculated by summing up the gradation for each pixel of the image data obtained in the image data obtaining step. A frequency distribution creating step of creating, and calculating a statistic indicating a characteristic of an area divided by a predetermined gradation of the frequency distribution, and when the statistic indicates a value sufficient to constitute a base, the image And a background determination step of determining that an area constituting the background exists.

[0008] In the invention according to claim 1 configured as described above, the image background determination method determines an area constituting a background in an image by each pixel constituting image data based on a predetermined frequency distribution. In such a case, the image data obtaining step obtains image data in which an image is expressed in multiple gradations by pixels in a dot matrix. Next, in the frequency distribution creating step, the image data of each pixel of the image data acquired in the image data acquiring step is analyzed, and the gradation of the image data of each pixel is totaled. Then, a frequency distribution based on the gradation and the frequency of each gradation is created based on the totaled result. Here, in the background determination step, in the frequency distribution described above, a region for determining the presence or absence of a background is classified according to a predetermined gradation, and a statistic for displaying characteristics of the divided region is calculated. If this statistic has a value sufficient to determine the background in the image data, it is determined that the background exists in the image. That is, the statistic of the section divided by the predetermined gradation is calculated from the frequency distribution of the gradation of each pixel constituting the image data, and if the statistic is larger or smaller than the predetermined threshold, the input is performed. It is determined that a background exists in the image obtained. Specifically, when each or the total of the relative frequencies of the region divided by this predetermined gradation is a predetermined threshold value and is overwhelmingly large, or when the standard deviation of this region is calculated, If it is equal to or less than a predetermined threshold value, it is determined that a background exists. The case where the relative frequency is overwhelmingly large indicates that the relative frequency is overwhelmingly large in a range that can be regarded as the background, and it is needless to say that the relative frequency is different from the overwhelming size captured from a numerical sense. For example, even if the relative frequency of an area divided by a predetermined gradation is 15%, it may be considered that the relative frequency is overwhelmingly large when judging from a part forming an image. The predetermined threshold value may be a predetermined fixed value, or may be appropriately changed according to the frequency distribution of the gradation of the image data of the input image. Further, the area divided by the predetermined gradation can be appropriately changed according to the desired base to be determined. When determining the base of the high gradation, the area near the high gradation may be divided, When determining the background of the gradation, an area near the low gradation may be divided. Here, the background in the input image described above indicates, for example, when the input image is a document image, a set of pixels representing an area of a document sheet, that is, a background or a back-face. The color component of the background is not particularly limited since it is appropriately changed according to the background determined as described above.

In the image data obtaining step, it is sufficient that the image data can be obtained by expressing the image in multiple gradations by using dot matrix pixels. Therefore, the input source of the image may be a scanner or a digital camera,
If it is possible to obtain image data expressed in multiple gradations by using pixels in a dot matrix, the image data can be changed as appropriate. In the frequency distribution creating step, it is only necessary to be able to create a frequency distribution in which the gradation of each pixel of the image data acquired in the image data acquiring step is counted and the tone tendency of the image can be recognized. Therefore, the pixels for which the gradation is counted may be implemented for all the pixels of the input image, or may be appropriately sampled and implemented. Needless to say, if sampling is used, the calculation time can be reduced. In such a case, a sampling image may be acquired at the stage of the image data acquiring step described above. The background determination step calculates a statistic in an area obtained by dividing the frequency distribution created in the frequency distribution creating step by a predetermined gradation, and exists in the image acquired in the image data acquiring step based on the statistic. It is only necessary that the base can be determined. Therefore, the statistic calculated as described above may be the relative frequency of an area divided by a predetermined gradation in the frequency distribution, or the standard deviation of this area. Of course, the present invention is not limited to these statistical values, and various statistical values, for example, those that determine the presence of a base using the nearest value, the median value, and the average value may be used. Conditions that can determine the presence of the background may be set by combining statistical values.

Each pixel is provided with gradation values for each of R (red), G (green), and B (blue) as data when the input image is a color image. Is provided as data. If the frequency distribution creation process is the former,
The RGB gradation values of each pixel are totaled for each gradation to create a frequency distribution. In the latter case, the luminance gradation of each pixel is totaled to generate a frequency distribution. Also, for an RGB color image, the luminance may be calculated from the RGB data, and the luminance gradation may be totaled to create a frequency distribution. Here, as an example of the latter, according to the second aspect of the present invention, in the image data base determination method according to the first aspect, the frequency distribution creating step calculates the luminance of each pixel and calculates a level of the same luminance. The configuration is such that keys are totaled and a frequency distribution is created.
In the invention according to claim 2 configured as described above,
In the frequency distribution creating step, if the input image is a color image, the luminance of each pixel is calculated from the RGB data of each pixel, and a gradation value indicating shading is obtained. If the input image is a binary image, a gradation value indicating the density of the pixel is obtained. Then, the gradations of each luminance are totaled to create a frequency distribution.

As an example of the former for creating the above-described frequency distribution, the invention according to claim 3 is the image data background determination method according to claim 1, wherein the frequency distribution creating step includes: In addition to the decomposition, the gradation of each element color is totaled, and a frequency distribution for each element color is created. In the invention according to claim 3 configured as described above, in the frequency distribution creating step, each pixel of the input color image is set to an element color, that is, the image data of each pixel is converted to an R color.
In addition to performing color separation into GB element colors, gradations are totaled for each element color, and a frequency distribution is created.

Here, the background determination step determines whether or not a background exists in the image based on the luminance distribution of each pixel constituting the image data or the frequency distribution based on the gradation of element colors. judge. Various methods can be adopted as a method of determining the presence of the base. Here, as a specific example of a method of determining the presence of a base from the frequency distribution, the invention according to claim 4 is based on claims 1 to
4. The image data background determination method according to claim 3, wherein the background determination step calculates a relative frequency of a region divided by a predetermined gradation in the frequency distribution, and calculates the relative frequency of the calculated relative frequency. When each or the sum is equal to or more than a predetermined threshold value, it is configured that it is determined that there is a region constituting the base in the image. In the invention according to claim 4 configured as described above, the background determination step calculates a relative frequency of an area divided by a predetermined gradation in the frequency distribution. If each of the calculated relative frequencies or the sum is equal to or greater than a predetermined threshold value, it is determined that a background region exists in the image. In other words, when the number of pixels in the divided area estimated as the background is equal to or larger than the threshold value as compared with the total number of pixels, it is determined that the background exists in the image. Needless to say, the method of determination is not limited to the method performed when the threshold is equal to or higher than the predetermined threshold. From the opposite viewpoint, the relative frequency other than the divided area becomes equal to or lower than the threshold. Therefore, the present invention is not limited to the determination method of being equal to or less than the threshold value, and can be appropriately changed as long as the presence of the base can be determined from the relative frequency.

According to a fifth aspect of the present invention, there is provided an image data base determining method according to any one of the first to third aspects. The background determination step calculates the relative frequency in each tone of the area divided by the predetermined tone of the frequency distribution, and when the sum of the tone having the predetermined relative frequency is equal to or more than a predetermined threshold, The configuration is such that it is determined that there is a region constituting the background in the image. In the invention according to claim 5 configured as described above, the background determination step calculates a relative frequency at each tone in an area divided by a predetermined tone in the frequency distribution. When the sum of the gradations having the predetermined relative frequency is equal to or larger than the predetermined threshold value, it is determined that the background area exists in the image.
Specifically, the area divided by the predetermined gradation is represented by gradation 20.
From 0 to gradation 255, the above-mentioned predetermined relative frequency is 10
Consider the case where the threshold is 10. First, in the background determination step, a relative frequency is calculated for each of 56 gray levels in this area. Then, it is determined whether or not each relative frequency is 10%. Here, gradation 2
If the relative frequency from 30 to 255 exceeds 10%, the total number of tones satisfying this condition is 26 tones. Next, it is determined whether or not the sum of the gradations is equal to or larger than a threshold value. In such a case, since the total is equal to or larger than the threshold value, it is determined that there is a region constituting the base in the image.

Further, as another example of a method of judging the existence of a region constituting a background on the basis of a frequency distribution, the invention according to claim 6 is the image data according to any one of claims 1 to 3. In the background determination method, the background determination step calculates a standard deviation in an area divided by a predetermined gradation of the frequency distribution, and, when the standard deviation is equal to or less than a predetermined threshold, adds a background to the image. It is configured to determine that the region to be configured exists. In the invention according to claim 6 configured as described above, the background determination step calculates a standard deviation in an area divided by a predetermined gradation of the frequency distribution, and the standard deviation is equal to or less than a predetermined threshold. In the case of, it is determined that there is an area constituting the background in the image. If the standard deviation is less than or equal to the threshold,
This indicates that the frequency distribution has a sharp peak in a region divided by a predetermined gradation. Here, the base has a similar color component to represent the color of the paper. For this reason, the color components of the background are counted to the same degree on the frequency distribution. At this time, the frequency distribution near the gradation at which the background is counted has a sharp peak. Therefore, it is possible to determine the background by calculating the standard deviation and using the fact that the standard deviation is equal to or smaller than the threshold value.

[0013] The existence of a region constituting the background of the image is determined based on the relative frequency and the standard deviation of the region divided by a predetermined gradation. Here, as the determination method, the determination may be performed using only the relative frequency and the standard deviation as described above, or a determination method may be employed in combination with other statistical values. According to a seventh aspect of the present invention, in the image data background determination method according to any one of the fourth to sixth aspects, the background determination step includes the step of dividing the frequency distribution by a predetermined gradation. , The representative value is calculated, and the representative value is combined to determine that there is an area constituting the background in the image. In the invention according to claim 6 configured as described above, the background determination step calculates a representative value in an area divided by a predetermined gradation of the frequency distribution, and combines the representative value to form a background on the image. It is determined that the region to be configured exists. Here, the representative value may be a most probable value, an average value, or a median value of an area divided by a predetermined gradation, and may be appropriately changed. is there.

Here, in the frequency distribution, since the tone of the pixel of the noise component included in the input image also appears in the frequency, the noise component may influence the calculation result of the statistic. Therefore, as a preferable method for reducing the noise component that has entered the frequency distribution,
According to an eighth aspect of the present invention, in the image data background determination method according to any one of the first to seventh aspects, the background determination step includes calculating a statistical value of an area divided by a predetermined gradation of a frequency distribution. Is calculated, a smoothing process is performed on the same frequency distribution. In the invention according to claim 8 configured as described above, the background determination step performs a smoothing process on the same frequency distribution when calculating the statistical value of the area divided by the predetermined gradation of the frequency distribution. carry out. Thus, since the statistic is calculated based on the frequency distribution from which the noise component has been removed, the calculation result is not affected by the noise component.

As described above, by performing predetermined image processing on each of the pixels constituting the determined base, it is possible to add a picture to the base and an image other than the base. Therefore, the invention according to claim 9 is based on claims 1 to
9. The image data background determination method according to claim 8, wherein the background determination step modifies the image data of each pixel according to the region constituting the background when the image has a region constituting the background. It is configured to include an image data modifying step of performing a modifying process. In the invention according to claim 9 configured as described above, the image data modifying step includes the step of: if the image includes a region forming a base, the image determining unit determines each pixel according to the region forming the base. A retouching process for retouching the image data is performed. Here, the image data retouching step may be a retouching process for retouching the image data of each pixel in accordance with the region constituting the same base. The retouching process is performed when it is determined that the region exists. May be executed according to a fixedly determined one, or may be executed according to a variablely determined area. Further, as an example of the modification processing, there is a background removal processing for removing a region constituting the background. When the input image is a document, the background removal process is a process of changing the gradation of the pixel representing the area of the document paper to the maximum gradation. That is, when a document image is printed after the modification process, the pixel whose gradation is set to the maximum gradation as described above is not printed, and the pixel portion remains on the paper. Therefore, apparently, the pixels in the portion representing the area of the paper are removed, and it is possible to obtain a printed matter having a squeezed base and characters.

According to a tenth aspect of the present invention, as a specific example of the image data modifying method, in the image data base determining method according to the ninth aspect, the image data modifying step forms a base of the image. When the region is near the highlight, a correction curve having a parameter that maximizes the gradation of each pixel in the vicinity of the highlight is generated, and each of the correction curves obtained in the image data obtaining step based on the correction curve is generated. The configuration is such that the gradation of the pixel is corrected. In the invention according to claim 9 configured as described above, in the image data modifying step, when an area constituting the base of the image is near a highlight, the tone of each pixel near the highlight is set to the maximum tone. A correction curve having the parameters to be generated is generated, and the gradation of each pixel obtained in the image data obtaining step is corrected based on the correction curve.

On the other hand, if the input image is a sentence image,
The image other than the background is a character, and if it is a photographic image, the image other than the background is a photograph. If the image data is corrected based on the same correction curve as that composed of a single black color, such as characters, for images that contain various colors, as in this photo, the gradation jumps in the photo portion It can get bigger. Therefore, according to an eleventh aspect of the present invention, in the image data background determination method according to any one of the ninth and tenth aspects, the background determination step determines the presence or absence of an object included in the image based on a predetermined method. If it is determined that there is an object, the image data modifying step changes the parameter of the correction curve. In the invention according to claim 11 configured as described above, the background determination step determines the presence or absence of an object included in the image based on a predetermined method, and if there is an object, the image data modification step includes the correction Change curve parameters. In other words, when there is an object corresponding to a photograph part, the width to be clamped to the maximum gradation is narrowed, and when an image is composed of characters and the like,
Increase the width to clamp to the maximum gradation. This makes it possible to prevent gradation jumps in the photographic part of the image after the retouching processing in an image including a photographic part, and to reduce the retouching image in a binary image composed of characters and the like. It becomes something with a beam.

As described above, the method of determining the existence of the region constituting the background in the image based on the predetermined frequency distribution of the image data is not necessarily limited to the method, and the method is implemented by incorporating the method into the entity. Therefore, it can be easily understood that the device can be used as a device for realizing the function. Therefore, according to the twelfth aspect of the present invention, there is provided an image data acquiring unit for acquiring image data in which an image is expressed by a plurality of gradations using dot matrix pixels, A frequency distribution creating unit that aggregates gradations and creates a frequency distribution, and a statistic that displays characteristics of an area divided by a predetermined gradation of the frequency distribution is calculated, and the statistic forms a base. When the value indicates a sufficient value, the image processing apparatus includes a background determination unit that determines that an area constituting the background exists in the image. That is, there is no difference in that the present invention is not necessarily limited to the method and is effective as a substantial device.

By the way, an image data base determination device for determining the presence of a region constituting a base in an image based on a predetermined frequency distribution of image data may exist alone or may be incorporated in a certain device. The concept of the invention is not limited to this, and may include various aspects, for example, it may be used in a state where it is used. Therefore, it can be changed as appropriate, such as software or hardware. As an example of an embodiment of the idea of the present invention, in the case of software of an image data base determination device that determines a region constituting a base in an image based on a predetermined frequency distribution of image data, the image data is recorded on a recording medium on which the software is recorded. Naturally exist and must be said when used.

As one example, the invention according to claim 13 is a medium in which an image data base determination control program for determining an area constituting a base in an image based on a predetermined frequency distribution of image data is recorded. Image data obtaining step of obtaining image data in which a plurality of gradations are represented by pixels in a dot matrix form, and a frequency for creating a frequency distribution by summing up the gradation for each pixel of the image data obtained in the image data obtaining step. A distribution creating step, calculating a statistic indicating a characteristic of an area divided by a predetermined gradation of the frequency distribution, and when the statistic indicates a value sufficient to constitute a base, the base is added to the image. And a background determination step of determining that there is a region to be configured.

Of course, the recording medium may be a magnetic recording medium, a magneto-optical recording medium, or any recording medium to be developed in the future. Also, the duplication stages of the primary duplicated product, the secondary duplicated product, and the like are equivalent without any question. In addition, the present invention is not limited to the case where the present invention is used even when the supply is performed using a communication line. further,
The concept of the present invention is not completely different even when part is software and part is realized by hardware, and part is stored on a recording medium and read as needed as needed. Such a form may be adopted.

[0022]

As described above, according to the present invention, a region constituting a background in an image is determined based on a predetermined frequency distribution of image data, and when a background region exists, a predetermined modification corresponding to the background is performed. It is possible to provide an image data base determination method capable of executing a process and attaching a base of an image reproduced by image data to an image other than the base. According to the second aspect of the invention, it is possible to create a frequency distribution by summing up the gradation of each pixel of the input image based on a simple method.
Furthermore, according to the third aspect of the present invention, it is possible to create a frequency distribution appropriately indicating a state of an image for a color image. Furthermore, according to the invention of claim 4, since the presence or absence of the base in the image is determined based on the relative frequency of the area divided by the predetermined gradation, the determination can be easily performed. Further, according to the invention according to claim 5, since the determination is made based on a predetermined relative frequency of an area divided by a predetermined gradation and exceeding a predetermined threshold value, the background in the image can be more accurately determined. Can be determined. Further, according to the invention of claim 6, it is possible to determine the presence or absence of a base in an image based on the standard deviation of an area divided by a predetermined gradation. Furthermore, according to the seventh aspect of the invention, it is possible to more accurately determine the existence of the region constituting the base by determining the combination of other statistics of the region divided by the predetermined gradation. become. Furthermore, according to the invention of claim 8, since the feature amount is extracted from the frequency distribution in which the noise component included in the input image is reduced, it is possible to more accurately determine the presence or absence of the background. Furthermore, according to the ninth aspect of the present invention, it is possible to perform a predetermined image data modifying process according to the presence or absence of a base. Further, according to the tenth aspect of the present invention, it is possible to remove an area near a highlight constituting a base of an image by a simple method.

Further, according to the present invention, when an object such as a photograph exists in an input image, it is possible to perform a preferable image data modifying process. Further, according to the invention of claim 12,
A region constituting a background in the image is determined based on a predetermined frequency distribution of the image data, and if a background region exists, a predetermined modification process is performed in accordance with the background, and the background of the image reproduced by the image data is performed. It is possible to provide an image data base determination device capable of applying a color to an image other than the base and the image other than the base. Further, according to the invention according to claim 13, the region constituting the background in the image is determined based on the predetermined frequency distribution of the image data, and if the region of the background exists, the predetermined modifying process according to the background is performed. According to the present invention, it is possible to provide a medium in which an image data base determination control program capable of attaching a base of an image reproduced by image data and an image other than the base is recorded.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a claim correspondence diagram of an image data base determination method according to an embodiment of the present invention. In the figure, the image data base determination method roughly determines the presence of a region constituting a base in an image based on a predetermined frequency distribution of image data forming the image. Specifically, in the image data obtaining step A1, image data in which an image to be subjected to background determination is expressed in multiple gradations by dot matrix pixels is obtained. Next, the frequency distribution creating step A2 totals the gradation for each pixel of the image data acquired in the image data acquiring step A1, and creates a frequency distribution. Then, the background determination step A3 calculates a statistic indicating the characteristics of the area divided by the predetermined gradation of the frequency distribution, and if the statistic indicates a value sufficient to form the background, the base image determination step A3 includes It is determined that there is a region constituting the base. Here, in the background determination step A3, when there is a region constituting the background near the high gradation of the image, the image data modification is performed by modifying the image data of each pixel according to the region constituting the background. Step A4 is provided. The image data modifying step A4 generates a correction curve having a parameter for setting the vicinity of the high gradation, that is, the gradation of each pixel forming substantially white to the maximum gradation, that is, white, and based on the correction curve. To correct the gradation of each pixel obtained in the image data obtaining step.

Next, FIG. 2 is a perspective view showing the appearance of a color copying apparatus which is applied to constitute an image data base determination apparatus which embodies the present image data base determination method. The color copying apparatus 10 includes a color scanner 20 and a copy server 3
0, and a color printer 40, and the color scanner 20 based on the control of the copy server 30.
When the image is scanned, the copy server 30 performs image processing on the image data read by the scan to generate print data, and the color printer 40 performs printing based on the print data.

FIG. 3 shows a schematic configuration of the color scanner 20, which employs a flatbed type. In the figure, an illumination lamp 22 and a line sensor 23 are slidably supported below a transparent plate 21 on which an object to be scanned is placed, and a driving belt 24a and a pulley 24b for driving these lamps. Drive motor 2
4c are connected to the control circuit 25. When reading an image, when the illumination lamp 22 is turned on based on a control signal from the control circuit 25, the object to be scanned is illuminated via the transparent plate 21. Therefore, the reflected light from the scan target illuminates the transparent plate 21. The light is radiated to the line sensor 23 via the light source.

Here, the line sensor 23 is provided with RGB filters and CCD elements corresponding to the three primary colors of light, one row for each color, usually three rows, and the three rows of CCD elements extend in the horizontal direction of the scanning object. The color arrangement for one row is read and output as image data. On the other hand, the control circuit 25 drives the drive motor 24c to
The illumination lamp 22 and the line sensor 24 are integrally moved in the vertical direction of the scan target, and image data is acquired and output from the line sensor 23 each time the illumination lamp 22 and the line sensor 24 are moved by a minute distance. Accordingly, externally, the object to be scanned is sub-scanned in the vertical direction while main scanning in the horizontal direction, and two-dimensional image data is generated.

FIGS. 4 and 5 show the copy server 30 in a schematic block diagram. The copy server 30 is roughly equivalent to a computer, and a RAM 33, a ROM 34 and an operation panel 35 are connected to a bus 32 of the CPU 31.
And the hard disk 36 and the I / F 37 are connected. Here, the color scanner 20 and the color printer 40 are connected via the I / F 37. Further, a basic calculation program and a conversion table are written in the ROM 34, and the CPU 31 executes the calculation program while using the RAM 33 as a work area, and refers to the conversion table as needed. In the present embodiment, the I / F 37 is not specified, but the I / F 37 is used for the color scanner 20 and the color printer 40.
Can be connected to the copy server 30 and may be connected by an LPT port or may be connected by a USB port or SCSI.

The hard disk 36 has a scanner driver 38a for driving the color scanner 20 and a printer driver 38b for driving the printer 40. The scanner driver 38a receives image data from the color scanner 20 and the printer driver 38b is a color printer 40. The image data can be input and output to and from each other. Then, the hard disk 36 uses the image data as a buffer for temporarily storing the image data, reads the image data input by the scanner driver 38a, detects an area constituting the background included in the image data, and detects the detected area. An image data background determination control program 39 and the like which execute image data modification processing corresponding to the background area, output the image data subjected to the image data modification processing to the printer driver 38b, and cause the color printer 40 to execute printing. Stored. In addition, the operation panel 35
Is a ten key 3 for inputting a scan start button 35a, inputting the number of prints, and setting items for modifying an image.
In addition to various operation buttons such as 5b, a liquid crystal display 35c for confirming operation information is also provided.
1 is capable of monitoring the operation status of the operation panel 35 via the bus 32.

FIG. 6 schematically shows the structure of the color printer 40, which employs an ink jet system in which color ink is ejected onto a recording paper in a dot matrix form to perform printing. More specifically, a print head 41 including three print head units 41a,
Head controller 42 for controlling the print head and a print head girder moving motor 4 for moving the print head 41 in the girder direction
3, a paper feed motor 44 for feeding print paper in the row direction, a print head controller 42, a print head digit moving motor 43, and a printer controller 45 which serves as an interface between the paper feed motor 44 and external devices. .

The color printer 40 uses four color inks as print inks, and each print head unit 41a has two independent rows of print nozzles. The color ink to be supplied can be changed for each row of print nozzles. In this case, black ink (K) is supplied to both rows of the print head unit 41a on the left side in the figure, and the print head unit 41a on the right side in the figure.
With respect to, the magenta ink (M) is supplied to the left column, the yellow ink (Y) is supplied to the right column, and the cyan ink (C) is supplied to the left column for the print head unit 41a in the middle of the drawing. The right column is unused.

Although four color inks are used in this embodiment, three print head units 41 are used.
It is also possible to use six color inks by maximizing the use of the two rows of print nozzles in a. In this case, dark and light inks are used for cyan and magenta, and a total of six colors can be used using yellow and black. In the present embodiment, the present image data base determination device is applied as the integrated color copying device 10 formed integrally with the copy server 30 as a core, but the color scanner 51 shown in FIG. And a personal computer 5 equipped with a color printer 52
Needless to say, the third embodiment can be similarly realized even if a color copying system is adopted.

FIG. 8 is a flowchart showing an outline of the processing contents of the image data base determination processing according to the present invention, out of the color copying processing executed by the copy server 30 described above. Referring to FIG.
0 is the flatbed 2 of the color scanner 20.
When a document to be scanned is placed on the operation panel 1, the operation panel 3
At 5a, the scan start button 35a is pressed down. Thus, the color scanner 20 starts scanning. First, in order to generate image data composed of low-resolution pixels for the entire image of the flatbed 21 including the image of the document, a pre-scan is performed (step S10).
0). Then, it is determined from the generated image data based on a predetermined method whether or not there is a region constituting a base in the image data of the document image (step S200). Next, the color scanner 20 operates the flatbed 21 to execute predetermined image data modification processing described later based on the determination result, and obtains a high-resolution main scan that acquires detailed image data of the document image. Is started (step S300). Then, image data read processing is performed on the image data read by the main scan using a correction curve based on a predetermined statistical value of the area determined to be the background in step S200 (step S40).
0). When the image data modification process is completed, an image data conversion process for generating print data to be output to the color printer 40 is executed (step S500). As a result, image data modification processing is performed on the image data of the document image input in step S100 in consideration of the background area of the document image.

In the present embodiment, step S100
In step S200, a pre-scanning process is executed to determine a region constituting the background of the image based on the low-resolution sampled image data, and a step S300 is performed for the detailed image data acquired in the main scanning process. Although the configuration for executing the image data modification process in S400 is adopted, it goes without saying that the pre-scan process in step S100 is removed, and the area constituting the base of the image is determined based on the image data acquired by the main scan process. Alternatively, a configuration for executing image data modification processing may be employed.

Next, the respective steps S100 to S500 will be described in more detail with reference to the flowcharts of FIGS. The flowchart of FIG. 9 shows the processing content of the pre-scan processing of step S100. As described above, when the operator of this color copying apparatus places a document on the flatbed 21 as a scan target and depresses the scanner start button 35a, the I / O
An image reading command is sent to the color scanner 20 via O37 to start scanning (step S1).
01). Then, the pre-scan resolution set by the operator using the numeric keypad 35b is read (step S10).
5). Here, the control circuit 25 of the color scanner 20 turns on the illumination lamp 22, outputs a drive command to the drive motor 24c, and starts scanning of the image by sliding the illumination lamp 22 and the line sensor 23 (see FIG. 1). Step S110). Each time the control circuit 25 moves by a predetermined distance, the control circuit 25 generates image data of pixels obtained by dividing the image read by the line sensor 23 according to resolution (step S115), and transmits the image data to the copy server 30. The copy server 30 receives this image data via the I / F 37 and spools it on the hard disk 36. Here, if it is determined that all the scanning has been completed for the divided pixels (step S120), the spooled image data is stored in the hard disk 36 (step S125).

Accordingly, the pre-scan processing of acquiring and storing image data by executing low-resolution scanning in this manner constitutes an image data acquiring step A1. In the present embodiment, a configuration in which the pre-scan is executed at a predetermined low resolution is adopted.
pi or 60 dpi. The resolution may be stored in the RAM 34, the ROM 35, or the hard disk 36 in advance, or can be appropriately set by the predetermined method from the keyboard or mouse of the operation panel 35 or the personal computer 53 as described above. You may.

Then, a frequency distribution of each pixel included in the image data is created from the image data according to the flowchart of the background determination process in step S200 shown in FIG. 10, and the existence of the background area of the image is determined from the frequency distribution. I do. In the figure, first, the image data stored in the hard disk 36 in step S125 is read (step S201). Here, the color components of R (red), G (green), and B (blue) data constituting the color of each pixel of the image data are extracted. Since each color component has a density of gradation 0 to 255, the gradation Y of the RGB data is substituted into the following equation (1) for each pixel to calculate the luminance Y (step S205). Y = 0.30R + 0.59G + 0.11B (1) When the luminance is calculated for all the pixels of the image data according to the equation (1), the number of pixels is totaled for each gradation 0 to 255 of the luminance. Create the frequency distribution shown. Next, each gradation 0
Calculate the relative frequency at ~ 255. Frequency I of each gradation
Is represented by the following equation (2). I = f (n) n = 0 to 255 (2) Accordingly, the relative frequency in each gradation can be calculated by the following equation (3) (step S210).

[Formula 1] Then, in this frequency distribution, an extraction section of the background distribution, which is a region constituting the background of the image, is set (step S2).
15). In setting the section of the background distribution, first, the maximum frequency in the same frequency distribution is determined by the following equation (4). fmod = max [f (n)] n = 0 to 255 (4) Then, the gradation corresponding to the maximum frequency fmod is set as the closest value nmod. The closest value nmod is a gradation that forms the top of the frequency distribution as shown in FIG. Then, using the most probable value nmod, the gradations M1 and M2 for determining the extraction section of the background distribution are calculated based on the following equation (5).

M1 = nmod−N N <= nmod = 0 N> nmod (5) M2 = nmod + N−1 N <= 256-nmod = 255 N> 256-nmod Here, the constant N is predetermined. Is a positive integer. Specifically, N may be around 10. With the gradations M1 and M2, the extraction section of the background distribution is determined to be the section [M1, M2] as shown in FIG. Next, the accumulation of the relative frequency of each pixel in the extraction section of the background distribution determined as described above is calculated (step S220). This relative frequency can be calculated by the following equation (6) using the above equation (3).

[Formula 2] This relative frequency R can be indicated by the area of the hatched portion surrounded by the section [M1, M2] shown in FIG. 11 and the frequency distribution. As described above, the calculated relative frequency R in the extraction section of the background distribution and the most likely value nm in the frequency distribution
The existence of the background distribution is determined using the odd (step S225). In such a case, when the condition of the following equation (7) is satisfied, it is determined that the image has a region constituting the base.

R> Rth and nmod> nth (7) Here, Rth and nth are predetermined positive integers and constitute a predetermined threshold value. Specifically, R
th is about 0.15 and nth is 18
It is about 0. Of course, these numerical values are merely examples, and can be changed as appropriate. In this way, it is determined whether or not there is a region constituting the base. In the present embodiment, the processing for calculating the luminance and determining the portion constituting substantially white as the background is configured. However, this processing is performed for each color component based on the frequency distribution of each color component, and the respective frequencies are calculated. By considering the tendency of the distribution, it is also possible to determine the base formed by each color or a mixture thereof. Therefore, the luminance is calculated from the gradation that forms the color component of each pixel,
In addition to creating a frequency distribution of image data, creating a background distribution for determining an area constituting the background of the image from the same frequency distribution, and determining whether a background exists in the image based on a predetermined statistic of the background distribution. Is determined, step S2
The background determination processing of 10 to S225 is a frequency distribution creation step A2
And a base determination step A3.

Next, when it is determined that the image has a background, that is, a substantially white area formed by the ground of the paper of the predetermined amount of the document, an image described later corresponding to the background area is determined. In order to perform the data modification process, the main scan process is performed on the document image of the scan target placed on the color scanner 20. The processing content of the main scan processing is shown in the flowchart of FIG. At first,
The resolution of the main scan set by the operator using the numeric keypad 35b is read (step S301). Needless to say, the resolution is set to be higher than the resolution of the above-described pre-scan processing. And color scanner 2
The 0 control circuit 25 turns on the illumination lamp 22, outputs a drive command to the drive motor 24c, and starts scanning the image by sliding the illumination lamp 22 and the line sensor 23 (step S305). Every time the control circuit 25 moves by the distance, the control circuit 25 generates image data of pixels obtained by dividing the image read by the line sensor 23 according to resolution (step S310), and transmits the image data to the copy server 30. On the copy server 30 side, this image data is
It is received via F37 and spooled on the hard disk 36. Here, if it is determined that all the scanning has been completed for the divided pixels (step S315), the spooled image data is stored in the hard disk 36 (step S320). Therefore, the main scan processing of executing the main scan at a high resolution to acquire and store the image data of the document image while forming the image data constitutes an image data acquisition step A1 together with the pre-scan processing.

As described above, when it is determined that there is an area constituting the base, each pixel near substantially white is clamped to white, that is, the maximum gradation in the image data modification processing. Then, in the printing by the color printer 40, the ink is not applied to the print medium, so that the clamped portion remains as a white paper ground. Accordingly, in the image of the document, the contrast between the base paper region and the black portion of the character becomes clear, and it is possible to modify the image into a good-looking image with a sharp edge.

Next, the outline of the image data modifying process shown in the flowchart of FIG. 13 will be described, and the details of each process will be described below. . In the figure, first, a correction curve determination process is performed to determine a correction curve indicating a correspondence relationship in which modification is performed on each pixel of the image data (step S401). The gradation of each color component of the pixel is sequentially modified (step S450), and image data is generated.

FIG. 14 is a flowchart showing the contents of the correction curve determination process executed in step S401. In the figure, the most probable value nmod of the frequency distribution determined by the equation (4) is obtained (step S405).
Then, it is determined whether or not the gray level of the lowest value nmod is the gray level 255, that is, the maximum gray level (step S4).
10). Next, a section for calculating the statistic of the background distribution is set (step S415). The background distribution set here may be the section [M1, M2], or when the region to be the background is a substantially white portion, one of the gradations for dividing the region is set to the gradation 255. Alternatively, the other may be calculated by the following equation (8) and set. A = nmod−B * (255−nmod) (8) Here, the constant B is a variable determined in advance and is expressed by the following equation (9).
It is determined to satisfy the condition of. 0 <B <nmod / (255-nmod) (9) The variable B may be around 2 specifically. As described above, the section for calculating the statistic of the background distribution is the section [A, 25
5]. Next, the average value “nave” in this section [A, 255] is calculated by the following equation (10), and the standard deviation nstd is calculated by the following equation (11) (step S420).

[Equation 3]

(Equation 4)

Using the average value nave and the standard deviation nstd, a threshold value T of the correction curve is calculated based on the following equation (12) (step S425). T = nave−Cnstd (12) Here, the constant C is set to satisfy the condition of the following equation (13). C = C2 1−R> = Cth2 (13) = C1 Cth1 <= 1−R <Cth2 Further, C1 and C2 are predetermined positive integers, and Cth1 uses Rth. Is set by the following equation (14). Cth2 = 1−Rth (14)

In the present embodiment, C1 is set to about 4,
C2 is set to about 2, and Cth1 is set to about 0.7. When the threshold value T is calculated in this way, a correction curve is determined. In the present embodiment, as shown in FIG. 15, the correction curve clamps the input gray scale after the threshold T to the output gray scale 255 and has a slope 255 / T between the input gray scales 0 to T. It is formed by a primary straight line. Of course, it is sufficient if the input gradation of the gradation 255 can be clamped to the output gradation 255 from the threshold value T, and a quadratic curve may be formed between the input gradations 0 to T or a primary straight line having a different slope. It may be changed as appropriate. This correction curve is created for each of the RGB data. If the closest value nmod is 255 in step S410, a primary line having a slope 1 connecting (0, 0) and (255, 255) is generated between the input gradation and the output gradation. That is, the gradation of the threshold value T is set to 255.

Next, the processing contents of the image data modification processing in step S450 will be described with reference to the flowchart of FIG.
In the figure, first, image data generated by the main scan processing is obtained (step S455). Then, each pixel of the image data is scanned, and the gradation of each color component included in each pixel is set as an input gradation, substituted into a correction curve, and an output gradation is calculated (step S460). Step S455
It is determined whether or not the modification process based on the correction curve has been completed for all the pixels of the image data acquired in (Step S465).
Then, the next pixel is scanned, and the modification process is sequentially performed based on the correction curve. If the modification processing has been completed for all the pixels, the image data composed of the output gradation is stored in the hard disk 36 (step S470).

The image data generated as a result of the image data modifying process is subjected to a color conversion process and the like, sent to the color printer 40, and printed. Here, the processing content of the image data conversion processing executed before the modified image data is sent to the color printer 40 is shown in the flowchart of FIG. In the figure, first, image data modification processing is executed, and image data in which each pixel is constituted by output gradation is input (step S501), and color conversion is performed (step S505). Assuming that the image data has general RGB 256 gradations, the printer 50 needs printing color image data of CMYK 2 gradations, so that color conversion and gradation conversion are required. Therefore,
In step 505, the color image data of 256 gradations of RGB is converted into the color image data of 256 gradations of CMYK. At this time, a color conversion process may be performed using a LUT based on a standard method. Next, the CMYK 256 gradations
Halftoning to YK2 gradation (Step S51)
0), the halftoned data is transmitted from the personal computer 10 to the printer 50 by parallel communication (step S5).
15).

FIG. 18 shows changes in the state of the image data before and after the execution of the image data modifying process. FIG. 18A shows image data before execution, and FIG. 18B shows image data after execution. Note that FIG. 3 shows each pixel constituting image data by each small section, and a pixel of gradation 0 indicates a black portion in the image. On the other hand, a pixel having a gradation of 255 indicates white in an image, that is, a paper area of a document image. Here, FIG.
In FIG. 8A, it can be seen that a gray pixel indicated by oblique lines exists at the boundary between the black part and the paper area. Because of the presence of such pixels, the boundary between the black and white portions becomes ambiguous, and as shown in FIG. 19A, the image displayed as a document becomes a continuous image. On the other hand, when the above-described image data modification processing is executed, as shown in FIG. 18B, since the gray part is clamped to the maximum gradation 255, a clear boundary can be created between the black part and the white part. It can be seen that the image has a sharp edge as shown in FIG.

As described above, the document is scanned by the color scanner 40, and the area of the ground of the paper constituting the base in the image of the document, that is, the substantially white area is converted into the predetermined frequency of the image data constituting the image. The determination can be made based on the distribution. Also, when the presence of the background is determined, the substantially white background area is corrected to the maximum gradation by the image data correction processing based on the correction curve. It is possible to add a stitching beam, and it is possible to remove a noise component appearing on the background such as a back fog.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to a claim in an image data base determination method according to an embodiment of the present invention.

FIG. 2 is a schematic external view of a color copying apparatus applied for realizing the image data base determination method.

FIG. 3 is a schematic diagram illustrating a configuration of a scanner of the color copying apparatus.

FIG. 4 is a schematic block diagram showing a configuration of a copy server of the color copying apparatus.

FIG. 5 is a schematic block diagram showing a configuration of the copy server.

FIG. 6 is a schematic diagram showing a configuration of a color printer of the present color copying apparatus.

FIG. 7 is a schematic external view of a computer system showing a modification of the present color copying apparatus.

FIG. 8 is a flowchart showing an outline of a color copying process executed by the copy server;

FIG. 9 is a flowchart showing processing contents of a pre-scan processing executed by the copy server.

FIG. 10 is a flowchart showing processing contents of a background determination processing executed by the copy server.

FIG. 11 is a diagram showing a frequency distribution of image data created by the background determination processing.

FIG. 12 is a flowchart showing the contents of a main scan process executed by the copy server.

FIG. 13 is a flowchart showing processing contents of image data modification processing executed by the copy server.

FIG. 14 is a flowchart showing processing contents of a correction curve determination processing executed by the copy server.

FIG. 15 is a diagram illustrating an example of a correction curve determined in the correction curve determination process.

FIG. 16 is a flowchart showing processing contents of image data modification processing executed by the copy server.

FIG. 17 is a flowchart showing processing contents of image data conversion processing executed by the copy server.

FIG. 18 is a diagram showing a configuration of a pixel before and after execution of the image data modifying process modified by the image data modifying process.

FIG. 19 is a diagram showing a state in which an image having a roll-up is obtained by the image data modifying process.

[Explanation of symbols]

 A1: image data acquisition step A2: frequency distribution creation step A3: background determination step A4: image data modification step

 ──────────────────────────────────────────────────続 き Continued from the front page F term (reference) 5B057 AA11 BA28 CA01 CA02 CA12 CA16 CB01 CB02 CB12 CB16 CC03 CE05 CE11 CE17 CE18 CH11 CH18 DC23 5C077 MM20 MP06 MP08 NN03 PP02 PP15 PP27 PP32 PP33 PP38 PP43 PP68 PQ08 PQ19 PQ20 TT06

Claims (13)

[Claims] An image data base determination method for determining an area constituting a base in an image based on a predetermined frequency distribution of the image data, the method comprising the steps of: An image data acquiring step to be acquired; a frequency distribution creating step of creating a frequency distribution by summing up gradations for each pixel of the image data acquired in the image data acquiring step; and dividing by a predetermined tone of the frequency distribution Calculating a statistic indicating the characteristics of the selected region, and determining that the image has a region constituting the base when the statistic indicates a value sufficient to form the base. An image data base determination method, characterized in that: 2. The method according to claim 1, wherein the frequency distribution creating step includes calculating a luminance of each pixel and totalizing a gradation of the same luminance to create a frequency distribution. An image data base determination method, characterized in that: 3. The image data background determination method according to claim 1, wherein in the frequency distribution creating step, each pixel is color-separated into element colors, the gradation of each element color is totaled, and each element color is calculated. An image data base determination method, wherein a frequency distribution is created for each image. 4. The image data background determination method according to claim 1, wherein the background determination step includes determining a relative frequency of an area divided by a predetermined gradation in the frequency distribution. An image data base determination method, comprising: calculating, when each or the total of the calculated relative frequencies is equal to or more than a predetermined threshold value, determining that an area constituting a base exists in the image. 5. The image data background determination method according to claim 1, wherein the background determination step includes a step of determining a relative position of each of the regions divided by the predetermined gradation of the frequency distribution. An image data base determination method, comprising: calculating a frequency; and determining, when a total of gradations having a predetermined relative frequency is equal to or more than a predetermined threshold, an area constituting a background in the image. 6. The image data background determination method according to claim 1, wherein the background determination step calculates a standard deviation in an area divided by a predetermined gradation of the frequency distribution. An image data base determination method, wherein when the standard deviation is equal to or smaller than a predetermined threshold, it is determined that an area constituting a base exists in the image. 7. The image data background determination method according to any one of claims 4 to 6, wherein the background determination step includes determining a representative value in a region of the frequency distribution divided by a predetermined gradation. An image data base determination method, comprising calculating and determining that an area constituting a base exists in an image by combining the representative values. 8. The image data background determination method according to claim 1, wherein said background determination step calculates a statistical value of an area divided by a predetermined gradation of a frequency distribution. In doing so, a smoothing process is performed on the same frequency distribution. 9. The image data background determination method according to claim 1, wherein the background determination step includes, when an image includes a region constituting the background, the region configuring the background. An image data modifying step of performing a modifying process of modifying the image data of each pixel according to the image data. 10. The image data background determination method according to claim 9, wherein the image data modifying step includes: when an area forming the background of the image is near a highlight, the floor of each pixel near the highlight. An image data base determination method, comprising: generating a correction curve having a parameter for setting a key to a maximum gradation, and correcting a gradation of each pixel obtained in an image data obtaining step based on the correction curve. 11. The image data background determination method according to claim 10, wherein the background determination step determines the presence or absence of an object included in the image based on a predetermined method. In the modifying step, a parameter of the correction curve is changed. 12. An image data obtaining means for obtaining image data in which an image is expressed by a plurality of gradations of pixels in a dot matrix, and a gradation is totalized for each pixel of the image data obtained by said image data obtaining means. A frequency distribution creating means for creating a frequency distribution, and calculating a statistic indicating a characteristic of an area divided by a predetermined gradation of the frequency distribution, wherein the statistic indicates a value sufficient to constitute a base An image data background determination device, comprising: a background determination unit that determines that a region constituting a background exists in the image. 13. A medium in which an image data base determination control program for determining an area constituting a base in an image based on a predetermined frequency distribution of image data is recorded, wherein the image is formed by multi-gradation using dot matrix pixels. An image data acquiring step of acquiring the expressed image data; a frequency distribution creating step of creating a frequency distribution by summing up gradations for each pixel of the image data acquired in the image data acquiring step; Calculates a statistic that indicates the characteristics of the area divided by the gradation of, and if the statistic indicates a value sufficient to form the background, it is determined that there is an area constituting the background in the image. And a recording medium for storing an image data base determination control program.