JP7226007B2 - Image processing device, image processing method, and program - Google Patents

Description

The technical field disclosed in this specification relates to an image processing device, an image processing method, and a program.

Conventionally, when performing image output processing such as printing based on image data generated by an image input device such as a scanner or digital camera, the image indicated by the image data is divided into multiple blocks, and the feature is that each block is obtained. Techniques for performing image processing on an image of image data using quantities are known. For example, in Patent Document 1, a document image is divided into a plurality of blocks, a color is determined for each block, and a numerical value (run length) of continuous blocks of colors other than white is compared with a threshold value to determine a character region. and a halftone region is disclosed.

JP-A-3-208467

It is known that the preferred viewing distance (visible distance) for the user differs depending on the size of the printed matter. For example, compared to A4-size printed matter, small-sized printed matter such as business cards tend to have smaller printed characters and a shorter viewing distance. On the other hand, in the case of a large-sized printed matter such as a poster, it is assumed that the user will view the printed matter at a certain distance from the printed matter, and the observation distance is long. Since the conventional technology does not consider this viewing distance, there is room for improvement in performing more suitable image processing.

This specification discloses a technique that allows an image processing apparatus that performs image processing based on image data to perform image processing suitable for an observation distance.

An image processing apparatus that aims to solve this problem is an image processing apparatus that includes a computer, wherein the computer performs an image data acquisition process for acquiring image data, and the image data acquired by the image data acquisition process. A size information acquisition process for acquiring size information specifying the size of a print image that is an image to be printed when printing is performed based on an original image that is an image indicated by data; and the size acquired by the size information acquisition process. a block size determination process for determining a block size based on the information; a division process for dividing the original image into a plurality of blocks according to the block size determined by the block size determination process;
A calculation process of calculating a run length, which is a continuous value of the blocks divided by the division process and which satisfies a predetermined condition, and a character using the run length calculated by the calculation process. and a region determination process for determining whether an area is an area or a halftone area.

The image processing apparatus disclosed in this specification determines the size of the block to be divided based on the size information of the print image, and divides the original image into a plurality of blocks according to the determined block size. For example, for large-size prints, the observation distance is long and the need for fine images is low. It is divided into small size blocks due to the high necessity. Dividing into large-sized blocks reduces the processing load, but may not result in detailed determination. When divided into small-sized blocks, detailed determination is possible, but the processing load is large. The image processing apparatus can be expected to perform image processing suitable for the viewing distance by dividing the printed image into blocks of sizes corresponding to the size of the printed image.

A control method, a computer program, and a computer-readable storage medium storing the computer program for implementing the functions of the above apparatus are also novel and useful.

According to the present invention, a technology is realized that enables an image processing apparatus that performs image processing based on image data to perform image processing suitable for an observation distance.

2 is a block diagram showing an electrical configuration of the MFP according to this embodiment; FIG. 6 is a flow chart showing the procedure of region division processing; 7 is a flowchart showing the procedure of size determination processing; FIG. 5 is an explanatory diagram showing an example of change in near-point distance; FIG. 5 is an explanatory diagram showing an example of observation distance and viewing angle; FIG. 4 is an explanatory diagram showing an example of a state divided into blocks; FIG. 4 is an explanatory diagram showing an example of run lengths;

Embodiments of an image forming apparatus will be described in detail with reference to the accompanying drawings. This embodiment discloses a multifunction peripheral (hereinafter referred to as "MFP") having an image processing function including an image forming function and an image reading function.

An electrical configuration of the MFP 100 of this embodiment will be described. The MFP 100 of this embodiment includes a control board 30 including a CPU 31, a ROM 32, a RAM 33, and a nonvolatile memory 34, as shown in FIG. The MFP 100 also includes an image forming device 10 , an image reading device 20 , a communication interface (hereinafter referred to as “communication IF”) 37 , and an operation panel 40 , which are electrically connected to the control board 30 . It is

The ROM 32 stores a boot program and the like for booting the MFP 100 . The RAM 33 is used as a work area when various processes are executed, or as a storage area for temporarily storing data. The nonvolatile memory 34 is, for example, an HDD or a flash memory, and is used as an area for storing various programs, data such as image data, and various settings. CPU 31 is an example of a computer.

Imaging device 10 includes a configuration for forming an image on paper. The image forming device 10 may be an inkjet printer, an electrophotographic printer, or any other type of device. Further, the image forming device 10 may be a device capable of forming a color image, or may be a device that forms only a monochrome image. Also, the MFP 100 may include a plurality of image forming devices 10 .

The image reading device 20 includes a configuration for reading an image formed on paper and acquiring image data. The image reading device 20 of the MFP 100 may be a color image scanner that reads a color document and acquires color image data, or may be a monochrome image scanner that acquires only monochrome image data.

The communication IF 37 includes a configuration for communicating with an external device such as a personal computer. MFP 100 may be compatible with multiple types of communication methods. The operation panel 40 includes a configuration for display such as a display and a configuration for receiving instruction input such as an input button. The operation panel 40 may be, for example, a touch panel or the like that has both a display function and an input reception function.

The MFP 100 has a function of acquiring image data and executing printing based on an original image, which is an image indicated by the acquired image data. The image data may be data read and acquired by the image reading device 20 of the MFP 100 or data acquired from an external device via the communication IF 37 . MFP 100 temporarily stores the acquired image data in RAM 33 or nonvolatile memory 34, and performs various image processing on the image indicated by the image data before generating data for printing.

The image processing executed by the MFP 100 includes, for example, determination processing between character areas and halftone areas. The character area is an area containing binary images such as characters and line drawings, and the halftone area is an area containing halftone images such as photographs and halftone dots. When the acquired image data is image data of an image including a text area and a halftone area, the MFP 100 determines whether it is a text area or a halftone area, and performs appropriate processing for each area. Specifically, for example, the MFP 100 can generate an easy-to-see printed matter with sharp characters and smooth photographs by performing edge enhancement processing on character regions and smoothing processing on halftone regions.

In this embodiment, image data is divided into a plurality of blocks of the same size, and each block is determined as a character area or a halftone area. It is desirable that the block size is large enough so that the processing load for area determination is not too large, and small enough that multiple areas do not coexist.

Next, an area determination method in MFP 100 of the present embodiment will be described. A procedure of region division processing according to the present embodiment will be described with reference to the flowchart of FIG. This area dividing process is executed by the CPU 31, for example, when an instruction to execute printing is received.

In the area dividing process, the CPU 31 first acquires dot data of an image designated as a print target (S101). S101 is an example of image data acquisition processing. The data format of the image to be printed, which is specified by the print instruction, is of various formats. The CPU 31 acquires dot data based on the image data of the designated image. For example, if the received print instruction is a copy instruction, the CPU 31 acquires dot data read by the image reading device 20 . Alternatively, if the instruction is to print PDL data acquired from an external device, the CPU 31 rasterizes the PDL data and acquires dot data. The dot data may be YMCK data or RGB data. Also, the image data may be data read from the nonvolatile memory 34 or the RAM 33 .

Then, the CPU 31 executes size determination processing for determining the size of blocks into which the acquired dot data is divided (S102). The procedure of size determination processing will be described with reference to the flowchart of FIG.

In the size determination process, the CPU 31 first acquires the paper size (S201). The CPU 31 acquires the paper size of the paper to be printed, for example, based on the print parameters included in the print instruction. S201 is an example of size information acquisition processing. The paper size may be obtained directly from the print parameters, or may be obtained using other information included in the print parameters. For example, when a paper feed tray is specified as a print parameter, the CPU 31 may acquire from the image forming device 10 the paper size of the paper set in the specified paper feed tray. Paper size is an example of size information.

The CPU 31 determines whether or not the print instruction is for Nin1 printing (S202). N-in-1 printing is a printing mode in which images for a plurality of pages are combined into one page and printed, and N is a numerical value indicating the original number of pages to be combined into one page. For example, in 2-in-1 printing, images for two pages are aggregated and printed on one page. Nin1 printing is an example of aggregate printing.

When determining that the instruction is Nin1 printing (S202: YES), the CPU 31 changes the paper size to a size within which one image is printed (S203). For example, if the print instruction is to perform 2-in-1 printing on A3 paper, the CPU 31 acquires A3 as the paper size in S201, and changes the paper size to A4 in S203.

After S203, or if it is determined that the N-in-1 printing is not instructed (S202: NO), the CPU 31 acquires the observation distance D corresponding to the paper size (S204). The viewing distance D is the distance between the human eye and the printed matter when viewing the entire printed matter, and the larger the printed matter, the greater the viewing distance D. In this embodiment, the viewing distance is set in advance for each size of printed matter. Specifically, the observation distance D for A3 size is 100 cm, the observation distance D for A4 size is 30 cm, and the observation distance D for business card size is 10 cm. A suitable block size can be easily determined since the approximate viewing distance can be inferred from the paper size.

The observation distance D described above is the distance when the printed matter is viewed in its entirety, and when the printed matter is viewed in detail, it is preferable to apply a closer near-point distance as the observation distance D. This periapsis distance is known to change with aging, for example, as shown in FIG. If the observer is in his or her thirties, it is preferable that the near-point distance is short and the observation distance D is also smaller than the set value described above. On the other hand, if the observer is 60 years old or older, it is preferable that the near point distance is long and the observation distance D is set larger than the above-described set value.

Therefore, in this embodiment, the CPU 31 accepts designation of the age group of the observer who views the printed matter to be formed (S205). The age group may be accepted as a print parameter, or may be accepted through the operation panel 40 of the MFP 100 . Then, the CPU 31 adjusts the viewing distance D based on the received age group (S206). For example, if the observer is in his or her thirties, the CPU 31 sets the observation distance D to 1/3 of the set value. On the other hand, if the observer is 60 years old or older, the CPU 31 sets the observation distance D to twice the set value. The CPU 31 does not change the observation distance D if the observer is between 40 and 60 years old, or if the observer's age group is unknown.

Next, the CPU 31 determines whether or not the color mode of the print instruction is monochrome printing (S207). S207 is an example of color mode acquisition processing. If it is determined that the instruction is not for monochrome printing but for color printing (S207: NO), the CPU 31 acquires the paper type of the paper selected for printing (S208). S208 is an example of paper type acquisition processing. Paper types include, for example, photo glossy paper, matte paper, plain paper, thick paper, and OHP paper.

CPU 31 determines whether or not the selected paper type is photo paper (S209). When determining that photo paper such as glossy paper or matte paper is selected (S209: YES), the CPU 31 sets the viewing angle θ to 10 degrees (S210). The paper type is an example of application information.

The viewing angle is an angle that indicates the range in which the user can pay attention to an object in the entire visual field. The viewing angle is large for objects such as photographs and paintings that are viewed as a whole, and is small for objects such as characters and figures that require attention to detail. For example, it is said that the viewing angle of a photograph for which a relatively wide area is viewed as a whole is about 10 degrees, and the viewing angle of a character for detailed observation is about 2 degrees. Since the viewing angle differs depending on the printing application, and the printing application can be estimated from the selected paper type, in this embodiment, the CPU 31 determines the viewing angle based on the color mode and the paper type. In the present embodiment, the viewing angle θ is set to 10 degrees in the case of color printing and an instruction to print on photographic paper. When printing color images on glossy paper, matte paper, etc., it is highly likely to be used for photography.

On the other hand, if it is determined to be monochrome printing (S207: YES), or if it is determined that it is color printing but not photo paper (S209: NO), the CPU 31 determines the viewing angle θ to be 2 degrees. (S211). In the case of monochrome printing, there is a high possibility that the image is a document, chart, or the like, so the possibility that it is for photography is low, and the CPU 31 uses a narrower viewing angle than for photography. Thereby, for example, as shown in FIG. 5, the observation distance D and the viewing angle θ are determined.

The CPU 31 determines the block size L from the observation distance D determined in S206 and the viewing angle θ obtained in S210 or S211 (S212), and ends the size determination process. S212 is an example of block size determination processing. The block size L is the length of one side of one block when dot data is divided into a plurality of blocks.

In S212, the CPU 31 determines the block size L (cm) by the following (Formula 1).
L (cm) = D (cm) x tan θ x 2 (Formula 1)
In this embodiment, since the viewing distance D based on the paper size and the viewing angle θ based on the printing application are reflected in determining the block size L, a more suitable block size L can be determined for each image to be printed.

By applying the set value of the observation distance D and the two types of viewing angles θ (see FIG. 5) to this (Equation 1), the block size L is obtained as follows.
Observation distance: 100 cm Viewing angle: 10 degrees Block size: Approx. 35.2 cm
Observation distance: 100 cm Viewing angle: 2 degrees Block size: Approx. 7.0 cm
Observation distance: 30 cm Viewing angle: 10 degrees Block size: Approx. 10.6 cm
Observation distance: 30 cm Viewing angle: 2 degrees Block size: Approx. 2.0 cm
Observation distance: 10 cm Viewing angle: 10 degrees Block size: Approx. 3.4 cm
Observation distance: 10 cm Viewing angle: 2 degrees Block size: Approx. 0.6 cm

Returning to the description of the region determination processing in FIG. The CPU 31 divides the dot data obtained in S101 into square blocks each having a block size L determined in the size determination process (S103). S103 is an example of division processing. For example, as shown in FIG. 6, the print image 51 when arranged in the paper Q to be printed is divided into blocks B of L cm square. For example, in a copy process in which image data obtained by reading an A4 original at 300 dpi is printed on A4 size paper, when L=2 cm, the CPU 31 converts 236 dots per side from 300×20/25.4. Divide into square blocks. Note that the margin around the paper Q may be omitted.

Furthermore, the CPU 31 determines the color of each divided block (S104). S104 is an example of color determination processing. As for the color of the block, for example, a color other than white that appears most frequently in the block is determined from seven colors of CMYKRGB. In addition, when all the dots in the block are white, the CPU 31 determines the color of the block to be white. Further, when there is a dot with a density higher than a predetermined threshold value in a block, the CPU 31 may store that block as a character candidate.

Note that it is not necessary to target all pixels in a block for determination. For example, processing such as thinning out pixels may be performed so that the same predetermined number of samples is obtained regardless of the block size. By doing so, the processing load is about the same regardless of the block size.

Then, the CPU 31 calculates a run length, which is a continuous value of blocks satisfying a predetermined condition, in the main scanning direction (S105). S105 is an example of calculation processing. The predetermined condition is, for example, that the block color is determined to be a color other than white, and the run length is the number of consecutive blocks other than white. In this way, for example, as shown in FIG. 7, the run length is short on line m because the run length is interrupted between characters, and the run length is short on line n because blocks other than white are continuous. is long. In S104, since the colors other than white with the highest frequency are set as the block colors, the run length is long even in halftone dot areas.

The CPU 31 regards a block whose run length is shorter than a predetermined threshold value as a character candidate, and determines whether the character is a black character or a color character based on the color determined in S104. In S104, when there is a dot with a density higher than a predetermined threshold, it is determined as a character candidate, so that the CPU 31 does not determine a low density area as a character area even if the run length is short.

Furthermore, the CPU 31 performs edge detection in the sub-scanning direction (S106). In S105, if a horizontal line that is part of the figure is included, the run length will be long and there is a high possibility that it will not be a character candidate. For example, the CPU 31 determines whether or not there is an edge within a range of several blocks in the sub-scanning direction. As a result, even a horizontal line that is long in the main scanning direction becomes a character candidate.

Based on the results of S105 and S106, the CPU 31 determines the area of the image data (S107), and ends the area dividing process. S107 is an example of area determination processing. For example, if there is a character candidate in either the main scanning direction or the sub-scanning direction and there is a pixel in the block in which the maximum value of YMC is equal to or greater than the threshold value, the CPU 31 regards this block as a character region. I judge. On the other hand, the CPU 31 determines that an area with a long run length is, for example, an area in which halftones or halftone dots are continuous, and is a halftone area. Further, the CPU 31 determines that an area where white blocks are continuous is a background area.

That is, in the MFP 100 of the present embodiment, the size of the block used for division by the block color determination unit is determined based on the print settings including the size of the paper to be printed and the purpose of printing. Blocks can be used to perform region determination.

After that, MFP 100 performs different processes depending on the character area and the halftone area, and generates print data suitable for printing. For example, the MFP 100 may use the result of determining whether an area is a text area or a halftone area to specify a color, and may perform gradation correction, edge enhancement correction, and dither correction based on the color specification result. can be

As described above in detail, according to the MFP 100 of the present embodiment, the block size is made variable according to the size of the print image, and area determination is performed on a block-by-block basis according to the block size. When a large block size is used, fine area determination is not achieved, but the processing time tends to be short. On the other hand, when a small block size is used, the processing time may be long, but fine area determination is possible. In this embodiment, the block size is determined based on the size of the image to be printed. For example, since the viewing distance tends to vary depending on the physical size of the print image printed on paper, the MFP 100 determines the block size based on the viewing distance. By determining the block size based on the observation distance, the size of the image area for one block in the image formed on the human retina becomes substantially the same. Therefore, compared to the fixed size determined by the size of the hardware, for example, it is highly likely that the block size will be appropriate for each image, and image processing that is suitable for the viewing distance can be expected. .

It should be noted that the present embodiment is merely an example, and does not limit the present invention in any way. Therefore, the technology disclosed in this specification can naturally be improved and modified in various ways without departing from the gist thereof. For example, it is applicable not only to MFPs but also to printers, copiers, facsimiles, etc., as long as they have an image forming function.

Further, for example, the configuration is not limited to the configuration in which all processing is performed by the MFP 100, and some processing may be performed by another device. That is, the image processing apparatus that performs the processing of this embodiment may be the MFP 100, a printer, a PC that transmits image data to the printer, or a server connected to the printer. A PC or a server may acquire image data, perform the area division processing shown in FIG. 2 and various image processing after area division, generate print data, and transmit the generated data to the MFP 100 or printer. Also, various image processing after segmentation may be performed by another device.

Also, the size of the print image is not limited to being determined based on the paper size, and may be determined based on the print parameters of the print job. For example, when poster printing or image scaling is set, the size of the print image may be determined based on the size after scaling.

In addition, it is not limited to the example of calculating the block size L by the above-described (formula 1). For example, a plurality of types of block sizes are prepared in advance, and from among them, the block size closest to the result of (formula 1) is selected. It may be configured to For example, prepare a large block of L = 10 cm, a medium block of L = 2 cm, and a small block of L = 0.5 cm. A medium block may be used for up to 10 cm, and a small block may be used for less than 2 cm. In this case, for example, hardware for performing image processing may be prepared for each block size, and image processing may be performed using each piece of hardware. Also, the block size may be adjusted so as to be divisible according to the total number of dots in the vertical and horizontal directions of the dot data.

In the case of copying, the MFP 100 may perform pre-scanning to read the document at a low resolution, and distinguish between the character area and the halftone area based on the low-resolution image data obtained by the pre-scanning. can be

Further, it is not necessary to adjust the observation distance D according to the observer's age group. In that case, S205 and S206 of the size determination process may be deleted, and the process may proceed to S207 after S204.

Further, in any flowchart disclosed in the embodiments, multiple processes in any multiple steps can be arbitrarily changed in execution order or executed in parallel as long as there is no contradiction in the processing contents.

Also, the processing disclosed in the embodiments may be performed by a single CPU, multiple CPUs, hardware such as an ASIC, or a combination thereof. Further, the processes disclosed in the embodiments can be realized in various forms such as a recording medium recording a program for executing the processes, a method, and the like.

31 CPUs
100 MFPs

Claims (9)

An image processing device comprising a computer,
The computer is
image data acquisition processing for acquiring image data;
A size information acquisition process for acquiring size information specifying a size of a print image, which is an image to be printed when printing is performed based on an original image, which is an image represented by the image data acquired in the image data acquisition process;
a block size determination process for determining a block size based on the size information acquired in the size information acquisition process;
a division process for dividing the original image into a plurality of blocks with the block size determined by the block size determination process;
a calculation process of calculating a run length, which is a continuous value of the blocks divided by the division process and which satisfies a predetermined condition;
an area determination process for determining whether a character area or a halftone area is determined using the run length calculated in the calculation process;
and run
Further, the computer
In the size information acquisition process, as the size information, a paper size to be printed when performing printing based on the original image is acquired;
Further, the computer
In the block size determination process, using the observation distance corresponding to the paper size acquired in the size information acquisition process, the longer the observation distance is, the larger the size of the block is determined;
The observation distance is predetermined for each paper size, and the first observation distance corresponding to the first paper size corresponds to the second observation distance corresponding to the second paper size larger than the first paper size. short compared to the observation distance,
An image processing apparatus characterized by: In the image processing device according to claim 1 ,
The computer is
In the block size determination process, when aggregate printing is set to combine N pages of images into one page, an image size corresponding to 1/N of the paper size acquired in the size information acquisition process is obtained. using the distance to determine the size of the block;
An image processing apparatus characterized by: In the image processing device according to claim 1 or claim 2 ,
The computer is
In the block size determination process, usage information specifying a printing usage is further used to determine the size of the block,
The usage information includes a photographic usage that is an overall viewing usage and a non-photographic usage that is a usage that focuses on details.
An image processing apparatus characterized by: In the image processing device according to claim 3 ,
The computer is
executing paper type acquisition processing for acquiring a paper type to be printed when printing is performed based on the original image;
In the block size determination process, the paper type acquired in the paper type acquisition process is used as the usage information, and a viewing angle corresponding to the usage information is used, and the larger the viewing angle, the larger the size of the block. value and
The viewing angle is determined in advance for each paper type. Large, compared to the viewing angle of 2,
An image processing apparatus characterized by: In the image processing device according to claim 4 ,
The computer is
executing a color mode acquisition process for acquiring a color mode for printing based on the original image;
In the block size determination process, when the color mode acquired in the color mode acquisition process indicates monochrome, the size of the block is determined using the second viewing angle.
An image processing apparatus characterized by: In the image processing device according to any one of claims 1 to 5 ,
The computer is
executing a color determination process for determining a color of the block for each of the blocks divided by the dividing process;
In the calculation process, the run length is calculated under the predetermined condition that the color determined in the color determination process is other than white.
An image processing apparatus characterized by: In the image processing device according to claim 1,
The computer is
In the size information acquisition process, as the size information, a paper size to be printed when performing printing based on the original image is acquired;
Further, the computer
executing paper type acquisition processing for acquiring a paper type to be printed when printing is performed based on the original image;
Further, the computer
Observation distance is defined for each paper size,
The viewing angle is specified for each paper type,
Further, the computer
In the block size determination process, using the observation distance D corresponding to the paper size acquired in the size information acquisition process and the viewing angle θ corresponding to the paper type acquired in the paper type acquisition process, the following determining the length of one side of the block based on the length L calculated from the formula (1) of
L=D×tan θ×2 (1)
An image processing apparatus characterized by: An image processing method for determining whether an original image is a text area or a halftone area,
an image data acquisition step of acquiring image data;
a size information acquisition step of acquiring size information specifying a size of a print image, which is an image to be printed when printing is performed based on the original image, which is an image represented by the image data acquired in the image data acquisition step; ,
a block size determining step of determining a block size based on the size information obtained in the size information obtaining step;
a dividing step of dividing the original image into a plurality of blocks with the block size determined in the block size determining step;
a calculating step of calculating a run length, which is a continuous value of blocks satisfying a predetermined condition, which are the blocks divided in the dividing step;
a region determination step of determining whether the run length is a character region or a halftone region using the run lengths calculated in the calculation step;
including
In the size information obtaining step, as the size information, a paper size to be printed when performing printing based on the original image is obtained;
In the block size determination step, using the observation distance corresponding to the paper size acquired in the size information acquisition step, the longer the observation distance is, the larger the size of the block is determined;
The observation distance is predetermined for each paper size, and the first observation distance corresponding to the first paper size corresponds to the second observation distance corresponding to the second paper size larger than the first paper size. short compared to the observation distance,
An image processing method characterized by: A program executable by a computer of an image processing device,
to the computer;
image data acquisition processing for acquiring image data;
A size information acquisition process for acquiring size information specifying a size of a print image, which is an image to be printed when printing is performed based on an original image, which is an image represented by the image data acquired in the image data acquisition process;
a block size determination process for determining a block size based on the size information acquired in the size information acquisition process;
a division process for dividing the original image into a plurality of blocks with the block size determined by the block size determination process;
a calculation process of calculating a run length, which is a continuous value of the blocks divided by the division process and which satisfies a predetermined condition;
an area determination process for determining whether a character area or a halftone area is determined using the run length calculated in the calculation process;
and
Furthermore, in said computer,
In the size information acquisition process, a paper size to be printed when performing printing based on the original image is acquired as the size information,
Furthermore, in said computer,
In the block size determination process, using an observation distance corresponding to the paper size acquired in the size information acquisition process, the longer the observation distance is, the larger the size of the block is determined;
The observation distance is predetermined for each paper size, and the first observation distance corresponding to the first paper size corresponds to the second observation distance corresponding to the second paper size larger than the first paper size. short compared to the observation distance,
A program characterized by

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