JP2002247343A - Image processing device, method therefor and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove moires in a multi-level image generated on the basis of a binary image. SOLUTION: A buffer region for the angle α for rotating a target block is determined by using a conversion table (S201), and a ratio (weight) of region where the buffer region and the block after rotating superimpose is calculated for each pixel (S202). Next, all the weights for the pixels each having value of 1 which are binary images corresponding to the buffer region are added (S203). Subsequently, an added value of weight S' in the case that a bit value k to be normalized, a maximum value of k bit and all the pixel values in the buffer region are 1 is specified from a table on the basis of the rotation angle α(S204), and an added value S is normalized using S' as the maximum value of the bit value k (S205). This normalized value is used as a pixel value in the buffer region (S206).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for generating a multivalued image based on a binary image, a method thereof, and a storage medium.

[0002]

2. Description of the Related Art In the printing industry, test printing is performed before actual printing. The test printing can be obtained by correcting a difference in resolution between a printing machine that performs actual printing and a device that performs test printing and color characteristics unique to hardware with respect to the original image. The result (proof) of correcting the original image for test printing needs to maintain sufficient accuracy as test printing.

[0003] Further, when trial printing of binary image printing using halftone dots is performed, due to the problem of cost and time, binary and multi-level conversion that can be performed at lower cost and in shorter time is performed on the original image. Image was used. At the time of this binary / multi-value conversion, attention is paid to a specific point, and it is determined whether or not the binary value is ON or OFF with respect to a pixel in an area of n pixels × n pixels in the vicinity thereof. The ratio is normalized by k bits (for example, 0 to 255 in the case of 8 bits) and multi-valued.

[0004]

However, the prior art has the following problems.

[0005] 1) When halftone dots of each color are printed at different rotation angles in binary image printing, moire (interference fringes) is generated in a test print subjected to binary / multi-value conversion in the prior art, and the test print is not printed. Sufficient accuracy cannot be obtained as a proof.

2) If a rotation process is performed on the entire image in order to prevent moire, or if the scanning direction of the image is changed to match the scanning direction of each color, the amount of calculation becomes enormous,
Proofs cannot be created in practical time.

[0007] 3) In order to reduce the amount of calculation as much as possible, in the vicinity of a specific point, when determining whether the binary value of a pixel in an area of n pixels × n pixels is ON or OFF, n is reduced. Good. However, if the original image has a high resolution, it is necessary to increase n accordingly, so that n cannot be reduced.

The present invention has been made in view of the above problems, and has as its object to remove moiré from a multi-valued image generated based on a binary image.

[0009]

In order to achieve the object of the present invention, for example, an image processing apparatus of the present invention has the following arrangement. That is, an image processing apparatus that generates a multi-valued image based on a binary image, a dividing unit that divides the binary image into rectangular blocks having a desired size, and a target block that is divided by the dividing unit. Is rotated by a desired angle to set a rectangular area including the target block after rotation, and according to a ratio of the rectangular area and the target block after rotation by the area setting means overlapping with each other. A pixel value setting unit that sets a pixel value of a pixel included in the rectangular region; and a generating unit that generates a multi-valued image using the rectangular region having a pixel value by the pixel value setting unit. Is provided.

[0010] Further, there are provided input means for inputting a binary image, and charging means for charging, based on the binary image input to the input means, a target for inputting the binary image to the input means.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail according to preferred embodiments with reference to the accompanying drawings.

[First Embodiment] FIG. 1 is a block diagram showing a schematic configuration of an image processing apparatus according to this embodiment.
A CPU 101 controls the entire image processing apparatus using the program codes and data stored in the RAM 102 and the ROM 103, and performs image processing to be described later.

A RAM 102 temporarily stores program codes and data loaded from the external storage device 104, and is used as a work area when the CPU 101 is executing a process.

A ROM 103 stores program codes and data for controlling the entire image processing apparatus for executing the control procedure shown in FIG. Also, a character code for displaying characters on the display unit 105 is stored.

An external storage device 104 stores program codes and data installed from a storage medium such as a CD-ROM or a floppy (registered trademark) disk.

A display unit 105 includes a CRT and a liquid crystal display, and is capable of displaying various system messages to the user and displaying various image processing results described later.

Reference numeral 106 denotes an interface unit (I / F)
Section) for connecting to other devices. In the present embodiment, a device for inputting an image to the image processing apparatus is connected via the I / F unit 106.

Reference numeral 107 denotes a bus connecting the above-described units.

Next, image processing (moire removal processing) performed by the image processing apparatus according to the present embodiment having the above configuration will be described below with reference to FIG. 2 showing a flowchart of this image processing. In addition, as shown in FIG.
The value image 301 is stored in a predetermined area A in the RAM 112,
A block-shaped area 30 of n pixels × n pixels according to the resolution
2 (hereinafter, referred to as a block). This flowchart is a flowchart of a process for one block. The processing according to the flowchart shown in FIG. Also, when generating the following multi-valued image,
A new image is generated instead of overwriting a binary image.

First, a buffer area (the size of m pixels × m pixels m>
n) Determine a predetermined area B of the RAM 112 (Step S20)
1). The rotation angle α is a value uniquely determined by an external printing device (rotary press). As shown in FIG. 4, when n = 4, the buffer area is the smallest rectangular area (401) including the target block 402 rotated by α.
In this figure, the size of the buffer area 401 is 5 ×
5, that is, m = 5. FIG. 5 shows a conversion table describing the relationships among n, α, and m. Although the rotation angle α is uniquely determined by the rotary press as described above, specifically, as shown in FIG. 5, it is determined according to the resolution of the rotary press. This conversion table is stored in the ROM 103 in advance. Alternatively, the data may be read from the external storage device 104 and stored in the RAM 102.

Next, the ratio (weight) of the area where the buffer area and the block of interest overlap is obtained for each pixel (step S202). Specifically, from FIG.
In each pixel, the ratio of the colored portion is determined for each pixel.

The method for obtaining the value will be described below. Since the ratio for each pixel is uniquely determined when the size of the buffer area and the rotation angle α are determined, it is created in advance and stored in the ROM 103 or the RAM 102 as a table (weight table) shown in FIG. . Then, if necessary, it can be obtained using this table. As a result, the entire processing can be speeded up without having to calculate the ratio for each pixel for each buffer area.

Each element of the weight table corresponds to each pixel of the buffer area shown in FIG. 4, and the numerical value in each element of the weight table is the above-described ratio obtained for each pixel of the buffer area. In the same table, the pixels of the buffer area 401 corresponding to the elements described as 100 overlap the target block 402 by 100%, and
1 is a block with 100% color. On the other hand, in the same table, the pixels of the buffer area 401 corresponding to the element described as 2
02 and 2%, this pixel in buffer area 401 includes 2% and a slightly colored area.

Next, 2 corresponding to each pixel in the buffer area
With reference to the value image, it is determined whether the binary value of this pixel is ON or OFF (pixel value is 1 or 0). Then, all the weights corresponding to the pixels having the pixel value of 1 are added. However, in the actual calculation, the pixel value of the binary image corresponding to each pixel in this buffer area is P (i, j) (see FIG. 7), and the weight corresponding to each pixel in this buffer area is a (i, j). ), It can be calculated by the following equation (step S203). Note that i, j
Is an index of each pixel value in the buffer area.

S = ΣΣa (i, j) × P (i, j) This addition is an addition in each buffer area, and
If the size of the buffer area is m × m, 0 ≦ i ≦ m,
0 ≦ j ≦ m. Also, the following ΣΣ is defined as 0 ≦ i ≦ m, 0 ≦ j
Addition within the range of ≦ m.

The sum S is normalized by k bits. If k = 8, the range of values of S is 0 ≦ S
≤ 255. Here, the added value S ′ (= ΣΣa (i, i) when all the pixel values in the buffer area are 1
j)) corresponds to 255 in the above normalization, so that the bit value k to be normalized, the maximum value of the k bits, and the added value S ′
Is specified from the table shown in FIG. 5 based on the rotation angle α (step S204), and the normalized value C of the added value S can be calculated as follows (step S20).
5).

C = 255 × S / S ′ Note that this equation is an equation when k = 8.

Thus, the value C is set as all the pixel values in the buffer area (step S206).

As a result of the processing according to the above flowchart, the images in the buffer area generated are arranged as shown in FIG. 8 to generate a multi-valued image.

In the figure, 801a, 802a, 80
3a is a block in the binary image, and 801b, 8
02b and 803b are area buffers. Since the area buffer has a larger number of vertical and horizontal pixels than the block, if the area buffer is arranged adjacently without overlapping, the multi-valued image will be larger than the binary image. Therefore, as shown in the figure, a multi-valued image is generated by overlapping the buffer area according to the size larger than the block.

As described above, the image processing apparatus and the image processing method according to the present embodiment perform the rotation calculation for each block in the moire removal processing of the multi-valued image generated based on the binary image. When calculating the ratio of the area where the rotated block and the buffer area overlap each other for each pixel, the calculation is performed using the table, so that the overall processing speed can be improved.

In the overlapping area, the color of the buffer area is further determined according to the number of pixels having a pixel value of 1 in the binary image. Therefore, the direction of the halftone dot does not affect the determination of this color. Moire can be removed.

The program code according to the flowchart shown in FIG. 2 is stored in the RAM 102,
It is read and executed by the PU 101.

[Second Embodiment] The image processing apparatus and method described in the first embodiment is an apparatus and method for generating an image for test printing. This apparatus is arranged at a predetermined position as a server, and by connecting computers of a plurality of requesters via the I / F unit 106, each requester transmits a binary image to the server. Based on the binary image received from the requester, it is possible to construct a system for providing a service for transmitting a multivalued image by processing according to the flowchart shown in FIG.

It is also possible to charge a client who has received this service according to a fixed fee system.

FIG. 9 shows a schematic configuration of the above system.

FIG. 3 shows an example in which only one client computer is connected to the server in order to make the present embodiment easy to understand, but the present embodiment is not limited to this, It is clear from the following description that the present invention can be applied to a person.

A program code according to the flowchart shown in FIG. 2 is stored in a memory (not shown) in the server 903, and the binary image transmitted from the client computer 901 via the Internet 902. Various processes described in the first embodiment are performed on the data by the above-described program code stored in the server 903, and a multi-value image is generated. And the server 90
3 transmits the multi-valued image to the client computer 901 again via the Internet 902.

When charging the client for generating a multi-valued image, the server 903 transmits the binary image according to the number of the transmitted binary images, for example. An e-mail is sent to the computer 901 together with the charge, and a text prompting the user to pay the charge. Note that, in addition to the number of binary images, for example, a fee may be charged according to the data amount of the binary image transmitted from the computer 901.

[Other Embodiments] Even if the present invention is applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), an apparatus (one device) For example, the present invention may be applied to a copying machine, a facsimile machine, and the like.

Another object of the present invention is to supply a storage medium (or a recording medium) recording software program codes for realizing the functions of the above-described embodiments to a system or an apparatus, and to provide a computer (a computer) of the system or the apparatus. Or a CPU or MPU) reads out and executes the program code stored in the storage medium,
It goes without saying that this is achieved. In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.
In addition, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also based on the instructions of the program code,
The operating system (OS) running on the computer performs part or all of the actual processing,
It goes without saying that a case where the function of the above-described embodiment is realized by the processing is also included.

Further, after the program code read from the storage medium is written into the memory provided in the function expansion card inserted into the computer or the function expansion unit connected to the computer, the program code is read based on the instruction of the program code. , The CPU provided in the function expansion card or the function expansion unit performs part or all of the actual processing,
It goes without saying that a case where the function of the above-described embodiment is realized by the processing is also included.

When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the above-described flowchart (shown in FIG. 2).

[0044]

As described above, according to the present invention, moire can be removed from a multi-value image generated based on a binary image.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of an image processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a flowchart of image processing performed by the image processing apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram showing an n × n rectangular area according to the resolution of a binary image 301;

FIG. 4 is a diagram showing an overlap between a buffer area and a block of interest for each pixel.

FIG. 5 is a diagram showing a conversion table.

FIG. 6 is a diagram showing a table in which the ratio of each pixel constituting a buffer area and the target block overlaps.

FIG. 7 is a diagram showing P (i, j).

FIG. 8 is a diagram illustrating a method of arranging images in a buffer area.

FIG. 9 is a diagram illustrating a schematic configuration of a system according to a second embodiment of the present invention.

Claims (15)

[Claims] An image processing apparatus for generating a multi-valued image based on a binary image, comprising: a dividing unit that divides the binary image into rectangular blocks having a desired size; Area setting means for rotating the target block by a desired angle, and setting a rectangular area including the target block after rotation, and the rectangular area by the area setting means and the target block after rotation overlap with each other. A pixel value setting unit that sets a pixel value of a pixel included in the rectangular region according to the ratio, and a multi-valued image is generated using the rectangular region having a pixel value by the pixel value setting unit. An image processing apparatus comprising: a generation unit. 2. An input unit for inputting a binary image, and a charging unit for charging a target to which the binary image has been input to the input unit based on the binary image input to the input unit. The image processing apparatus according to claim 1, wherein: 3. The image processing apparatus according to claim 1, wherein the setting unit sets the rectangular area according to a size of the block of interest and the desired angle. 4. The method according to claim 1, wherein the setting unit sets the rectangular area using a table in which the size of the rectangular area according to the size of the block of interest and the desired angle is described. The image processing device according to claim 3. 5. The image processing apparatus according to claim 1, wherein the pixel value setting unit further includes a calculating unit configured to calculate a total value of a ratio of an effective pixel among pixels forming the rectangular area and the target block after the rotation. The image processing apparatus according to claim 1, wherein a pixel value of a pixel included in the rectangular area is set based on the total value by the calculation unit. 6. The image processing apparatus according to claim 5, wherein the valid pixel is a pixel having a bit value of 1 in a binary image. 7. The method according to claim 1, wherein the calculating unit calculates the sum of the overlapping ratio of the pixel constituting the rectangular area and the target block after the rotation using a table for each pixel. The image processing apparatus according to claim 5 or 6, wherein 8. The image processing apparatus according to claim 1, wherein the desired size is determined based on a resolution of the binary image. 9. The multi-valued image is generated by superposing and arranging the rectangular areas according to a difference in size between the rectangular area and the block of interest. The image processing device according to claim 1. 10. An image processing method for generating a multi-valued image based on a binary image, comprising: a dividing step of dividing the binary image into rectangular blocks having a desired size; An area setting step of rotating the target block by a desired angle and setting a rectangular area including the target block after rotation, and the rectangular area in the area setting step and the target block after rotation overlap with each other. A pixel value setting step of setting a pixel value of a pixel included in the rectangular area according to the ratio, and a multi-valued image is generated using the rectangular area having a pixel value obtained in the pixel value setting step. An image processing method comprising: a generating step. 11. An input step of inputting a binary image via predetermined input means, and inputting the binary image to the predetermined input means by a binary image input to the predetermined input means. 11. The image processing method according to claim 10, further comprising a charging step of charging the target. 12. A storage medium for storing a program code functioning as an image processing device for generating a multi-valued image based on a binary image, wherein the binary image is divided into rectangular blocks having a desired size. Program code for a dividing step, program code for an area setting step of rotating the target block divided by the dividing step by a desired angle, and setting a rectangular area including the target block after rotation, and the area setting step A program value of a pixel value setting step of setting a pixel value of a pixel included in the rectangular area according to an overlapping ratio of the square area and the block of interest after the rotation. A program code for generating a multi-valued image using the rectangular area having pixel values according to Body. 13. The binary code input to the predetermined input means by a program code of an input step of inputting a binary image through a predetermined input means, and the binary image input to the predetermined input means. 13. The storage medium according to claim 12, further comprising: a program code of a charging process for charging an object to which an image is input. 14. A program having a function of generating a multi-valued image based on a binary image, comprising: a program of a dividing step of dividing the binary image into rectangular blocks having a desired size; A program of an area setting step of rotating the block of interest divided by the step by a desired angle and setting a square area including the block of interest after rotation; A program of a pixel value setting step of setting a pixel value of a pixel included in the rectangular area according to a ratio at which the target block overlaps, and using the rectangular area having a pixel value in the pixel value setting step And a program for generating a multi-valued image. 15. A program for an inputting step of inputting a binary image via a predetermined input means, and a binary image input to the predetermined input means, the binary image being input to the predetermined input means. 15. The program according to claim 14, further comprising: a program for a charging process for charging a target to which is input.