JP2006287603A - Mesh point region discrimination apparatus and mesh point region discrimination program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mesh point region discrimination apparatus capable of improving discrimination accuracy of an isolated point and furthermore carrying out mesh point region discrimination with high accuracy when an input image is a color image. <P>SOLUTION: The mesh point region discrimination apparatus includes: isolation point discrimination means 21R, 21G, 21B for applying isolation point discrimination to each of planes of at least two configuration colors among a plurality of configuration colors RGB of a received color image; count means 22R, 22G, 22B for counting the number of isolation points discriminated by the isolation point discrimination means in a mesh point discrimination region by each plane; and a mesh point region discrimination means 23 for discriminating whether or not the mesh point discrimination object region of the input image is a mesh point region on the basis of the count values by each plane. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is used in, for example, an image forming apparatus such as a copying machine, a printer, a scanner, and the like, and performs a dot region determination device for determining a dot region on an input color image, and a computer for dot region determination processing The present invention relates to a halftone dot region discrimination program to be executed.

  In an image forming apparatus such as a copying machine, when an original composed of half dots is read and screen processing or the like is performed while holding the half dots of the original, the half dots interfere with each other to cause moiré.

  For this reason, in general, a process is performed in which a half point of the input image is determined by determining a part composed of the half point of the input image and performing a smoothing process on the part.

Conventionally, as a method for discriminating a halftone dot portion of an input image as described above, Patent Document 1 discloses that brightness (brightness) data is created from an input image, the dynamic range difference between the central pixel and the peripheral pixel of the data, and the dot size A technique has been proposed in which isolated points are discriminated from each other, and the number of isolated points is counted to determine whether or not it is a halftone dot region.
Japanese Patent No. 2777378

  However, as described in Patent Document 1, in isolated point determination based on lightness (luminance), when an input image is a color image, dots configured as isolated points in each constituent color plane such as RGB are as follows: There is a problem that the data is combined by converting to lightness data, and cannot be determined as an isolated point, and the accuracy of determining the dot area is poor.

  The present invention has been made in order to solve the above-described problem. When the input image is a color image, the isolated point discrimination accuracy can be improved, and the halftone dot region discrimination can be performed with high accuracy. It is an object of the present invention to provide a halftone dot region discrimination device and a halftone dot region discrimination program for causing a computer to execute a halftone dot region discrimination process.

The above problem is solved by the following means.
(1) With respect to each of at least two component color planes of the plurality of component colors of the input color image, the isolated point determination unit for performing isolated point determination and the isolated point determination unit for each plane Counting means for counting the number of isolated points in the target area to be determined, and based on the count value for each of the planes, it is determined whether the target area of the input image is a target area. And a dot region discriminating device.
(2) The dot area determination unit determines whether or not the dot area to be determined is a dot area for each plane, and determines that the dot area to be determined on at least one plane is the dot area. In this case, the halftone dot region discrimination device according to the preceding item 1, wherein it is determined that the halftone dot discrimination target region of the input image is a halftone dot region.
(3) A step of performing isolated point determination for each of at least two component color planes of the plurality of component colors of the input color image, and determining the half point of the determined isolated point for each plane. For causing the computer to execute a step of counting the number in the target area, and a step of determining whether or not the halftone dot discrimination target area of the input image is a halftone spot area based on the count value for each plane. A dot area discrimination program.
(4) In the dot area determining step, it is determined for each plane whether the dot area is a dot area, and the dot area to be determined of at least one plane is determined to be an dot area. In this case, the program for discriminating dot area according to item 3 above, wherein the dot area to be discriminated in the input image is discriminated as a dot area.

  According to the invention described in item (1) above, isolated point determination for each of at least two component color planes of a plurality of component colors of the input color image, and a point determination target for the determined isolated point Counting is performed on the area, and based on the count value for each plane, it is determined whether or not the target area of the input image is the target area. Therefore, it is possible to determine the isolated point based on the brightness (luminance) of the input image. In this way, it is possible to eliminate the inconvenience that dots configured as isolated points are combined by converting to lightness data and cannot be identified as isolated points, and high-precision isolated point determination can be performed. A dot area discrimination can be performed.

  According to the invention described in (2) above, it is determined for each plane whether or not the above-described area determination target area is an area dot area, and the area determination target area of at least one plane is the area dot area. If it is discriminated, it is discriminated that the target area of the input image is the dot area, so that accurate spot area determination can be performed.

  According to the invention described in item (3) above, it is possible to cause the computer to perform high accuracy halftone dot region determination by high accuracy isolated point determination as described in item (1).

  According to the invention described in item (4) above, it is possible to make an accurate dot area discrimination as described in item (2) above by a computer.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing an electrical configuration of a color image forming apparatus (hereinafter simply referred to as an image forming apparatus) provided with a halftone area discriminating apparatus according to an embodiment of the present invention. The image forming apparatus 1 includes, for example, an MFP (Multi Function Peripherals) that is a multi-function image forming apparatus having a plurality of functions such as a copy function, a printer function, a scanner function, and a data transmission function such as image data. Yes.

  The image forming apparatus 1 includes a network interface unit (network I / F) 11, a scanner unit 12, an operation unit 13, a storage unit 14, a printing unit 15, a CPU 16, a ROM 17, and a RAM 18.

  The network interface unit 11 functions as a communication unit for connecting the image forming apparatus 1 to the network 2. In this embodiment, image data and other data transmitted from an external device such as a user terminal (not shown) can be received via the network interface unit 11.

  The scanner unit 12 reads a monochrome or color document and converts it into image data.

  The operation unit 13 includes a display device having a touch panel and a keyboard, and has a display function and a function for a user to perform an operation.

  The storage unit 14 stores image data input from the scanner unit 12 or the user terminal, setting data such as a print mode input by the user using the operation unit 13, and the like.

  The printing unit 15 prints document image data read by the scanner unit 12 and print data transmitted from a user terminal on paper.

  In addition to overall control of the entire image forming apparatus 1, the CPU 16 performs a halftone area discrimination process on the input image data in this embodiment, and performs a smoothing process on the identified halftone spot area. To do. Specific contents of the halftone dot discrimination process will be described later.

  The ROM 17 stores a program for operating the CPU 16 and other data.

  The RAM 18 is for securing an operation area of the CPU 16.

  The discrimination of the dot is based on the feature that the dot is composed of isolated points. First, the isolated point is determined for the input image data, and then the set of isolated points is configured as the dot. It is executed by determining whether or not it is.

  FIG. 2 is a functional block diagram of a halftone dot discrimination device included in the image forming apparatus 1 of FIG. In the following description, it is assumed that the input image is a color image.

  21R, 21G, and 21B are isolated point discriminating units corresponding to R (red), G (green), and B (blue), which are constituent colors of color image data. The RGB planes of the input image Input to the isolated point discriminating units 21R, 21G, and 21B. Each isolated point determination unit 21R, 21G, 21B determines whether or not each of the RGB planes is an isolated point from the dynamic range and isolated point size of the input image.

  FIG. 3 shows a matrix of pixels when the isolated point discriminating units 21R, 21G, and 21B perform isolated point discrimination. In the case of 1-dot isolated point discrimination, as shown in FIG. 3A, the gradation number of the center pixel A is determined from the minimum gradation value Min (B1 to B8) of the B1 to B8 pixels around the center pixel A. If the subtracted Min (B1 to B8) -A is larger than a certain threshold value Th1, the isolated point determining unit 21 determines that it is a 1-dot isolated point.

  In the case of a 2 × 2 dot isolated point, as shown in FIG. 3B, the center pixel A1 is calculated from the minimum gradation value Min (B1 to B12) of the B1 to B12 pixels around the center pixels A1 to A4. If the average value Ave (A1 to A4) of A4 to A4 is subtracted and Min (B1 to B12) −Ave (A1 to A4) is greater than a certain threshold value Th2, it is determined that it is a 2 × 2 dot isolated point. .

  In this way, each isolated point determination unit 21R, 21G, 21B determines an isolated point having a size of P × P dots (P is an arbitrary natural number) for each RGB plane.

  The isolated point discrimination results of the RGB planes by the isolated point discriminating units 21R, 21G, and 21B are sent to the isolated point counting units 22R, 22G, and 22B.

  The isolated point counting units 22R, 22G, and 22B count the number of isolated points in the same half point discrimination target region having a predetermined matrix size larger than the P × P for each of the RGB planes, and the result. Is transmitted to the dot area determination unit 23.

  Based on the count value of the isolated points for each plane in the dot detection target region, the dot point determination unit 23 determines whether the dot detection target region is a dot point region for each plane.

  The determination of whether or not it is a halftone dot region may be performed using a known method as described in, for example, Patent Document 1 (Japanese Patent No. 2777378). As an example, in the target spot determination target area and the surrounding spot determination target area, the target spot determination target area in which the number of isolated points is equal to or greater than a predetermined threshold is greater than the predetermined threshold. There is a method for discriminating that the target area of the spot is a spot area.

  Then, the dot area determination unit 23 determines that at least one plane is determined to be the dot area based on the determination result as to whether or not it is the dot area for the same area of the RGB planes. If it exists, the half point discrimination target region of the input image data is judged as a half point region.

  As described above, since it is determined whether or not the entire input image is the dot area based on the determination result of whether or not each of the RGB planes is the dot area, the isolated point determination based on the brightness (luminance) of the input image is performed. In this way, it is possible to eliminate the inconvenience that dots configured as isolated points are combined by converting to lightness data and cannot be identified as isolated points, and high-precision isolated point determination can be performed. A dot area discrimination can be performed.

  FIG. 4 is a flowchart showing the contents of the dot area discrimination process executed by the CPU 16 shown in FIG. This processing is performed by the CPU 16 executing a discrimination processing program stored in the ROM 17 or the like. In the following description and drawings, the step is abbreviated as “S”.

  In S1, isolated point discrimination is performed for each RGB plane of the input image.

  Next, in S2, the number of isolated points in the halftone dot discrimination target area is counted for each RGB plane, and in S3, it is determined whether or not the halftone dot discrimination target area is a half dot area for each plane. In step S4, it is determined whether or not at least one plane is determined to be a dot area for the same target area of each plane, and it is determined that at least one plane is a dot area. If it is determined (YES in S4), it is determined in S5 that the target area of the input image is the target area and any plane is determined not to be the target area. (NO at S4), it is determined at S6 that the above-mentioned area determination area of the input image is not an area.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, isolated point determination is performed using three RGB planes, and it is determined whether or not the area is a halftone dot region, but determination may be performed using two of the three RGB planes. Further, two or more planes of cyan, magenta, and yellow may be used instead of RGB.

1 is a block diagram showing an electrical configuration of an image forming apparatus having a halftone dot area discriminating apparatus according to an embodiment of the present invention. It is a functional block diagram of a dot area discriminating device. It is a figure which shows the matrix of a pixel in the case of performing isolated point discrimination | determination. 3 is a flowchart showing the contents of halftone dot area discrimination processing performed by the image forming apparatus of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 12 Scanner part 13 Operation part 14 Memory | storage part 15 Printing part 16 CPU
21R, 21G, 21B Isolated point discriminating unit 22R, 21G, 21B Isolated point counting unit 23 Ami point discriminating unit

Claims (4)

Isolated point determining means for performing isolated point determination for each of at least two component color planes of the plurality of component colors of the input color image;
Counting means for counting the number of isolated points discriminated by the isolated point discriminating means in the area to be discriminated for each plane for each plane;
Based on the count value for each of the planes, the dot area determination means for determining whether or not the dot area to be determined of the input image is a dot area;
A halftone dot region discriminating apparatus comprising:   The dot area determination means determines whether or not the dot area to be determined is a dot area for each plane, and determines that the dot area to be determined of at least one plane is the dot area 2. The dot region determination device according to claim 1, wherein the dot image determination target region of the input image is determined to be a dot region. Performing isolated point determination for each of at least two component color planes of the plurality of component colors of the input color image;
For each plane, counting the number of the identified isolated points in the area to be determined by the dots;
Based on the count value for each of the planes, it is determined whether or not the area of the input image is a dot area,
This is a program for discriminating dot areas for causing a computer to execute. In the dot area determination step, for each plane, it is determined whether or not the dot area to be determined is a dot area, and if it is determined that the dot area to be determined on at least one plane is an area 4. The program for discriminating a dot area according to claim 3, wherein the dot area to be discriminated in the input image is discriminated as a dot area.

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