JP2010020463A - Line drawing processor, line drawing processing method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology to easily and precisely separate a dotted portion from a line drawing. <P>SOLUTION: A line drawing processor 100 sequentially determines the curvature value of pixels constituting an outline portion along the outline portion of a drawing region DR and quantifies the degree of bending of each pixel position at the outline portion. The line drawing processor 100 detects the pixels bending in the direction to extend the drawing region DR (inflection point P) based on the comparison with a predetermined reference value and separates a projecting region ER projected from the drawing line DL from the drawing region DR by connecting the inflection points P in a predetermined positional relation by a separation line L. The line drawing processor 100 removes the separated projecting region ER from an image by removing a drawing pixel set below a predetermined reference area. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for separating halftone dots from line drawings.

  Manga is a typical example of uncolored line drawing. In general, manga is a (monochrome) line drawing with a unique Japanese texture, unlike Western comics (Comic). In other words, in manga, the expression of gradation (color shade) and the emotion of characters are expressed by patterns such as halftone dots, solids, and effect lines by applying Screen Tone (registered trademark), and drawing lines such as contour lines. The character is very different from comics with many color expressions.

  Traditionally, manga is printed on paper media and supplied to the market, but for the reasons such as the cost of color printing being too high, all but the first page of magazines and other color pages were produced only in monochrome (uncolored) representation. .

  However, with the development of communication technology of terminal devices such as mobile phones, the number of sites where digitalized manga can be subscribed via a communication line has increased rapidly, and the opportunity to view manga on a liquid crystal monitor has increased. Along with this, there is an increasing demand for manga that has been colored (colored and colored). Also, since there is no monochrome manga culture outside Japan, it is necessary to color monochrome manga in order to expand the manga business overseas.

  Production work for coloring monochrome manga includes the process of separating various tones (such as halftone dots) from line drawings, the process of coloring lines from which tones are separated, and, in some cases, clipping This includes the process of coloring the tone and reflecting it in the original line drawing.

  Here, in manga production, generally, a tone is pasted along a drawing line so as not to create an unnatural gap between the drawing line and the tone portion. Therefore, a part of the pattern (halftone dot) constituting the tone area is overlapped with the drawing line. However, the halftone dot overlapped with the drawing line needs to be completely separated from the original image. .

  For example, Patent Document 1 proposes a technique for removing a halftone dot overlapped on the drawing line. Specifically, in Patent Document 1, after thinning a line drawing, a branch portion generated by a halftone dot overlapped on a drawing line is identified, and the branch portion is selectively deleted. Then, by returning the thin line to the original line width, the halftone dots overlapping the drawing line are separated.

JP-A-2005-31818

  However, the technique described in Patent Document 1 has a problem in that when a line drawing is thinned, a thin line derived from a drawing line is pulled to the halftone dot side and bent in a portion where the drawing line and the halftone dot overlap. It was. Therefore, even if the branch portion protruding from the bent portion can be accurately deleted, the bending of the thin line derived from the drawing line remains. Therefore, there is a problem that when the thin line is returned to the original thickness line, the bent portion remains as it is.

  In addition, the technique described in Patent Document 1 has a problem that it is inconvenient from the viewpoint of image processing because it is necessary to acquire vector format data or perform RIP processing in order to perform coloring processing. It was.

  The present invention has been made in view of the above problems, and an object thereof is to provide a technique for accurately and easily separating a halftone dot portion from a line drawing.

  In order to solve the above problems, the invention of claim 1 is a line drawing processing apparatus for separating a halftone dot from a line drawing, and a protruding start portion and a protruding portion of a protruding area protruding outward with respect to a drawing line extending in a predetermined direction. Separation that separates the protruding area from the drawing area by connecting a detection means for detecting the end part along the outline of the drawing area and a separation line between the protruding start part and the protruding end part. Separating means for generating an image, and removing means for removing the protruding region separated by the separating means for the separated image.

  The invention of claim 2 is the line drawing processing apparatus according to the invention of claim 1, wherein the removing means is separated by the separating means by removing a drawing pixel set having a predetermined reference area or less. The protruding region is removed.

  The invention according to claim 3 is the line drawing processing apparatus according to claim 1 or 2, wherein each of the positions of the connected pixels connected to two or more continuous pixels continuously arranged in a predetermined direction is provided. When the curvature value is defined, the detecting means includes a curvature value determining means for determining a curvature value for each pixel constituting the outline portion of the drawing area, and among the pixels constituting the outline portion of the drawing area, An inflection point detecting means for detecting, as an inflection point, a pixel having a curvature value determined to bend in a direction in which the drawing area is expanded, and the predetermined inflection points detected by the inflection point detection means The inflection points in the positional relationship are defined as the protrusion start portion and the protrusion end portion.

  The invention of claim 4 is the line drawing processing apparatus according to claim 3 of the invention, wherein the inflection point detecting means has a predetermined proximity to each pixel for each pixel of the contour portion of the drawing area. An average value of curvature values of a plurality of pixels included in the range is calculated for each pixel, and based on a comparison between the average value and the predetermined reference value, it is determined that the image is bent in a direction in which the drawing area is expanded. The detected pixel is detected as the inflection point.

  The invention according to claim 5 is the line drawing processing apparatus according to any one of claims 1 to 4, wherein a removal area in which halftone dots are to be removed from the line drawing is set based on a predetermined operation input. It further comprises a removal area setting means, wherein the detection means detects the protrusion start part and the protrusion end part included in the removal area set by the removal area setting means.

  The invention according to claim 6 is the line drawing processing apparatus according to any one of claims 1 to 5, wherein the binary drawing is obtained by binarizing the line drawing with a predetermined threshold value. A contour extraction unit that generates a contracted image by contracting a drawing region included in the binary image, and extracts a contour portion of the drawing region from a difference between the binary image and the contracted image Means for detecting the protrusion start portion and the protrusion end portion along the contour portion extracted by the contour extraction means.

  The invention of claim 7 is a line drawing processing method for separating a halftone dot from a line drawing, wherein a drawing start portion and a protruding end portion of a protruding region protruding outward with respect to a drawing line extending in a predetermined direction are drawn. The projecting region is separated from the drawing region by connecting a detection step for detecting along a contour portion of the region and a separation line between the projecting start portion and the projecting end portion detected in the detecting step. A separation step of generating a separation image, and a removing unit that removes the protruding region separated by the separation step from the separation image.

  The invention according to claim 8 is a computer-readable program, wherein the computer reads the program, and the CPU of the computer executes the program in the memory, thereby drawing lines extending in a predetermined direction. On the other hand, a detection means for detecting the protrusion start portion and the protrusion end portion of the protrusion region protruding outward along the outline portion of the drawing region and the protrusion start portion and the protrusion end portion are connected by a separation line. Thus, a halftone dot is obtained from a line drawing provided with a separating unit that generates a separated image obtained by separating the protruding region from the drawing region, and a removing unit that removes the protruding region separated by the separating unit for the separated image. The computer is caused to function as a line drawing processing device to be separated.

  According to the first to eighth aspects of the present invention, the protruding region is separated from the drawing region by detecting the protruding start portion and the protruding end portion of the protruding region of the drawing region and connecting them with a separation line. Therefore, the halftone dots connected to the drawing line can be easily and precisely removed.

  According to the second aspect of the present invention, the separated protruding region can be easily removed by a relatively simple process.

  According to the third aspect of the present invention, the degree of bending at the position of each pixel constituting the outline of the drawing area is quantified based on the defined curvature value, so that the protrusion of the protruding area of the drawing area is calculated. Since the start portion and the projecting end portion can be detected, it is possible to effectively remove the halftone dots connected to the drawing line.

  Further, according to the invention described in claim 4, it is possible to prevent the rattling of the contour portion from being determined as the protruding region by averaging the curvature values. Therefore, it is possible to realize halftone dot separation with high accuracy.

  According to the fifth aspect of the present invention, by providing the removal area setting means, it is possible to specify in detail the area where the halftone dots are to be removed. Therefore, since the removal process according to the type of halftone dot can be realized, the halftone dot can be precisely removed from the line drawing.

  According to the invention described in claim 6, a contour line having a predetermined pixel width can be efficiently extracted.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.

<1. First Embodiment>
<1.1. Configuration and Function>
[Schematic configuration]
FIG. 1 is an external view of a line drawing processing apparatus 100 according to the first embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration of the line drawing processing apparatus 100.

  The line drawing processing apparatus 100 mainly includes a CPU 10, a storage unit 11, an input unit 12, a display unit 13, a disk reading unit 14, a communication unit 15, and a scanner 16, and has a function as a general computer.

  The CPU 10 operates according to the program 2 stored in the storage unit 11 to execute various data calculations and control signal generation, and controls each configuration of the line drawing processing apparatus 100. The functional blocks realized by the CPU 10 will be described later.

  The storage unit 11 includes a RAM and a hard disk, which serve as a temporary working area for the CPU 10, and a read-only ROM (not shown). The storage unit 11 has a function as a recording medium for storing the program 2 and various data. The program 2 may be transferred from the recording medium 9 to the storage unit 11 via the disk reading unit 14 or may be transferred to the storage unit 11 via the communication unit 15.

  The input unit 12 is used to input a user instruction to the line drawing processing apparatus 100. That is, the input unit 12 functions as an input device in the line drawing processing apparatus 100. Specifically, the input unit 12 corresponds to, for example, a keyboard, a mouse, a pen tablet (registered trademark), and various buttons.

  The display unit 13 displays various data as images on the screen. That is, the display unit 13 functions as a display device in the line drawing processing apparatus 100. Specifically, the display unit 13 corresponds to, for example, a CRT monitor or a liquid crystal display, but may have a part of the function of the input unit 12 like a touch panel display.

  The disk reading unit 14 is a device that reads data stored in the portable recording medium 9 and transfers the data to the storage unit 11. That is, the disk reading unit 14 functions as a data input device in the line drawing processing apparatus 100.

  The line drawing processing apparatus 100 according to the present embodiment includes a CD-ROM drive as the disk reading unit 14. However, the disk reading unit 14 is not limited to this, and may be, for example, an FD drive, a DVD drive, or an MO device. If the disk reading unit 14 has a function of recording data on the recording medium 9, the disk reading unit 14 can substitute a part of the function of the storage unit 11.

  The communication unit 15 has a function for performing communication via the network between the line drawing processing device 100 and another device group (not shown).

  The scanner 16 is a reading device for reading a line drawing, has a large number of image sensors, and has a function for acquiring a line drawing recorded on a paper medium or the like as digital data.

  FIG. 3 is a diagram showing functional blocks of the line drawing processing apparatus 100 together with a data flow. The image acquisition unit 20, the region setting unit 21, the first removal unit 22, the contour extraction unit 23, the curvature value determination unit 24, the inflection point detection unit 25, the separation unit 26, and the second removal unit 27 illustrated in FIG. These are functional blocks realized by the CPU 10 operating according to the program 2.

[Image acquisition unit 20]
FIG. 4 is a diagram illustrating an example of the line drawing I1 read by the scanner 16. As shown in FIG. 4, a line drawing (part of a manga) printed on a printing substrate (paper or the like) is read by the scanner 16, whereby line drawing data DI <b> 1 is acquired, and the image acquisition unit 20 stores it in the storage unit 11. Stored.

  The line drawing to be processed by the line drawing processing apparatus 100 may be an analog image (original) written on paper or the like, or may be an image digitized in the past for publication. A case of processing a monochrome binary level line drawing (monochrome image) will be described.

  In the present embodiment, the pixels constituting the drawing pixels such as drawing lines and halftone dots are pixels of “black (gradation value = 0 in 8-bit representation, gradation value = 0 in 1-bit representation)”. In the following description, it is assumed that the pixels in the plain portion are composed of pixels of “white (gradation value = 255 in 8-bit representation = 1 gradation value in 1-bit representation)”. For example, the drawing pixels constituting the drawing line may be composed of “white” pixels.

  As shown in FIG. 4, a general achromatic line drawing has an area composed of a large number of halftone dots (halftone area TR), and the background or the color of an object has a pattern such as a halftone dot. It is expressed using. The line drawing processing apparatus 100 in the present embodiment accurately separates and removes such halftone dots from the line drawing I1.

[Area setting unit 21]
The area setting unit 21 sets a removal area RR where halftone dots should be removed from the line drawing based on a predetermined operation input by the operator. Specifically, the region setting unit 21 displays a region setting screen (not shown) on the display unit 13 together with the line drawing I1. Then, the operator selects and trims (trims) a region where the halftone dots are to be removed while visually confirming the line drawing I1 displayed on the display unit 13. Information (information such as size and position) of the removal region RR set by the operator's operation input is stored in the storage unit 11 by the region setting unit 21 as region setting data D1.

  As described above, since the operator designates the removal region RR in advance, the image processing can be performed under finer conditions than the case where the entire line drawing I1 is set as the processing target at a time. Halftone dot removal processing can be realized.

  The above-described removal region RR is specified by, for example, an operator specifying a region using a rectangular frame selection tool prepared in advance (see FIG. 4). However, the selection tool is not limited to this, and a frame selection tool having another predetermined shape such as a circle (including an ellipse) may be prepared.

  The setting of the removal region RR may be realized by the operator specifying the region using a tool (drawing tool) for the operator to draw on the network image. Furthermore, the region setting unit 21 is not limited to the configuration described above, and may have any configuration as long as the removal region RR can be designated.

  In the present embodiment, the region setting unit 21 sets the removal region RR for the line drawing I1, but for an image (removed image I2) in which halftone dots to be described later are substantially removed. Thus, the removal region RR may be set.

[First removal unit 22]
The first removal unit 22 removes a drawing pixel set portion having a predetermined reference area or less from the line drawing I1 represented by the line drawing data DI1. More specifically, the first removal unit 22 has a relatively small pixel set of specific bits (here, black dots) such as minute dots generated as noise during reading by the scanner 16 or the like, or halftone dots in the halftone area TR. A set of gradation-drawing pixels) is removed from the line drawing I1 (specifically, in the removal region RR of the line drawing I1). The image data from which these dots have been removed (removed image data DI2) is stored in the storage unit 11.

  The predetermined reference area here is, for example, the pixel area per unit of a large number of halftone dots included in the halftone dot region TR included in the line drawing I1 (or a pixel area slightly larger than that). The By setting the reference in this way, halftone dots can be efficiently removed from the line drawing I1.

  FIG. 5 is a diagram showing a removed image I2 obtained by removing halftone dots from the line drawing I1 shown in FIG. As shown in FIG. 5, in the removal image I2, the first removal unit 22 substantially removes halftone dots in the halftone area TR included in the line drawing I1.

  In the halftone dot removal process by the first removal unit 22, as shown in the area surrounded by the broken line in FIG. 5, the halftone dot that overlaps the drawing line is not removed and remains as a shape protruding from the drawing line. . In the line drawing processing apparatus 100 according to the present embodiment, it is possible to efficiently remove halftone dots remaining on the drawing line from the removed image I2 by each process described later.

[Outline Extraction Unit 23]
Returning to FIG. 3, the contour extracting unit 23 extracts a contour portion of the drawing region DR in order to detect a protruding portion formed of a halftone dot overlapped on the drawing line. The contour extraction unit 23 includes a contraction processing unit 231 and a difference processing unit 232, and a predetermined gradation value (here, black) is set for the inside of the removal region RR set by the region setting unit 21 in the removal image I2. The contour portion of the drawing region DR including the pixel of (gradation value) is extracted.

  FIG. 6 is a diagram showing a contour extraction image I4 obtained by extracting the contour line OL from the removal image I2. The contour extracting unit 23 generates contracted image data DI3 by contracting the drawing region DR composed of pixels of the black gradation value of the removed image I2 by one contraction by the contraction processing unit 231.

  Here, for example, when the “black” drawing region DR is contracted, if there is at least one “white” pixel in the vicinity of the “black” target pixel in the binary image, A process of replacing a pixel with a “white” pixel. The replacement conditions are not limited to those described above, and can be set as appropriate. Further, the present invention is not limited to identifying the neighborhood of 8 pixels of the pixel of interest and performing the contraction process. For example, the neighborhood of 4 pixels may be identified to perform the contraction process.

  When the contracted image data DI3 is generated, the contour extracting unit 23 performs a difference calculation process (exclusive OR operation) on the contracted image data DI3 and the original removed image data DI2 by the difference processing unit 232, thereby drawing region DR. Are extracted (contour line OL having a width of one pixel).

  As shown in FIG. 6, halftone dots Dot1 (indicated by broken lines in FIG. 6) that exist in isolation in the removed image I2 are removed by the first removal unit 22. By performing the above-described contraction process and difference calculation process on such a removed image I2, the drawing region DR (here, composed of the drawing line DL and a part of the halftone dot Dot1 overlapping the drawing line). A contour extraction image I4 composed of the contour line OL is generated. Data (contour extraction data DI4) representing the generated contour extraction image I4 is stored in the storage unit 11 by the contour extraction unit 24 (see FIG. 3).

  Note that the contour extraction method is not limited to the above-described method. For example, the contour may be extracted by detecting an edge from the removed image I2 using a predetermined filter.

[Curvature value determination unit 24]
Returning to FIG. 3, the curvature value determining unit 24 uses the contour to detect the protrusion start portion and the protrusion end portion of the protrusion region ER protruding from the drawing line DL extending in a predetermined direction from the extracted contour line OL. The degree of bending at each pixel position on the line OL is digitized.

  For example, in the removed image I2 shown in FIG. 6, in the drawing region DR where the drawing line DL and the halftone dot Dot1 overlap, the halftone dot Dot1 protrudes from the drawing line DL extending in a predetermined direction (vertical direction here). The protruding region ER is formed. Since the protruding region ER exists, the contour OL has a protruding start portion (a portion surrounded by a square) and a protruding end portion (a portion surrounded by a triangle) that bend in the direction of extending the drawing region DR outward.

  In the present embodiment, in order to detect the protruding region ER on the drawing region DR, the protruding start portion and the protruding end portion are detected. Therefore, the curvature value determination unit 24 calculates the contour line OL of the drawing region DR based on the curvature value defined in advance for each position of the connected pixels connected to two or more consecutive pixels that are continuously arranged as a reference. The degree of bending of each pixel constituting is quantified. A method for determining the curvature value will be described with reference to FIGS.

  FIG. 7 is a diagram showing the definition matrix F1. The definition matrix F1 is composed of 3 × 3 squares, arranged in a center along a predetermined direction (here, connected to be adjacent to each other) and squares M, and curvature values (here Then, -3, -2, -1, 0, +1, +2, +3) are composed of seven squares defined respectively.

  FIG. 8 is a diagram for explaining a method of determining a curvature value using the definition matrix F1. In the example shown in FIG. 8, the removed image I2 includes the drawing areas DR1 and DR2. In addition, the drawing area DR1 has a non-drawing area inside, and the drawing area DR2 extends to the frame line W that defines the removed image I2.

  The curvature value determination unit 24 determines a curvature value for each pixel of the contour line OL while referring to the definition matrix F1 along the contour line OL having a width of one pixel extracted from the drawing regions DR1 and DR2. .

  When the curvature value is determined using the definition matrix F1, for the contour line OL on the outer periphery side of the drawing region DR1, the curvature value determination unit 24 proceeds in the clockwise direction on the contour line OL while the curvature value of each pixel. Are sequentially determined. On the other hand, for the contour line OL on the inner periphery side of the drawing region DR1, the curvature value determination unit 24 sequentially determines the curvature value of each pixel while proceeding counterclockwise on the contour line OL.

  In addition, for the portion overlapping the frame line W of the drawing region DR2, the contour line OL is not extracted in the above-described contraction process and difference calculation process. Therefore, the curvature value determining unit 24 complements a virtual auxiliary line to a portion overlapping the frame line W, thereby connecting the extraction lines OL with an auxiliary line, and configuring the auxiliary line OL constituting the outer peripheral portion of the drawing region DR. The curvature value in each pixel is sequentially determined while proceeding clockwise on the auxiliary line.

  Further, the curvature value determination unit 24 appropriately defines the definition matrix F1 based on the position of the next pixel (connected pixel) connected to the pixel (continuous pixel) including the specific pixel on the contour line OL and the previous pixel (continuous pixel). By referencing, the curvature value of the next connected pixel is determined. Next, a method for determining a curvature value using the definition matrix F1 will be described with a specific example.

  FIG. 9 is a diagram illustrating an example of pixels constituting the outline OL of the drawing region DR.

  Note that the pixels p1 to p10 illustrated in FIG. 9 constitute a part of the outline OL of the outer peripheral portion of the drawing region DR. Therefore, since the curvature value determination unit 24 determines the curvature value clockwise along the contour line OL as described above, the curvature value of each pixel is determined in the order of the pixels p1, p2, p3. The

  Further, the contour line OL shown in FIG. 9 forms a straight line in the pixels p1 to p4, and bends in the direction in which the drawing region DR is expanded (the outside direction of the drawing region DR) in the pixels p5, p7, and p9. Further, the pixels p6, p8, and p10 are bent in a direction in which the drawing region DR is contracted (inward direction of the drawing region DR).

  For example, when focusing on the pixel p2, if the arrangement direction of the pixel p2 and the preceding pixel p1 is made to coincide with the arrangement direction of the cell M and the cell B of the definition matrix F1, the position of the next pixel p3 is defined. In the matrix F1, it corresponds to a grid defined as curvature value = 0. Therefore, the curvature value of the next pixel p3 is determined to be 0.

  Similarly, when all the curvature values up to the pixel p10 are determined, the curvature values at the pixels p3 and p4 are 0, the curvature values at the pixels p5, p7, and p9 are +2, and the curvature values at the pixels p6, p8, and p10 are −. 2 That is, when the curvature value is determined using the definition matrix F1 shown in FIG. 9, the curvature value is 0 in the pixels constituting the portion where the contour line OL is not bent, and the pixel is bent at the direction in which the drawing region DR is expanded. Then, the curvature value is determined to be a positive value, and the curvature value is determined to be a negative value in a pixel that is bent in the direction in which the drawing region DR is contracted.

  As described above, the curvature value determination unit 24 determines the curvature value at each pixel position on the contour line OL while referring to the definition matrix F1 along the contour line OL, and generates the curvature value data D2. The generated curvature value data D2 is stored in the storage unit 11.

[Inflection point detector 25]
In general, the contour line OL of the drawing region DR has rattling (a fine protrusion or dent corresponding to several pixels that occurs in the contour line OL portion that extends linearly) due to a reading error of the scanner 16 or the like. Yes. Therefore, since the curvature value data D2 includes the curvature values of the wobbling portions, when the curvature of the contour line OL is evaluated based on the curvature value data D2, the contour line OL extending linearly. There is a possibility that it is erroneously determined that there is a protruding portion.

  Therefore, the inflection point detection unit 25 further calculates an average curvature value for each pixel from the curvature value data D2, and detects a pixel having an average curvature value exceeding a predetermined reference value as the inflection point P. First, a method for calculating the average curvature value will be described with reference to FIG.

  FIG. 10 is a diagram for explaining a method of calculating the average curvature value. The inflection point detection unit 25 calculates the average curvature value of the specific pixel by taking the average of the curvature values of a plurality of pixels within a predetermined range close to the specific pixel.

  When the curvature values of the pixels p11 to p16 constituting the contour line OL are 0, 0, 0, +2, -2, and 0, respectively, for example, when obtaining the average gradation value of the pixel p13, the present embodiment The inflection point detection unit 25 in the embodiment averages the curvature value of the pixel p13 and the curvature values (+2 and 0, 0, 0, -2) of the two pixels before and after the pixel (pixels p11, p12, p14, p15). The value is the average gradation value of the pixel p13. Therefore, the average gradation value in the pixel p13 is 0. Similarly, the average gradation value of the pixel p14 is calculated as 0.

  The pixel p14 has a curvature value as a bent portion (curvature value = + 2) at the stage where the curvature value is determined, but the value is 0 when the average curvature value is calculated. That is, by using the average curvature value for the evaluation of the degree of bending of the contour line OL, it is possible to effectively suppress erroneous determination that the bending occurs in a portion extending substantially linearly like the pixels p11 to p16. .

  In the present embodiment, the average curvature value is calculated from the curvature values of a total of five pixels, that is, the pixels for which the average curvature value is to be obtained and the two adjacent pixels adjacent to the pixel. However, the present invention is not limited to this. Instead, the number of pixels to be averaged can be set freely. However, in order to obtain a numerical value that accurately reflects the degree of curvature, it is desirable to select a curvature value of a pixel within a range as close as possible to the pixel whose average curvature value is to be calculated.

  FIG. 11 is a diagram illustrating the contour line OL of the contour extraction image I4 illustrated in FIG. 6 together with the average curvature value of each pixel. In addition, in FIG. 11, the average curvature value about some pixels is shown among the pixels which comprise the outline OL.

  As shown in FIG. 11, the average curvature values are all 0 in the linearly extending contour OL (the left straight line). Therefore, it is expressed by a numerical value (0 in this case) that no bending occurs. On the other hand, in the contour line OL (left side line) including the protruding portion where the halftone dots overlap on the drawing line, the average curvature value of the contour portion derived from the drawing line DL is 0, but the protruding start portion (square) of the protruding region ER. The average curvature value at the portion surrounded by () and the end portion of projection (enclosed with a triangle) is +1.3. In the contour portion derived from the dot Dot1, the average curvature value is a value of 0 to −0.6.

  Here, the inflection point detection unit 25 detects a pixel (inflection point P) having an average curvature value equal to or greater than a predetermined reference value. For example, when a predetermined reference value is “+1” and a pixel having an average curvature value equal to or greater than the reference value is an inflection point P, the inflection point detection unit 25 includes a protrusion start portion and a protrusion end portion (that is, , A portion that bends in the direction of extending the drawing area DR) is detected as an inflection point P.

  In this way, an appropriate reference value is set, and the inflection point detection unit 25 compares the reference value with the average curvature value of each pixel on the contour line OL, so that the protrusion region ER on the contour line OL is detected. The protrusion start portion and the protrusion end portion can be efficiently detected as the inflection point P.

  In the present embodiment, as described with reference to FIG. 8, the curvature value determination unit 24 calculates the curvature value while proceeding clockwise on the contour line OL for the contour line OL on the outer periphery side of the drawing region DR. The curvature value is determined for the inner contour line OL while proceeding counterclockwise on the contour line OL, but the method for determining the curvature value is not limited to this.

  For example, the curvature value determination unit 24 is configured to determine the curvature value counterclockwise for the outer contour line OL, and to determine the curvature value clockwise for the inner contour line. May be. However, in this case, when the curvature value is determined using the definition matrix F1, the curvature value of the pixel that is bent in the direction in which the drawing region DR is expanded is negative, and the curvature value of the pixel that is bent in the direction in which the drawing region DR is contracted. Is a positive value. Therefore, when the inflection point P is detected by the inflection point detector 25, the reference value needs to be a negative value.

  Further, the curvature value determining unit 24 sets the definition file F1 in the same direction (clockwise (or counterclockwise)) for each of the outer contour line OL and the inner contour line OL of the drawing region DR. The curvature value may be determined sequentially. In this case, the condition for the inflection point detection unit 25 to detect the inflection point P may be appropriately set to different conditions for the outer peripheral side and the inner peripheral side.

  In the inflection point detection data D3 acquired by the above processing, only the position information of the inflection point P is described, and which inflection point P is the protrusion start portion of the protrusion region ER. Or it is unknown whether it is a protruding end part. Therefore, the inflection point detection unit 25 detects the inflection point P having a predetermined positional relationship as the protrusion start portion and the protrusion end portion.

  Whether or not the positions of the two inflection points P are in a predetermined positional relationship is determined based on, for example, the distance between the inflection points P or the arrangement direction of the inflection points P. Here, as shown in FIG. 6, when the halftone dot Dot1 overlaps the drawing line DL, the length of these overlapping portions (distance d, see FIG. 12A) is the halftone dot that exists in isolation. It becomes smaller than the size of Dot1. Therefore, in the present embodiment, the inflection point detection unit 25 detects the two inflection points P that are in a distance relationship equal to or smaller than the size of the halftone dot Dot1, thereby setting the protrusion start portion and the protrusion end portion.

  Note that pixel position information detected as the inflection point P at the protrusion start portion and the protrusion end portion is stored in the storage unit 11 as the inflection point detection data D3.

[Separator 26]
The separation unit 26 connects (connects) the inflection points P detected as the protrusion start portion and the protrusion end portion by the separation line L by referring to the inflection point detection data D3. Thereby, the protruding region ER is separated from the original drawing region DR.

  FIG. 12 is a diagram for explaining how the separation unit 26 separates the protruding region ER. FIG. 12A is a diagram illustrating the corresponding position of the inflection point P in the removed image I2 having a predetermined positional relationship. FIG. 12B is a diagram illustrating a separated image I5 in which the separation unit 26 connects the inflection points P having a predetermined positional relationship with the separation line L.

  By referring to the inflection point detection data D3, the corresponding position in the removed image I of the inflection point P that is in a predetermined positional relationship (here, the distance d between the inflection points P is equal to or smaller than the size of the halftone dot Dot1). Specifically, as shown in FIG. 12B, these inflection points P are connected by a separation line L having a predetermined pixel width having a gradation value outside the outline OL of the drawing region DR.

  Here, in the present embodiment, the gradation value of the pixel outside the contour portion is a white (plain) gradation value. Therefore, the protruding region ER is separated from the drawing region DR by drawing the white separation line L between the inflection points P having a predetermined positional relationship. That is, the separation line L separates the drawing area DR including the drawing line DL and the halftone dot Dot1 overlapping the drawing line DL into the drawing line DL and the halftone dot Dot1 (a part thereof).

  Note that the pixel width of the separation line L can be freely set. However, in order to prevent the drawing line DL from being narrowed by the separation line L, the pixel width is preferably set to one pixel width. Further, in order to completely separate the protruding region ER from the drawing region DR, the separation unit 26 may be configured so that the outer pixels sandwiching the inflection points P are connected by a separation line L.

  As described above, the image data (separated image data DI5) with the separation line L added to the removed image data DI2 is stored in the storage unit 11 by the separation unit 26 (see FIG. 3).

[Second removal unit 27]
Returning to FIG. 3, the second removal unit 27 detects a drawing pixel set having a predetermined reference area or less for the separated image I5 to which the separation line L is added by the separation unit 26, and By replacing the detected drawing pixel set with a white (plain) pixel value, a part of the halftone dot Dot1 separated from the drawing line DL is removed.

  Here, (a part of) the dot Dot1 separated from the drawing line DL is smaller in size than the dot Dot1 that originally exists in isolation. Therefore, the second removal unit 27 includes a drawing pixel set (separated protruding region ER) having a size smaller than or equal to this by using the value of the area of the dot Dot1 (or a value smaller than that) as the reference area. ) Is removed from the separated image I5. The halftone dot removal image data DI6 generated thereby is stored in the storage unit 11 by the second removal unit 27.

  The above is the description of the configuration and functions of the line drawing processing apparatus 100 in the present embodiment. Next, the operation of the line drawing processing apparatus 100 when removing the halftone dot DT1 from the line drawing I1 will be described.

<1.2. Operation>
FIG. 13 is a flowchart of the operation of the line drawing processing apparatus 100.

  First, the line drawing processing apparatus 100 photoelectrically reads the line drawing I1 recorded on a paper medium or the like by the scanner 16, and acquires the line drawing data DI1 binarized by the image acquisition unit 20 (step S1). The acquired line drawing data DI1 is stored in the storage unit 11. Note that the method of acquiring the line drawing data DI1 is not limited to reading by the scanner 16, and the line drawing data DI1 stored on the storage unit 11 or the recording medium 9 or on the network in a digital data state in advance is stored. You may make it acquire suitably.

  When the line drawing data DI1 is acquired, the line drawing processing apparatus 100 sets the removal region RR for removing halftone dots that overlap the drawing line by the region setting unit 21 (step S2). Specifically, the region setting unit 21 displays the line drawing I1 and the region setting screen on the display unit 13, and the operator designates a region where halftone dots are to be removed according to the display unit 13, thereby setting the removal region RR. . Information about the set removal area RR (area size, position, etc.) is stored in the storage unit 11 as area setting data D1.

  When the region setting processing is completed, the line drawing processing apparatus 100 uses the first removal unit 22 to remove the drawing pixel set having a predetermined reference area or less, thereby removing the line drawing I1 (specifically, the removal region of the line drawing I1). The removal image data DI2 is generated from (RR) (step S3). As a result, a relatively small pixel set of specific bits (here, pixels having a black gradation, such as minute dots generated as noise during reading by the scanner 16 and halftone dots in the halftone dot area TR of the line drawing I1). Set) is removed from the line drawing I1.

  When the removed image data DI2 is generated, the line drawing processing apparatus 100 causes the contour extracting unit 23 to extract the contour portion of the drawing region DR of the removed image I2 (step S4). Specifically, the contour extraction unit 23 performs contraction processing on the removed image I2 by the contraction processing unit 231, thereby acquiring contracted image data DI3 in which the drawing region DR is contracted by one pixel width. Then, the contour extraction unit 23 extracts the contour line OL of one pixel width of the drawing region DR from the removal image I2 by taking the difference between the contracted image data DI3 and the removal image data DI2 by the difference processing unit 232.

  When the outline OL of the drawing region DR is extracted, the line drawing processing apparatus 100 determines the curvature value at each pixel position on the outline OL, thereby quantifying the degree of curvature at each pixel of the outline OL (step S5). ). Specifically, while using the definition matrix F1 shown in FIG. 7, the curvature value in each pixel is sequentially determined in a predetermined rotation direction along the contour line OL extracted in step S4.

  When the curvature value is determined, the line drawing processing apparatus 100 calculates an average curvature value for each pixel on the contour line OL by the inflection point detection unit 25 and also inflections pixels having an average curvature value exceeding a predetermined reference value. A point P is detected (step S6). The average curvature value of a specific pixel is calculated by averaging the curvature values of a plurality of pixels within a predetermined range close to the specific pixel.

  Note that the calculation of the average curvature value does not necessarily have to be performed for all the pixels. For example, among the pixels constituting the contour OL, the average curvature value determined in step S5 exceeds the reference value. The inflection point detection unit 25 may be configured to calculate the curvature value.

  When the detection of the inflection point P is completed in step S <b> 6, the line drawing processing apparatus 100 sets two inflection points P having a predetermined positional relationship among the inflection points P detected by the inflection point detection unit 25. While selecting a pixel, the separation part 26 connects the said pixel with the separation line L, and isolate | separates the protrusion area | region ER from the drawing area DR (step S7). Note that the addition of the separation line L is performed on the removal image data DI2, and the separation image data DI5 is generated.

  When the protruding region ER is separated from the drawing region DR by the separation line L, the line drawing processing apparatus 100 removes a drawing pixel set having a predetermined reference area or less from the separated image I5 by the second removal unit 27. As a result, the protruding area ER (mainly part of the halftone dot Dot1 overlapping the drawing line DL) of the drawing area DR is removed (step S8). As a result, image data (halftone-removed image data DI6) from which the halftone dot Dot1 has been precisely removed from the original line drawing I1 is generated.

  The above is description of operation | movement of the line drawing processing apparatus 100 in this Embodiment. The generated halftone dot-removed image data DI6 is, for example, colored by color processing or by taking a difference from the original line drawing data DI1 to obtain an image mainly composed of halftone dots Dot1 (that is, a line drawing). Or an image obtained by extracting a halftone dot region TR from I1).

  As described above, in the present embodiment, the protrusion start portion and the protrusion end portion of the protrusion region ER of the drawing region DR are detected, and the protrusion region ER is separated from the drawing region DR by connecting them with the separation line L. Because of the separation, the halftone dot Dot1 coupled to the drawing line DL can be easily and precisely removed.

  Further, by quantifying the degree of bending at the position of each pixel constituting the contour of the drawing region DR based on a predefined curvature value, the protrusion start portion and the protrusion end portion of the protrusion region ER of the drawing region DR are determined. Since it can be detected, it is possible to easily remove the dot Dot1 coupled to the drawing line DL.

  Further, by averaging the curvature values, it is possible to prevent the rattling of the contour line OL of the drawing line DL from being determined as the protruding region. Therefore, it is possible to realize the separation of the halftone dot Dot1 with high accuracy.

  In addition, by setting the removal area RR in advance, it is possible to specify in detail the area where the dot Dot1 should be removed. Therefore, since removal processing according to various types of halftone dots can be realized, the halftone dot Bot1 can be precisely removed from the line drawing I1.

<2. Second Embodiment>
In the first embodiment, the case of removing halftone dots overlapped on the drawing line has been mainly described, but the scope of application of the present invention is not limited to this. In addition, about the structure similar to 1st Embodiment, the same code | symbol is attached | subjected suitably and description is abbreviate | omitted. The same applies to the following embodiments.

FIG. 14 is a diagram for explaining a method for removing the halftone dot 2 in the second embodiment. In FIG. 14,
FIG. 14 (a) = line drawing I1a including a halftone dot Dot2 in which a part of each other overlaps (continues)
FIG. 14B = first separated image I5a obtained by separating the halftone dots Dot2 by the separation line La,
FIG. 14 (c) = second image obtained by removing the halftone dot Dot2 from the first separated image I5a, and then separating the protruding area ER consisting of a part of the halftone dot Dot2 overlapping the drawing line DL from the drawing area DR by the separation line Lb. Separated image I5b,
FIG. 14 (d) = second halftone dot removal image I6b obtained by further removing halftone dots overlapping the drawing lines from the first halftone dot removal image I6a.
Respectively.

  In the present embodiment, as shown in FIG. 14A, a method of accurately removing halftone dots in a case where a portion where drawing line DL and halftone dot Dot2 overlap and a portion where halftone dot Dot2 overlap each other are mixed. Will be described.

  First, as in the first embodiment, the line drawing processing apparatus 100 extracts the contour line OL, calculates the average curvature value of each pixel on the contour line OL, and inflections exceeding a predetermined reference value. A point P (a part surrounded by a square and a circle) is detected. In the present embodiment, the line drawing processing apparatus 100 adds the separation lines La and Lb stepwise by the separation unit 26 in order to remove the halftone dot Dot2 more precisely.

  That is, as shown in FIG. 14B, the separating unit 26 separates the connection between the halftone dots Dot2 from the inflection points P detected in FIG. Then, inflection points P that are within a predetermined distance (for example, the size of halftone dots) are joined together by a separation line La. With such a condition setting, a separation line La is drawn at an inflection point P (a portion surrounded by a circle) where the halftone dots Dot2 overlap. Thereby, the 1st separated image I5a which isolate | separated the coupling | bonding of halftone dots Bot2 is produced | generated.

  Next, the line drawing processing apparatus 100 removes a drawing pixel set having a predetermined reference area or less from the first separated image I5a by the second removal unit 27. As a result, the halftone dot 2 other than the halftone dot Dot2 that overlaps the drawing line DL (the halftone dot Dot2 connected to each other) can be removed.

  Further, the line drawing processing apparatus 100 detects an inflection point P (a portion surrounded by a square) within a predetermined distance (for example, the size of a halftone dot) by the inflection point detection unit 25 and connects them by a separation line Lb. As a result, the second separated image I5b is generated by separating the halftone dot Dot2 overlapping the drawing line DL from the drawing line DL.

  Furthermore, the line drawing processing apparatus 100 removes a drawing pixel set having a predetermined reference area or less from the second separated image I5b by using the second removal unit 27, so that the halftone dots overlapped on the drawing line (that is, the drawing region DR) are removed. The protruding region ER) is removed.

  As described above, the selection of the inflection point P having a predetermined positional relationship can be set in detail by drawing the separation lines La and Lb step by step. As a result, the removal of the halftone dot Dot2 in the connected state can be executed precisely.

<3. Third Embodiment>
In the first and second embodiments, the line drawing I1 binarized by the image acquisition unit 20 is the target of the image processing of the line drawing processing apparatus 100. Of course, the image to be processed is limited to the binarized image. Is not something

  FIG. 15 is a diagram for explaining a method of separating the protruding region ER in the third embodiment. FIG. 15A shows a gray image I1b composed of pixels with low gradation values (low gradation), intermediate density gradation values (intermediate gradation), and high gradation values (high gradation). A region DR (consisting of a drawing line and a halftone dot) is shown. FIG. 15B shows a separated image I5c obtained by adding separation lines Lc, Ld, and Le to the gray image I1b shown in FIG.

  The line drawing processing apparatus 100 can precisely remove the halftone dots included in the gray image I1b in the multi-tone representation as shown in FIG. Specifically, the line drawing processing apparatus 100 according to the present embodiment binarizes the gray image I1b with a predetermined threshold when the contour extracting unit 23 extracts the contour portion of the drawing region DR.

  Here, the threshold for binarization is a gradation value between a low gradation and an intermediate gradation, a gradation value between an intermediate gradation and a high gradation, and a gradation value between a high gradation and a white gradation. By setting each gradation value, a binary image is acquired. Then, by executing the above-described contraction processing and difference calculation processing for each of these binary images, the contour line OL in the low gradation region, the contour line OL in the intermediate gradation region, and the contour line OL in the high gradation region are respectively obtained. Extracted.

  When the contour line OL for each gradation area is extracted, the line drawing processing apparatus 100 determines the curvature value of the pixels constituting each contour line OL by the curvature value determination unit 24, and further, the inflection point detection unit 25 determines each gradation. An inflection point P is detected for each outline OL of the region. Then, the line drawing processing apparatus 100 separates the separation line Lc for separating the protruding portion of the low gradation region by the separation unit 26, the separation line Ld for separating the protruding portion of the intermediate gradation region, and the protruding portion of the high gradation region. A separated image I5c is created by adding the separation line Le to the original gray image I1b.

  At this time, the separation lines Lc, Ld, and Le are drawn with gradation values outside the outline of each gradation region. For example, in the case of the separation line Lc, the pixel of the gradation outside the outline of the low gradation area (intermediate gradation, low gradation or white gradation), and in the case of the separation line Ld, outside the outline of the intermediate gradation area. If the separation line Le is a pixel having a gray scale (low gray scale or white gray scale), the pixel is composed of a gray scale (white gray scale) pixel outside the outline of the high gray scale region.

  Thus, by adding the separation lines Lc, Ld, and Le to the gray image I1b, the protruding area ER of each gradation area can be separated from the drawing area DR for each gradation. With respect to the separated image I5c, the line drawing processing apparatus 100 uses the second removal unit 27 to remove a drawing pixel set that is equal to or smaller than a predetermined reference area and includes pixels having a specific gradation value. Thereby, the separated protruding region ER can be accurately removed.

  The line drawing processing apparatus 100 according to the present embodiment detects the inflection point P for each of a plurality of gradation areas, but detects the inflection point P only for a part of the gradation areas. You may comprise.

  In the present embodiment, after the protruding region ER is separated from the drawing region DR by the separation lines Lc, Ld, and Le, the second removal unit 27 has a drawing pixel set (having a specific gradation) having a predetermined reference area or less. Although it has been described that the protruding region ER is removed by removing a set of pixels), the method of removing the protruding region ER is not limited to this, and may be realized by a duplicate removal method described below.

  FIG. 16 is a diagram for explaining a duplicate removal method for removing the protruding region ER. 16A shows the separated image I5d, and FIG. 16B shows the halftone dot removed image I6b obtained by removing the protruding region ER from the separated image I5d. Here, a case will be described in which the protruding region ER is removed with reference to two inflection points P in the contour portion of the high gradation region.

  In the duplicate removal method, the second removal unit 27 first has a range (range CR1) that is located outside the inflection point P on the separation line Le and extends in a direction substantially orthogonal to the separation line Le. Duplicate. Note that the horizontal width of the range CR1 in this direction is set to be longer than the sum of the width of the drawing line DL and the width of the protruding region ER (part of halftone dots). The vertical width of the range CR1 (the length in the direction substantially parallel to the direction in which the separation line Le extends) is set to a predetermined pixel width (for example, one pixel width).

  Then, the second removal unit 27 duplicates the image of the range CR1 and sequentially pastes the image along the separation line Le to the position of the range CR2 (see FIG. 16A), thereby causing the protruding region ER of the separated image I5c. A halftone dot removed image I6b is created (see FIG. 16B).

  When the protruding region ER is removed by simply removing a set of drawing pixels that are equal to or smaller than the reference area, the low gradation region is added to the high gradation region and the intermediate gradation region on the finally obtained drawing line. There is a possibility that a part of the protruding portion remains. On the other hand, the duplicate removal method is equivalent to a process of extending and interpolating a part of the original drawing line DL (the drawing line DL part of the range CR1), so that the protruding region is maintained while maintaining the characteristics of the original drawing line DL. ER can be removed.

  In addition, when the gradation value of each pixel does not correspond between the pixel of the range CR2 shown in FIG. 16A and the pixel of the range CR1, the second removal unit 27 sets the range CR1 and the range CR2 to each other. The protruding region ER may be removed while performing an interpolation process so that the gradation value changes stepwise.

<4. Modification>
Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made.

  For example, in the above embodiment, the inflection point detection unit 25 has been described as determining the two inflection points P as the protrusion start portion and the protrusion end portion based on the distance between the inflection points P and the arrangement direction. (Distance determination, direction determination). However, the determination method is not limited to these. For example, the inflection point detection unit 25 preliminarily draws a virtual separation line L between the inflection points P selected at random, and is separated at that time. It is also possible to measure two areas of inflection points P in a positional relationship in which it is determined that the area is smaller than the area of the halftone dots (area determination). Further, after the inflection point detection unit 25 performs distance determination and direction determination to narrow down some candidates from the inflection points P, the inflection point P of these candidates is further subjected to area determination, and finally The two inflection points P may be determined as the protrusion start portion and the protrusion end portion.

  In the above embodiment, the first removal unit 22 has been described as removing a drawing pixel set having a predetermined reference area or less. However, the present invention is not limited to this. For example, Japanese Patent Application Laid-Open No. 2001-86368 discloses. By applying the disclosed technique, it is possible to roughly remove halftone dots Dot1 and Dot2. That is, the range of the halftone dot region TR is determined based on the periodicity of the halftone dot region TR included in the line drawing I1 (vertical and horizontal distances between the halftone dots), and the range within the range in the line drawing I1 is determined. What is necessary is just to erase a drawing pixel.

  Further, the characteristics of the halftone dot region TR are generated by generating a gray scale image in which the halftone dots Dot1 and Dot2 are spatially smoothed by reducing the whole image of the line drawing I1 or by a median filtering process of a predetermined size. By detecting the gradation value of the portion where Bot2 is smoothed, the range of the halftone dot region TR where the original halftone dots Dot1 and Dot2 existed can be determined. The halftone dots Dot1 and Dot2 may be removed by removing the drawing pixels within the corresponding range in the line drawing I1 based on the determined range.

  In the above embodiment, the case where the contraction processing unit 231 performs the contraction process by identifying the 8 neighborhoods and extracts the contour line OL has been mainly described. However, the contraction process is performed by identifying the 4 neighborhoods of the target pixel. When the above is performed, continuous pixels connected in an oblique direction appear at a part of the contour line OL. When determining the curvature value of each pixel along such a contour OL, in addition to the definition matrix F1 shown in FIG. 7, 3 × 3 squares in which squares B and M are arranged obliquely. The definition matrix may be prepared as appropriate.

  Further, in the above embodiment, after the degree of bending in each pixel of the contour line OL is digitized, the protrusion start portion and the protrusion end portion of the protrusion region ER are detected. This is because each pixel of the contour line OL is detected. This is equivalent to detecting a portion that bends in the direction of extending the drawing area DR based on the arrangement position information. Therefore, the line drawing processing apparatus 100 may detect the protrusion start portion and the protrusion end portion based on the pixel arrangement information on the contour line OL without digitizing the degree of bending of the contour line OL.

  Moreover, each structure demonstrated by the said embodiment and each modification can be suitably combined unless it mutually contradicts.

1 is an external view of a line drawing processing apparatus according to a first embodiment of the present invention. It is a figure which shows the structure of a line drawing processing apparatus. It is a figure which shows the functional block of a line drawing processing apparatus with the flow of data. It is a figure which shows an example of the line drawing read by the scanner. It is a figure which shows the removal image which removed the halftone dot from the line drawing shown in FIG. It is a figure which shows the outline extraction image which extracted the outline from the removal image. It is a figure which shows a definition matrix. It is a figure for demonstrating the determination method of a curvature value using a definition matrix. It is a figure which shows an example of the pixel which comprises the outline of a drawing area. It is a figure for demonstrating the calculation method of an average curvature value. It is a figure which shows the outline of the outline extraction image shown in FIG. 6 with the average curvature value of each pixel. It is a figure for demonstrating a mode that a separation part isolate | separates a protrusion area | region. It is a flowchart of operation | movement of a line drawing processing apparatus. It is a figure for demonstrating the removal method of the halftone dot in 2nd Embodiment. It is a figure for demonstrating the isolation | separation method of the protrusion area | region in 3rd Embodiment. It is a figure for demonstrating the replication removal method which removes a protrusion area | region.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Line drawing processing apparatus 2 Program 20 Image acquisition part 21 Area | region setting part 22 1st removal part 23 Contour extraction part 231 Shrinkage processing part 232 Difference processing part 24 Curvature value determination part 25 Inflection point detection part 26 Separation part 27 2nd removal part CR1, CR2 range D1 area setting data D2 curvature value data D3 inflection point detection data DI1 line drawing data DI2 removal image data DI3 contraction image data DI4 contour extraction data DI5 separation image data DI6 halftone removal image data DL drawing line DR drawing area Dot1 , Dot2 halftone dot ER protruding area F1 definition matrix I1, I1a line drawing I1b gray image I2 removal image I4 contour extraction image I5, I5a, I5b, I5c, I5d separation image I6a, I6b halftone dot removal image L, La, Lb, Lc, Ld, Le Separation line OL Contour line P Inflection point RR removal area TR halftone area p1 to p15 pixels

Claims (8)

A line drawing processing device for separating halftone dots from a line drawing,
Detecting means for detecting a protrusion start portion and a protrusion end portion of a protruding region protruding outward with respect to a drawing line extending in a predetermined direction along a contour portion of the drawing region;
Separating means for generating a separated image in which the protruding area is separated from the drawing area by connecting the protruding start part and the protruding end part with a separation line;
Removing means for removing the protruding region separated by the separating means with respect to the separated image;
A line drawing processing apparatus comprising: The line drawing processing apparatus according to claim 1,
The line removal processing apparatus characterized in that the removal means removes the protruding region separated by the separation means by removing a drawing pixel set having a predetermined reference area or less. The line drawing processing apparatus according to claim 1 or 2,
When a curvature value is defined for each position of connected pixels connected to two or more continuous pixels arranged continuously in a predetermined direction,
The detection means includes
Curvature value determining means for determining a curvature value for each pixel constituting the contour portion of the drawing area;
An inflection point detecting means for detecting, as an inflection point, a pixel having a curvature value determined to bend in a direction in which the drawing area is expanded, among the pixels constituting the outline portion of the drawing area;
Including
An inflection point having a predetermined positional relationship among the inflection points detected by the inflection point detecting means is defined as the protrusion start portion and the protrusion end portion. The line drawing processing apparatus according to claim 3,
The inflection point detecting means includes
For each pixel of the contour portion of the drawing area, an average value of curvature values of a plurality of pixels included in a predetermined range close to each pixel is calculated for each pixel,
A line drawing processing apparatus that detects, as the inflection point, a pixel that is determined to bend in a direction in which the drawing area is expanded based on a comparison between the average value and the predetermined reference value. The line drawing processing apparatus according to any one of claims 1 to 4,
A removal region setting means for setting a removal region in which halftone dots are to be removed from the line drawing based on a predetermined operation input;
Further comprising
The detection means includes
A line drawing processing apparatus for detecting the protrusion start portion and the protrusion end portion included in the removal region set by the removal region setting means. The line drawing processing apparatus according to any one of claims 1 to 5,
Binarization means for acquiring a binary image by binarizing the line drawing with a predetermined threshold;
A contour extracting means for generating a contracted image by contracting a drawing region included in the binary image and extracting a contour portion of the drawing region from a difference between the binary image and the contracted image;
Further comprising
The line drawing processing apparatus characterized in that the detection means detects the protrusion start portion and the protrusion end portion along the contour portion extracted by the contour extraction means. A line drawing processing method for separating halftone dots from a line drawing,
A detection step of detecting a protrusion start portion and a protrusion end portion of a protruding region protruding outward with respect to a drawing line extending in a predetermined direction along a contour portion of the drawing region;
A separation step of generating a separated image in which the protruding region is separated from the drawing region by connecting the protruding start portion and the protruding end portion detected in the detection step with a separation line;
Removing means for removing the protruding region separated by the separation step from the separated image;
A line drawing processing method comprising: A computer-readable program,
When the computer reads the program and the CPU of the computer executes the program in a memory,
Detecting means for detecting a protrusion start portion and a protrusion end portion of a protruding region protruding outward with respect to a drawing line extending in a predetermined direction along a contour portion of the drawing region;
Separating means for generating a separated image in which the protruding area is separated from the drawing area by connecting the protruding start part and the protruding end part with a separation line;
Removing means for removing the protruding region separated by the separating means with respect to the separated image;
A program that causes the computer to function as a line drawing processing apparatus.