JP2011109223A - Image conversion method, image conversion apparatus, image conversion system and image conversion program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image conversion method which ensures correct restoration, even when an image added with texture in which color information is included has gradation which changes smoothly and continuously in a solidly painted area. <P>SOLUTION: The image conversion method has an area in which texture is superimposed, a process to extract the texture of the area, a process to extract a strength modulation component of the texture, and a process to reduce the strength modulation component of the texture from an image of the area in which the texture is superimposed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image conversion method, an image conversion apparatus, an image conversion system, and an image conversion program.

  Conventionally, various proposals have been made so that a color image that can be identified by a healthy person can be recognized by other methods for color blind persons who cannot be identified in the same way.

  As a proposal like this, a chromatic color fill area is extracted from a color image, and multiple parallel straight lines are added to the fill area at different angles corresponding to the color (hue) of the fill area. The color of the filled area is determined by adding multiple parallel straight lines with different intervals corresponding to, and adding different parallel line arrows (lengths) corresponding to the saturation of the filled area. There is known an image processing apparatus that adds hatching that expresses (see Patent Document 1, for example).

JP 2008-77307 A

  While the above proposal has been made, there is also a desire to restore the original image from an image created by replacing color information with a texture or the like so as to be recognized by a color blind person.

  However, the above-mentioned Patent Document 1 expresses hue, brightness, and saturation with hatching angles and intervals, and arrow intervals, but there is a response to the case where the filled region has a gradation that changes smoothly and continuously. In addition, there is a problem that when an area with hatching or an arrow is restored to the original image, the original image cannot be accurately reproduced.

  In view of the above problems, the present invention provides an image conversion method capable of accurately restoring an image created by adding a texture including color information, even when the image has a gradation that changes smoothly and continuously in a filled area, An object of the present invention is to provide an image conversion apparatus, an image conversion system, and an image conversion program.

  The above object is achieved by the following configuration.

  (1) An image conversion method for reducing the texture from an image in which color information is converted into a texture and the texture is superimposed, and a step of detecting the texture superimposed region and the texture in the region And a step of extracting an intensity modulation component of the texture, and a step of reducing the intensity modulation component of the texture from an image of a region where the texture is superimposed.

  (2) The texture is hatched, and the color information is converted into the hatching tilt angle, and a step of obtaining the hatching tilt angle and the original image based on the hatching tilt angle are obtained. Obtaining the color information. The image conversion method according to (1), further comprising:

  (3) The image conversion method according to (2), wherein the hatching includes two types having different inclination angle ranges, and the two types of hatching have a predetermined frequency ratio.

  (4) An image conversion unit that uses the image conversion method according to any one of (1) to (3), wherein color information is converted into a texture, and the image conversion is performed from an image on which the texture is superimposed. An image conversion apparatus that reduces the texture using a unit.

  (5) An image conversion system comprising: the image conversion apparatus according to (4); and an image output unit that outputs an image converted by the image conversion apparatus.

  (6) An image conversion program that reduces the texture from an image in which color information is converted into a texture and the texture is superimposed, and a texture superimposed region extraction unit that extracts a region on which the texture is superimposed; The texture extraction unit that extracts the texture from the image of the region in which the texture is extracted by the overlap region extraction unit, the texture intensity modulation component extraction unit that extracts the intensity modulation component of the texture, and the texture overlap region extraction unit An image conversion program that causes a computer to function as an intensity modulation component reduction unit that reduces an intensity modulation component of a texture extracted by the texture intensity modulation component extraction unit from an image of a region extracted in (1).

  (7) The texture is hatched, and the color information is converted into the hatching tilt angle, and a texture angle obtaining unit for obtaining the hatching tilt angle and an original based on the hatching tilt angle The image conversion program according to (6), further comprising: a color information acquisition unit that acquires color information of an image.

  According to the present invention, even when an image created by adding a texture including color information has a gradation that changes smoothly and continuously in a filled area, an image conversion method and image conversion that can be accurately restored An apparatus, an image conversion system, and an image conversion program can be provided.

It is a schematic diagram which shows an example of the image produced by adding the texture containing the color information. It is a figure which shows an example of prescription | regulation of the direction (inclination angle) of the straight line of hatching matched with chromaticity. It is a figure which shows the example of the intensity | strength modulation | alteration of hatching at the time of superimposing hatching. It is a block diagram which shows the main function parts of the image conversion system which concerns on this Embodiment. It is a flowchart which shows the operation | movement outline of the image conversion system which concerns on this Embodiment. It is a figure which shows an example of the extraction method of a hatching superimposition part. It is a flowchart which shows the procedure outline of frequency filtering. It is a figure which shows the effect of reduction of an intensity modulation component. It is a flowchart which shows the modification of the operation | movement outline of the image conversion system which concerns on this Embodiment. It is a schematic diagram explaining how to obtain the inclination angle of the initial hatching straight line from the inclined image portion. It is a figure which shows an example of the inverse transformation which acquires color information from the direction (inclination angle) of the straight line of hatching. It is a figure explaining how to determine the color to output when the stored chromaticity is the chromaticity of a point outside the color gamut of the image output unit. It is a schematic diagram which shows the image part before image conversion, and the image part after image conversion.

  Hereinafter, the present invention will be described in detail with reference to embodiments, but the present invention is not limited thereto.

  First, an image created by adding a texture including color information, which is a conversion target of the image conversion method, the image conversion apparatus, and the image conversion program according to the present embodiment will be described. Note that the texture refers to a pattern to be superimposed on the image, and in the following embodiments, the description will be made by using hatched hatching as the texture.

  FIG. 1 is a schematic diagram illustrating an example of an image created by adding a texture including color information. FIG. 1A shows the entire surface of the sheet, and FIG. 1B is an enlarged view of an image printed on the sheet.

  This sheet is prepared so that the color information of the filled area of the image can be recognized by another method different from the color.

  On the sheet 10 shown in FIG. 1A, an image portion 1, a front portion 2, and a character portion 3 are printed. Further, as shown in the enlarged view of the image portion 1 in FIG. 1B, for example, the image portion 1 has a pattern similar to the hatching existing from the original image before adding the texture including the color information. It is printed including the areas 14, 15, and 16 that are included, and areas 11, 12, and 13 (hereinafter referred to as hatched overlapping portions) in which hatching that is a texture including color information is superimposed. The hatching superimposing units 11, 12, and 13 define and superimpose a hatching straight line direction (inclination angle) corresponding to the chromaticity of the filled region.

  The hatched inclination angle is defined in correspondence with the chromaticity of the filled area, and the superimposed image is the conversion target.

  In addition, as what defines and superimposes the direction (inclination angle) of the straight line of hatching corresponding to chromaticity, for example, the one described in International Publication No. 2009/0201115 by the present applicant can be used. . In the present embodiment, the description will be made assuming that the inclination angle of hatching is defined as follows.

  FIG. 2 is a diagram illustrating an example of the definition of the direction (tilt angle) of the hatching straight line corresponding to the chromaticity.

Figure 2 is 'a chromaticity diagram, the u'v'u'v in chromaticity diagram, for example, the color region C of which may be human feel, parallel dashed lines separated by a dashed line A ₁ and the distance S A case is shown in which it is set so as to be surrounded by A ₂ and a solid line B ₂ which is separated from the solid line B ₁ by a distance M. In this example, an example is shown in which all the color areas C that can be perceived by humans are included. However, the present invention is not limited to this and is set so as to include a specific area. It may be what was done.

Furthermore, for example, a line of dashed _{A 1} +30 degrees, a line of dashed _{A 2} to correspond to the inclination angle of -30 degrees, equally divided in the range of the spacing S of the broken line _{A 1} and _{A 2} +30 degrees to -30 degrees ( For example, when the tilt angle is 0 degree, the middle line of the broken lines A ₁ and A ₂ is made to correspond to the tilt angle of +45 degrees on the solid line B ₁ and +135 degrees on the solid line B ₂ , and the solid lines B ₁ and B equally dividing ₂ intervals M in the range of +45 degrees to +135 degrees (e.g., in the case of the inclination angle 90 degrees solid line B ₁ and B ₂ midline) and is defined to. At this time, the hatching inclination angle corresponding to the chromaticity at the point N in the region C is determined as follows. Note that the direction with an inclination angle of 0 degrees corresponds to the positive X-axis direction in the case of XY coordinates.

First, a straight An parallel to dashed line _{A 1} passing through the point N, consider a linear Bn parallel to the solid line _{B 1} passing through the point N, the distance _{S n} from the broken line _{A 1} of the straight line An, the solid straight line Bn _{B 1 Is} used to determine the tilt angle as follows.

Inclination angle of first hatch = 30− (S _n / S) × 60 (degrees)
Second hatch inclination angle = 45 + (M _n / M) × 90 (degrees)
That is, the chromaticity at the point N is converted into two types of hatching inclination angles. Further, the frequency of the second hatching is set to twice the frequency of the first hatching.

  The two types of hatching determined in this way are represented as chromaticity at the point N and are superimposed on the filled area filled with the chromaticity at the point N. Hereinafter, the first hatching is referred to as sub-hatching, and the second hatching is referred to as main hatching.

  The frequency ratio of the main hatching and the sub hatching and the range of the inclination angle of each straight line are not limited to this, and the frequency ratio may be a predetermined value, and the range of the inclination angle is the main hatching. And a range determined in advance so as not to overlap in the sub-hatching.

  Further, the main hatching and the sub-hatching are superimposed with a predetermined intensity modulation component determined in advance with respect to the brightness, saturation, or other changes in the filled area, as in the example shown in FIG. 3 below. The

  FIG. 3 is a diagram illustrating an example of intensity modulation of hatching when hatching is superimposed. FIG. 3 (a) shows an example of brightness change in the filled area, and FIG. 3 (b) shows a case where hatching having an intensity modulation component by a rectangular wave with a predetermined amplitude is superimposed on the filled area shown in FIG. 3 (a). FIG. 3C shows a case where hatching having an intensity modulation component by a sine wave having a predetermined amplitude is superimposed on the filled region shown in FIG. In FIG. 3, only one of the main hatching and the sub hatching is illustrated.

FIG. 3A shows the brightness change state of the filled area, with the vertical axis being the brightness of the filled area. This example is an example in which the lightness of the painted area continuously changes from the high lightness indicated by _NH in the figure G to the low lightness indicated by _NL in the figure.

  FIG. 3B shows a lightness change state when hatching having an intensity modulation component by a rectangular wave having a pitch (period) P and an amplitude a is superimposed on the filled region having the lightness change shown in FIG. FIG. 3C shows a brightness change state when hatching having an intensity modulation component by a sine wave of pitch (period) P and amplitude a is superimposed. That is, the hatching that is a texture is superimposed so as to have a predetermined intensity modulation along the change even when the filled region has a continuous change.

  In FIG. 3, the change in brightness has been described as an example, but the present invention may be applied to a change in saturation and the like.

  The hatching superimposing units 11, 12, and 13 illustrated in FIG. 1B show a case where hatching having an intensity modulation component by a rectangular wave is superimposed, but is superimposed by hatching having an intensity modulation component by a sine wave. It may be. Further, for example, different intensity modulation components may be applied such that one of the main hatching and the sub hatching is a rectangular wave and the other is a sine wave.

Further, when deleting the superimposed hatching, information about the intensity modulation component of the superimposed hatching can be embedded in the image as a mark or a watermark so as to be clearer. Similarly, the setting information for the broken lines A ₁ and A ₂ and the solid lines B ₁ and B ₂ on the above chromaticity diagram is marked or It can also be embedded in the image as a watermark.

  FIG. 4 is a block diagram showing main functional units of the image conversion system 100 according to the present embodiment. In addition, each part, such as a known power switch and a power supply circuit, is abbreviate | omitted.

  As shown in FIG. 4, the image conversion system 100 according to the present embodiment is roughly divided into an input image data generation unit 20, an image conversion unit 30, and an image output unit 40. The input image data generation unit 20, the image conversion unit 30, and the image output unit 40 are configured to be controlled by a control unit 31. A storage unit 32 and an operation unit 33 are connected to the control unit 31.

  The input image data generation unit 20 is an image input unit to which a texture including color information to be converted is added. The input image data generation unit 20 is configured by, for example, a scanner that reads an image of a sheet shown in FIG. Is done. The image data to be converted is sent to the image conversion unit 30. If the input image has already been converted into data, it may be configured to input directly from the input terminal.

  The image conversion unit 30 extracts the image unit 1 (see FIG. 1) from the image data generated by the input image data generation unit 20, and the texture hatching is superimposed in the extracted region of the image unit 1. A region (hatched superimposing portion) is extracted and a hatching angle is detected.

  Further, it has a function of extracting hatching intensity modulation components and reducing the hatching intensity modulation components from the hatching superimposing unit.

  In addition, the image conversion unit 30 detects a direction serving as a reference for the inclination angle of the hatching that is a texture, obtains an angle between each superimposed hatching and the reference direction, and uses this hatching as a reference direction The original color information is obtained from the angle formed by the above, and the hatched overlapped area is converted into the obtained color to restore the original color image.

  The image output unit 40 includes a display device such as an LCD or an organic EL, a printer such as an electrophotographic method or an ink jet method, an optical pickup device that records image data on an optical disk, and the like. A monochrome image in which the intensity modulation component is reduced or a color image in which the intensity modulation component of hatching is reduced and the original color is restored is output.

  Based on the control of the control unit 31, the storage unit 32 generates image data generated by the input image data generation unit 20, monochrome image data processed by the image conversion unit 30 with reduced hatching intensity modulation components, The original color image data restored by reducing the intensity modulation component of hatching is stored.

  The control unit 31 reads an operation program from a ROM (not shown), develops it in a RAM as a work area (not shown), and controls the input image data generation unit 20, the image conversion unit 30, the image output unit 40, and the storage unit 32. To control.

  In the present application, at least a portion having the image conversion unit 30 is referred to as an image conversion device, and a case where at least one of the input image data generation unit 20 or the image output unit 40 is connected is referred to as an image conversion system. Yes.

  The image conversion apparatus or image conversion system according to the present embodiment may exist alone or may be incorporated in an existing image processing apparatus, image display apparatus, printer, or the like. Further, when incorporated in another device, the image processing unit and the control unit of the other device may be combined.

  FIG. 5 is a flowchart showing an outline of the operation of the image conversion system 100 according to the present embodiment. The flowchart shown in FIG. 5 is a flowchart in the case of reducing hatching intensity modulation components, which are superimposed textures. Hereinafter, it demonstrates according to a flow.

  First, a sheet image on which an image to be input is printed is read (step S101).

  The input image data generation unit 20 reads this input image. If the input image has already been converted into data, the input image data generation unit 20 or the image conversion unit 30 may be directly input from the connection terminal. The read image data is sent to the image conversion unit 30 and stored in the storage unit 32.

  The image conversion unit 30 performs the following processing on the input image data based on a program read from a ROM (not shown).

  First, it is determined whether or not the image is a conversion target image having a hatching superimposition unit (step S102). That is, it is determined whether or not the input image is an image produced by superimposing hatching including color information to be converted.

  For this determination, for example, a watermark or a mark indicating that the image is a conversion target image with hatching superimposed may be embedded as a symbol, and the determination may be made by detecting the presence or absence of the symbol. Moreover, an operator may input from the operation unit 33.

  If the input image data is to be converted (step S102; Yes), the image unit 1 is extracted from the input image data (step S103).

  The extraction of the image unit 1 is determined by, for example, the ratio of the area occupied by image data other than the sheet color such as characters and pictures recognized as an image to the unit area of the sheet (referred to as a printing rate in the present application). Generally, in the table part 2 and the character part 3 shown in FIG. 1, the printing rate is 10% or less, and only the image part 1 shows a high printing rate. For this reason, for example, an area where the printing rate exceeds 10% is determined to be an approximate image portion. Of course, other methods may be used to extract the image portion 1.

  Next, a hatching overlapping portion is extracted from the extracted image portion 1 and a hatching straight line direction (tilt angle) is detected (step S104).

  The hatching superimposing portion is extracted by extracting a block of n pixels × n pixels from the image data of the image portion 1 and performing a Fourier transform, and information on frequency and angle can be detected at the same time. Further, the boundary of the hatching superimposing portion can be extracted by performing the above conversion while shifting several blocks of n pixels × n pixels. n is preferably a power of 2. In this case, fast Fourier transform can be used, and calculation can be performed at high speed. However, the present invention is not limited to this, and an n pixel × m pixel block may be extracted. Alternatively, pattern matching, straight line extraction by Hough transform, or the like may be used. Instead of the Fourier transform, other transforms, for example, orthogonal transform such as cosine transform or wavelet transform may be used.

  FIG. 6 is a diagram illustrating an example of a method for extracting a hatching superimposition unit. FIG. 6 shows a case where Fourier transform is performed.

  As illustrated in FIG. 6A, an n pixel × n pixel block 1 a is extracted from the image 1. At this time, if the extracted block 1a includes, for example, a small pitch hatching H (main hatching) and a large pitch hatching L (subhatching) as shown in FIG. When Fourier transformation is performed, a result as shown in FIG. 6C is obtained.

In the chart shown in FIG. 6C, the center indicates the spatial frequency 0, and the frequency is higher toward the outside. When Fourier transform is performed on the block 1a shown in FIG. 6B, the transformed data are positions separated from the center by an amount corresponding to the frequency in the direction orthogonal to the straight lines of the main hatching H and the subhatching L, as shown in the figure. It concentrated on _(H F, reference _{L F} in the figure). Thereby, extraction of a hatching superimposition part and detection of the direction (inclination angle) of a straight line can be performed.

  Thus, the ratio of the frequency of the main hatching H and the frequency of the subhatching L is set in advance (doubled in this example), and the inclination angle of the straight line is set within a predetermined range (this book) In the example, the inclination angle of the straight line of the main hatching H is +45 degrees to +135 degrees, the inclination angle of the straight line of the subhatching L is -30 degrees to +30 degrees, or diagonal positions thereof, so that the color information is obtained. It becomes easier to determine whether the target texture is just a pattern of the original image.

  That is, as shown in FIG. 1, even if the areas 14, 15, 16 having a pattern similar to the hatching existing from the original image and the hatching overlapping areas 11, 12, 13 coexist in the image portion 1. It becomes easier to discriminate from the difference between one or two extracted frequencies.

  Furthermore, by superimposing the main hatching H and the sub-hatching L, the frequency band changes even when the aspect ratio is enlarged or reduced in the process of handling the image produced by superimposing the hatching. However, since the ratio between the two frequencies does not change and the tilt angle information is in a predetermined range, it is easier to determine whether the texture is for color information or a simple original image pattern.

  Similarly, by extracting the block 1b (not shown) adjacent to the block 1a and repeating the Fourier transform operation over the entire surface of the image portion 1, the position of the hatching overlapping portion in the image portion 1 and the direction of the straight line of the hatching Can be detected.

  Next, the hatched intensity modulation component is extracted from each of the hatching superimposing portions extracted in step S104, and the intensity modulation component is reduced (step S105).

  In extracting the intensity modulation component of hatching, information is obtained from a mark or watermark embedded in the image in advance. When this information is not embedded, use a technique that removes the area by frequency filtering (for example, band rejection) or a technique that divides the hatching area for each pixel and reversely modulates the intensity modulation component. Can do.

  FIG. 7 is a flowchart showing an outline of the procedure of frequency filtering.

As a frequency filtering procedure, a Fourier transform, which is a two-dimensional frequency analysis, is performed on the hatched overlapped region extracted in step S104 (step S151). Specifically, for the extracted hatching superimposing unit, the blocks are sequentially extracted as described with reference to FIG. As a result, as indicated by L _F and H _F in FIG. 6C, two frequency components are extracted within the above-described frequency ratio and angle with the origin in between.

Next, the angle and frequency (L _F and H _F ) extracted in step S151 are designated to reduce the intensity modulation component value (step S152). In order to reduce the intensity modulation component, first, the intensity modulation component is determined from the extracted angle and frequency component values. As this determination method, the intensity modulation component is obtained by reducing it to the same value as the other component values or the frequency component value becomes 0, and the intensity modulation component of this hatching is reduced.

  Next, the reduced frequency component is subjected to inverse Fourier transform, and the data output obtained by the inverse Fourier transform is reflected in the data of the central pixel of the extracted block (step S153).

  Such an operation is performed by shifting the block by one pixel, and a restored image of the hatched region is created (step S154).

  Although the example in which the block is shifted one pixel at a time has been described, for the purpose of reducing the amount of calculation, the shift amount may be slightly increased and restored by averaging the information of adjacent blocks and the weight. Alternatively, the data may be restored in units of blocks.

  Further, before performing the frequency filtering, an area (the same hatching area) in which the frequency and the direction of the straight line of hatching are the same is extracted from the hatching superimposition unit extracted in step S104. 7 may be performed. As an example of extracting the same hatching area, there is a method in which, for example, if the product of the intensity modulation component and the density value for each pixel of the hatching overlapping portion is equal to or greater than a predetermined value, the blocks are regarded as the same. By doing in this way, the boundary of the area | region which reduces an intensity | strength modulation component becomes more reliable.

  Note that step S151 may use the result of extracting the hatching overlapped portion performed in step S104.

  In addition, the method of dividing the hatching area for each pixel and performing the reverse modulation so that the intensity modulation component is eliminated can be obtained by using the position information of the hatching area, the hatching component that is a texture component, and the frequency analysis technique to determine the peak frequency and the frequency. A method for estimating an intensity modulation component for each pixel using a parameter of a component value difference (texture enhancement value) obtained from a frequency other than the frequency and subtracting the intensity modulation component of the corresponding pixel from the intensity for each position of the image There is also.

  Note that “reduction of intensity modulation component” in the present application includes the complete deletion of the intensity modulation component.

  As a result, the hatching is deleted from the image in which the hatching is superimposed as shown in FIGS. 3B and 3C, and the original smoothly changing gradation as shown in FIG. The restored original image can be obtained.

  FIG. 8 is a diagram illustrating the effect of reducing the intensity modulation component. 8A is an image having a gradation before hatching is superimposed, FIG. 8B is an image in which hatching is superimposed on the image in FIG. 8A, and FIG. 8C is FIG. 8B. The image after reducing the intensity | strength modulation | alteration component of hatching from the image on which this hatching was superimposed is shown.

  As shown in FIG. 8B, by performing “reduction of intensity modulation component” from the image with hatching superimposed in FIG. 8B by the above-described method, gradation is obtained as shown in FIG. Even in the area having the same, it is possible to restore the image before hatching is accurately superimposed.

  Returning to FIG. 5, the image obtained by reducing the intensity modulation component obtained in step S <b> 105 and the image of the non-hatched superimposed region are combined and synthesized (step S <b> 106).

  Next, the image obtained in step S106 is stored in the storage unit (step S107).

  Next, the restored image is output using the image output unit 40 (step S108), and the process ends.

  On the other hand, if it is determined in step S102 that the input image data is not to be converted (step S102; No), the process jumps to step S108, and the image input in step S101 is output (step S108). And exit.

  FIG. 9 is a flowchart showing a modified example of the schematic operation of the image conversion system according to the present embodiment. The flowchart shown in FIG. 9 is a flowchart in the case of reducing the hatching that is the superimposed texture and restoring the original color image. In the flow shown in FIG. 9, the same part as the flow shown in FIG. 5 is omitted, and only different parts will be described.

  Steps S101 to S103 in FIG. 9 are the same as steps S101 to S103 in FIG.

  Next, the reference direction of the extracted image unit 1 is detected (step S204). The reference direction of the image part 1 is a direction used as a reference of the angle when the color information is converted into a hatching inclination angle and superimposed on the painted part.

  The image unit 1 may be slightly rotated and tilted at the time of printing or at the time of reading the input image, and an error occurs when restoring color information from the tilt angle of hatching. In this step, the reference direction of the image portion 1 is obtained in order to eliminate this error.

  For detecting the reference direction of the input image, the reference direction may be obtained from the boundary line of the image part. When there is a character part, the line and character of the sentence are discriminated by OCR (Optical Character Reader). The reference direction may be obtained from the direction of the line or character. Further, when the input image includes a two-dimensional code such as a QR code or an index for specifying a position, this may be used.

  By detecting the reference direction of the image portion 1 and comparing it with the edge line of the read sheet, the inclination angle of the entire image portion 1 with respect to the sheet can be obtained.

  Next, a hatching overlap portion is extracted from the extracted image portion 1, and the direction (inclination angle) of the hatching straight line is detected (step S205). The extraction of the hatching overlapped portion is the same as that described in step S104 in FIG. 5 and FIG.

  Next, an angle formed by the detected direction of the straight line of hatching and the reference direction of the image unit 1 obtained in step S204 is calculated (step S206). As a result, it is possible to obtain an accurate initial inclination angle of the hatching when the color information is converted into the inclination angle of the hatching straight line.

  FIG. 10 is a schematic diagram for explaining how to obtain the inclination angle of the initial hatching straight line from the inclined image portion.

  As shown in FIG. 10A, an image when color information is converted into a hatching inclination angle, that is, an initial image is a region indicated by a solid line, and the entire image is rotated in a counterclockwise direction when printing or reading an input image. A case will be described in which the image is rotated by an angle β (β <0) and the input image data is rotated to an area indicated by a broken line. In this case, as shown in FIG. 10B, when the angle between the straight direction of the main hatching H of the hatching superimposing unit 12 and the horizontal direction of the input image is simply detected, the angle α is obtained. When the image is rotated at the time of printing or at the time of reading the input image, the angle α is different from the angle when the color information is converted into the inclination angle of the straight line of the main hatching H. However, the inclination angle of the straight line of the initial main hatching H can be accurately calculated by detecting and taking into account the reference direction BL of the image portion 1 detected in step S204 described above. Will be able to.

  Similarly, regarding the inclination angle of the sub-hatching L, if the angle with respect to the horizontal direction of the input image is γ, the inclination angle of the straight line of the initial sub-hatching L is accurately corrected by correcting to (γ−β). It becomes possible to calculate.

  In addition, when there are a plurality of combinations of detected inclination angles of the main hatching H and the sub-hatching L as in the hatching superimposing units 11, 12, and 13 shown in FIG. 1B and FIG. 10B. Similarly, the inclination angle of the initial hatching line is calculated for all, and stored in correspondence with the position of the hatching superimposing portion.

  Next, the information of the color of the hatching overlapping portion is acquired from the angle formed by the direction of the straight line of hatching calculated in step S206 and the reference direction of the image portion 1 obtained in step S204 (step S207).

  The acquisition of the color information may be obtained by performing inverse conversion based on the rules for converting the original color information into the inclination angle of the hatching straight line. An example is shown below.

FIG. 11 is a diagram illustrating an example of inverse conversion for obtaining color information from the direction of the hatching straight line (inclination angle). The broken lines A ₁ and A ₂ and the solid lines B ₁ and B ₂ in the u′v ′ chromaticity diagram shown in FIG. 11 are the same as those shown in FIG. Note that the setting information of the broken lines A ₁ and A ₂ and the solid lines B ₁ and B ₂ on the chromaticity diagram is obtained from marks and watermarks embedded in the image. A triangular area D shown in the color area C that can be perceived by humans shown in FIG. 11 indicates a portion (color gamut) of the color space that can be expressed or reproduced by the image output unit 40 (see FIG. 4). ing. Hereinafter, the region D is referred to as a color gamut.

  First, the following is obtained from the inclination angle of the sub-hatching L and the inclination angle of the main hatching H obtained in step S206.

Sx = {− (inclination angle of sub-hatching L−30) × S} / 60
Mx = {(inclination angle of main hatching H−45) × M} / 90
Then, as shown in FIG. 11, apart Sx from the dashed line _{A 1} in the interval S, apart straight line parallel to dashed line _{A 1,} the broken line _{B 1} in the interval M by Mx, and a straight line parallel to the dashed line _{B 1} Find the chromaticity of the intersection X. The chromaticity at this point X is the original color of the original image.

  When there are a plurality of combinations of inclination angles of the main hatching H and the sub-hatching L, the chromaticity of each original image is obtained in the same manner and stored in correspondence with the position of the hatching superimposing unit.

  Further, such a reverse conversion result may be written in advance as a LUT (Look Up Table) in a ROM (not shown) or the like and referred to.

  Next, the hatched intensity modulation component is extracted from each of the hatching superimposing portions extracted in step S205, and the intensity modulation component is reduced (step S208). The method for extracting the intensity modulation component of hatching and reducing the intensity modulation component is as described above. Note that “reduction of intensity modulation component” in the present application includes the complete deletion of the intensity modulation component.

  Next, the image obtained by reducing the intensity modulation component obtained in step S208 and the image of the non-hatched superimposed region are combined and synthesized (step S209).

  Next, the hatched overlapping area is replaced with the color acquired in step S207 (step S210). Thereby, the restoration of the original color image is completed.

  Next, the restored color image is stored in the storage unit 32 (step S211).

  Next, the restored color image is output using the image output unit 40 (step S212), and the process ends. In addition, as an output from the image output unit 40, a color name may be displayed on the hatching superimposing unit.

  On the other hand, if it is determined in step S102 that the input image data is not to be converted (step S102; No), the process jumps to step S212, and the image input in step S101 is output (step S212). And exit.

  The above is the outline of the operation of the image conversion system according to the present embodiment.

  In this example as well, an area (the same hatching area) in which the frequency and the direction of the straight line of hatching are the same is extracted from the hatching overlapped part extracted in step S205, and the same hatching area is shown in FIG. Processing may be performed.

  In this way, the intensity modulation component of hatching, which is a texture, is extracted, and the corresponding intensity modulation component is reduced for each of the hatching superimposing portions, thereby adding the texture including color information. Even when the image has a gradation that changes smoothly and continuously in the filled region, the image can be accurately restored (see FIG. 8). Furthermore, by replacing each hatched region with the acquired color, the gradation can be accurately restored and an accurate color image can be restored.

  Note that when the original image is restored, it is preferable to remove information embedded in the image as a mark or a watermark.

  Further, at the time of outputting the restored color image in step S212, the color gamut D that can be expressed by the connected image output unit as shown in FIG. If the chromaticity of the point F is outside, the color to be output is determined as follows.

  FIG. 12 is a diagram for explaining how to determine the color to be output when the stored chromaticity is the chromaticity of a point outside the color gamut of the image output unit.

  For example, the point E on the boundary of the color gamut D that is closest to the point F is obtained, and the chromaticity of the point E is output. As another example, the point F and the gray point G in the color gamut D are connected by a straight line, an intersection H between the straight line and the boundary line of the color gamut D is obtained, and the chromaticity of the point H is output. In other words, if there is a difference between the color gamut where the input image is displayed and the color gamut that can be displayed by the image output unit, the color gamut mapping method used for color reproduction between different media can be used. That is.

  The initial color information obtained from the input image is stored in the storage unit according to the present embodiment, and this initial response is performed when the connected image output unit cannot express the color. is there.

  FIG. 13 is a schematic diagram illustrating an image portion before image conversion and an image portion after image conversion. FIG. 13A shows an image portion (input image) before image conversion, and FIG. 13B shows an image portion (output image) after image conversion.

  As shown in FIG. 13B, the hatch superimposing units 11, 12, and 13 shown in FIG. 13A reduce the hatching intensity modulation component and restore the original image color.

  In FIG. 13, the image is expressed in monochrome according to the specification of the patent application drawing, but in actuality, the image is output with the chromaticity obtained by the above description.

  In the flowcharts shown in FIG. 5 and FIG. 9, it is configured to determine whether or not the image is a conversion target image after reading the input image. However, the present invention is not limited to this. If there is a hatching superimposing portion, it is determined that the image is a conversion target image. If there is no hatching superimposing portion, it is determined that the image is not a conversion target image. In this case, what is necessary is just to insert the operation | movement of step S102 of FIG. 5 between step S104 and step S105. Similarly, the operation of step S102 in FIG. 9 may be inserted between step S205 and step S206.

  In the present embodiment, the brightness gradation is described. However, the present invention is not limited to this, and the present invention can be applied to a case where the chromaticity changes smoothly, that is, the hatching is curved instead of a straight line.

  In addition, as an image conversion program for performing the above-described image conversion, a texture superimposed region extraction unit, a texture extraction unit, and a texture angle acquisition unit correspond to step S104 in FIG. 5 and step S205 in FIG. The color information acquisition unit corresponds to step S208 in FIG. Further, the texture intensity modulation component extraction unit and the intensity modulation component reduction unit correspond to step S105 in FIG. 5 and step S208 in FIG. 9, that is, the flow of FIG.

  In the above embodiment, the example in which hatching is superimposed has been described. However, the present invention is not limited to this example, and may be converted into a predetermined texture inclination angle and superimposed. is there.

DESCRIPTION OF SYMBOLS 1 Image part 2 Table part 3 Character part 10 Sheet | seat 12 Hatching superimposition part 20 Input image data generation part 30 Image conversion part 31 Control part 32 Storage part 33 Operation part 40 Image output part

Claims (7)

An image conversion method for reducing the texture from an image in which color information is converted into a texture and the texture is superimposed,
A region where the texture is superimposed, and detecting the texture of the region;
Extracting an intensity modulation component of the texture;
And a step of reducing an intensity modulation component of the texture from an image of the region on which the texture is superimposed. The texture is hatched, and the color information is converted into an inclination angle of the hatch,
A step of obtaining an angle of inclination of the hatching;
The image conversion method according to claim 1, further comprising: obtaining color information of an original image based on the hatching inclination angle.   The image conversion method according to claim 2, wherein the hatching includes two types having different inclination angle ranges, and the two types of hatching have a predetermined frequency ratio.   An image conversion unit that uses the image conversion method according to any one of claims 1 to 3, wherein color information is converted into texture, and the image conversion unit is used from an image on which the texture is superimposed. And reducing the texture.   An image conversion system comprising: the image conversion apparatus according to claim 4; and an image output unit that outputs an image converted by the image conversion apparatus. An image conversion program for reducing the texture from an image in which color information is converted into a texture and the texture is superimposed,
A texture superimposed region extracting unit for extracting a region on which the texture is superimposed;
A texture extracting unit that extracts the texture from an image of the region in which the texture is extracted by the superimposed region extracting unit;
A texture intensity modulation component extraction unit for extracting an intensity modulation component of the texture;
A computer is caused to function as an intensity modulation component reduction unit that reduces an intensity modulation component of a texture extracted by the texture intensity modulation component extraction unit from an image of an area extracted by the texture superimposed region extraction unit. Image conversion program. The texture is hatched, and the color information is converted into an inclination angle of the hatch,
A texture angle obtaining unit for obtaining an inclination angle of the hatching;
A color information acquisition unit that acquires color information of the original image based on the hatching inclination angle;
The image conversion program according to claim 6, further comprising: