JP4854042B2 - Image generation method, image generation apparatus, and image generation program - Google Patents

Description

  The present invention relates to a method for detecting an edge from a digital image, and more particularly to an image generation method and an image generation apparatus that generate a second image including edge information from a first image composed of a plurality of pixels.

  As a method for detecting an edge from a digital image, a method using a difference value between a certain pixel in the image and its neighboring pixels or neighboring pixels, and a method using a filter such as a Laplacian filter are known.

  Such an edge detection method has a problem that it is strongly influenced by noise in the image. As a method for solving this problem, a method of reducing the influence of noise by performing a smoothing process such as a band limiting filter for removing noise components or a Gaussian filter is known.

  For example, Japanese Patent Application Laid-Open No. 8-315157 (Patent Document 1) describes an invention in which noise included in an image input using a low-pass filter is removed and an edge of the image from which noise is removed is detected. is doing. Since noise can be removed while preserving the shape of the edge, effective edges can be extracted appropriately.

  Further, edge detection using a Laplacian filter and smoothing using a Gaussian filter are described as non-patent documents 1 as well-known techniques.

  Further, the intensity of the edge to be detected and the intensity of the noise to be removed differ depending on the image. Therefore, in order to detect a desired edge while eliminating the influence of noise, it is necessary to appropriately set a parameter for noise removal processing and a parameter for edge detection processing. The parameter here refers to, for example, a filter coefficient.

  Various other prior art documents related to the present invention are also known. For example, Japanese Patent Laying-Open No. 2000-32402 (Patent Document 2) discloses an image conversion apparatus including an area cutout unit and a feature amount extraction unit. The area cutout unit cuts out predetermined pixel data from the input image data. The feature amount extraction unit calculates an autocorrelation coefficient for each input image data for each local area. This autocorrelation coefficient is used as a measure of the feature amount representing the blur amount of the image data. The feature quantity extraction unit calculates two autocorrelation coefficients. In addition, the feature amount extraction unit determines a normalized autocorrelation coefficient (inclination amount) and outputs a corresponding code.

  Japanese Patent Laying-Open No. 2005-190400 (Patent Document 3) discloses a face image detection system including an edge calculation unit. In the face image detection system, first, a detection target area is determined, the detection target area is normalized to a predetermined size, and the edge strength of the normalized area is obtained for each pixel. The normalized area is blocked based on the autocorrelation coefficient (divided into a plurality of blocks).

  Japanese Patent Laying-Open No. 2008-15814 (Patent Document 4) discloses an image analysis apparatus including a three-dimensional feature extraction unit. The three-dimensional feature extraction unit calculates a feature vector from the input image data. As a method for calculating a feature vector, a cubic higher-order local autocorrelation is used. The local area is limited to a 3 × 3 × 3 area around the reference point.

JP-A-8-315157 (FIG. 1, paragraphs 0007 and 0015) JP 2000-32402 A (FIG. 1, FIG. 4, paragraphs 0017 to 0023) JP-A-2005-190400 (FIGS. 1 and 3, paragraphs 0028 to 0030 and 0042 to 0044) JP 2008-15814 A (FIG. 1, FIG. 9, paragraphs 0061 to 0062) Ryoichi Suematsu and Hirohisa Yamada, “Image Processing Engineering”, Corona, P100-103, P96-97

  However, the edge detection method based on the known technique described in Non-Patent Document 1 and the method described in Patent Document 1 require both noise removal processing and edge detection processing. As a result, there is a problem that there are many parameters to be set in order to detect a desired edge while eliminating the influence of noise. Further, when the edge direction to be detected is either horizontal or vertical, it is necessary to use an appropriate setting parameter depending on each case.

  Patent Document 2 described above merely discloses an image conversion apparatus that converts a first image signal into a second image signal that is a signal whose image quality is improved from that of the first image signal. In Patent Document 2, the autocorrelation coefficient for each input image data is calculated locally. The calculated autocorrelation coefficient is used as a measure of the feature amount representing the blur amount of the image data. There is only.

  Patent Document 3 merely discloses a technical idea of obtaining normalized edge strength for each pixel and forming a block based on the autocorrelation coefficient. In other words, in Patent Document 3, the block size is determined based on the autocorrelation coefficient.

  Patent Document 4 discloses a technical idea of calculating a feature vector using a cubic higher-order local autocorrelation.

  In any case, none of Patent Documents 1 to 4 and Non-Patent Document 1 disclose or suggest any detection of an edge using an autocorrelation coefficient.

  Therefore, a problem to be solved by the present invention is to provide a method for detecting an edge from an image without performing image noise removal processing in advance.

  Another object of the present invention is to provide a method for detecting an edge from an image with a small number of parameter settings.

  A first aspect of the present invention is a method for generating a second image including edge information from a first image composed of a plurality of pixels, the step of sequentially selecting a pixel of interest from the first image Extracting a small region including the selected pixel of interest; calculating at least one local autocorrelation coefficient for the pixel of interest using pixels in the small region; and selecting The step of repeatedly executing the step of extracting and the step of calculating; and the step of generating the second image using a local autocorrelation coefficient group for the first image obtained by the step of repeatedly executing; And an image generation method.

  According to a second aspect of the present invention, there is provided an image generation apparatus that generates a second image including edge information from a first image composed of a plurality of pixels, wherein the first image is generated with respect to the first image. For a target pixel selected from the image, a small region extraction unit that extracts a small region including the target pixel and at least one local autocorrelation coefficient for the target pixel is calculated using the pixels in the small region Autocorrelation coefficient calculating means for selecting a new pixel of interest from pixels that have not yet been selected as the pixel of interest in the first image in a predetermined order, and for the selected new pixel of interest, Execution instruction means for instructing repeated execution of small area extraction by the small area extraction means and local autocorrelation coefficient calculation by the autocorrelation coefficient calculation means; and local self for the first image obtained by the repeated execution Relationship Image generating apparatus comprising an image converting means for generating the second image using the group.

According to a third aspect of the present invention, a computer that generates a second image including edge information from a first image including a plurality of pixels, and sequentially selecting a target pixel from the first image; A procedure for extracting a small region including the selected pixel of interest, a procedure for calculating at least one local autocorrelation coefficient for the pixel of interest using a pixel in the small region, the procedure for selecting, and the extraction A procedure for repeatedly executing the calculating procedure, a procedure for generating the second image using a local autocorrelation coefficient group for the first image obtained by the repeated execution procedure,
An image generation program for executing

  In the edge detection method of the present invention, first, the local autocorrelation coefficient in a range limited to a small region including the pixel of interest is first calculated with respect to the pixels in the first image, and then the repeatedly calculated local autocorrelation coefficient is calculated. A second image (edge detection image) is generated using the autocorrelation coefficient group. At this time, smoothing processing within the region is also performed together with edge detection by calculating the local autocorrelation coefficient. Therefore, the smoothing process for removing noise and the edge detection process can be realized simultaneously only by the process of calculating the autocorrelation coefficient in the region.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
An image generation apparatus 10 according to the first embodiment of the present invention will be described with reference to FIG. The image generation device 10 is a device that generates a second image including edge information from a first image composed of a plurality of pixels.

  The illustrated image generating apparatus 10 includes a digital image input unit 12, an edge detection target region setting unit 14, a repeated execution support unit 16, a small region extraction unit 18, a calculation target region setting unit 20, a local self-phase. The relation number calculation unit 22, the coefficient storage unit 24, the all pixel completion determination unit 26, the edge image generation unit 28, and the edge image output unit 30 are configured.

  The digital image input unit 12 inputs an input image and outputs a digital image signal (a). The edge detection target area setting unit 14 receives the digital image signal (a) and selects a first area to be subjected to edge detection from the whole or a part of the digital image signal (a). An image (b) is generated.

  The repeat execution instructing unit 16 sets an arbitrary pixel as the target pixel (d) at the start of processing for the first image (b). Thereafter, the repeat execution instructing unit 16 selects a new target pixel from pixels that have not yet been selected as the target pixel based on the incomplete determination (h) supplied from the all-pixel completion determination unit 26 described later. Select and set the pixel of interest (d). In any case, the repeated execution instruction unit 16 functions as a target pixel selection unit that sequentially selects target pixels from the first image.

  The small area extraction unit 18 extracts a small area (e) including the target pixel (d) based on the target pixel (d) specified by the repeated execution instruction unit 16. At any rate, the small area extraction unit 18 extracts the small area (e) including the target pixel (d) selected by the repeated execution instruction unit (target pixel selection unit) 16.

  The calculation target area setting unit 20 includes one or more calculation target areas for calculating a local autocorrelation coefficient group (g), which will be described later, included in the small area (e) supplied from the small area extraction unit 18. Set (f). In other words, the calculation target area setting unit 20 sets at least one calculation target area (f) in the small area (e) that can set the vertical and horizontal including the target pixel (d) independently.

  The local autocorrelation coefficient calculation unit 22 calculates a local autocorrelation coefficient group (g) from one or more calculation target regions (f) supplied from the calculation target region setting unit 20 as described later. . In other words, the local autocorrelation coefficient calculation unit 22 uses at least one local autocorrelation coefficient (g) corresponding to each calculation target area (f) using the pixels in the calculation target area (f). calculate.

  In any case, the combination of the calculation target region setting unit 20 and the local autocorrelation coefficient calculation unit 22 uses at least one local autocorrelation coefficient (g) for the pixel of interest (d) using the pixels in the small region (e). ) To calculate. As will be described later, this calculation unit sets a displacement amount to at least one pixel and calculates at least one local autocorrelation coefficient (g) for the same target pixel (d).

  The coefficient storage unit 24 records the values of one or more local autocorrelation coefficient groups (g) calculated by the local autocorrelation coefficient calculation unit 22 and the coordinates of the target pixel (d) at the time of calculation. And output as history information (c).

  Based on the history information (c) supplied from the coefficient storage unit 24, the all-pixel completion determination unit 26 determines whether there is a pixel not selected as the target pixel (d) in the first image (b). Determine if. At completion, the all-pixel completion determination unit 26 supplies the completion determination (k) to the edge image generation unit 28. When not completed, the all-pixel completion determination unit 26 supplies the incomplete determination (h) to the repeat execution instruction unit 16.

  In any case, the all-pixel completion determination unit 26 cooperates with the repetition execution instruction unit 16 to perform the repetition execution instruction unit (target pixel selection unit) 16, the small region extraction unit 18, and the calculation unit (calculation target region setting unit). 20, the local autocorrelation coefficient calculation unit 22) functions as an iterative execution unit that repeatedly executes.

  The edge image generation unit 28 generates all local autocorrelation coefficients based on the history information (c) recorded in the coefficient storage unit 24 when the all-pixel completion determination unit 26 outputs the completion determination (k). From the group (g), a second image (l) indicating an edge image is generated. In other words, the edge image generation unit 28 generates the second image (l) using the local autocorrelation coefficient group (c) for the first image (b) obtained by the repetitive execution unit.

  As will be described later, the edge image generation unit 28 converts the values of each autocorrelation coefficient in the local autocorrelation coefficient group (g) so as to be within a predetermined range, and the same target pixel ( When a plurality of local autocorrelation coefficients (g) converted with respect to d) are obtained, one of them is selected.

  The edge image output unit 30 outputs the second image (l) indicating the edge image generated by the edge image generation unit 28 as an output image.

  The hardware configuration (computer system) that realizes the image generation apparatus 10 illustrated in FIG. 1 may be configured by an input device, an output device, and an information processing device, although not illustrated. The input device corresponds to the digital image input unit 12. The output device corresponds to the edge image output unit 30. The information processing apparatus includes an edge detection target region setting unit 14, a repeat execution instruction unit 16, a small region extraction unit 18, a calculation target region setting unit 20, a local autocorrelation coefficient calculation unit 22, a coefficient storage unit 24, and all pixel completion. It corresponds to the determination unit 26 and the edge image generation unit 28. The input device includes, for example, an image sensor, an imaging sensor such as a CCD (Charge Coupled Device) sensor, and a CMOS (Complementary Metal Oxide Semiconductor) sensor. The output device includes, for example, a liquid crystal display or a CRT (cathode ray tube) display. The information processing apparatus includes a storage unit (ROM or RAM) that stores programs and data, and a processing unit (CPU) that controls the input device, the output device, and the storage unit in accordance with the program stored in the storage unit. Consists of.

  Next, the operation of each component will be described.

  The digital image input unit 12 inputs an input image and outputs a digital image signal (a).

  FIG. 2 is a diagram illustrating an operation mode of the edge detection target region setting unit 14. The edge detection target area setting unit 14 receives the digital image signal (a) and selects a first area to be subjected to edge detection from the whole or a part of the digital image signal (a). An image (b) is generated.

  By allowing a method of limiting the processing target area not only to the entire image but also to a part of the screen, it is possible to efficiently apply the method when edge detection is performed only on a necessary area.

  At the start of processing for the first image (b) generated by the edge detection target area setting unit 14, the repeat execution instructing unit 16 sets any one pixel as the initial target of the target pixel (d). Set as pixel.

  After the initial pixel of interest, the repeat execution instructing unit 16 receives the notification of the incomplete determination (h) from the all pixel completion determining unit 26, and extracts the small region (e) and the local autocorrelation coefficient group. (G) In order to repeatedly execute the calculation, a new target pixel is selected to generate an updated target pixel, which is given to the small region extraction unit 18 as the target pixel (d).

  The generation of the updated target pixel, which is the update of the target pixel (d), is still set as the target pixel from the initial target pixel and the updated target pixel setting history based on the history information (c) supplied from the coefficient storage unit 24. The update target pixel is selected from the pixels that have not been updated. This history management is intended to set all the images included in the first image (b) as the target pixel (d) without leaking.

  FIG. 3 is a diagram illustrating an operation mode of the small region extraction unit 18. The small region extraction unit 18 extracts a small region (e) including the target pixel (d) based on the target pixel (d) specified by the repeated execution instruction unit 16.

  Specifically, with respect to one target pixel (d), the calculation target area setting unit 20 described later uses one or more types such as an 8 × 8 pixel area, a 4 × 4 pixel area, and a 4 × 2 pixel area. The calculation target area (f) is set. The small area extraction unit 18 sets all the one or more calculation target areas (f) in the small area (e). In all cases such as the 8 × 8 pixel region, neighboring pixels outside the 8 × 8 pixel region are also required for the calculation of the local autocorrelation coefficient group (g). Therefore, the small area extraction unit 18 sets the small area (e) including these outer neighboring areas.

  The calculation target region setting unit 20 calculates one or more calculation target regions for calculating a local autocorrelation coefficient group (g) as a region included in the small region (e) supplied from the small region extraction unit 18. Set (f).

  According to such a calculation target area setting unit 20, the horizontal and vertical types of the 8 × 8 pixel area, the 4 × 4 pixel area, the 4 × 2 pixel area, the 4 × 4 pixel area, or other sizes are used. By setting a plurality of types of calculation target areas (f) such as horizontal and vertical, it is possible to set smoothness having an appropriate size, horizontal edge preservation, and vertical edge preservation.

  FIG. 4 is a diagram illustrating an operation mode of the calculation target area setting unit 4. In FIG. 4, three calculation object areas (f) are illustrated as an example. That is, the three types of calculation target regions (f) shown in FIG. 4 are a first calculation target region R1 composed of 4 × 2 pixel regions, a second calculation target region R2 composed of 4 × 4 pixel regions, and This is a third calculation target region R3 including an 8 × 8 pixel region.

  The local autocorrelation coefficient calculation unit 22 calculates a local autocorrelation coefficient corresponding to each of the one or more calculation target regions (f) supplied from the calculation target region setting unit 20, and calculates the local autocorrelation relationship. A number group (g) is derived.

  In order to describe the operation of the local autocorrelation coefficient calculation unit 22 in detail, the following is assumed. A pixel in the small area (e) is expressed as I (x, y). The displacement amounts in the x direction and the y direction are expressed as τ1 and τ2, respectively. In addition, each calculation target region (f) such as an 8 × 8 pixel region, a 4 × 4 pixel region, or a 4 × 2 pixel region is represented by a calculation target region variable Ri.

  At this time, the calculation of the local autocorrelation coefficient ρ_Ri (x, y, τ1, τ2) between the pixels separated by the displacement amounts τ1, τ2 in the calculation target region variable Ri for the pixel of I (x, y) is By the calculation shown in the following formula (1).

Here, the calculation of E_Ri [calculation formula] indicates an average value of calculation results indicated by [calculation formula] in the calculation target region variable Ri.

  For one pixel of interest (d), there is a local autocorrelation coefficient calculated as much as the number of combinations of the calculation target region variable Ri and the displacement amounts τ1 and τ2. Here, these local autocorrelation coefficients are collectively referred to as a local autocorrelation coefficient group (g).

  In the case of three overlapping calculation target regions (f) exemplified as an example in FIG. 4, I (x, y) · I (x + τ1), (y + τ2) previously calculated corresponding to the overlap portion It is possible to increase the processing speed by using the result of multiplication for the area to be calculated later. This speeding up will be described in detail in a second embodiment to be described later.

  Hereinafter, as an example, an example of a method for calculating the local autocorrelation coefficient when the calculation target region is 8 × 8 pixels will be described.

  At this time, a plurality of calculation target areas can be considered for the target pixel. However, considering the calculation of the autocorrelation coefficient, it is desirable to take the calculation target region so that the target pixel is located at the center of the calculation target region. However, when the size of the calculation target area is an even number, there is no center pixel, so that the vertical and horizontal shifts by one pixel. In consideration of these points, when Expression (1) is expressed, the following Expression (2) is obtained.

In equation (2), int (z) is a decimal point truncation operation on the value z.

For example, assume that the coordinates of the pixel of interest I (x, y) are x = 10, y = 10, and the displacement amounts τ1, τ2 are τ1 = 1 and τ2 = 1, respectively. In this case, the numerator on the right side in the formula (2) is a value obtained by dividing the sum of I (15,15) × I (16,16) by 64 from I (6,6) × I (7,7), The denominator on the right side is a value obtained by dividing the sum of I (15,15) ² by 64 from I (6,6) ² . At this time, the pixels used in the calculation in the numerator and denominator are different, but these pixels are all included in the small region (e).

  The coefficient storage unit 24 stores the values of one or more local autocorrelation coefficient groups (g) calculated by the local autocorrelation coefficient calculation unit 22 together with the coordinates of the target pixel (d) at the time of calculation, Managed as history information (c).

  The all-pixel completion determination unit 26 determines whether there is a pixel that is not selected as the target pixel (d) in the first image (b). When there is a pixel that is not selected as the target pixel (d), the all-pixel completion determination unit 26 notifies the repeated execution instruction unit 16 of the incomplete determination (h). When all the pixels of the first image (b) are selected as the target pixel (d) and there are no longer any pixels that are not selected as the target pixel (d), the all-pixel completion determination unit 26 determines the completion ( k) is notified to the edge image generation unit 28.

  When the completion determination (k) is received from the all-pixel completion determination unit 26, the edge image generation unit 28 calculates the local self-phase relationship calculated for each target pixel (d) of the first image (b). For one or more local autocorrelation coefficients included in the number group (g), a local autocorrelation coefficient (g) that is a representative value is selected according to a certain rule. The edge pixel generation unit 28 selects a representative local autocorrelation coefficient for each target pixel (d) and then converts the representative local autocorrelation coefficient into an edge pixel value. The edge image generation unit 28 generates a second image (l) by performing conversion into edge pixel values for all the target pixels (d) of the first image (b).

  FIG. 5 is a block diagram showing an operation mode of the edge image generation unit 28. FIG. 5 illustrates, as an example of the operation mode, a first calculation target region R1 including a 4 × 2 pixel region, a second calculation target region R2 including a 4 × 4 pixel region, and a third calculation target region R2 including an 8 × 8 pixel region. The calculation result for three types of calculation target regions (f) of the calculation target region R3 is illustrated. Further, the values of τ1 and τ2 indicating the displacement amounts in the x direction and the y direction are illustrated as fixed values of one pixel, respectively. Therefore, in this operation example, for each target pixel (d), as the local autocorrelation coefficient group (g), three types of local autocorrelation coefficients, that is, the first local autocorrelation coefficient ρ1 = ρ_R1 (x , Y, 1, 1), the second local autocorrelation coefficient ρ2 = ρ_R2 (x, y, 1, 1), and the third local autocorrelation coefficient ρ3 = ρ_R3 (x, y, 1, 1). Possess.

  The edge image generation unit 28 converts the values taken by the autocorrelation coefficients in the autocorrelation coefficient group (g) so that they fall within a predetermined range. Specifically, the edge image generation unit 28 performs a restriction process on a range of [0 ≦ ρ ≦ 1] including both end values for each local autocorrelation coefficient. This is because the calculation results of local autocorrelation coefficients for various horizontal and vertical block sizes and displacement values τ1 and τ2 are originally in the range of 0 to 1 when the calculation target region is narrow. Since there are cases where the number exceeds 1 even after normalization, forcible restriction processing is performed to keep the maximum value to 1.

  After the restriction process to [0 ≦ ρ ≦ 1] is performed, the edge image generation unit 28 independently multiplies each local autocorrelation coefficient by 255, rounds it down by an INT operation, and performs X1 , X2, and X3 calculate the edge pixel values shown in FIG.

  Further, the edge image generation unit 28 sets a minimum value by MIN calculation from all the edge pixel values obtained from one to plural for each target pixel (d) in the obtained first image (b). Select and form an edge pixel value for the pixel of interest (d).

  The image composed of the edge pixel values formed in this way is the second image (l).

  Here, the selection of the minimum value by the MIN calculation is performed after the conversion within the range of 0 to 255, but it may be performed before or after the conversion.

In general, the relationship of the following equation (3) is present between the mean square error ε ² between adjacent pixels, the signal variance σ ² , and the autocorrelation coefficient ρ when the displacement amount is 1 pixel. is there.

As a result, the autocorrelation coefficient ρ is expressed using the mean square error ε ² and the signal variance σ ^2, and the following equation (4) is derived.

  This equation (4) means that the strength of the correlation corresponds to the strength of the edge, and that the autocorrelation coefficient ρ is strongly related to the luminance component of the edge region and the strength of the edge region. I mean.

  For this reason, it is possible to obtain X (x, y) as the edge pixel value in the output edge detection image by converting the local autocorrelation coefficient to the pixel value 0 to 255.

  The edge image output unit 30 outputs the second image (l) indicating the edge image generated by the edge image generation unit 28 as an output image.

  As described above, according to the first embodiment of the present invention, the following effects can be obtained.

  Edges in an image can be detected without separately performing a process for removing noise. When it is desired to detect the vertical edge in the image with higher accuracy, the vertical edge in the image can be detected with higher accuracy by making the vertical size of the region larger than the horizontal size. When it is desired to detect the horizontal edge in the image with higher accuracy, it is possible to detect the horizontal edge in the image with higher accuracy by making the horizontal size of the region larger than the vertical size. That is, by setting only two parameters, the vertical size and horizontal size of the area, it is possible to perform flexible edge detection according to the degree of noise in the image, the strength of the edge to be detected, and the direction.

  In addition, for example, after performing edge detection with the vertical size of the region set larger than the horizontal size, set the horizontal size of the region larger than the vertical size to perform edge detection, and integrating the results. By performing edge detection processing a plurality of times while changing the above, it is possible to respond to various requests.

[Second Embodiment]
Next, an image generation apparatus according to the second embodiment of the present invention will be described. The image generation apparatus according to the second embodiment is obtained by adding an improvement to reduce the total calculation amount to the image generation apparatus 10 according to the first embodiment shown in FIG. There are many parts that overlap with the image generation apparatus 10 according to the first embodiment shown in FIG. Therefore, below, only a different part from the image generation apparatus 10 which concerns on 1st Embodiment is demonstrated.

  In the image generating apparatus according to the second embodiment, the operation in the location autocorrelation coefficient calculating unit 22 is different from the image generating apparatus 10 according to the first embodiment, and the local autocorrelation coefficient group (g) is calculated. Improvements to reduce the amount of computation at the time are added.

  As an example, the process of calculating the local autocorrelation coefficient when the pixel of interest is I (x, y), the displacements τ1, τ2 are τ1 = 1, τ2 = 0, and the calculation target region m × n is 4 × 2. Will be described.

  The expression for calculating the local autocorrelation coefficient shown in the image generation apparatus 10 of the first embodiment, Expression (2), is obtained by dividing the coefficient 1 / mn that is commonly multiplied by the denominator and the numerator, and the following expression ( 5).

  By substituting the values in this example into the variables of this equation (5), the following equation (6) is obtained.

  Here, when the next pixel of interest is a pixel shifted by one pixel to the right, I (x + 1, y), the calculation of the local autocorrelation coefficient for this pixel is expressed by the following equation (7).

  In the calculation of Expression (7) performed after the calculation of Expression (6), for example, the denominator in Expression (6),

For the leftmost column, i = −1, which becomes unnecessary when the pixel is shifted to the right by one pixel.

Is the rightmost column that newly enters the calculation target area by shifting one pixel to the right, and the calculation part for i = 3

Is added, the denominator calculation result in equation (7) is obtained. That is, the total calculation amount can be reduced by repeatedly subtracting the calculation results for the columns that are no longer needed and adding only the calculation results for the columns that are newly required.

  Here, as an example, the example in which the target pixel is shifted in the horizontal direction (one pixel right) has been described.

  In the image generation method according to the first aspect of the present invention, the calculating step includes a calculation target area (f) in which the vertical and horizontal including the target pixel (d) can be set independently in the small area (e). Setting at least one, and calculating at least one local autocorrelation coefficient (g) corresponding to each calculation target region (f) using pixels in the calculation target region (f). May include. In the calculating step, at least one local autocorrelation coefficient (g) for the same target pixel (d) may be calculated by setting a displacement amount for at least one pixel. In the generating step, the value taken by each autocorrelation coefficient in the local autocorrelation coefficient group (g) is converted so as to be within a predetermined range, and the same target pixel (d) is converted. If a plurality of local autocorrelation coefficients are obtained, a step of selecting one of them may be included.

  The image generation apparatus according to the second aspect of the present invention may further include an edge detection target region setting unit that generates the first image (b) from all or part of the digital image (a). The autocorrelation coefficient calculating means may calculate the local autocorrelation coefficient (g) using a part or all of the pixels in the small region (e). The autocorrelation coefficient calculating means sets at least one calculation target area (f) within the small area (e) in which the vertical and horizontal widths including the target pixel (d) can be set independently. A local autocorrelation coefficient calculating unit that calculates at least one local autocorrelation coefficient (g) corresponding to each of the calculation target areas (f) using the pixels in the calculation target area (f), May be included. The autocorrelation coefficient calculating means may calculate at least one local autocorrelation coefficient (g) for the same target pixel (d) by setting the displacement amount to at least one pixel. The image conversion means converts the value of each autocorrelation coefficient in the local autocorrelation coefficient group (g) so that it falls within a predetermined range, and the local autocorrelation relationship with respect to the same target pixel (d). When a plurality of numbers are obtained, the second image (l) may be generated by selecting one of them.

  In the image generation program according to the third aspect of the present invention, the calculation procedure is as follows: a calculation target area (f) in which the vertical and horizontal including the target pixel (d) can be set independently is set in the small area (e). A procedure for setting at least one, and a procedure for calculating at least one local autocorrelation coefficient (g) corresponding to each of the calculation target regions (f) using pixels in the calculation target region (f). May include. In the calculation procedure, at least one local autocorrelation coefficient (g) for the same target pixel (d) may be calculated by setting a displacement amount for at least one pixel. The procedure for generating is the same as the procedure for converting the values taken by each autocorrelation coefficient in the local autocorrelation coefficient group (g) so as to be within a predetermined range, and the same target pixel (d). If a plurality of local autocorrelation coefficients obtained are obtained, a procedure for selecting one of them may be included.

  When the sizes m and n of the small area (e) are set large, the degree of smoothing increases, and the effect of removing noise increases and the effect of edge enhancement decreases. If m and n are set to be small, the degree of smoothing is reduced, the effect of removing noise is weakened, and the effect of edge enhancement is enhanced.

  If m and n are set so that m is larger than n, the degree of smoothing in the vertical direction of the region is reduced, the horizontal edges are well preserved, and the effect of horizontal edge enhancement is increased. .

  On the other hand, if m and n are set so that n is larger than m, the degree of horizontal smoothing of the region is reduced, the vertical edges are well preserved, and the effect of vertical edge enhancement is increased. .

  As mentioned above, although preferred embodiment was described about this invention, this invention is not limited to embodiment mentioned above, Of course, various deformation | transformation and change are possible within the range which does not deviate from the meaning (theme) of this invention. is there.

  An example of typical industrial use as an application example of the present invention is to extract a person or the like from an image.

1 is a block diagram illustrating an image generation apparatus according to a first embodiment of the present invention. It is a figure for demonstrating the operation | movement form of the edge detection area | region setting part used with the image generation apparatus shown in FIG. It is a figure for demonstrating the operation | movement form of the small area extraction part used with the image generation apparatus shown in FIG. It is a figure for demonstrating the operation | movement form of the calculation object area | region setting part used with the image generation apparatus shown in FIG. It is a block diagram for demonstrating the operation | movement form of the edge image generation part used with the image generation apparatus shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image generation apparatus 12 Digital image input part 14 Edge detection object area | region setting part 16 Repeat execution instruction part 18 Small area extraction part 20 Calculation object area | region setting part 22 Local autocorrelation coefficient calculation part 24 Coefficient memory | storage part 26 Determination of completion of all images Unit 28 edge image generation unit 30 edge image output unit

Claims (5)

A method for generating a second image including edge information from a first image composed of a plurality of pixels,
Sequentially selecting pixels of interest from the first image;
Extracting a small region including the selected pixel of interest;
Setting at least one calculation target area within the small area, which can independently set the vertical and horizontal including the pixel of interest;
Calculating at least one local autocorrelation coefficient corresponding to each of the calculation target regions using the pixels in the calculation target region, and expressing the pixels in the small region as I (x, y) a step of when, x-direction, y-direction displacement amount .tau.1, by setting the .tau.2, at least one calculating the local autocorrelation coefficient for the same pixel of interest,
Repeatedly executing the selecting step, the extracting step, the setting step, and the calculating step;
Converting each autocorrelation coefficient in the local autocorrelation coefficient for the first image obtained by the repetitive execution step so as to fall within a predetermined range;
If a plurality of the converted local autocorrelation coefficients are obtained for the same pixel of interest, the step of generating the second image by selecting the minimum value among them ,
An image generation method including: An image generation device that generates a second image including edge information from a first image composed of a plurality of pixels,
A small region extracting means for extracting a small region including the target pixel for the target pixel selected from the first image with respect to the first image;
A calculation target region setting unit that sets at least one calculation target region in the small region that can independently set the vertical and horizontal including the pixel of interest;
A local autocorrelation coefficient calculating unit that calculates at least one local autocorrelation coefficient corresponding to each of the calculation target areas using pixels in the calculation target area, wherein the pixels in the small area are represented by I ( x, when expressed as y), x-direction, y-direction displacement amount .tau.1, by setting the .tau.2, and self correlation coefficient calculation unit for at least one calculating the local autocorrelation coefficient for the same pixel of interest,
Selecting a new pixel of interest from pixels that have not yet been selected as the pixel of interest in the first image in a predetermined order, and extracting the small region by the small region extraction means for the selected new pixel of interest; Execution instruction means for instructing repeated execution of setting of a calculation target area by the calculation target area setting unit and calculation of a local autocorrelation coefficient by the autocorrelation coefficient calculation unit ;
A value taken by each autocorrelation coefficient in the group of local autocorrelation coefficients for the first image obtained by the repeated execution is converted so as to fall within a predetermined range, and When a plurality of autocorrelation coefficients are obtained, by selecting a minimum value among them, an image conversion means for generating the second image;
An image generation apparatus comprising: The image generation apparatus according to claim 2 , further comprising an edge detection target region setting unit that generates the first image from all or part of the digital image. The image generation apparatus according to claim 2 , wherein the autocorrelation coefficient calculation unit calculates the local autocorrelation coefficient using a part or all of the pixels in the small region. A computer that generates a second image including edge information from a first image composed of a plurality of pixels,
A procedure for sequentially selecting a target pixel from the first image;
A procedure for extracting a small region including the selected pixel of interest;
A procedure for setting at least one calculation target area in the small area, which can independently set the vertical and horizontal including the pixel of interest;
A procedure for calculating at least one local autocorrelation coefficient corresponding to each of the calculation target areas using the pixels in the calculation target area, and expressing the pixels in the small area as I (x, y) when, the procedure x-direction, y-direction displacement amount .tau.1, by setting the .tau.2, at least one calculating the local autocorrelation coefficient for the same pixel of interest,
A step of repeatedly executing the step of selecting, the step of extracting, the step of setting, and the step of calculating;
A procedure of converting the values taken by each autocorrelation coefficient in the group of local autocorrelation coefficients for the first image, obtained by the iterative execution procedure, to fall within a predetermined range;
In the case where a plurality of the converted local autocorrelation coefficients are obtained for the same pixel of interest, a procedure for generating the second image by selecting the minimum value among them ,
An image generation program for executing

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