JP2003203232A - Image processing apparatus, image processing program, and recording medium storing image processing program - Google Patents

Abstract

(57) [Problem] To provide an image processing device capable of performing more appropriate sharpening processing. SOLUTION: An image processing apparatus 2 for sharpening a digital image includes an edge strength calculating means 32 for calculating an edge strength of a target pixel to be processed based on a pixel value of an original image; A storage device 22 for storing a look-up table 41 for defining the correspondence between the intensity and a predetermined sharpening intensity; and a sharpening means 33 for converting a pixel value of a target pixel for sharpening.
And The sharpening means 33 includes the edge strength calculating means 3
The sharpening strength corresponding to the edge strength calculated in 2 is obtained based on the look-up table 41, and the sharpening degree is adjusted based on the obtained sharpening strength to convert the pixel value of the target pixel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing device for performing sharpening processing, an image processing program, and a recording medium recording the image processing program.

[0002]

2. Description of the Related Art Conventionally, a sharpening process has been developed as an image process for enhancing edges in a digital image. As the sharpening process, for example, a selective sharpening process or a high frequency filtering process is known.

In the selective sharpening process, an edge detection operator is made to act on a digital image processed by a two-dimensional filter for each pixel, and the pixel is processed according to the magnitude relationship between the obtained edge intensity and a predetermined threshold value. This is a sharpening process that determines whether or not to perform the sharpening process.

Further, the high frequency filtering process is a sharpening process in which only a portion having a large density change is sharpened by emphasizing a high frequency region in a frequency space relating to the density in an image.

[0005]

However, the above-described conventional sharpening process may not always be an appropriate process depending on the target image.

In the selective sharpening process, an edge having a large density change is emphasized, and an edge not so large is not emphasized. That is, in the selective sharpening process, a uniform process is performed in which pixels having originally low edge strength are converted so that the edge strength is small and pixels having high edge strength are further increased. Further, even in the high frequency filtering process, the edge of the pixel having a large density change is still emphasized.

On the other hand, in an actual image, for example,
On the contrary, in the case of a pixel having a high edge strength, it may be possible to obtain a desirable image by reducing the degree of sharpening.
In addition, when sharpening is not performed on pixels with an edge strength up to a certain size, and when the edge strength is higher than that, a desirable image can be obtained by adjusting the degree of sharpening according to the increase of the edge strength. There is also.

As described above, the conventional sharpening processing has a problem that the processing result is not always a desirable image because the sharpening degree cannot be adjusted.

The present invention has been made in view of the above problems, and an object thereof is to provide an image processing apparatus, an image processing program, and a recording medium recording the image processing program, which enables more appropriate sharpening processing. To provide.

[0010]

An image processing apparatus according to claim 1 of the present invention is an image processing apparatus for converting pixel values of an original image in order to sharpen a digital image, and solves the above problems. In order to do so, the edge strength calculation means for calculating the edge strength of the target pixel to be processed based on the pixel value of the original image, the correspondence relationship between the edge strength and the sharpening strength predetermined for the edge strength. And a sharpening means for converting the pixel value of the target pixel for sharpening, wherein the sharpening means is the edge strength calculated by the edge strength calculating means. To obtain a sharpening intensity corresponding to the definition information stored in the storage means, adjust the sharpening degree based on the obtained sharpening intensity, and convert the pixel value of the target pixel. It is characterized.

In the above arrangement, the edge strength calculation means calculates the edge strength of the target pixel. Further, the sharpening means adjusts the degree of sharpening based on the sharpening strength corresponding to the calculated edge strength and converts the pixel value of the target pixel. Then, the correspondence between the edge strength and the sharpening strength is stored in the storage means as predetermined definition information.

Therefore, by appropriately setting the definition information, the correspondence between the edge strength and the sharpening strength can be flexibly set. As a result, the processing is not limited to simple processing such as sharpening a pixel having a relatively high edge strength, and the degree of sharpening is gradually increased according to the magnitude of the edge strength, or pixels having an edge strength up to a certain size are processed. Does not perform sharpening, and if the edge strength becomes higher than that, the degree of sharpening is increased according to the increase of the edge strength, and on the contrary, the degree of sharpening is suppressed in the case of a pixel having a large edge strength. Such sharpening processing can be realized.

As a result, by appropriately setting the definition information, it is possible to perform more appropriate sharpening processing on the original image to be processed according to what kind of image is desired as the processing result. It becomes possible to provide.

A computer may function as each of the above means. Therefore, an image processing program according to claim 6 of the present invention uses a computer for converting a pixel value of an original image to sharpen a digital image, and an edge of a target pixel to be processed based on the pixel value of the original image. Edge strength calculation means for calculating strength, edge strength,
A storage unit that stores definition information that defines a correspondence relationship between the edge strength and a predetermined sharpening strength, and sharpening corresponding to the edge strength calculated by the edge strength calculating unit for sharpening. Intensity is obtained based on the definition information stored in the storage means, and the sharpening means adjusts the degree of sharpening based on the obtained sharpening strength to function as a sharpening means for converting the pixel value of the target pixel. I am trying.

An image processing apparatus according to claim 2 of the present invention is
The image processing apparatus according to claim 1, wherein the input information is input by an input unit that receives an input from a user, and based on the input information for changing the content of the definition information stored in the storage unit. It is preferable to further include definition information changing means for changing the contents of the definition information stored in the storage means.

In the above structure, the definition information changing unit changes the contents of the definition information when the user or the like inputs the input information by the input unit. Thereby, the user or the like can appropriately change the content of the sharpening process to a more appropriate one and execute the process depending on what kind of image is desired as a processing result with respect to the original image to be processed. . That is, it becomes possible to provide an image processing apparatus capable of flexibly changing the content of the sharpening process according to the user's request.

Similarly, an image processing program according to a seventh aspect of the present invention is the image processing program according to the sixth aspect, which is input information input by an input unit that receives an input from a user, It is preferable that the computer further functions as definition information changing means for changing the content of the definition information stored in the storage means based on the input information for changing the content of the definition information stored in the storage means.

An image processing apparatus according to claim 3 of the present invention is
The image processing apparatus according to claim 2, wherein a sharpening strength curve representing a correspondence relationship between the edge strength and a sharpening strength predetermined with respect to the edge strength is created based on the definition information stored in the storage means. The definition information changing means further includes a display control means for displaying on the display means, and when the definition information changing means receives, as the input information, information for instructing the deformation of the sharpening intensity curve, the sharpness deformed according to the input information. It is preferable to change the contents of the definition information stored in the storage means so as to match the conversion strength curve.

In the above arrangement, the display control means causes the display means to display the sharpening strength curve representing the correspondence between the edge strength and the sharpening strength. The user or the like can make an input for modifying the sharpening strength curve by the inputting means while looking at the sharpening strength curve displayed on the display means. When this input is input as the input information, the definition information changing means changes the contents of the definition information so as to match the deformed sharpening strength curve.

As a result, the user or the like can change the correspondence between the edge strength and the sharpening strength while visually recognizing the correspondence. As a result, it becomes possible to provide an image processing apparatus that can more easily and freely change the correspondence between the edge strength and the sharpening strength.

Similarly, an image processing program according to an eighth aspect of the present invention is the image processing program according to the seventh aspect, based on the definition information stored in the storage means,
The computer further functions as display control means for displaying on the display means a sharpening strength curve representing the correspondence between the edge strength and a sharpening strength predetermined for the edge strength, and the definition information changing means is configured to When the information for instructing the deformation of the sharpening intensity curve is input as the input information, the content of the definition information stored in the storage unit is changed so as to match the sharpening intensity curve deformed according to the input information. Preferably.

An image processing apparatus according to claim 4 of the present invention is
In the image processing device according to any one of claims 1 to 3, it is preferable that the definition information is a look-up table that associates the edge strength with a sharpening strength predetermined with respect to the edge strength.

With the above arrangement, the sharpening means can obtain the sharpening strength by a simple process.
Processing in a short time becomes possible.

Similarly, in the image processing program according to claim 9 of the present invention, in the image processing program according to any one of claims 6 to 8, the definition information indicates the edge strength and the edge strength. It is preferably a look-up table that correlates with a predetermined sharpening strength.

An image processing apparatus according to claim 5 of the present invention is
In the image processing device according to any one of claims 1 to 4, the edge strength calculation means includes a pixel value of the target pixel and a plurality of pixels having a predetermined positional relationship with the target pixel. It is preferable to calculate the difference from the average pixel value as the edge strength.

With the above arrangement, the edge strength calculating means can calculate the edge strength by a simple process as compared with the process using Fourier transform, for example, and the process can be performed in a short time. Become.

Similarly, in the image processing program according to a tenth aspect of the present invention, in the image processing program according to any one of the sixth to ninth aspects, the edge strength calculation means sets the pixel value of the target pixel to the pixel value. It is preferable to calculate the difference between the target pixel and the average pixel value of a plurality of pixels having a predetermined positional relationship as the edge strength.

A recording medium recording the image processing program according to claim 11 of the present invention is characterized by recording the image processing program according to any one of claims 6 to 10.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. 1 to 8.

1. Overall Configuration FIG. 2 is a block diagram showing a schematic configuration of the image output system according to the present embodiment. This image output system is configured to include a film scanner 1, an image processing device 2, and a photo printing device 3.

The film scanner 1 irradiates a negative film which is a photographic film with light from a light source and receives the transmitted light with a CCD (Charge Coupled Device) or the like to thereby record an image recorded on the negative film. Is to read. The film scanner 1 inputs the read image data to the image processing apparatus 2 for each of red component, green component and blue component.

The photographic printing device 3 is a device for printing an image on photographic paper by exposing a photographic paper, which is a photosensitive material, on the basis of the image data processed by the image processing device 2. As a head for irradiating the printing paper with light according to the digital image data, a light modulator that can modulate the irradiation light to the printing paper for each pixel according to the digital image data is used. As the light modulation element, for example, PLZ
T exposure head, DMD (digital micromirror device), LCD (liquid crystal display), LED (Light Emi)
tting diode) panel, laser, FOCRT (Fiber Opt)
ic Cathode Ray Tube), CRT (Cathode Ray Tube) and the like.

The image processing apparatus 2 performs sharpening processing on the image data sent from the film scanner 1 and supplies the sharpened image data to the photographic printing apparatus 3.

In this embodiment, the film scanner 1 will be described as an apparatus for inputting image data to the image processing apparatus 2. However, in addition to the film scanner 1, the image data may be input to the image processing apparatus 2 from another device such as a digital camera capable of generating image data, or a device such as a personal computer that stores the image data. Image data may be provided to the image processing apparatus 2 from a recording medium such as a floppy (registered trademark) disk or a communication network such as the Internet.

Further, in the present embodiment, the photographic printing apparatus 3 will be described as an output destination of the image data from the image processing apparatus 2. However, in addition to the photo printing device 3, another device such as a printer or a display for reproducing an image based on the image data after the image processing, or a device such as a personal computer for accumulating the image data after the image processing is used from the image processing device 2. The image data may be output to the image data, and the image processing apparatus 2 may output the image data to a recording medium such as a floppy disk or a communication network such as the Internet.

2. Configuration of Image Processing Device FIG. 1 is a block diagram showing a schematic configuration of the image processing device 2 according to the present embodiment. The image processing device 2 is composed of, for example, a personal computer, and includes a central processing device 21, a storage device (storage means) 22, and an interface 2.
3 and a memory 24 are connected via a data bus 25 in a data communicable state, an input device (input means) 26, and a display device (display means) 27. There is.

The image data sent from the film scanner 1 is input to the main body 20 of the image processing apparatus 2 via the interface 23. The input image data is
The image is once stored in the storage device 22 or the memory 24, and image processing is performed by the central processing unit 21. The image data subjected to the image processing is output to the photo printing apparatus 3 via the interface 23.

The central processing unit 21 is a CPU (Central Pr
Ocessing Unit) etc., and the control means 3
1, the edge strength calculation means 32 and the sharpening means 33 are provided. Further, the central processing unit 21 preferably includes definition information changing means 34 and display control means 35 as described later. Here, the control means 31
Is a block that performs general control in the image processing apparatus 2, such as data exchange with the central processing unit 21, the storage device 22, the interface 23, and the memory 24. The edge strength calculation means 32 and the sharpening means 3
3, the function of each block of the definition information changing unit 34 and the display control unit 35 will be described later.

The storage device 22 is composed of a hard disk or the like, and stores data used for calculation in the central processing unit 21, and particularly stores a look-up table 41 and a sharpening filter 42 which will be described later. ing.
The storage device 22 may also store a program or the like that defines the procedure of processing performed by the central processing unit 21.

The interface 23 functions not only as an input / output interface for the image data, but also as an input interface for input information from the input device 26 and an output interface for output information to the display device 27.

The memory 24 is a random access memory (RAM).
function as a function of temporarily storing the image data input to the interface 23, and as a work area for temporarily storing data used in processing such as calculation in the central processing unit 21. It has the function of.

The input device 26 is composed of a keyboard, a mouse and the like, and the display device 27 is composed of a display and the like.

In general, the image processing device 2 is the input device 2
6 and the display device 27, the image processing device 2 according to the present invention may not include the input device 26 and the display device 27.

3. Sharpening process by the image processing device The image processing device 2 having the above-mentioned configuration performs the sharpening process on the image data input from the film scanner 1 and outputs it to the photographic printing device 3. The sharpening process will be described below.

The "sharpening process" is an image process for generating an image in which edges existing in the original image are further emphasized.

First, a general sharpening process will be described. The image data is monochrome image data, and the pixel value of each pixel (target pixel) in the monochrome image data is set to f (i, j) (i and j represent the coordinates of the target pixel), and sharpening corresponding to this is performed. The processed pixel value is g
(I, j). In this case, g (i, j) is, g (i, j) = f (i, j) -∇ 2 f (i, j) ... can be expressed (equation 1) and.

[0047] Formula 1 in -∇ ² f (i, j), and is approximated using the pixel values of pixels located around the target pixel, for ^{example, -∇ 2 f (i, j} ) = 4f (i, j) -f (i + 1, j) -f (i-1, j) - f (i, j + 1) -f (i, j-1) ... ( equation 2) ^{or, -∇ 2 f (i, j} ) = 8f (i, j) -f (i-1, j-1) -f (i, j-1) -f (i + 1, j-1) -f (i-1, j) -f (i, j + 1) -f (i-1, j + 1) -f (i, j + 1) -f (i + 1, j + 1) (Equation 3).

Here, Expression 2 is a case where the pixel values of the pixels adjacent to the target pixel in the front, rear, left, and right are used, and Expression 3 is a case where the pixel values of the pixels adjacent to the target pixel are used.

The operations of Equations 2 and 3 are generally called "sharpening filter" (or "Laplacian operator") for the target pixel, and are represented as shown in FIGS. 3 (a) and 3 (b), respectively. . In the present invention, FIG. 3 (a) may be used as the sharpening filter, and FIG.
May be used, and still another sharpening filter may be used. Therefore, in the following, the sharpening filter used in this embodiment is generalized and expressed as shown in FIG.

In the present embodiment, a sharpening filter of 3 × 3 pixels will be described, but other types of sharpening filters such as a sharpening filter of 5 × 5 pixels can be used. However, when a 5 × 5 pixel sharpening filter is used, the amount of calculation tends to be large and the calculation time tends to be long. From the viewpoint of reducing the amount of calculation, it is preferable to use a 3 × 3 sharpening filter. desirable. Further, from the viewpoint of image quality after processing, a sharpening filter of 3 × 3 pixels is often sufficient.

Further, it is possible to use a sharpening filter of 3 × 3 pixels and a sharpening filter of 5 × 5 pixels separately for each image region. For example, a sharpening filter of 3 × 3 pixels may be used for an image region where edges exist at short intervals, and a sharpening filter of 5 × 5 pixels may be used for other image regions. Good.

By the way, the image input to the image processing apparatus 2 is
If the image data is color image data, the color image
The image data is composed of, for example, RGB color data.
A variety of people are required to perform sharpening processing on this color image data.
The law is considered. For example, for each RGB color data,
The method of performing the sharpening process described above
Of the G data, which the human eye is sensitive to changes in brightness,
A method of performing sharpening treatment may be considered. Also, RGB
Obtain the saturation or gray density from the data for each color and
A method of sharpening these values, for each RGB color
Data is L^*a^*b ^*Brightness when converted to color system data
L indicating the degree^*Method for sharpening data of
Can also be considered.

In the present invention, any of the above methods may be adopted. Therefore, in the following, description will be made without distinguishing the type of image data. The “pixel value” means a value indicated by the data in each pixel of the image data, and, for example, in the data of each color of RGB, means the value indicating the density of each color of RGB.

Next, the sharpening process in this embodiment will be described with reference to FIG. 1 and FIG. Figure 4
3 is a flowchart showing a flow of sharpening processing in the image processing apparatus 2 of FIG.

When image data is input from the film scanner 1 (step S1), the image data is stored in the memory 2
4 is stored. Here, the input image data is mx
It is composed of n pixels. This image data is in memory 2
When stored in 4, the pixel value of each pixel is expanded in the memory space based on the coordinates of each pixel.

Then, the variables i and j are set to 1 for initialization (step S2), and the pixel at the (i, j) coordinate is set as the target pixel to be sharpened (step S).
3).

Then, the edge strength calculating means 32 calculates the edge strength of the target pixel (step S).
4, S5). The edge strength calculation means 32 first determines the pixel values (pixels adjacent to the target pixel in the front, rear, left, and right) of pixels around the target pixel and having a preset positional relationship with respect to the target pixel (for example, An average value (average pixel value) of the pixel values of the original image is calculated (step S4). Next, the edge strength calculation means 32
Calculates the difference (density difference) between the pixel value of the target pixel and the average pixel value, and sets the calculated value as the edge strength (step S5).

The calculation of the edge strength by the edge strength calculating means 32 is not limited to the above method, but the above method is preferable because the edge strength can be calculated by a relatively simple calculation.

The "edge" refers to a portion where the density (pixel value) in the image changes abruptly, and the "edge strength" refers to a value indicating the degree of the above change. The edge strength to be calculated by the edge strength calculating means 32 may be any value as long as it represents the degree of density change at the edge. In addition to the above, in order to calculate the edge strength, ∇ ² f is calculated by the Laplacian operator described above.
(I, j) may be calculated, or another type of edge strength may be calculated by a general edge detection operator other than this. Further, the saturation or gray density may be obtained from the data of each color of RGB, and the edge strength may be calculated based on these values, and the data of each color of RGB may be L ^* a ^* b ^*.
The edge strength may be calculated based on L ^* data indicating the lightness when converted into the color system data.

Then, the sharpening means 33 performs a sharpening process on the target pixel (steps S6 to S9). The sharpening means 33 first acquires the sharpening filter 42 (see FIG. 3C) stored in the storage device 22 (step S6). Next, the sharpening means 33 causes the storage device 22.
Referring to the lookup table 41 stored in
The sharpening strength corresponding to the edge strength calculated in step S5 is acquired (step S7). Next, the sharpening means 3
3 corrects the sharpening filter 42 acquired in step S6 based on the sharpening strength acquired in step S7 (step S8). And the sharpening means 33
The pixel value of the target pixel is converted based on the sharpening filter 42 corrected in step S8 (step S
9).

In order to perform the processing of steps S4 to S9 as described above on each pixel, the target pixels are sequentially moved (steps S10 to S13, S3), and step S4.
~ The process of S9 is repeated.

The sharpening process in steps S6 to S9 will be described in more detail. The "sharpening strength" is a parameter for adjusting the degree of sharpening. The sharpening filter 42 is modified by multiplying each element of the sharpening filter 42 by this sharpening strength. The modified sharpening filter 42 can be represented as in FIG. In FIG. 5A, w (-1, -1), w (-
1,0), w (-1,1), w (0, -1), w (0,
0), w (0,1), w (1, -1), w (1,0),
w (1,1) is the sharpening strength.

Usually, the sharpening strength is w (-1, -1) = w
(-1,0) = w (-1,1) = w (0, -1) = w
(0,0) = w (0,1) = w (1, -1) = w (1,
Since 0) = w (1,1), this case will be described below, and the sharpening strength is represented by w.

[0064] In this case, the equation 1 may be expressed as g (i, j) = f (i, j) -w · ∇ 2 f (i, j) ... ( Equation 4). Therefore, the processing performed by the sharpening means 33 in step S8 is −w · ∇ in equation 4.
^{2 This} is a process of calculating f (i, j). Further, the processing performed by the sharpening means 33 in step S9 is the processing of calculating the equation 4. When the calculation of Expression 4 is expressed by one filter, it becomes as shown in FIG. The −∇ ² f (i, j) in Equation 4 and the filter of FIG. 5 (b) are specific to the target pixel, and these can change when the target pixel moves to another pixel.

However, the ratio may be set to each of the above values depending on the purpose of the sharpening process. By setting the ratio in this way, the degree of sharpening can be changed depending on the direction of the original image. For example, in order to increase the degree of sharpening in the vertical direction of the original image, w (-
1st for (1,0), w (0,0), w (1,0)
W (-1, -1), w (0, included in the column and the third column
-1), w (1, -1) and w (-1,1), w
(0,1) and w (1,1) may be set to a high ratio. Increasing the degree of sharpening in the vertical direction in the original image can be used, for example, when it is desired to emphasize the contour of the building in an image showing the building.

When the sharpening strength is increased, the edges in the image after the sharpening processing can be further emphasized, and when the sharpening strength is decreased, the edges in the image after the sharpening processing can be made inconspicuous. Sharpening means 33
Is based on the look-up table 41
Set according to the edge strength.

The edge strength input to the lookup table 41 is represented by a value within the range of 0 to 255 when the original image is an 8-bit color depth image. Also,
The sharpening intensity output from the lookup table 41 is
It is represented by a value within a range from 0 to a predetermined maximum value, and the predetermined maximum value is set to a practical value in consideration of the influence of the sharpening on the image.

A suitable correspondence relationship between the edge strength and the sharpening strength is not uniquely determined and will differ depending on the image to be sharpened. As the correspondence relationship between the edge strength and the sharpening strength, for example, the relationships as shown in FIGS. 6A to 6C can be considered.

FIGS. 6 (a) to 6 (c) are drawings showing an example of the correspondence between the edge strength and the sharpening strength in the look-up table 41, and are graphs showing this correspondence. 6A to 6C, the horizontal axis represents the edge strength as an input to the lookup table 41, and the vertical axis represents the sharpening strength as an output from the lookup table 41. There is.

FIG. 6A shows an example in which the sharpening strength is set in proportion to the edge strength. This example is suitable, for example, when the original image is an out-of-focus image. In this case, the background and other parts of the original image are originally blurred, and the sharpening strength is set low for parts with low edge strength (low-frequency parts) so that the object or other part of the original image should be in focus. The sharpening strength can be set to be large for a portion (high-frequency portion) where the edge strength is relatively large. As a result, a natural sharpened image can be obtained by emphasizing the edge of the portion that should originally be in focus as compared with other portions.

FIG. 6B shows that the sharpening strength is set to almost 0 in a portion where the edge strength is relatively small and almost no sharpening is performed, and when the edge strength increases to some extent, a smooth curve is formed according to the increase of the edge strength. Along with this, an example is shown in which the sharpening strength is increased. This example is suitable, for example, when the original image is an image of a person's face taken close-up. In this case, it is the skin portion of the person in the original image, and the sharpening is not applied to the portion having a small edge strength, and the portion such as the hair of the person in the original image having a large edge strength is provided. Can be sharpened appropriately. As a result, it is possible to suppress the image having rough skin due to the granular pattern in the skin portion while sharpening as a whole.

In FIG. 6 (c), the sharpening strength is increased in a portion where the edge strength has an intermediate value, and the sharpening strength is decreased along a smooth curve as the edge strength approaches the minimum value and the maximum value. An example of setting to do so is shown. This example is suitable, for example, in the case where an image in which the original image is in focus is further sharpened. In this case, there is no need to sharpen the part that has focus and the edge strength is large, so do not sharpen too much and selectively sharpen the part with intermediate edge strength. You can This makes it possible to obtain an image having a deeper depth of focus than the original image.

The look-up table 41 may correspond the edge strength and the sharpening strength in a one-to-one correspondence, but the range of the value of the edge strength is divided into a plurality of areas, and each area is divided into a plurality of areas. One sharpening strength may be associated. In this case, graphs showing the correspondence between the edge strength and the sharpening strength are shown in FIGS. 7 (a) to 7 (c).
It will change gradually as shown in. Note that FIG.
6A to FIG. 6 are respectively shown in FIG.
It corresponds to (c). By doing so, the amount of data to be stored as the lookup table 41 can be reduced.

Further, the storage device 22 may store a function such as equation 5 which defines the correspondence relationship between the edge strength e and the sharpening strength w instead of the lookup table 41. w = F (e) (Equation 5) A linear function can be used to define the correspondence shown in FIG. 6 (a), and the correspondence shown in FIG. 6 (c) can be defined. A quadratic function can be used. Sharpening means 3
For 3, the sharpening strength w corresponding to the edge strength e may be calculated based on this function.

As described above, the storage device 22 may store the information defining the correspondence between the edge strength and the sharpening strength determined for the edge strength. Hereinafter, such information will be referred to as definition information. Although the lookup table 41 and the function are described as the definition information here, the definition information may be information other than these.

This definition information may be stored in the storage device 22 at the manufacturing stage of the image processing apparatus 2, for example. It is preferable that the definition information can be changed. This is because the definition information suitable for the image is different depending on the image to be sharpened as described above. That is, in the image processing device 2 that processes images of various forms, by switching the definition information according to the original image to be processed and the desired processing result,
This is because an image closer to the desired image can be obtained.

Therefore, it is preferable that the central processing unit 21 is provided with the definition information changing means 34. The definition information changing means 34 changes the contents of the definition information stored in the storage device 22 based on the input information input by the input device 26. The input device 26 is information (input information) for changing the content of the definition information stored in the storage device 22.
Is to be entered.

Various methods can be considered as a method of changing the definition information. When a lookup table is used as the definition information, the following method can be considered. For example, a value for replacing each value of the edge strength and the sharpening strength set in the look-up table may be input as input information, and each of the above values may be directly rewritten. Further, by storing a plurality of types of lookup tables in the storage device 22 and inputting information specifying the lookup table as input information, the lookup tables are actually used from among the stored lookup tables. A look-up table may be selected.

Also, when a function is used as the definition information, the function may be directly rewritten in the same manner as described above, and the function to be actually used may be selected from a plurality of stored functions. May be.

More preferably, it is conceivable that the central processing unit 21 is provided with the display control means 35 to change the definition information as follows.

FIG. 8 is a drawing showing an example of the display contents displayed on the display screen 51 of the display device 27 of FIG. On the display screen 51, a graph 52 showing the correspondence between the edge strength and the sharpening strength based on the definition information stored in the storage device 22 (as shown in FIGS. 6A to 6C). Graph) is displayed. In graph 52,
The sharpening strength curve 53 shows the correspondence between the edge strength and the sharpening strength. The display is controlled by the display control means 35.

That is, the display device 27 displays the sharpening intensity curve 53, and the display control means 35 displays the sharpening intensity curve 53 on the basis of the definition information stored in the storage device 22. To be displayed.

The user of the image processing apparatus 2 uses the mouse or the like as the input device 26 while looking at the graph 52,
By moving one point of the sharpening strength curve 53 with the pointer 54, the sharpening strength curve 53 is transformed into a desired shape. In FIG. 8, the sharpening strength curve 53 before deformation is shown by a dashed line, and the sharpening strength curve 53 after deformation is shown by a solid line.

When the user modifies the sharpening strength curve 53 as described above, the definition information changing means 34
The content of the definition information is changed so as to match the sharpening strength curve 53 transformed by the user.

As described above, if the content of the definition information is changed by changing the shape of the sharpening strength curve 53, the user can easily understand the sharpening degree visually, and the image processing is performed. The operability of the device 2 can be improved.

It is preferable that the display control means 35 further displays on the display screen 51 an image 55 based on the image data sharpened based on the sharpening intensity curve 53. As a result, the user can operate while confirming how the deformation of the sharpening strength curve 53 affects the image 55, and thus the operability of the image processing apparatus 2 can be further improved.

As described above, the image processing apparatus 2 converts the pixel values of the original image in order to sharpen the digital image, and uses the edge strength calculating means 32, the storage device 22, and the sharpening means 33. I have it. Here, the edge strength calculation means 32 calculates the edge strength of the target pixel to be processed based on the pixel value of the original image. The storage device 22 stores definition information that defines the correspondence between the edge strength and the sharpening strength that is predetermined for the edge strength. The sharpening means 33 obtains the sharpening strength corresponding to the edge strength calculated by the edge strength calculating means 32 for sharpening based on the definition information, and determines the degree of sharpening based on the obtained sharpening strength. Adjust to transform the pixel value of the target pixel.

Since the sharpening means 33 adjusts the degree of sharpening in this way, it is not limited to simply switching whether or not to perform the sharpening process, but also depending on the sharpening strength determined based on the edge strength. It enables stepwise adjustment.

The degree of sharpening can be adjusted, for example, by multiplying each element of the sharpening filter acting on the target pixel by a coefficient w as the sharpening strength (see FIG. 5A). In other words, it can be realized by subtracting the product of the second derivative of the pixel value of the target pixel and the coefficient w from the pixel value of the target pixel (see equation 4). However, the method of adjusting the degree of sharpening may be other than this, and the degree of influence of the sharpening process on the image (the degree of edge enhancement) may be adjusted.

As a result, by appropriately setting the definition information, it is possible to realize more appropriate sharpening processing according to what kind of image is desired as a processing result for the original image to be processed. become.

Further, the image processing apparatus 2 receives the contents of the definition information based on the input information input by the input device 26 and the input information for changing the contents of the definition information stored in the storage device 22. It is preferable to further include definition information changing means for changing. This makes it possible for the user to make the content of the sharpening process more appropriate depending on what kind of image is desired as the processing result for the original image to be processed (the scene of the original image, the user's preference, etc.). The processing can be executed by appropriately changing it.

Further, the image processing device 2 is based on the definition information stored in the storage device 22, and the sharpening intensity curve showing the correspondence between the edge intensity and the sharpening intensity predetermined for the edge intensity. It is preferable to further include a display control unit 35 for displaying on the display device 27. This allows the user to visually recognize and change the correspondence between the edge strength and the sharpening strength,
It enables easier and more flexible changes.

4. Note that each of the control unit 31, the edge strength calculation unit 32, the sharpening unit 33, the definition information changing unit 34, and the display control unit 35 described above is a program (image processing) executed by the central processing unit 21. Program).

The image processing program is stored in a computer-readable recording medium such as the storage device 22. The above image processing program is
In addition to the storage device 22, for example, it may be supplied by a program medium read by a drive device (not shown) provided in the image processing device 2 as an external storage device.

The program medium is a recording medium which can be separated from the image processing apparatus 2, and is a tape system such as a magnetic tape or a cassette tape, a magnetic disk such as a floppy disk or a hard disk, or a CD-ROM / M.
Disk systems for optical disks such as O / MD / DVD, card systems such as IC cards (including memory cards) / optical cards,
Alternatively, it may be a medium that fixedly carries a program, including a semiconductor memory such as a mask ROM, EPROM, EEPROM, and flash ROM.

Further, the image processing program may be downloaded to the image processing apparatus 2 through a communication network including the Internet. When the image processing program is downloaded from the communication network, the download program may be stored in the storage device 22 or the like in advance, or may be installed from another recording medium. In addition to the programs, the contents stored in the program media are
Data may be included.

As described above, the image processing program of this embodiment causes the computer (main body 20 of the image processing apparatus 2) to set the pixel value of the original image in order to convert the pixel value of the original image to sharpen the digital image. An edge strength calculation unit 32 that calculates the edge strength of the target pixel to be processed based on the above, and stores the definition information that defines the correspondence between the edge strength and the sharpening strength that is predetermined for the edge strength. The sharpening strength corresponding to the edge strength calculated by the edge strength calculating means 32 for the sharpening is calculated based on the definition information stored in the storage device 22, and based on the sharpening strength obtained. Sharpening means 3 for adjusting the degree of sharpening and converting the pixel value of the target pixel
Function as 3.

Further, the image processing program of the present embodiment is defined based on the input information input by the input device 26 and the input information for changing the content of the definition information stored in the storage device 22. The computer may further function as the definition information changing unit 34 that changes the content of information.

Further, the image processing program of the present embodiment, based on the definition information stored in the storage device 22, shows the sharpness indicating the correspondence between the edge strength and the sharpening strength predetermined for the edge strength. Displaying the intensity curve 2
The computer may be further caused to function as the display control means 35 for displaying on 7. At this time, when the definition information changing means 34 receives as the input information the information for instructing the modification of the sharpening strength curve, the definition information changing means 34 changes the content of the definition information so as to match the modified sharpening strength curve according to the input information. change.

[0100]

As described above, in the image processing apparatus according to the first aspect of the present invention, the sharpening means stores the sharpening strength corresponding to the edge strength calculated by the edge strength calculating means in the storage means. Based on the definition information, the degree of sharpening is adjusted based on the obtained sharpening intensity, and the pixel value of the target pixel is converted.

Therefore, by appropriately setting the definition information, the correspondence between the edge strength and the sharpening strength can be flexibly set. As a result, the processing is not limited to simple processing such as sharpening a pixel having a relatively high edge strength, and the degree of sharpening is gradually increased according to the magnitude of the edge strength, or pixels having an edge strength up to a certain size are processed. Does not perform sharpening, and if the edge strength becomes higher than that, increase the sharpening degree according to the increase of the edge strength, or suppress the sharpening degree on the contrary for pixels with high edge strength. Such sharpening processing can be realized.

As a result, by appropriately setting the definition information, it is possible to perform a more appropriate sharpening process on the original image to be processed depending on what kind of image is desired as the processing result. It becomes possible to provide.

An image processing program according to a sixth aspect of the present invention causes a computer to function as an edge strength calculation means, a storage means, and a sharpening means.

The image processing apparatus according to claim 2 of the present invention is
It is preferable that the image processing apparatus according to claim 1 further comprises definition information changing means for changing the content of the definition information based on the input information for changing the content of the definition information stored in the storage means.

In the above arrangement, the user or the like appropriately changes the content of the sharpening processing to a more appropriate one depending on what kind of image is desired as the processing result for the original image to be processed. Can be executed.

Similarly, in the image processing program according to claim 7 of the present invention, in the image processing program according to claim 6, it is preferable that the computer further functions as definition information changing means.

The image processing apparatus according to claim 3 of the present invention is
The image processing apparatus according to claim 2, further comprising display control means for displaying the sharpening strength curve on the display means based on the definition information, and the definition information changing means instructs deformation of the sharpening strength curve as input information. When the information is input, it is preferable to change the content of the definition information so as to match the deformed sharpening strength curve.

With the above arrangement, the user or the like can change the correspondence between the edge strength and the sharpening strength while visually recognizing it. As a result, it becomes possible to provide an image processing apparatus that can more easily and freely change the correspondence between the edge strength and the sharpening strength.

Similarly, in the image processing program according to claim 8 of the present invention, in the image processing program according to claim 7, the computer further functions as display control means, and the definition information changing means sharpens as input information. When the information instructing the deformation of the intensity curve is input, it is preferable to change the content of the definition information so as to match the deformed sharpening intensity curve.

An image processing apparatus according to claim 4 of the present invention is
In the image processing apparatus according to any one of claims 1 to 3, it is preferable that the definition information is a look-up table that associates the edge strength with a sharpening strength that is predetermined with respect to the edge strength.

With the above arrangement, the sharpening means can obtain the sharpening strength by a simple process.
Processing in a short time becomes possible.

Similarly, in the image processing program according to claim 9 of the present invention, in the image processing program according to any one of claims 6 to 8, the definition information includes the edge strength and the edge strength in advance. It is preferably a look-up table that correlates with a defined sharpening strength.

An image processing apparatus according to claim 5 of the present invention is
The image processing apparatus according to any one of claims 1 to 4, wherein the edge strength calculation means has a pixel value of the target pixel and an average pixel of a plurality of pixels having a predetermined positional relationship with respect to the target pixel. It is preferable to calculate the difference from the value as the edge strength.

With the above arrangement, the edge strength calculation means can calculate the edge strength by a simple process as compared with the process using Fourier transform, for example, and the process can be performed in a short time. Become.

Similarly, in the image processing program according to claim 10 of the present invention, the edge strength calculating means in the image processing program according to any one of claims 6 to 9 is:
It is preferable to calculate the difference between the pixel value of the target pixel and the average pixel value of a plurality of pixels having a predetermined positional relationship with respect to the target pixel as the edge strength.

A recording medium recording the image processing program according to claim 11 of the present invention records the image processing program according to any one of claims 6 to 10.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a schematic configuration of an image output system according to an embodiment of the present invention.

FIG. 3A is a drawing showing an example of a sharpening filter, FIG. 3B is a drawing showing another example of a sharpening filter, and FIG. 3C is a 3 × 3 pixel sharpening filter in general. It is the drawing which represented.

FIG. 4 is a flowchart showing a flow of sharpening processing in the image processing apparatus of FIG.

5A is a drawing showing a modified sharpening filter, and FIG. 5B is a drawing showing a filter for converting a pixel value of a target pixel based on the sharpening filter of FIG. .

6A to 6C are graphs showing an example of a correspondence relationship between edge strength and sharpening strength.

FIGS. 7A to 7C are graphs showing other examples of the correspondence between the edge strength and the sharpening strength.

8 is a diagram showing an example of display contents displayed on a display screen of a display device included in the image processing apparatus of FIG.

[Explanation of symbols]

1 film scanner 2 Image processing device 3 Photo printing equipment 20 body 21 Central processing unit 22 Storage device (storage means) 23 Interface 24 memory 25 data bus 26 Input device (input means) 27 Display device (display means) 31 Control means 32 Edge Strength Calculation Means 33 Sharpening Means 34 Definition information changing means 35 Display control means 41 Look Up Table 42 Sharpening filter 51 Display screen 52 Graph 53 Sharpening strength curve 54 pointer

Continued front page    F-term (reference) 5B057 BA02 CA01 CA02 CA08 CA12                       CA16 CB01 CB02 CB08 CB12                       CB16 CC01 CE03 CH07 CH08                 5C077 LL08 LL09 MP01 MP07 MP08                       PP03 PP46 PP47 PP68 PQ12                       PQ23

Claims (11)

[Claims] 1. An image processing apparatus for converting a pixel value of an original image for sharpening a digital image, edge strength calculating means for calculating an edge strength of a target pixel to be processed based on a pixel value of the original image. And a storage unit that stores definition information that defines a correspondence relationship between an edge strength and a sharpening strength that is predetermined with respect to the edge strength, and a sharpening that converts the pixel value of the target pixel for sharpening. The sharpening means obtains a sharpening strength corresponding to the edge strength calculated by the edge strength calculating means based on the definition information stored in the storage means, and based on the obtained sharpening strength. The image processing apparatus is characterized in that the pixel value of the target pixel is converted by adjusting the degree of sharpening. 2. The image processing apparatus according to claim 1, wherein the content of the definition information stored in the storage means, which is input information input by an input means for receiving an input from a user, is changed. The image processing apparatus, further comprising definition information changing means for changing the contents of the definition information stored in the storage means based on the input information. 3. The image processing apparatus according to claim 2, wherein the correspondence relationship between the edge strength and a sharpening strength predetermined for the edge strength is based on the definition information stored in the storage means. The definition information changing means further comprises display control means for displaying a sharpening strength curve to be displayed on the display means, and when the information for instructing the deformation of the sharpening strength curve is inputted as the input information, the definition information changing means An image processing apparatus, characterized in that the content of the definition information stored in the storage means is changed so as to match the sharpening intensity curve deformed accordingly. 4. The image processing apparatus according to claim 1, wherein the definition information is a look-up table that associates edge strength with a sharpening strength predetermined for the edge strength. An image processing device characterized by: 5. The image processing apparatus according to claim 1, wherein the edge strength calculation means has a pixel value of the target pixel and a predetermined positional relationship with respect to the target pixel. An image processing apparatus, which calculates a difference from an average pixel value of a plurality of pixels in 1 as edge strength. 6. A computer for converting a pixel value of an original image to sharpen a digital image, an edge strength calculating means for calculating an edge strength of a target pixel to be processed based on a pixel value of the original image, and an edge. A storage unit that stores definition information that defines a correspondence relationship between intensity and a sharpening intensity that is predetermined for the edge intensity, and corresponds to the edge intensity calculated by the edge intensity calculating unit for sharpening. Function as a sharpening means for converting the pixel value of the target pixel by adjusting the sharpening degree on the basis of the definition information stored in the storage means and adjusting the sharpening degree based on the obtained sharpening strength. An image processing program characterized by: 7. The image processing program according to claim 6, for changing the contents of the definition information stored in the storage unit, which is input information input by an input unit that receives an input from a user. An image processing program that causes a computer to further function as a definition information changing unit that changes the contents of the definition information stored in the storage unit based on the input information. 8. The image processing program according to claim 7, wherein a correspondence relationship between an edge strength and a sharpening strength predetermined for the edge strength is created based on the definition information stored in the storage means. When the computer further functions as display control means for displaying the sharpening strength curve to be displayed on the display means, and the definition information changing means receives information for instructing deformation of the sharpening strength curve as the input information, An image processing program, characterized in that the contents of the definition information stored in the storage means are changed so as to match the sharpening intensity curve transformed according to the input information. 9. The image processing program according to claim 6, wherein the definition information is a look-up table that associates an edge strength with a sharpening strength predetermined for the edge strength. An image processing program characterized by: 10. The image processing program according to claim 6, wherein the edge strength calculation means has a pixel value of the target pixel and a predetermined positional relationship with respect to the target pixel. An image processing program, wherein a difference from an average pixel value of a plurality of pixels in the above is calculated as an edge strength. 11. A recording medium on which the image processing program according to any one of claims 6 to 10 is recorded.