JP2012175368A - Image sharpening device, image output apparatus, and image sharpening program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image sharpening device, an image output apparatus, and an image sharpening program, capable of forming an image that has optimal sharpness for printing.SOLUTION: An image sharpening device, an image output apparatus, and an image sharpening program of the present invention, includes: an image input unit (12) that obtains an image to be printed; a blur degree determination unit (14,24) that determines blur degree of the image obtained by the image input unit (12); an output size obtaining unit (18) that obtains the output size at the time of printing of the image; an unsharpness calculation unit (20) that calculates unsharpness from sharpness that is optimal for printing in the output size obtained by the output size acquisition unit (18) on the basis of blur degree determined by the blur degree determination unit (14,24); and a sharpening unit (22) that obtains the sharpness image that is optimal for printing by performing sharpening to the image on the basis of the unsharpness obtained by the unsharpness calculation unit (20).

Description

  The present invention relates to an image sharpening device, an image output device, and an image sharpening program.

  In the era of silver halide cameras, printing on the order of L size was common, but in recent years, with the widespread use of digital cameras and printers, printing of large photographs such as A4 size and A3 size can be done easily. became. However, when printing at a large size, blurring that cannot be recognized at the time of printing at a small size becomes noticeable. For this reason, a method for sharpening according to the print size has been proposed (see, for example, Patent Document 1).

Special table 2004-527043 gazette

  The conventional method described above performs sharpening according to the print size regardless of the sharpness of the original image. Therefore, sharpening is also performed on an image having sufficient sharpness. Sharpening a sufficiently sharp image not only wastes wasted time and power, but may also cause image degradation such as unnatural edge enhancement and increased noise due to unnecessary sharpening.

  An object of the present invention is to provide an image sharpening device, an image output device, and an image sharpening program capable of creating an image having the optimum sharpness for printing.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this.

According to the first aspect of the present invention, an image input unit (12) that acquires an image to be printed and a blur degree determination unit (14, 24) that determines the degree of blur of the image acquired by the image input unit (12). ), An output size acquisition unit (18) for acquiring an output size when printing the image, and the output size acquisition unit based on the degree of blur determined by the blur degree determination unit (14, 24) Calculated by the insufficient definition calculation unit (20) that calculates the insufficient definition that is insufficient from the definition suitable for printing at the output size acquired in (18), and the insufficient definition calculation unit (20). And a sharpening unit (22) for sharpening the image on the basis of the insufficient sharpness and obtaining a sharpened image suitable for printing. (10) , 200).
The invention described in claim 2 is the image sharpening device (10, 200) according to claim 1, wherein the image size acquisition unit (16) acquires the image size of the image acquired by the image input unit. The insufficient definition calculation unit (20) corrects the insufficient definition according to the image size acquired by the image size acquisition unit (16) when calculating the insufficient definition. The image sharpening device (10, 200) characterized by the above.
The invention described in claim 3 is an image output device comprising the image sharpening device (10, 200) described in claim 1 or 2 and an output unit for outputting the image.
According to a fourth aspect of the present invention, the computer causes the image input means for acquiring the image to be printed, the blur degree determination means for determining the degree of blur of the image acquired by the image input means, and the image to be printed. Output size acquisition means for acquiring the output size at the time and lack of clarity suitable for printing with the output size acquired by the output size acquisition means based on the degree of blur determined by the blur degree determination means A deficient sharpness calculating means for calculating the deficient sharpness, and a sharpened image suitable for printing by sharpening the image based on the deficient sharpness calculated by the deficient sharpness calculating means. An image sharpening program characterized in that the image sharpening program functions as a sharpening means for acquiring the image. The invention according to claim 5 is the image sharpening program according to claim 4. The computer further functions as an image size acquisition unit that acquires an image size of an image, and the image size acquisition unit is configured according to the image size acquired by the image input unit when calculating the insufficient sharpness. An image sharpening program characterized by correcting the insufficient sharpness.
Note that the configuration described with reference numerals may be modified as appropriate, and at least a part of the configuration may be replaced with another component.

  According to the present invention, it is possible to provide an image sharpening device, an image output device, and an image sharpening program capable of creating an image having a sharpness optimum for printing.

It is a block diagram which shows the structure of an image sharpening apparatus. It is a block diagram which shows the structure of the blurring degree determination part of 1st Embodiment. 3 shows an example of a blur filter used in the blur addition processing unit of FIG. 2. It is explanatory drawing of the blur determination principle in a blurring degree determination part. It is a block diagram which shows the structure of the blurring degree determination part of 2nd Embodiment.

(First embodiment)
Hereinafter, an image sharpening apparatus 10 according to a first embodiment of the present invention will be described with reference to the drawings and the like. FIG. 1 is a block diagram showing the configuration of the image sharpening device 10. The image sharpening device 10 of this embodiment is used as a pre-process for printing by a printer.

  The image sharpening device 10 includes, for example, an image input unit 12 to which an original image taken with a digital camera or the like is input. In addition, the image sharpening device 10 determines the degree of blur of the original image input from the image input unit 12 from a blur degree determination unit 14 (to be described later) and the original image input from the image input unit 12. An image size acquisition unit 16 that acquires the image size of the original image and an output size acquisition unit 18 that acquires the output size of the image at the time of printing are provided.

  The image sharpening device 10 may further include an output size selection unit. In this case, the output size acquisition unit 18 may acquire the output size by reading the output size selected by the output size selection unit. . When the output size is set by an external device, the output size may be acquired by reading the output size set by the external device.

  Furthermore, the image sharpening device 10 is insufficient with an insufficient sharpness calculation unit 20 that determines a lacking sharpness with respect to an optimal sharpness when printing an image acquired by the image input unit 12. And a sharpening unit 22 that compensates for the sharpness of the image and makes the image optimal for printing.

  Next, the configuration of the blur degree determination unit 14 will be described. FIG. 2 is a block diagram illustrating a configuration of the blur degree determination unit 14. The blur degree determination unit 14 adds blur to the original image Vo acquired by the image input unit 12 to create the blur added image Vb, the contrast evaluation value Sb of the blur added image Vb, the original The contrast evaluation value calculation unit 144 that calculates the contrast evaluation value So of the image Vo, the contrast evaluation value Sb of the blurred image Vb, and the contrast evaluation value So of the original image Vo are compared, and the contrast comparison value Sb / So is obtained. A contrast comparison unit 146 to be obtained and a blur evaluation unit 148 that evaluates the degree of blur from the contrast comparison value Sb / So are provided.

The operation of the image sharpening device 10 will be described.
In FIG. 1, when the original image Vo to be printed is input from the image input unit 12, the degree of blur is determined by the blur degree determination unit 14 illustrated in FIG. 2.
The processing in the blur degree determination unit 14 is performed as follows.
First, the blur addition processing unit 142 adds blur to the original image Vo.
As the blur addition process, for example, a method using a known Gaussian filter is used. FIG. 3 shows an example of a blur filter used in the blur addition processing unit 142 of FIG. Although a Gaussian filter having a matrix size of 5 × 5 and a standard deviation of 1 is shown here, other Gaussian filters, other averaging filters, and the like can be used in principle. A convolution-added image is generated by convolving this filter with the original image.

  Next, the contrast evaluation value calculation unit 144 calculates a contrast evaluation value Sb for the image Vb to which blur is added by the blur addition processing unit 142.

The contrast evaluation value is obtained as follows.
If the luminance component of each pixel constituting the two-dimensional image spreading on the xy plane is V (m, n) (m: pixel number in the x direction, n: pixel number in the y direction), the contour in the x direction of this image is The contrast evaluation value S considered is
S = Σ (V (m, n + 1) −V (m, n)) ² (1)
It becomes.

Further, a contrast evaluation value S in consideration of the y-direction contour of the image,
S = Σ (V (m + 1, n) −V (m, n)) ² (2)
And the contrast evaluation value S may be used.

Furthermore, considering the contours in both the x and y directions of the image, the contrast evaluation value S is
S = Σ (V (m, n + 1) −V (m, n)) ² + Σ (V (m + 1, n) −V (m, n)) ² (3)
By using the contrast evaluation value S, the contrast of the entire image can be evaluated more accurately. In the equations (1) to (3), Σ represents the sum of pixel numbers m and n.

  On the other hand, the contrast evaluation value calculation unit 144 also calculates the contrast evaluation value So of the image Vo to which the blur supplied directly from the image input unit 12 is not added.

Then, the contrast comparison unit 146 calculates a contrast ratio Sb / So between the contrast evaluation value Sb of the image Vb to which blur is added and the contrast evaluation value So of the image Vo to which no blur is added.
Next, the blur evaluation unit 148 evaluates the degree B of blur based on the contrast ratio Sb / So calculated by the contrast comparison unit 146.

  FIG. 4 is an explanatory diagram of the blur determination principle in the blur degree determination unit 14. The horizontal axis indicates the amount of blur indicating the degree of blur of the image, and the vertical axis indicates the contrast evaluation value calculated by the contrast evaluation value calculation unit 144.

If the input image is a sharp image that is in focus, the contrast of the blurred image is greatly reduced. Therefore, the ratio Sb1 / So1 between the contrast evaluation values of the original image Vo and the blurred additional image Vb is a small value.
On the other hand, since the original blurred image has a small decrease in contrast even when blur is added, the ratio Sb2 / So2 between the contrast evaluation values of the original image Vo and the blur added image Vb is a large value.
Therefore, it is possible to determine the degree of blur of the image based on the ratio Sb / So of the contrast evaluation values of the original image Vo and the blurred additional image Vb. Let B be the degree of blur obtained from this determination result.

  Returning to FIG. 1, the image sharpening device 10 acquires the image size of the original image input by the image size acquisition unit 16. Further, the output size acquisition unit 18 acquires the set output size.

The insufficient sharpness calculation unit 20 obtains an allowable degree of blurring that can be allowed with the selected output size.
The permissible degree of blur may be obtained by referring to an allowable amount in advance and holding data in a table or the like.
Let this allowable blurring degree be P (1, 2, 3, 4, etc. depending on the level). B (blurring degree) −P (allowable blurring degree) is the insufficient sharpness L.

Here, the degree of blurring of the image is generally a value corresponding to the degree of edge crushing. Here, the blur degree determination unit 14 has, for example, 10 pixels when there are 10 pixels of gray pixels having an intermediate luminance value when there is an edge of a black-and-white boundary and the edge is crushed due to the blur and changes from white to black. It is defined as blurring.
However, even with the same 10-pixel blur, an image of 6M pixels and an image of 24M pixels appear to be differently blurred at the same print size.
Therefore, the insufficient sharpness calculation unit 20 corrects the degree of sharpening that is insufficient depending on the image size.

Specifically, the deficiency definition calculation unit 20 takes into account the blur amount determined by the blur degree determination unit 14 and the image size, for example, when the image size is S. L = α * (BP /S^0.5)
Etc. are changed.

  The sharpening unit 22 changes the degree of sharpening according to the magnitude of the insufficient sharpness L. Specifically, in the case of USM (unsharp mask), for example, the sharpening unit 22 changes the degree of sharpening by changing the standard deviation and intensity. When L <0, the image is sufficiently sharp with respect to its output size, so there is no need for sharpening.

  As described above, according to the first embodiment, sharpening is performed according to the output size of printing based on the sharpness of the original image. Therefore, an image having sufficient sharpness is not sharpened, wasted time and power is wasted, and image degradation such as unnatural edge enhancement and increased noise due to unnecessary sharpening occurs. There is nothing.

(Second Embodiment)
Next, the image sharpening device 200 of the second embodiment will be described. The image sharpening device 10 according to the first embodiment shown in FIG. 1 and the image sharpening device 200 according to the second embodiment have different blur degree determination units, but the other components are the same, and the description of the same parts Is omitted.

  FIG. 5 shows a configuration of the blur degree determination unit 24 of the second embodiment. The blur degree determination unit 24 of the image sharpening device 200 according to the second embodiment includes a first blur addition processing unit 241 that performs a blur addition process with a different blur addition degree on the image Vo input from the image input unit 12. A second blur addition processing unit 242, a contrast evaluation value calculation unit 244, a contrast comparison unit 246, and a blur evaluation unit 248 are provided.

The degree of blur addition between the first blur addition processing unit 241 and the second blur addition processing unit 242 is different. The first blur addition processing unit 241 adds blur to the original image to create the first blur addition image Vb1, and the second blur addition processing unit 242 adds blur to the original image to create the second blur addition image Vb2. To do. It is assumed that the amount of blur added by the second blur addition processing unit 242 is larger than the amount of blur used by the first blur addition processing unit 241.
For example, the blur filter used in the first blur addition processing unit 241 has a matrix size of 5 × 5 and standard deviation 1, and the blur filter used in the second blur addition processing unit 242 has a matrix size of 15 × 15 and standard deviation 3.

  Alternatively, the blur filter used in the second blur addition processing unit 242 may be the same as the first filter, and may be repeated a plurality of times. The contrast values of the first blur added image Vb1 and the second blur added image Vb2 created in this way are S1 and S2. The degree of blurring of the image can be determined by the ratio of the contrast values S1 and S2 and S2 / S1. Since the amount of change in contrast value due to blurring is easily affected by image noise, this method can reduce the effect of noise.

As mentioned above, according to 2nd Embodiment, in addition to the effect of 1st Embodiment, it has the following effects.
The image Vo input from the image input unit 12 is subjected to different blur addition processing in the first blur addition processing unit 241 and the second blur addition processing unit 242, and then each of the blurs added in the contrast comparison unit 246 is performed. The contrast ratio is calculated from the images Vb1 and Vb2, and the presence or absence of blur is automatically determined. Therefore, it is possible to reduce the influence of information (such as noise) other than the edge portion of the image, and more accurately determine whether or not the image is blurred.

(Third embodiment)
In the above embodiment, the image sharpening devices 10 and 24 have been described. However, the present invention is not limited to this and may be an image sharpening program. The image sharpening program may be recorded on a recording medium such as a CD.
In this case, when the image sharpening program is installed in the computer, the computer is caused to input, for example, an image input means for inputting an original image taken by a digital camera or the like, and a blur of the original image input by the image input means. Degree determination, blur degree determination means, image size acquisition means for acquiring the image size of the original image from the original image input by the image input means, and output size acquisition for acquiring the output size of the image at the time of printing It functions as a means. And these means operate | move similarly to each part of 1st Embodiment. The image determination program may be a program that performs the operation of the image determination apparatus 110 of the second embodiment on a computer.

(Deformation)
The present invention is not limited to the above-described embodiment, and various modifications and changes as described below are possible, and these are also within the scope of the present invention.
Although the image sharpening device and the image sharpening program have been described in the present embodiment, the present invention is not limited to this, and the image sharpening device and the image sharpening program are installed in an image output device such as a printer having an image output unit. May be.

  In addition, although embodiment and a deformation | transformation form can also be used in combination as appropriate, detailed description is abbreviate | omitted. Further, the present invention is not limited to the embodiment described above.

  10, 200: Image sharpening device, 12: Image input unit, 14, 24: Blur degree determination unit, 16: Image size acquisition unit, 18: Output size acquisition unit, 20: Insufficient sharpness calculation unit, 22: Sharpening Part

Claims (5)

An image input unit for acquiring an image to be printed;
A blur degree determination unit that determines the degree of blur of the image acquired by the image input unit;
An output size acquisition unit for acquiring an output size when printing the image;
Based on the degree of blur determined by the degree-of-blurring determination unit, the insufficient definition calculation that calculates the insufficient definition that is insufficient from the definition suitable for printing at the output size acquired by the output size acquisition unit. And
A sharpening unit that sharpens the image based on the insufficient sharpness calculated by the insufficient sharpness calculation unit, and acquires a sharpened image suitable for printing;
An image sharpening device comprising: The image sharpening device according to claim 1,
An image size acquisition unit that acquires an image size of the image acquired by the image input unit;
The insufficient definition calculation unit corrects the insufficient definition according to the image size acquired by the image size acquisition unit when calculating the insufficient definition;
An image sharpening device. The image sharpening device according to claim 1 or 2,
An output unit for outputting the image;
An image output apparatus characterized by the above. Computer
An image input means for acquiring an image to be printed;
A blur degree determination means for determining a blur degree of an image acquired by the image input means;
An output size acquisition means for acquiring an output size when printing the image;
Based on the degree of blur determined by the degree-of-blurring determination unit, the insufficient definition calculation that calculates the lack of definition that is insufficient from the definition suitable for printing at the output size acquired by the output size acquisition unit. Means,
Performing sharpening on the image based on the insufficient sharpness calculated by the insufficient sharpness calculating means, and functioning as a sharpening means for obtaining a sharpened image suitable for printing,
An image sharpening program characterized by The image sharpening program according to claim 4,
Computer
Function as an image size acquisition means for acquiring the image size of the image,
The image size acquisition unit corrects the insufficient definition according to the image size acquired by the image input unit when calculating the insufficient definition;
An image sharpening program characterized by

Images