JPH11266469A - Image evaluation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image evaluation device that evaluates an image based on changes in a high frequency component of the image. SOLUTION: The proposed image evaluation device is provided with transform means 12, 22 that apply Fourier transform to each video signal of a reference image and an evaluation object image in the same area, calculation means 14, 24 that calculate each power spectrum for a prescribed frequency area of the reference image and the evaluation object image after the Fourier transform by the transform means 12, 22 and a comparison means 3 that compares the power spectra calculated by the calculation means 14, 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for evaluating the degree of deterioration of an image, and more particularly to an image evaluation apparatus for calculating the degree of deterioration from a change in a high frequency component of an image.

[0002]

2. Description of the Related Art Conventionally, as a simple method for evaluating deterioration of a television image or the like, for example, Japanese Patent Application No. 1-2988 / 1990.
There is a method disclosed in Japanese Patent Publication No. 90. In this method, a difference between a noise amount of a predetermined area in an original image and a deteriorated image is measured to evaluate the deterioration.

[0003]

According to the above-described method for measuring the difference in the amount of noise in an image, if the image is deteriorated and a change in brightness accompanies the image, the change is directly reflected in the degree of deterioration. This causes a problem that deterioration cannot be accurately evaluated. An object of the present invention is to provide an image evaluation device that evaluates an image based on a change in a high-frequency component of the image.

[0004]

In order to solve the above problems and achieve the object, an image evaluation apparatus according to the present invention is configured as follows. An image evaluation apparatus according to the present invention includes a conversion unit that performs Fourier transform on each video signal in the same region of a reference image and an evaluation target image, and a predetermined frequency region of the reference image and the evaluation target image after Fourier transform by the conversion unit. Calculating means for calculating each power spectrum of
Comparing means for comparing the power spectra calculated by the calculating means.

[0005] As a result of taking the above measures, the following effects occur. According to the image evaluation device of the present invention, a predetermined frequency component is extracted by Fourier transform for the same target region in the reference image and the evaluation target image, and then the power spectrum of the high-frequency component in the extracted frequency component is extracted and integrated. . Then, from the changes in the power spectra of the reference image and the evaluation target image, it is possible to quantitatively determine the degree of deterioration or improvement of the image.

[0006]

FIG. 1 is a block diagram showing a configuration of an image evaluation apparatus according to an embodiment of the present invention. In FIG. 1, an original image processing unit 1 and a deteriorated image processing unit 2 include image memories 11 and 21, Fourier transform units 12 and 22, respectively.
The high frequency region designating sections 13 and 23 and the power spectrum integrating sections 14 and 24 are connected in this order. The power spectrum integrating units 14 and 24 are connected to the deterioration degree calculating unit 4 via the comparing unit 3.

[0007] A control unit (not shown) first includes an original image processing unit 1.
A non-degraded original image (still image) stored in the image memory 11 is read, an area is designated for the original image, and a Fourier transform unit 12 performs Fourier transform on the video signal of the designated area. . Next, a high-frequency region specifying unit 13 specifies a frequency range for extracting high-frequency components of the original image, and a power spectrum integrating unit 14 obtains and integrates a power spectrum for the frequency range.

Similarly, for the degraded image, the control unit reads the degraded image (still image) stored in the image memory 21 of the degraded image processing unit 2 and assigns the same area as the original image to the degraded image. The Fourier transform unit 22 performs Fourier transform on the video signal in the designated area. Next, in order to extract the high-frequency component of the deteriorated image in the high-frequency region specifying unit 23, the same frequency range as that of the original image is specified, and the power spectrum is obtained in the power spectrum integrating unit 24 for the frequency range. I do.

Next, power spectrum integrating units 14 and 24
, The integrated value of the power spectrum of the original image and the integrated value of the power spectrum of the deteriorated image are compared by the comparing unit 3, and the deterioration degree calculating unit 4 calculates the deterioration degree from the comparison result.

FIG. 2 shows an example of a power spectrum obtained by extracting high-frequency components in an undegraded image area. Also,
FIG. 3 is an example of a power spectrum obtained by extracting a high-frequency component of a deteriorated image area, which is a power spectrum obtained under the same conditions as in FIG. 2 and 3, the center of the XY plane is a low frequency region, and the periphery is a high frequency region. By comparing FIG. 2 and FIG. 3, the difference between the peripheral portions on the XY plane can be clearly understood. This indicates that when the image deteriorates, the power spectrum of the high-frequency component changes.

FIG. 4 is a diagram for explaining the designation of the frequency by the high frequency region designating sections 13 and 23. As described above, when the image is deteriorated, the power spectrum of the high-frequency component changes. Therefore, as shown in FIG.
2 to 3 are integrated, and power spectra as shown in FIGS. 2 and 3 are integrated. In this example, the integrated value p1 of the power spectrum in FIG. 2 and the integrated value p2 of the power spectrum in FIG. 3 are as follows: p1 = 49077; p2 = 37588; For example, assuming that the degree of deterioration R is R = (p2 / p1) × 100 (%), the degree of deterioration in this case is 76.6 (%).

When the image is not deteriorated, R =
It becomes 100 (%). Further, since the specified range of the frequency varies depending on the target image, a and b in FIG.
Set arbitrarily.

The present invention is not limited to the above-described embodiment, but can be implemented with appropriate modifications within a scope that does not change the gist.
For example, in the above embodiment, the degree of deterioration of an image that has deteriorated compared to the original image has been calculated, but the degree of improvement of an image that has improved compared to the original image can also be calculated. in this case,
The above-mentioned R obtained from the integrated value p1 of the power spectrum of the original image and the integrated value p2 of the power spectrum of the improved image indicates a value exceeding 100 (%).

(Summary of Embodiment) The configuration, operation and effect shown in the embodiment are summarized as follows. The image evaluation apparatus according to the embodiment includes a conversion unit (12, 22) for performing a Fourier transform on each video signal in the same region of the reference image and the evaluation target image, and a Fourier transform by the conversion unit (12, 22). Then, a calculating means (14, 24) for calculating each power spectrum in a predetermined frequency region of the reference image and the image to be evaluated, and a comparison for comparing the respective power spectra calculated by the calculating means (14, 24). Means (3).

Therefore, according to the image evaluation apparatus, after extracting a predetermined frequency component by Fourier transform for the same target region in the reference image and the evaluation target image, a power spectrum of a high-frequency component in the extracted frequency component is extracted. Integrate. Then, from the changes in the power spectra of the reference image and the evaluation target image, it is possible to quantitatively determine the degree of deterioration or improvement of the image.

[0016]

According to the image evaluation apparatus of the present invention, it is possible to quantitatively evaluate an image while paying attention to changes in high frequency components of the image.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an image evaluation device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a power spectrum obtained by extracting a high-frequency component of an undegraded image area according to the embodiment of the present invention.

FIG. 3 is a diagram showing an example of a power spectrum obtained by extracting a high-frequency component of a deteriorated image area according to the embodiment of the present invention.

FIG. 4 is a diagram for explaining designation of a frequency by a high-frequency region designation unit according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Original image processing part 11 ... Image memory 12 ... Fourier transformation part 13 ... High frequency area | region designation | designated part 14 ... Power spectrum integration part 2 ... Degraded image processing part 21 ... Image memory 22 ... Fourier transformation part 23 ... High frequency area | specification part 24 ... Power spectrum integration unit 3 Comparison unit 4 Deterioration degree calculation unit

Claims (1)

[Claims] 1. A conversion means for performing a Fourier transform on each video signal in the same area of a reference image and an evaluation target image, and after the Fourier transform by the conversion means, each power of a predetermined frequency region of the reference image and the evaluation target image. An image evaluation device, comprising: a calculating unit that calculates a spectrum; and a comparing unit that compares the power spectra calculated by the calculating unit.