Image processing apparatus, image processing method, and computer-readable recording medium

1. An image processing apparatus comprising:

circuitry configured to

acquire, from an image, a patch obtained by extracting a partial area of the image,

determine a value of a design parameter relating to processing of the patch according to an amount of information contained in the acquired patch and representing a state of distribution of pixel values,

generate a high-frequency patch from the patch by using the determined value of the design parameter,

determine the value of the design parameter that is at least any one of a sparse level representing a number of bases to be selected from a basis dictionary of the image, an extraction interval for extracting the partial area, and a patch size, based on the amount of information,

extract the partial area according to the extraction interval and the patch size,

determine the sparse level corresponding to the amount of information of the patch obtained by extracting the partial area according to a correspondence chart that stores a correspondence relation between the amount of information of the patch and the sparse level,

select combinations of medium-frequency bases and high-frequency bases corresponding in number to the determined sparse level, and

generate the high-frequency patch by taking linear sum of the high-frequency bases, where linear coefficients of each high-frequency bases are determined during the selection of corresponding medium-frequency bases.

2. The image processing apparatus according to claim 1 , wherein the circuitry is further configured to measure the amount of information contained in the patch by using at least any one of arrangement of pixels and an amount of characteristics that quantifies an amount of change in pixel value.

3. The image processing apparatus according to claim 1 , wherein the circuitry is further configured to determine the correspondence chart to be used from the relation between the amount of information of the patch obtained by extracting the partial area and frequency of the amount of information.

4. The image processing apparatus according to claim 1 , wherein the circuitry is further configured to

set an extraction interval smaller than or equal to a predetermined value when the amount of information is equal to or larger than a predetermined threshold, and

set an extraction interval equal to or larger than the predetermined value when the amount of information is smaller than the predetermined threshold.

5. The image processing apparatus according to claim 1 , wherein the circuitry is further configured to

acquire a surrounding patch obtained by extracting a surrounding area representing any one of an area that partially overlaps with the partial area, an area adjacent to the partial area, and an area distant from the partial area by a pixel or more and measures the amount of information of the acquired surrounding patch, and

set an extraction interval smaller than a predetermined value when the measured amount of information of the patch and the surrounding patch is equal to or larger than a predetermined threshold, and set an extraction interval equal to or larger than the predetermined value when the measured amount of information is smaller than the predetermined threshold.

6. The image processing apparatus according to claim 1 , wherein the circuitry is further configured to

measure the amount of information of the patch obtained by extracting the partial area in a predetermined size,

extract the partial area in a size equal to or smaller than the predetermined size when the measured amount of information is equal to or larger than a predetermined threshold,

extract the partial area in a size equal to or larger than the predetermined size when the measured amount of information is smaller than the predetermined threshold, and

select a basis dictionary in which bases in the same size as that of the medium-frequency patch are accumulated.

7. The image processing apparatus according to claim 1 , wherein the circuitry is further configured to

determine a plurality of design parameters according to at least any one of the measured amount of information and at least one type of amount of characteristics.

8. The image processing apparatus according to claim 1 , wherein the circuitry is further configured to convert the image into a high-resolution image.

9. An image processing method comprising:

acquiring, with circuitry, from an image, a patch obtained by extracting a partial area of the image;

determining, with the circuitry, a value of a design parameter relating to processing of the patch according to an amount of information contained in the acquired patch and representing a state of distribution of pixel values,

generating, with the circuitry, a high-frequency patch from the patch by using the determined value of the design parameter,

determining, with the circuitry, the value of the design parameter that is at least any one of a sparse level representing a number of bases to be selected from a basis dictionary of the image, an extraction interval for extracting the partial area, and a patch size, based on the amount of information,

extracting, with the circuitry, the partial area according to the extraction interval and the patch size,

determining, with the circuitry, the sparse level corresponding to the amount of information of the patch obtained by extracting the partial area according to a correspondence chart that stores a correspondence relation between the amount of information of the patch and the sparse level,

selecting, with the circuitry, combinations of medium-frequency bases and high-frequency bases corresponding in number to the determined sparse level, and

generating, with the circuitry, the high-frequency patch by taking linear sum of the high-frequency bases, where linear coefficients of each high-frequency bases are determined during the selection of corresponding medium-frequency bases.

10. A non-transitory computer-readable recording medium that contains an image processing program that causes a computer to execute:

acquiring, from an image, a patch obtained by extracting a partial area of the image;

determining a value of a design parameter relating to processing of the patch according to an amount of information contained in the acquired patch and representing a state of distribution of pixel values;

generating a high-frequency patch from the patch by using the determined value of the design parameter;

determining the value of the design parameter that is at least any one of a sparse level representing a number of bases to be selected from a basis dictionary of the image, an extraction interval for extracting the partial area, and a patch size, based on the amount of information;

extracting the partial area according to the extraction interval and the patch size;

determining the sparse level corresponding to the amount of information of the patch obtained by extracting the partial area according to a correspondence chart that stores a correspondence relation between the amount of information of the patch and the sparse level;

selecting combinations of medium-frequency bases and high-frequency bases corresponding in number to the determined sparse level; and

generating the high-frequency patch by taking linear sum of the high-frequency bases, where linear coefficients of each high-frequency bases are determined during the selection of corresponding medium-frequency bases.