Image processing apparatus, image processing method, program and semiconductor integrated circuit
An image processing apparatus includes a filter unit which filters image signals; a sampling unit which generates first digital image signals having a first resolution by sampling the filtered image signals at a predetermined sampling frequency; and a super-resolution unit which reconstructs a second digital image signal having a second resolution which is higher than the first resolution by performing super-resolution on the first digital image signals generated by the sampling unit, wherein the filter unit passes frequency components corresponding to or lower than the Nyquist frequency which is half the sampling frequency, and passes a part of frequency components within a range from the Nyquist frequency to the highest frequency which can be represented by the second resolution.
1. An image processing apparatus, comprising,
a filter unit configured to filter image signals;
a sampling unit configured to generate first digital image signals having a first resolution by sampling the filtered image signals at a predetermined sampling frequency; and
a super-resolution unit configured to reconstruct a second digital image signal having a second resolution which is higher than the first resolution by performing super-resolution interpolation on the first digital image signals generated by the sampling unit,
wherein the filter unit is configured to pass frequency components corresponding to or lower than a Nyquist frequency which is half the sampling frequency, and to pass a part of frequency components within a range from the Nyquist frequency to a highest frequency which can be represented by the second resolution.
2. The image processing apparatus according to claim 1 , further comprising:
an inverse filter unit configured to have a filter characteristic which is inverse to a filter characteristic of the filter unit and to filter the second digital image signal.
3. The image processing apparatus according to claim 2 ,
wherein the inverse filter unit is configured to attenuate the frequency components corresponding to or lower than the Nyquist frequency, and to pass the part of frequency components within the range from the Nyquist frequency to the highest frequency which can be represented by the second resolution.
4. The image processing apparatus according to claim 2 ,
wherein the inverse filter unit is configured to pass the frequency components corresponding to or lower than the Nyquist frequency, and to emphasize frequency components corresponding to or higher than the Nyquist frequency.
5. The image processing apparatus according to claim 2 ,
wherein the filter unit has a filter characteristic of having an attenuation slope in the range from the Nyquist frequency to the highest frequency, and has a filter characteristic of attenuating, to 0, a frequency component corresponding to the highest frequency.
6. The image processing apparatus according to claim 2 ,
wherein the filter unit is switchable among filter characteristics including a first filter characteristic and a second filter characteristic,
an attenuation slope starting with the Nyquist frequency and ending with the highest frequency in the first filter characteristic is greater than an attenuation slope starting with the Nyquist frequency and ending with the highest frequency in the second filter characteristic, and
the filter unit is configured to select the first filter characteristic in the case where the number of high-frequency components included in the image signal is less than a threshold value, and to select the second filter characteristic in the case where the number of high-frequency components included in the image signal is greater than a threshold value.
7. The image processing apparatus according to claim 1 ,
wherein the filter unit has a filter characteristic of having an attenuation slope in the range from the Nyquist frequency to the highest frequency, and has a filter characteristic of attenuating, to 0, a frequency component corresponding to the highest frequency.
8. The image processing apparatus according to claim 1 ,
wherein the filter unit is switchable among filter characteristics including a first filter characteristic and a second filter characteristic,
an attenuation slope starting with the Nyquist frequency and ending with the highest frequency in the first filter characteristic is greater than an attenuation slope starting with the Nyquist frequency and ending with the highest frequency in the second filter characteristic, and
the filter unit is configured to select the first filter characteristic in the case where the number of high-frequency components included in the image signal is less than a threshold value, and to select the second filter characteristic in the case where the number of high-frequency components included in the image signal is greater than a threshold value.
9. The image processing apparatus according to claim 8 ,
wherein the inverse filter unit is switchable among a first inverse filter characteristic which is inverse to the first filter characteristic and a second inverse filter characteristic which is inverse to the second filter characteristic, and
the inverse filter unit is configured to select one of the first inverse filter characteristic and the second inverse filter characteristic which corresponds to the selected one of the first filter characteristic and the second filter characteristic.
10. An image processing method comprising:
filtering image signals;
generating first digital image signals having a first resolution by sampling the filtered image signals at a predetermined sampling frequency; and
reconstructing a second digital image signal having a second resolution which is higher than the first resolution by performing super-resolution interpolation on the first digital image signals generated by the sampling unit,
wherein, in the filtering, frequency components corresponding to or lower than a Nyquist frequency which is half the sampling frequency are passed, and a part of frequency components within a range from the Nyquist frequency to a highest frequency which can be represented by the second resolution is passed.
11. A non-transitory computer-readable recording medium storing a program, the program causing a computer to execute steps comprising:
filtering image signals;
generating first digital image signals having a first resolution by sampling the filtered image signals at a predetermined sampling frequency; and
reconstructing a second digital image signal having a second resolution which is higher than the first resolution by performing super-resolution interpolation on the first digital image signals generated by the sampling unit,
wherein, in the filtering, frequency components corresponding to or lower than a Nyquist frequency which is half the sampling frequency are passed, and a part of frequency components within a range from the Nyquist frequency to a highest frequency which can be represented by the second resolution is passed.
12. A semiconductor integrated circuit, comprising:
a filter unit configured to filter image signals;
a sampling unit configured to generate first digital image signals having a first resolution by sampling the filtered image signals at a predetermined sampling frequency; and
a super-resolution unit configured to reconstruct a second digital image signal having a second resolution which is higher than the first resolution by performing super-resolution interpolation on the first digital image signals generated by the sampling unit,
wherein the filter unit is configured to pass frequency components corresponding to or lower than a Nyquist frequency which is half the sampling frequency, and to pass a part of frequency components within a range from the Nyquist frequency to a highest frequency which can be represented by the second resolution.