Image processing apparatus, method, and medium for correcting pixel values using parameters corresponding to image spatial frequencies

摘要

Image processing apparatus in which a spatial frequency around a pixel of interest and a statistic value of pixel values around the pixel of interest are calculated based on a pixel value of the pixel of interest and a pixel value of a pixel around the pixel of interest. Correction parameters are stored corresponding to sets of spatial frequencies and statistic values. A correction parameter is acquired corresponding to the spatial frequency around the pixel of interest and the statistic value of the pixel values around the pixel of interest, as a correction parameter for the pixel of interest. The pixel value of the pixel of interest is corrected using the correction parameter for the pixel of interest.

主权项

1. An image processing apparatus comprising:
a calculation unit configured to calculate, based on a pixel value of a pixel of interest and a pixel value of a pixel around the pixel of interest, a spatial frequency around the pixel of interest and a feature amount which is represented by using a difference between the pixel value of the pixel of interest and pixel values around the pixel of interest; a storage unit configured to store correction parameters corresponding to sets of the spatial frequency and the feature amount; an acquisition unit configured to acquire, from said storage unit, a correction parameter corresponding to the calculated spatial frequency and the calculated feature amount, as a correction parameter for a region including the pixel of interest and pixels around the pixel of interest, wherein a correction parameter corresponding to a higher spatial frequency is configured to provide a correction making each and every luminance of the entirety of the region brighter than a correction parameter corresponding to a lower spatial frequency, or a correction parameter corresponding to a larger feature amount is configured to provide a correction making each and every luminance of the entirety of the region brighter than a correction parameter corresponding to a smaller feature amount; and a correction unit configured to correct a luminance of the region using the acquired correction parameter; wherein the feature amount includes a first feature amount which is represented by using a difference between the pixel value of the pixel of interest and pixel values around the pixel of interest and a second feature amount which is represented by any one of an average value, a mode value, a median value, a minimum value or maximum value between the pixel value of the pixel of interest and pixel values around the pixel of interest, wherein the higher the spatial frequency is, the larger the first feature amount is, and the higher the second feature amount is, the brighter the correction unit corrects the luminance of the entirety of the region.