Image processing apparatus, method, and program

Abstract

An image processing apparatus, including a region setting unit for setting regions on a processing target image in which each pixel of the image is included according to a level of each pixel, a low frequency image generation unit for generating a low frequency image of the processing target image, a gain calculation unit for calculating a gain for each pixel of the processing target image such that the lower the level the greater the gain, wherein the unit calculates the gain such that pixels in each of the regions in which each pixel of the processing target image is included have substantially the same gain based on a region setting result and a level of each pixel of the low frequency image, and a processing unit for generating a processed image by performing dynamic range compression on the processing target image based on the gain.

1 . An image processing apparatus, comprising:
 a region setting unit for setting one or more regions on a processing target image in which each pixel of the image is included according to a level of each pixel;   a low frequency image generation unit for generating a low frequency image of the processing target image;   a gain calculation unit for calculating a gain for each pixel of the processing target image such that the lower the level the greater the gain, wherein the unit calculates the gain such that pixels in each of the one or more regions in which each pixel of the processing target image is included have substantially the same gain based on a region setting result and a level of each pixel of the low frequency image; and   a processing unit for generating a processed image by performing dynamic range compression on the processing target image based on the gain.   
   
   
       2 . The image processing apparatus of  claim 1 , wherein the gain calculation unit is a unit that calculates a provisional gain for each pixel of the low frequency image such that the lower the level the greater the gain and, based on the region setting result, calculates a representative value of the provisional gains of pixels in each of the one or more regions in which each pixel of the processing target image is included as the gain for each pixel of the processing target image. 
   
   
       3 . The image processing apparatus of  claim 1 , wherein the gain calculation unit is a unit that calculates, based on the region setting result, a representative value of pixels in each of the one or more regions in which each pixel of the low frequency image is included, and calculates the gain for each pixel of the processing target image such that the lower the level of the representative value the greater the gain. 
   
   
       4 . An image processing apparatus, comprising:
 a low frequency image generation unit for generating a plurality of low frequency images of different frequency bands from a processing target image;   a region setting unit for setting one or more regions on at least one of those of the plurality of low frequency images up to a predetermined frequency band, which is higher than a first frequency band, in which each pixel of the at least one low frequency image is included according to a level of each pixel of the at least one low frequency image;   a gain calculation unit for calculating a first gain for each pixel of a first low frequency image of the first frequency band such that the lower the level the greater the gain, calculating, based on a region setting result, a representative value of the first gains of pixels in each of the one or more regions in which each pixel of a second low frequency image of a second frequency band, which is next higher than the first frequency band, is included as a second gain of each pixel of the second low frequency image, and outputting a second gain calculated by repeating the calculation of a new second gain using a low frequency image of the next higher frequency band than that of the second low frequency image as a new second low frequency image and the second gain as a new first gain to the predetermined frequency band as a final gain of each pixel of the processing target image; and   a processing unit for generating a processed image by performing dynamic range compression on the processing target image based on the gain.   
   
   
       5 . A photographing apparatus, comprising:
 an imaging unit for obtaining a processing target image by photographing a subject; and   the image processing apparatus of  claim 1 .   
   
   
       6 . A photographing apparatus, comprising:
 an imaging unit for obtaining a processing target image by photographing a subject; and   the image processing apparatus of  claim 4 .   
   
   
       7 . An image processing method, comprising the steps of:
 setting one or more regions on a processing target image in which each pixel of the image is included according to a level of each pixel;   generating a low frequency image of the processing target image;   when calculating a gain for each pixel of the processing target image such that the lower the level the greater the gain, calculating the gain such that pixels in each of the one or more regions in which each pixel of the processing target image is included have substantially the same gain based on a region setting result and a level of each pixel of the low frequency image; and   generating a processed image by performing dynamic range compression on the processing target image based on the gain.   
   
   
       8 . An image processing method, comprising the steps of:
 generating a plurality of low frequency images of different frequency bands from a processing target image;   setting one or more regions on at least one of those of the plurality of low frequency images up to a predetermined frequency band, which is higher than a first frequency band, in which each pixel of the at least one low frequency image is included according to a level of each pixel of the at least one low frequency image;   calculating a first gain for each pixel of a first low frequency image of the first frequency band such that the lower the level the greater the gain;   calculating, based on a region setting result, a representative value of the first gains of pixels in each of the one or more regions in which each pixel of a second low frequency image of a second frequency band, which is next higher than the first frequency band, is included as a second gain of each pixel of the second low frequency image; and   outputting a second gain calculated by repeating the calculation of a new second gain using a low frequency image of the next higher frequency band than that of the second low frequency image as a new second low frequency image and the second gain as a new first gain to the predetermined frequency band as a final gain of each pixel of the processing target image; and   generating a processed image by performing dynamic range compression on the processing target image based on the gain.   
   
   
       9 . A computer readable recording medium on which is recorded a program for causing a computer to execute an image processing method, the method comprising the steps of:
 setting one or more regions on a processing target image in which each pixel of the image is included according to a level of each pixel;   generating a low frequency image of the processing target image;   when calculating a gain for each pixel of the processing target image such that the lower the level the greater the gain, calculating the gain such that pixels in each of the one or more regions in which each pixel of the processing target image is included have substantially the same gain based on a region setting result and a level of each pixel of the low frequency image; and   generating a processed image by performing dynamic range compression on the processing target image based on the gain.   
   
   
       10 . A computer readable recording medium on which is recorded a program for causing a computer to execute an image processing method, the method comprising the steps of:
 generating a plurality of low frequency images of different frequency bands from a processing target image;   setting one or more regions on at least one of those of the plurality of low frequency images up to a predetermined frequency band, which is higher than a first frequency band, in which each pixel of the at least one low frequency image is included according to a level of each pixel of the at least one low frequency image;   calculating a first gain for each pixel of a first low frequency image of the first frequency band such that the lower the level the greater the gain;   calculating, based on a region setting result, a representative value of the first gains of pixels in each of the one or more regions in which each pixel of a second low frequency image of a second frequency band, which is next higher than the first frequency band, is included as a second gain of each pixel of the second low frequency image; and   outputting a second gain calculated by repeating the calculation of a new second gain using a low frequency image of the next higher frequency band than that of the second low frequency image as a new second low frequency image and the second gain as a new first gain to the predetermined frequency band as a final gain of each pixel of the processing target image; and   generating a processed image by performing dynamic range compression on the processing target image based on the gain.