Image processing device and method, program, and record medium

An image processing device of an image capturing device that includes an image capturing unit that captures an image by receiving light from a subject, the image processing device comprising:

• a control unit that causes the image capturing unit to repeatedly and alternately perform image capturing with a first light exposure amount using a first light exposure time and image capturing with a second light exposure amount using a second light exposure time that is different from and longer than the first light exposure time, and to repeatedly and alternately output a first image generated by the image capturing with the first light exposure amount and a second image generated by the image capturing with the second light exposure amount;
• an image combination unit that generates a composite image by combining the first image and the second image;
• and
• a pixel value measurement unit that generates a histogram indicating an occurrence frequency of pixels of each pixel value in the first image and another histogram indicating another occurrence frequency of pixels of each pixel value in the second image,
• wherein the control unit
• generates a first index value as a pixel value at which a first cumulative frequency proportion obtained by dividing a cumulative frequency of the occurrence frequency of pixels of each pixel value up to the pixel value by a total number of pixels that compose the first image becomes a first reference value in the histogram of the first image, and controls the first light exposure amount so that a first target condition that the first index value has a predetermined relation with a predetermined first target value is satisfied, and
• generates a second index value as another pixel value at which a second cumulative frequency proportion obtained by dividing a cumulative frequency of the another occurrence frequency of pixels of each pixel value up to the another pixel value by a total number of pixels that compose the second image becomes a second reference value smaller than the first reference value in the another histogram of the second image, and controls the second light exposure amount so that a second target condition that the second index value has a predetermined relation with a predetermined second target value is satisfied.