Patent ID: 8554010

Claim:
An image processing apparatus, comprising: an input unit configured to input a plurality of sets of M-bit image data that are to be combined; a determining unit configured to determine reference image data serving as an exposure reference from among the plurality of sets of input M-bit image data; a composition unit configured to combine the plurality of sets of M-bit image data, and generate one set of N-bit composite image data (N>M); a characteristic parameter setting unit configured to set a characteristic parameter of tone compression on the N-bit composite image data such that a predetermined reference luminance in the reference image data does not change; and a generating unit configured to generate M-bit composite image data by compressing a luminance tone of an image component contained in the N-bit composite image data and having a frequency lower than a predetermined frequency based on the set characteristic parameter, wherein the image processing apparatus further comprises at least one of: a shadow pixel ratio determining unit configured to determine a shadow pixel ratio, which is the ratio of the number of pixels having a luminance value smaller than a first predetermined luminance value with respect to the total number of pixels, in the reference image data; and a highlight pixel ratio determining unit configured to determine a highlight pixel ratio, which is the ratio of the number of pixels having a luminance value larger than a second predetermined luminance value with respect to the total number of pixels in the reference image data, wherein the characteristic parameter setting unit sets a characteristic parameter that reduces a shadow detail loss of a pixel of the N-bit composite image data having a pixel value smaller than the predetermined reference luminance according to the shadow pixel ratio, and sets a characteristic parameter that reduces a highlight detail loss of a pixel of the N-bit composite image data having a pixel value larger than the predetermined reference luminance according to the highlight pixel ratio.