Patent ID: 7738699

Claim:
An image processing apparatus for processing an image group comprising a plurality of images obtained by imaging a same object under different exposure conditions to generate a wide dynamic range image, comprising: a photographing condition estimation element which estimates a photographing condition; an extraction element which extracts an appropriate exposure region from each image in the image group based on an image signal level of the image; a gradation correction element which selects, based on the photographing condition, a weight pattern comprising a two-dimensionally-arrayed plurality of weight coefficients, and which performs gradation correction on each of the extracted appropriate exposure regions based on a state of two-dimensional arrangement of the plurality of weight coefficients contained in the selected weight pattern; and a synthesis element which synthesizes the appropriate exposure regions subjected to gradation correction by the gradation correction element to generate the wide dynamic range image; wherein the gradation correction element comprises: a characteristic amount calculation element which calculates a characteristic amount with respect to the appropriate exposure region; a histogram generation element which generates a weighting histogram related to the characteristic amount based on the state of two-dimensional arrangement of the plurality of weight coefficients contained in the selected weight pattern; a gradation conversion curve calculation element which calculates a gradation conversion curve based on the histogram; and a conversion element which performs gradation conversion on the appropriate exposure region by using the gradation conversion curve.