Patent ID: 7286703

Claim:
An image correction apparatus comprising: an identification data memory storing, with regard to one or each of a plurality of light-source types, data representing a type of characteristic quantity that takes on values in which values obtained based upon an image that has been acquired by taking a picture under a light source of one light-source type and values obtained based upon an image that has been acquired by taking a picture under a light source of another light-source type are distinguished from each other; a photographic light-source discriminating device for discriminating, based upon a characteristic quantity that is calculated based upon the data representing the type of characteristic quantity regarding one or each of the plurality of light-source types stored in said identification data memory, under which light source among a predetermined one or plurality of light-source types an image represented by applied image data has been captured; a pixel extracting device for extracting pixels of a prescribed color, which has a color temperature in a color-temperature range corresponding to the photographic light-source type that has been discriminated by said photographic light-source discriminating device, from pixels constituting the image represented by the image data; an image correcting device for subjecting the image data to white-balance adjustment processing that corresponds to the photographic light-source type discriminated by said photographic light-source discriminating device, using pixels of a prescribed color extracted by said pixel extracting device; and an average color-difference calculating device for calculating an average color difference of the pixels of the prescribed color extracted by the pixel extracting device; wherein said image correcting device obtains a correction direction in a color-difference space in which the average color difference that has been calculated by said average color-difference calculating means becomes a prescribed value, obtains a color-difference histogram in which the color difference of each extracted pixel of the prescribed color is projected upon a straight defined in color-difference space by the correction direction, obtains correction coefficients in which an n% point that is nearer to the origin of the color-difference space in the color-difference histogram is adopted as the prescribed value, and subjects the image data to a white-balance correction based upon these correction coefficients.