1. An apparatus for extracting each of a plurality of characters from a character string having the plurality of characters arranged in a first direction and included in an image, comprising: an integrating device integrating a plurality of pixel values along a second direction orthogonal to the first direction at each of a plurality of coordinate positions along the first direction over the image; a setting device setting a section having a predetermined width at each of a plurality of different positions by shifting the section along the first direction over the image; a first extracting device extracting a first point where a pixel value integrated by the integrating device is the minimum value in each of the sections set by the setting device; a block setting device setting a plurality of blocks corresponding to sequences of the first points, wherein each distance between the adjacent first points in the sequence is not in excess of a predetermined threshold value; a second extracting device extracting a second point where a pixel value integrated by the integrating device is the minimum value in each of the plurality of blocks of first points, extracted by the first extracting device, in sequence along the first direction; an interpolating device calculating a base value at each of the plurality of coordinate positions along the first direction over the image from an interpolation based on the pixel values integrated by the integrating device at the second points extracted by the second extracting device; a compensating device subtracting the base value from the pixel value integrated by the integrating device as a compensated value at each of the plurality of coordinate positions along the first direction over the image; a recognition device recognizing an area having the compensated value compensated by the compensating device in excess of a predetermined threshold value as a character area; and a display device including a character string display part for displaying a character string having a plurality of characters and a character area display part surrounding each character included in the character area recognized by the recognition device.