1. An image processing apparatus comprising a character region identification portion identifying a character region of read image data obtained by reading an input image, said character region identification portion including an isolated point detection portion for detecting an isolated point of said read image data, said isolated point detection portion including: an isolated point filter operation portion performing a gradation operation for a target pixel region and a peripheral region of the target pixel region of said read image data, and a determination portion identifying an isolated point based on mutual gradation comparison, based on an operation result of said isolated point filter operation portion; an isolated point removal portion for making a replacement of image data at a point of detection result by said isolated point detection portion, said isolated point removal portion including: a first pixel specification portion specifying a pixel having maximum gradation of pixels in the peripheral region of said target pixel region, a second pixel specification portion specifying a pixel having minimum gradation of pixels in the peripheral region of said target pixel region, and a selection portion outputting said target pixel region as it is or replacing said target pixel region with a pixel specified by one of said first and second pixel specification portions for output based on a determination result of said determination portion; an edge identification portion performing edge identification of the read image data from which an isolated point is removed, and a character region specification portion specifying a character region of said read image data after said edge identification.