1. An image processing apparatus, comprising: segmentation process means for performing a segmentation process with respect to image data; density correction means for performing a density correction process with respect to the image data by referring to density correcting data which indicates a relation between density before correction and density after correction; the density correction process being a process in which density of a page background area included in an image corresponding to the image data is reduced; and processing mode control means for switching between (i) a first processing mode in which the segmentation process is performed with respect to the image data having been subjected to the density correction process and (ii) a second processing mode in which the segmentation process is performed with respect to image data having not been subjected to the density correction process, wherein; the image data is read out from a document, said document is a first document type which at least partially includes a continuous tone image area or a second document type which does not include a continuous tone image area, and the continuous tone image area is not an area constituted of halftone dots but an area whose tones are continuously made with silver particles or dye particles, and when receiving document type information indicating that the document from which the image data is being read out is of said first document type, the processing mode control means switches to said second processing mode to prevent an edge portion of the continuous tone image area from being wrongly detected as a text area, and when receiving document type information indicating that the document from which the image data being read out is of said second document type, the processing control means switches to said first processing mode to detect a text area with high accuracy.