1. An image processing apparatus comprising: document type classification means for determining whether input image data is image data for a text document or not; newspaper document classification means for determining whether the input image data is image data for a newspaper document or not; page-background region classification means for identifying a page-background region in the input image data; and page-background process means for performing a first page-background removal process to the image data if the following three conditions are met: (1) the input image data is the text document, (2) the input image data is not the newspaper document, and (3) a page-background removal process is to be performed to the input image data, and performing a second page-background removal process if the following three conditions are met: (1) the input image data is the text document, (2) the image input data is the newspaper document, and (3) the page-background removal process is to be performed to the input image data, the second page-background removal process being a process in which a density change of a text edge section is processed to become smoother than that in the first page-background removal process.