1. An image processing apparatus, which performs a black generation process and an under color removal process with respect to image data including a plurality of color components, comprising: a segmentation section for judging whether each pixel or each block including a plurality of pixels in the image data belongs to a black text/low density area or not; and an under color removal section for performing the under color removal process with respect to the image data, the under color removal section performing the under color removal process so that an under color removal value for each pixel of at least a part of pixels judged by the segmentation section to belong to a black text/low density area is larger than a minimum color component density level and smaller than a maximum color component density level of the pixel, the segmentation section including: a text area judging section for judging whether each pixel in the image data belongs to a text area or not; an edge detecting section for judging whether a pixel judged by the text area judging section to belong to a text area is an edge of a text or a line; a pattern matching section for judging whether a pattern of pixels judged by the edge detecting section to be an edge of a text or a line is identical with a template prepared in advance for detecting texts; a color judging section for judging whether a color of a pixel judged by the pattern matching section to belong to a pattern identical with the template is a chromatic color or an achromatic color; and a density judgment section for judging whether a pixel judged by the color judging section to be an achromatic color or a block of pixels each judged by the color judging section to be an achromatic color belongs to a high density area or a low density area, the segmentation section determining that a pixel is a pixel belonging to the black text/low density area, if (i) the pixel is judged by the edge detecting section to be an edge, (ii) the pixel constitutes a pattern judged by the pattern matching section to belong to a pattern identical with a template, (iii) a color of the pixel is judged by the color judging section to be an achromatic color, and (iv) the pixel is judged by the density judgment section to belong to a low density area, and the under color removal section performing the under color removal process such that an under color removal value for a pixel that belongs to the black text/low density area is set to be larger than a minimum color component density level and smaller than a maximum color component density level of the pixel, and such that an under color removal value for a pixel that belongs to an area other than the black text/low density area is set in accordance with a minimum color component density level of the pixel.