1. An image processing apparatus comprising: dividing means for dividing a two-dimensional image indicated by an image signal containing a plurality of pixel data indicative of pixels and composed of a plurality of pixels, into a plurality of division regions each composed of either one or plural pixels whose pixel data are similar to each other; designating means for designating a contour region composed of pixels of an outermost edge portion of an initial region containing an extract region to be extracted from the two-dimensional image; position computation means for obtaining a positional relationship between each pixel in the contour region designated by the designating means, and each of remaining pixels other than the pixels of the contour region in the two-dimensional image; weight computation means for obtaining a weighting factor of each division region on the basis of the positional relationships with respect to respective pixels in the division region, obtained by the position computation means; judging means for comparing the weighting factor of each division region obtained by the weight computation means with a predetermined judging value to thereby judge when the weighting factor is larger than the predetermined judging value that at least a portion of each respective division region is contained in the extract region, and to thereby judge when the weighting factor is smaller than the judging value that the division region is not contained in the extract region; and extracting means for extracting from the image signal, pixel data of pixels of a division region judged by the judging means such that at least a portion thereof is contained in the extract region.