1. An image processing apparatus comprising: a first edge width corrector for detecting edges in image data, generating first zoom ratio control values according to edge widths of the detected edges, and carrying out an interpolation calculation process on the image data according to the first zoom ratio control values, thereby correcting the edge widths; an enlargement processor for carrying out an enlargement process on the image data with edge widths corrected by the first edge width corrector in both the vertical and horizontal directions with respect to the image data; a second edge width corrector for detecting edges in the image data enlarged in the vertical and horizontal directions by the enlargement processor, generating second zoom ratio control values according to edge widths of the detected edges, and carrying out an interpolation calculation process on the enlarged image data according to the second zoom ratio control values, thereby correcting the edge widths; and an edge enhancer for detecting high frequency components of the image data with edge widths corrected by the second edge width corrector, calculating enhancement values for enhancing the edges according to the detected high frequency components, and adding the enhancement values to the image data with edge widths corrected by the second edge width corrector, thereby enhancing the edges.