1. A method for producing sharpness enhanced image data having halftone structures based on input image data that includes halftone structures, the method comprising: receiving the image data that includes halftone structures; blurring a copy of the image data, thereby generating blurred image data wherein a detectability of edges of the halftone structures is reduced from the detectability of the edges of the halftone structures in the received image data; detecting detectable edges remaining in the blurred image data; generating an edge enhancement image based on the detected edges; and combining the received image data that includes halftone structures with the generated edge enhancement image, thereby generating sharpness enhanced image data having halftone structures.