Contrast enhancement for enlarged images based on edge sharpening

Blurring effect is among the major visual degradations resulting from digital image enlargement. We introduce a set of sigmoidal functions to sharpen edges of enlarged images. We show that these functions have properties that are especially desirable for sharpening expanded edges. We then develop an adaptive contrast enhancement scheme based on edge sharpening using these functions. It is shown that this scheme results in images of better contrast and natural-looking sharp edges.