Jinhui Qin and Mahmoud R. El-Sakka, "A new wavelet-based
method for contrast/edge enhancement", IEEE International
Conference on Image Processing, ICIP'2003, Vol. 3, pp. 397 -
400, September 2003, Barcelona, Spain.
Contrast enhancement is usually achieved by histogram
equalizing image pixel gray-levels in the spatial domain to
redistribute them uniformly. Meanwhile, edge enhancement
attempts to emphasize the fine details in the original image.
But in the spatial domain it is hard to selectively enhance
details at different scales. Moreover, in the spatial domain,
applying contrast and edge enhancement techniques in
different orders may yield different enhancement results. To
overcome the above spatial domain enhancement issues, a new
wavelet-based image enhancement method is proposed. The
proposed method histogram-equalizes the
approximation-coefficients. At the same time, it high-boost
filters the detail-coefficients at selected resolution levels
separately. The experiments show that utilizing the proposed
method can achieve robust contrast and edge enhancement.
Moreover, the computation cost in the wavelet domain is less
than that in the spatial domain. This is especially true when
considering that currently most images are already
wavelet-compressed (the current JPEG 2000 standard is a
wavelet based scheme).