An Improved Multiscale Image Enhancement via Laplacian Pyramid

摘要

An improved multiscale image enhancement algorithm based on Laplacian pyramid (LP) is described. At each scale of the LP, the local variance threshold and relative enhancement are implemented by modifying the detail coefficients of the LP nonlinearly. With the local variance threshold, contrast enhancement occurs in high detail areas and little or no image sharpening occurs in smooth areas. And the objective of relative enhancement is to enhance the details with lower magnitude more than the details with higher magnitude in each scale of the LP. Since the low scales of the LP have subtler image features, we modify the local variance threshold and relative enhancement to take the different significance of different scale into account. So the low scales are more enhanced than the high ones. The given enhancement algorithm is simple to implement and suitable for generic image including CT and X-ray images. Experimental results show that the contrast improvement ratios of most images are increased while preserving the good visual assessment of original image.