scispace - formally typeset
Search or ask a question

Showing papers on "Contourlet published in 1989"


Proceedings ArticleDOI
Surendra Ranganath1
25 May 1989
TL;DR: In this paper, image pyramids are used to approximate the convolution of an image with a given mask and an optimally filtered image is synthesized from the multiresolution levels, which are maintained at the original sampling density.
Abstract: This paper uses multiresolution representations in two new techniques for image enhancement and restoration. The first method, based on image pyramids, is used for approximating the convolution of an image with a given mask. In this technique, a filter is designed using a least squares (ls) procedure based on filter functions synthesized from the basic pyramid equivalent filters. This approximates the mask frequency characteristic. Next, enhancement involves linearly combining scaled and filtered pyramid levels, using weights obtained from the is procedure. By this method, filtering and pyramid image coding can be combined, efficiently integrating enhancement into the reconstruction procedure for the coded image. The second method is an adaptive noise reduction algorithm. An optimally filtered image is synthesized from the multiresolution levels, which in this case, are maintained at the original sampling density. Individual pixels of the image representation are linearly combined under a minimum mean square error criterion. This uses a local signal to noise ratio estimate to provide the best compromise between noise removal and resolution loss.

2 citations


Proceedings ArticleDOI
08 May 1989
TL;DR: The authors discuss a hybrid pyramid coding scheme for image data compression that is based on two coding techniques: subband pyramid and Laplacian pyramid, which shows its efficiency and compactness.
Abstract: The authors discuss a hybrid pyramid coding scheme for image data compression that is based on two coding techniques: subband pyramid and Laplacian pyramid. Source data are first decomposed into seven bands by subband pyramid coding. Only the lowest band is further decomposed by the Laplacian pyramid technique to reduce correlations between pixels. The advantages of the hybrid pyramid scheme are its efficiency and compactness. In the coding process, each component is PCM coded. The computer simulation results show that the quality of the reconstructed image is good up to a compression ratio of 10:1. >

1 citations