Title
Post-processing enhancement of decompressed images using variable order Bezier polynomials and distance transform
Abstract
Summary form only given. We post-process images compressed by lossy JPEG algorithms (DCT and LOGO), following decompression, using Bezier polynomials for enhancement. Both JPEG algorithms, namely the DCT-based JPEG and the near-lossless baseline JPEG-LS (aka LOGO), employ spatial quantization. The DCT-based version introduces an artifact known as mosaic or “blockiness” by coarsely quantizing the DC coefficients. By quantizing the prediction errors, JPEG-LS introduces a “banding” artifact specially noticeable for quantization coarser than “8-off”. The human visual system (HVS) is specially sensitive to degradations on smooth regions in the image. We propose a post-processing algorithm based on blending for enhancement of the degraded smooth regions due to quantization. In this work, we use Bezier polynomials of variable orders. Enhancement is obtained by blending each pixel in low-activity regions so the artifacts are reduced. The coefficients of the Bezier polynomials for the various orders used (from 3rd to 7th order) are precomputed and stored in look-up tables for speed. Active pixels, detected by using a threshold of 3/2 of the quantization step size, are left alone. The threshold is theoretically justified, avoids the problem of threshold determination on ordinary segmentation, and excludes quantization noise. In order to avoid over-smoothing of large low activity regions, the Bezier polynomials' order used to blend each pixel Po,j is variable. Results are presented for lossy JPEG and JPEG-LS images for very low bit-rates
Year
DOI
Venue
1998
10.1109/DCC.1998.672303
Data Compression Conference
Keywords
Field
DocType
discrete cosine transforms,image enhancement,interference suppression,polynomials,quantisation (signal),DC coefficient,DCT,DCT-based JPEG,LOGO,active pixels,artifacts,banding artifact,blend,blockiness,decompressed images,distance transform,look-up tables,lossy JPEG algorithms,low-activity regions,mosaic,near-lossless baseline JPEG-LS,post-processing enhancement,prediction errors,quantization,smooth regions,spatial quantization,variable order Bezier polynomials
Computer vision,Lossy compression,Computer science,Human visual system model,Discrete cosine transform,Theoretical computer science,JPEG,Distance transform,Artificial intelligence,Pixel,Quantization (image processing),Quantization (signal processing)
Conference
ISSN
ISBN
Citations 
1068-0314
0-8186-8406-2
6
PageRank 
References 
Authors
0.54
0
2
Name
Order
Citations
PageRank
Mayer, J.160.54
Glen G. Langdon220982.77