Browsing by Author "Hung, Chao-Hsiung"

Now showing 1 - 4 of 4

A reduced-complexity image coding scheme using decision-directed wavelet-based contourlet transform
(2012-10-01)
Hung, Chao-Hsiung
;
Hang, Hsueh-Ming
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Recently the wavelet-based contourlet transform (WBCT) is adopted for image coding because it matches better image textures of different orientations. However, its computational complexity is very high. In this paper, we propose three tools to enhance the WBCT coding scheme, in particular, on reducing its computational complexity. First, we propose short-length 2-D filters for directional transform. Second, the directional transform is applied to only a few selected subbands and the selection is done by a mean-shift-based decision procedure. Third, we fine-tune the context tables used by the arithmetic coder in WBCT coding to improve coding efficiency and to reduce computation. Simulations show that, at comparable coded image quality, the proposed scheme saves over 92% computing time of the original WBCT scheme. Comparing to the conventional 2-D wavelet coding schemes, it produces clearly better subjective image quality. (c) 2012 Elsevier Inc. All rights reserved.
Decision-directed Adaptive Wavelet Image Coding with Diretional Decomposition
(2009)
Hung, Chao-Hsiung
;
Hang, Hsueh-Ming
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this paper, we e propose an adaptive wavelet coding scheme. A decision method is designed to identify whether the LH, HL, and HH wavelet subbands are suitable for directional decomposition. The basic concept behind this decision method is to detect the large impulses in the frequency domain. The transformed data are coded by the bit-plane arithmetic code to achieve scalability. Experimental results show that this adaptive scheme has better results than the 1-D wavelet transform and the original wavelet-based contourlet scheme that applies the directional transform to all the LH, HL and HH subbands.*
DIRECTION ALIGNMENT ALGORITHM FOR DIRECTION-ADAPTIVE DISCRETE WAVELET TRANSFORM
(2012)
Hung, Chao-Hsiung
;
Hang, Hsueh-Ming
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
2-D discrete wavelet transform (2-D DWT) represents non-vertical or non-horizontal edges inefficiently. Direction-adaptive discrete wavelet transform (DA-DWT) solves this problem by filtering along the directions of textures. DA-DWT partitions images into many blocks and finds the most suitable direction of each block. The block partition and direction information need to be transmitted as side information. A conventional DA-DWT often produces inconsistent directions of neighboring blocks and thus results in large amount of side information. In this paper, we propose a bottom-up direction alignment algorithm to align the block directions in local areas. Our algorithm can reduce 50% or more in side-information bits at the cost of negligible prediction error increase.
IMAGE CODING USING SHORT WAVELET-BASED CONTOURLET TRANSFORM
(2008)
Hung, Chao-Hsiung
;
Hang, Hsueh-Ming
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this paper, we propose two enhanced elements on the wavelet-based contourlet transform (WBCT) image coding scheme. A short-length 2-D non-separable directional filter bank is designed for significantly reducing the calculation. New zero coding context models are designed to improve coding efficiency. Experiments show that the proposed compression scheme produces better visual quality images, particularly, with fine and regular texture at low rates. The short-length directional filter bank performs nearly as well as their long-length counterpart.*