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2 Opto-Electronics Review

2 2011

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Variable-rate colour image quantization based on quadtree segmentation

Hu Y. C., Li C. Y., Chuang J. C., Lo C. C.

Opto-Electronics Review

2011

Vol. 19, No. 3

282-289

A novel variable-sized block encoding with threshold control for colour image quantization (CIQ) is presented in this paper. In CIQ, the colour palette used has a great influence on the reconstructed image quality. Typically, a higher image quality and a larger storage cost are obtained when a larger-sized palette is used in CIQ. To cut down the storage cost while preserving quality of the reconstructed images, the threshold control policy for quadtree segmentation is used in this paper. Experimental results show that the proposed method adaptively provides desired bit rates while having better image qualities comparing to CIQ with the usage of multiple palettes of different sizes.

Efficient greyscale image compression technique based on vector quantization

Hu Y. C., Chuang J. C., Lo C. C., Li C. Y.

Opto-Electronics Review

2011

Vol. 19, No. 1

104-113

In this paper, a novel greyscale image coding technique based on vector quantization (VQ) is proposed. In VQ, the reconstructed image quality is restricted by the codebook used in the image encoding/decoding procedures. To provide a better image quality using a fixed-sized codebook, the codebook expansion technique is introduced in the proposed technique. In addition, the block prediction technique and the relatively address technique are employed to cut down the required storage cost of the compressed codes. From the results, it is shown that the proposed technique adaptively provides better image quality at low bit rates than VQ.