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2 Fundamenta Informaticae

2 2005

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An Inverse Halftoning Technique Using Modified Look-Up Tables

Chang C.-C., Chan C.-S.

Fundamenta Informaticae

2005

Vol. 68, nr 3

207-220

In this paper, we shall propose a method to invert halftone images. We shall use a modified look-up table to reconstruct gray level images from halftone images. In the modified look-up table training phase, we shall use a sliding window to get halftone patterns and their corresponding gray-level lists. The modified look-up table can be obtained by calculating the centroid of the gray-level lists. In the image reconstruction phase, we shall use the sliding window to slide around the pixel to reconstruct so that we can get candidate gray values. The reconstructed gray value can be obtained by calculating the centroid of the candidate gray values. Experimental results have shown that our method indeed can get satisfied results.

An Image Hiding Scheme Based on Multi-bit-reference Substitution Table Using Dynamic Programming Strategy

Chan C.-S., Chang C. C.

Fundamenta Informaticae

2005

Vol. 65, nr 4

291--305

Simple least-significant-bit (LSB) substitution is the most straightforward way to embed the secret image in the host image. Based on the simple LSB substitution, the method using substitution table is proposed to improve the quality of the stego-image. In this paper, we shall bring up a new method that uses the un-embedded host pixel bits to partition the host pixel into different planes. This way, we can derive the optimal substitution table for each plane. By combining the optimal substitution tables, we can obtain the final result that we call the multi-bit-reference substitution table. After transforming the secret data according multi-bit-reference substitution table, we can embed the transformed secret data in the host image so that the host image will be degraded possibly less. The experimental results show that our method leads to good results.