PL
 |
EN
Preferencje help
Polish version English version Język
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 11

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
1
Content available remote New Bit Reduction of Vector Quantization Using Block Prediction and Relative Addressing
Hu Y-C., Tsai P., Lo C-C.
Fundamenta Informaticae
|
2008
|
Vol. 87, nr 3-4
313-329
EN
A low bit rate image coding scheme based on vector quantization is proposed. In this scheme, the block prediction coding and the relative addressing techniques are employed to cut down the required bit rate of vector quantization. In block prediction coding, neighboring encoded blocks are taken to compress the current block if a high degree of similarity between them is existed. In the relative addressing technique, the redundancy among neighboring indices are exploited to reduce the bit rate. From the results, it is shown that the proposed scheme significantly reduces the bit rate of VQ while keeping good image quality of compressed images.
2
Content available remote Grayscale Image Hiding Based on Modulus Function and Greedy Method
Hu Y-C., Tsou Ch-Ch., Su B-H.
Fundamenta Informaticae
|
2008
|
Vol. 86, nr 1-2
113-126
EN
A novel LSB-based image-hiding scheme that embeds secret data into the grayscale cover image is proposed in this paper. Several LSB-based image hiding schemes such as simple LSB substitution technique, optimal LSB substitution technique, greedy LSB substitution technique, modulus LSB substitution technique had been proposed. To provide good image quality of the stego-image while requiring a low computational cost, the greedy method and modulus function are employed in the proposed scheme. According to the results, the proposed scheme provides better image quality of stego-image than the comparative schemes while consuming a low computational cost.
3
Content available remote Fast VQ Codebook Generation Method Using Codeword Stability Check and Finite State Concept
Tsai P., Hu Y-C., Yeh H-L.
Fundamenta Informaticae
|
2008
|
Vol. 87, nr 3-4
447-463
EN
The codebook design in the vector quantization scheme is important because it affects the image quality of the encoded image. The Linde-Buzo-Gray (LBG) codebook generation algorithm is well known and a popular choice among codebook users. However, a heavy computational complexity is consumed for the iteratively clustering process in the LBG algorithm. In this paper, the similarity of codewords in consecutive rounds of the LBG algorithm is exploited to reduce the computational complexity. By checking the stability of codewords, the status of each codeword in the codebook can be determined. Only the unstable codewords are refined to generate the new codebook. The proposed method can be further improved by cooperating with the finite state technique. Experimental results show that the computational complexity of the proposed method is reduced to about 4% of the LBG algorithm while achieving a slightly worse image quality.
4
Content available remote Predictive Grayscale Image Coding Scheme Using VQ and BTC
Hu Y-C.
Fundamenta Informaticae
|
2007
|
Vol. 78, nr 2
239-255
EN
A predictive image compression scheme that combines the advantages of vector quantization and moment preserving block truncation coding is introduced in this paper. To exploit the similarities among neighboring image blocks, the block prediction technique is employed in this scheme. If a similar compressed image block can be found in the neighborhood of current processing block, it is taken to encode this block. Otherwise, this image block is encoded either by vector quantization or moment preserving block truncation coding. A bit-rate reduced version of the proposed scheme is also introduced. According to the experimental results, it is shown that the proposed scheme provides better image quality at a low bitrate than these comparative schemes.
5
Content available remote Block Prediction Vector Quantization for Grayscale Image Compression
Hu Y-C., Lin C-C., Chi K-L.
Fundamenta Informaticae
|
2007
|
Vol. 78, nr 2
257-270
EN
This paper presents a new image compression scheme based on vector quantization (VQ) that exploits the inter-block and intra-block correlations in grayscale images. The similar block prediction technique is designed to encode the image blocks by their similar neighboring encoded blocks. Besides, two codebooks are used in the proposed scheme to exploit the intra-block correlation within each image block. Experimental results show that the proposed scheme not only provides good image qualities but also cuts down the required bit rates.
6
Content available remote Spatial Domain Image Hiding Scheme Using Pixel-Values Differencing
Chang C-C., Chuang J-C., Hu Y-C.
Fundamenta Informaticae
|
2006
|
Vol. 70, nr 3
171-184
EN
In this paper, we present a spatial domain Image hiding scheme that embeds secret data in a gray-level image. Our scheme is inspired from Wu and Tsai's scheme that embeds secret bits in the difference values of consecutive pixels. To improve the hiding capacity of their scheme, the overlapping concept is proposed to produce more difference values from the cover image in this paper. Experimental results show that our scheme provides an average hiding capacity gain of 84.16% over Wu and Tsai's scheme while maintaining satisfactory image quality.
7
Content available remote Multiple Images Embedding Scheme Based on Moment Preserving Block Truncation Coding
Hu Y-C.
Fundamenta Informaticae
|
2006
|
Vol. 73, nr 3
373-387
EN
A low-complexity grayscale image embedding scheme that can embed multiple secret images is proposed in this paper. In this scheme, different users can extract different secret images according to the secret keys they hold. To reduce the storage cost of the secret images, each of the secret images is first compressed using an improved version of the moment preserving block truncation coding scheme. The compressed message of each secret image is then encrypted by the DES cryptography system with different secret key and then embedded into the host image using the modulus least-significant-bit substitution technique. According to the experimental results, it is shown that the proposed scheme consumes a little computational cost. Besides, different users can extract different number of secret images. In other words, the proposed scheme indeed provides a good approach for the hiding of grayscale images with access control.
8
Content available remote An Improved Tree-Structured Codebook Search Algorithm for Grayscale Image Compression
Hu Y-C., Chang C-C.
Fundamenta Informaticae
|
2006
|
Vol. 70, nr 3
251-260
EN
In this paper, an improved tree-structured codebook search algorithm is proposed. It is called the two-level codebook search algorithm (TLCS). The goal of this method is to reduce the computation cost of the multi-path-searching algorithm for TSVQ. It speeds up the codebook search by searching only a two-level codebook tree instead of the whole TSVQ codebook tree. According to the experimental results, a significant time reduction can be achieved with this method, compared to the multi-path-searching algorithm. In other words, our TLCS outperforms the multi-path-searching algorithm.
9
Content available remote A Novel Index Coding Scheme for Vector Quantization
Chang C-C., Chen G-M., Hu Y-C.
Fundamenta Informaticae
|
2006
|
Vol. 71, nr 2,3
215-227
EN
A novel method for the compression of the index table of vector quantization (VQ) is proposed in this paper. This method is designed based on the observation that neighboring image blocks are highly correlated. In other words, VQ-encoded neighboring image blocks tend to have similar indices if the codebook used in VQ is previously sorted by the principal component analysis technique. According to this characteristic, we find the same or similar indices around the current processing index to process it. In addition, the pre-statistics technique is employed to gather differences that appear most often in the index table. Simulation results indicate that the newly proposed scheme achieves significant reduction of bit rate without losing any image quality by the original VQ encoding.
10
Content available remote A Novel Image Ownership Protection Scheme Based on Rehashing Concept and Vector Quantization
Lin C-C., Hu Y-C., Chang C-C.
Fundamenta Informaticae
|
2006
|
Vol. 71, nr 4
443-451
EN
A novel watermarking scheme that is capable of hiding authorization data in a gray-level image is proposed in this letter. The proposed scheme generates a key stream to be the key to connect the authorized image and its watermark. The key stream is extra data rather than data being embedded into the authorized image. Such arrangement can guarantee the integrity of the image. To reduce the complexity in computing the key stream for the authorized gray-level image, two techniques are employed in the proposed scheme. One is the concept of rehashing, and the other is the vector quantization. The benefits of the proposal are to provide a key stream to prove the gray-level's ownership, and to keep the authorized image in its original state without any modification.
11
Content available remote A Novel Color Image Hiding Scheme Using Block Truncation Coding
Hu Y-C., Lin M-H., Jiang J-H.
Fundamenta Informaticae
|
2006
|
Vol. 70, nr 4
317-331
EN
In this paper, a novel color image hiding scheme that is capable of hiding two color secret images into a color host image is proposed. The secret images to be embedded are first compressed by the single bit map block truncation coding. DES encryption is then conducted on the compressed message before the secret image is embedded into the rightmost 3, 2, 3 bits of the R, G, B channels of every pixel in the host image. The experimental results show that our scheme provides an average secret image quality of 29.220 dB. In addition to the improved quality of both host images and retrieved secret images, our scheme further strengthens the protection of the secret images by conducting image compression and DES encryption on the secret image in advance. Therefore, our scheme not only extends the hiding capability of host images, but also is practical and secure.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.