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Image Processing, IET

Issue 4 • Date August 2009

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Displaying Results 1 - 6 of 6
  • Reduction of discrete cosine transform/ quantisation/inverse quantisation/inverse discrete cosine transform computational complexity in H.264 video encoding by using an efficient prediction algorithm

    Publication Year: 2009 , Page(s): 177 - 187
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (417 KB)  

    This study develops a novel prediction algorithm to effectively save the computational complexity of discrete cosine transform (DCT), quantisation (Q), inverse Q (IQ), and inverse DCT (IDCT) in video encoding for H.264 applications. Based on the DC value of the DCT coefficients that is equal to the sum of residual data in the 4times4 sub-macroblock (sub-MB), a mathematical model is built to develop a prediction algorithm for reducing the computations in the DCT/Q/IQ/IDCT process. Experimental results and comparisons demonstrate that the proposed prediction algorithm significantly reduces the encoding time while incurring little additional overhead, and lowers the bit rate with little peak signal-to-noise ratio degradation. View full abstract»

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  • Compressed image reproduction based on block decomposition

    Publication Year: 2009 , Page(s): 188 - 199
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (462 KB)  

    A compressed image reproduction scheme is proposed by properly decomposing and manipulating the coefficients of discrete cosine transform (DCT) directly in the compressed domain. The basic idea of the proposed approach is to decompose each DCT block into several sub-blocks and to adjust the brightness and detail components of a given image for compressing dynamic range and enhancing contrast. Image reproduction based on the subblock decomposition can be done more precisely than any approach based on the normal block-sized approach. First, DCT coefficients of each block are decomposed into several sub-blocks. Next each sub-block's coefficients are separated into brightness and detail components, and treated differently according to content analysis. Then, the enhanced coefficients are projected on the constraint sets to avoid some artefacts, and are composed back to the original order. The main advantages of the proposed algorithm are that (i) it can enhance the dynamic range and details without affecting the compressibility of the given image since it operates directly in the compressed domain, and (ii) it does not boost blocking artefacts around big edges without any further processing. In order to evaluate the proposed scheme, several base-line approaches are described and compared using enhancement quality measures. View full abstract»

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  • Typhoon cloud image enhancement and reducing speckle with genetic algorithm in stationary wavelet domain

    Publication Year: 2009 , Page(s): 200 - 216
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1258 KB)  

    By employing discrete stationary wavelet transform (SWT), generalised cross-validation (GCV), genetic algorithm (GA), and non-linear gain operator, an efficient de-noising and enhancement algorithm for typhoon cloud image is proposed. Having implemented SWT to a typhoon cloud image, noise in a typhoon cloud image is reduced by modifying the stationary wavelet coefficients using GA and GCV at fine resolution levels. Asymptotical optimal de-noising threshold can be obtained, without knowing the variance of noise, by only employing the known input image data. GA and non-linear gain operator are used to modify the stationary wavelet coefficients at coarse resolution levels in order to enhance the details of a typhoon cloud image. Experimental results show that the proposed algorithm can efficiently reduce the speckle in a typhoon cloud image while well enhancing the detail. In order to accurately assess an enhanced typhoon cloud image's quality, an overall score index is proposed based on information entropy, contrast measure and peak signal-noise-ratio (PSNR). Finally, comparisons between the proposed algorithm and other similar methods, which are proposed based on discrete wavelet transform, are carried out. View full abstract»

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  • Computation of Zernike moments in improved polar configuration

    Publication Year: 2009 , Page(s): 217 - 227
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (946 KB)  

    A polar system is used to compute Zernike moments to enhance their accuracy and to improve invariance to rotation. This requires reconfiguration of pixel arrangements that are normally available in rectangular grids in the cartesian coordinate system. This study presents an improved reconfiguration model of pixel arrangements that uses nearly 27.3% less number of pixels compared to the existing model, thus enhancing the computational efficiency of the proposed method by the same percentage. The performance of the proposed model is analysed in detail, which is observed to be at par with the existing method. View full abstract»

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  • Robust and transparent watermarking scheme for colour images

    Publication Year: 2009 , Page(s): 228 - 242
    Cited by:  Papers (3)  |  Patents (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1299 KB)  

    In this study, a robust and transparent watermarking scheme for colour images is proposed. The colour features for the human visual system are utilised to design the colour watermarking scheme. Through the exploitation of the perceptual redundancy of colour images, the proposed watermarking scheme is perceptually tuned to embed and detect the watermark in the perceptually significant sub-bands of luminance and chrominance components of colour images in the wavelet domain. The employment of the uniformity in the uniform colour space and the masking effect mainly due to local variations in luminance magnitude leads to that the perceptual redundancy of colour images can be measured. By using the estimated perceptual redundancy in the form of error visibility thresholds of wavelet coefficients of the colour image, high strength watermarks are invisibly embedded into coefficients of the host colour image for resisting compression and malicious attacks. Simulation results show that the estimation of perceptual redundancy is helpful to the design of the watermarking scheme for colour images. The performance in terms of robustness and transparency of the proposed watermarking scheme is superior to that of the existing scheme. View full abstract»

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  • A new steganographic scheme based on vector quantisation and search-order coding

    Publication Year: 2009 , Page(s): 243 - 248
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    In this paper, the authors propose a new steganographic scheme based on vector quantisation (VQ) and search-order coding (SOC). The capacity of the proposed scheme is higher than others based on VQ and the quality of stego-image is acceptive. In general, the capacity of the schemes based on VQ is usually 1-bit per block. In 2004, Yu et al. proposed a scheme to increase the capacity to 3-bit per pair of blocks. In the proposed scheme, the authors utilised multiple codebooks and chose the combinations of per pair of blocks, to embed the secret data. The capacity was increased to 6-bit per pair of blocks, and the quality was identical Yu et al.'s scheme. View full abstract»

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Aims & Scope

The range of topics covered by IET Image Processing includes areas related to the generation, processing and communication of visual information.

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