Papers by Keyword: Discrete Cosine Transform (DCT)

Abstract: Nowadays CBIR is getting more and more attention from organizations and researchers due to advances in digital imaging techniques. A lot of interest is getting paid to search images from large databases, as it is not only difficult and time-consuming task but sometimes frustrating for the users. This paper proposes the CBIR system based on color, texture and shape features. The proposed method employs the use of DCT and DWT along with Hierarchical k-means algorithm for faster retrieval of images. The efficiency of the given method is demonstrated by the results in the paper.

Abstract: In this paper, a print-scan resilient image watermarking scheme based on Radon transform and DCT(discrete cosine transform) is proposed. The watermark is preprocessed with a chaotic sequence, then the host image is transformed to frequency domain by block DCT. The preprocessed watermark is adaptively embedded into the transform domain coefficients by modulating the relationship between neighbor coefficients. The watermark detection process is accomplished without referring to the original image. Simulation results show good robustness against several attacks, such Jpeg compression, cropping, filtering and so on.

Abstract: In wireless communication, Orthogonal Frequency Division Multiplexing (OFDM) is a promising scheme against the multipath fading channel .However, due multi-carrier transmission , OFDM system has a major draw back of Peak-to-Average Power Ratio (PAPR) problem that affect the efficiency of HPA in the transmitter side. In the proposed scheme, a new technique is discussed for reducing PAPR in the OFDM system by using Discrete Cosine Transform (DCT) and adjacent sub carriers grouping with companding technique.A computer simulation is used to evaluate the performance of the proposed PAPR scheme.

Abstract: In this paper, we present a stepwise genetic programming algorithm to perform regression on a large number of noisy data, the purpose of which is to find a mathematical model for samples. To obtain an accurate statistical model of noisy sample points, discrete cosine transform was inserted into a standard GP algorithm. The energy-compaction property of DCT makes it very suitable for accelerating the implement of the standard GP algorithm and dealing with the noisy data samples. We tested the proposed algorithm with benchmark instances and compared it with several popular other algorithms. The experimental results have shown that the proposed algorithm is a powerful tool in finding optimal solutions.

Abstract: In this paper, we present a coordinate rotation digital computer (CORDIC) based fast algorithm for power of two point DCT. The proposed algorithm has some distinguish advantages, such as regular data flow like the Cooley-Tukey FFT, identical post-scaling factor, and the rotation angles of the CORDICs in DCT are arithmetic sequence. By using the sum formula and double angle formula, we dramatically reduce the CORDIC types in the proposed algorithm. For the purpose of gain fast speed, we use Carry Save Adder (CSA) as the basic cell of each part and Carry Look-ahead Adder (CLA) to produce the outputs in the final level. Compared with other known architectures, the proposed 2-point DCT architecture has lower hardware complexity, higher throughput and better synchronization

Abstract: Image filtering is one of the principal tools used in computer vision applications. Real systems store and manipulate high resolution images in compressed forms, therefore the implementation of the entire processing chain directly in the compressed domain became essential. This includes almost always linear filtering operations implemented by convolution. Linear image filtering implementation directly on the JPEG images is challenging for several reasons, including the complexity of transposing the pixel level convolution in the compressed domain, which may increase the processing time, despite avoiding the decompression. In this paper we propose a new computationally efficient solution for JPEG image filtering (as a spatial convolution between the input image and a given kernel) directly in the DCT based compressed domain. We propose that the convolution operation to be applied just on the periodical extensions of the DCT basis images, as an off-line processing, obtaining the filtered DCT basis images, which are used in data decompression. While this doesn't solve the near block boundaries filtering artefacts for large convolution kernels, for most practical cases, it provides good quality results at a very low computational complexity. These kind of implementations can run at real-time rates/ speeds and are suitable for developments of applications on digital cameras/ DSP/FPGA.

Abstract: The method of compression and reconstruction for wind turbine vibration signal based on Discrete Cosine Transform is presented. Two group wind turbine vibration signals are compressed and reconstructed by DCT. The compression ratio and the compression reconstruction accuracy are investigated. The relationship between compression ratio, NSRMSE and the number of the reserved data is clarified. The result facilitates the application of compression and reconstruction for wind turbine vibration signal based on DCT.

Abstract: With the rapid spread of image processing applications and the further development of multimedia technologies, compression standards become more and more important. This paper intends to explain JPEG (Joint Photographic Experts Group) compression, which is currently a worldwide standard for digital image compression, is based on the discrete cosine transform (DCT). Based on the research, the paper describes theory and algorithms of the JPEG DCT compression and implements a baseline JPEG codec (encoder/decoder) with MATLAB.

Abstract: Copyright protection has drawn much attentions especially in the advent of computer and the internet. Illagal copying of digital multimedia has been much easier because of widely using of the modern technologies.This paper proposes a novel digital watermarking algorithm based on the numbers of the blocked middle DCT positive and negative coefficients. Embedding watermark into the middle frequency of DCT is a perfect idea and it can receive a trade-off between robustness and imperceptibility.We utilized the embedding strength to get a balance between their robustness and imperceptibility. The results show that the algorithm is robust to print and scan process.

Abstract: Phase unwrapping is one of the key technologies in electronic speckle pattern interferometry. A new phase unwrapping algorithm, based on windowed Fourier transform is proposed. The high noisy phase map is denoised by the window Fourier transform approach and then is uwrapped by the discrete cosine transform. The method is tested in this paper using a circumferentially fixed circular plate with a point load at the centre and compared with not denoised wrapped phase map and unwrapped phase map. The result shows the new proposed phase unwrapping method in denoising and improving image quality has obvious superiority.