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Image Processing, IET

Issue 2 • Date April 2009

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Displaying Results 1 - 6 of 6
  • Contrast enhancement and phase-sensitive boundary detection in ultrasonic speckle using bessel spatial filters

    Page(s): 41 - 51
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1053 KB)  

    Speckle in ultrasonic image systems adversely impacts the contrast and resolution in the image. This poses serious problems in the interpretation of B mode images of internal organs such as breast, liver, kidney and so on. In the absence of sufficient contrast, classifying the regions of interest into benign and malignant masses becomes error prone. Since some of the masses are uniquely identified in terms of the boundaries, poor contrast and resolution will result in difficulties with their identification. A new class of spatial filters based on cylindrical Bessel functions of the first kind is proposed for speckle reduction. These filters with complex impulse responses were explored for enhancing the contrast of speckled images. Hypothesising that the phase of the filtered image carries boundary information, the phase characteristics of four speckled images are also studied for detecting boundaries. Results indicate that these filters do improve the contrast and enhance the boundaries. It is shown that the phase map clearly indicates the existence of boundaries. A simple thresholding applied to the phase highlights the boundaries. The results show the strength of the Bessel spatial filters in improving contrast and highlighting boundaries without resorting to any additional edge-detection algorithms. View full abstract»

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  • Multi-component image segmentation using a hybrid dynamic genetic algorithm and fuzzy C-means

    Page(s): 52 - 62
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1125 KB)  

    Image segmentation is an important task in image analysis and processing. Many of the existing methods for segmenting a multi-component image (satellite or aerial) are very slow and require a priori knowledge of the image that could be difficult to obtain. Furthermore, the success of each of these methods depends on several factors, such as the characteristics of the acquired image, resolution limitations, intensity in-homogeneities and the percentage of imperfections induced by the process of image acquisition. Recently, fuzzy C-means (FCM) and Genetic Algorithms were separately used in segmenting multi-component images but neither of them had successfully addressed the above concerns. GA was enhanced using Hill-climbing, randomising, and modified mutation operators, leading to what is called hybrid dynamic genetic algorithm (HDGA). Coupling HDGA and FCM creates an unsupervised segmentation method which could successfully segment two types of multi-component images (Landsat ETM+, and IKONOS II). Comparison with the four different methods FCM, hybrid genetic algorithm (HGA), self-organizing-maps (SOM), and the combination of SOM and HGA (SOM-HGA) reveals that FCM-HDGA segmentation method gives robust and reliable results, and is more time efficient. View full abstract»

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  • An effective calibration procedure for correction of parallax unmatched image pairs

    Page(s): 63 - 74
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (985 KB)  

    The stereo image pairs or two-view video sequences can be captured by two cameras at two horizontally different positions. If the stereo image pairs possess incompatible convergences of vertical parallax and horizontal parallax, human eyes generally cannot properly exhibit stereo visualisation. If the image pairs are taken from single camera or selected from a video sequence, perception of stereo visualisation will become even worse. The authors propose an effective calibration procedure to adjust the image pairs to achieve better stereo visualisation. The proposed calibration procedure contains six steps, including feature point extraction, bidirectional feature point matching, relative distance checking, image transformation, hole-filling and reshaping. Experimental results show that the proposed system can effectively adjust vertical and horizontal parallax such that the calibrated stereo image pairs can properly exhibit stereo scenes in stereoscopic display systems. Experimental results also reveal that the proposed method can achieve less vertical parallax than the existing rectification methods. View full abstract»

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  • Adaptive rate control for motion JPEG2000

    Page(s): 75 - 87
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1077 KB)  

    Rate and quality-constrained rate control is very effective for video applications, since it can maintain constant quality while eliminating local rate spikes. An adaptive rate control method based on image activity measures (ARCIAM) is proposed for Motion JPEG2000. The algorithm can efficiently adjust the compressed bit rates to meet the rate and quality constraints for different types of colour sequences. It predicts the rate-distortion (RD) slope thresholds for frames based on image activity measure (IAM) before entropy coding. Thus, the encoding of unnecessary coding passes can be avoided. Experimental results show that the proposed method can meet the quality and rate constraints, and can achieve quality performance comparable to post-compression rate distortion optimisation at the same bit rate. Under 3 bpp and 40 dB constraints, ARCIAM can reduce the total encoding time and tier-1 encoding time for sequences by more than 20 and 30 , respectively. Moreover, the memory requirement for buffering bit-streams and RD-slope information is reduced by more than 30 on average. Besides, the method can be incorporated into the line-based JPEG2000 encoding system easily, and has been implemented on Kakadu. View full abstract»

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  • Multi-direction search algorithm for block motion estimation in H.264/AVC

    Page(s): 88 - 99
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (783 KB)  

    Many efficient search algorithms such as three-step search, new three-step search, four-step search, block-based gradient descent search, diamond search and hexagon-based search are developed for block motion estimation (ME) to search for the optimal objective function. The block ME technique involves an optimisation problem. Although these algorithms can converge to a minimal point rapidly, they suffer from becoming trapped in local minimum if the objective function has multiple minima. To solve this problem, the hybrid multi-hexagon-grid search (UMHexagonS) algorithm has been proposed in H.264/AVC, in which an unsymmetrical-cross search and an uneven UMHexagonS are employed over a wide search range to find a nearly global minimum. The experiment shows that the hybrid UMHexagonS algorithm is computation expensive and is occasionally trapped in local minimum. The authors propose a novel and fast search algorithm, called multi-direction search (MDS) algorithm, which uses an MDS first to find all possible locally optimal points and then uses the extended hexagon search to refine these points for the final optimal motion vector. The experimental results indicate that a significant improvement in computation reduction (~30 and 50~ reduction in average search points, corresponding to 19 and 37~ reduction in total encoding time, for MDS and fast MDS, respectively) can be achieved while maintaining better coding performance, compared with the hybrid UMHexagonS algorithm. View full abstract»

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  • Histogram-based reversible data hiding for vector quantisation-compressed images

    Page(s): 100 - 114
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (915 KB)  

    Reversible data hiding is required and preferable in many applications such as medical diagnosis, military, law enforcement, fine art work and so on. The author proposes to use reversible data hiding applications with a vector quantisation (VQ)-compressed image. The histogram of the prediction VQ-compressed image is explored. The prediction VQ encoded image is identical to traditional VQ encoding. The index of prediction encoded VQ images is modified to embed secret data. Furthermore, the VQ images can be completely reconstructed by the recovery procedure. The experimental results show the performance of the proposed method and the efficiency of the embedding, extraction and recovery procedures. In comparison with other VQ-based schemes, the proposed method provides a higher hiding capacity and a better stego-image quality. Also, the lossless VQ image is recovered. 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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