| 1. |
- Aibinu, A.M., et al.
(författare)
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A New Method of Correcting Uneven Illumination Problem in Fundus Images
- 2007
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Konferensbidrag (refereegranskat)abstract
- Recent advancements in signal and image processing have reduced the time of diagnoses, effort and pressure on the screeners by providing auto diagnostic tools for different diseases. The success rate of these tools greatly depend on the quality of acquired images. Bad image quality can significantly reduce the specificity and the sensitivity which in turn forces screeners back to their tedious job of manual diagnoses. In acquired fundus images, some areas appear to be brighter than the other, that is areas close to the center of the image are always well illuminated, hence appear very bright while areas far from the center are poorly illuminated hence appears to be very dark. Several techniques including the simple thresholding, Naka Rushton (NR) filtering technique and histogram equalization (HE) method have been suggested by various researchers to overcome this problem. However, each of these methods has limitations at their own and hence the need to develop a more robust technique that will provide better performance with greater flexibility. A new method of compensating uneven (irregular) illumination in fundus images termed global-local adaptive histogram equalization using partially-overlapped windows (GLAPOW) is proposed in this paper. The developed algorithm has been tested and the results obtained show superior performance when compared to other known techniques for uneven illumination correction.
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| 2. |
- Aibinu, A.M., et al.
(författare)
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Automatic Diagnosis of Diabetic Retinopathy from Fundus Images Using Digital Signal and Image Processing Techniques
- 2007
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Konferensbidrag (refereegranskat)abstract
- Automatic diagnosis and display of diabetic retinopathy from images of retina using the techniques of digital signal and image processing is presented in this paper. The acquired images undergo pre-processing to equalize uneven illumination associated with the acquired fundus images. This stage also removes noise present in the image. Segmentation stage clusters the image into two distinct classes while the abnormalities detection stage was used to distinguish between candidate lesions and other information. Methods of diagnosis of red spots, bleeding and detection of vein-artery crossover points have also been developed in this work using the color information, shape, size, object length to breadth ration as contained in the acquired digital fundus image. Furthermore, two graphical user interfaces (GUIs) have also been developed during this work; the first is for the collection of lesion data information and was used by the ophthalmologist in marking images for database while the second GUI is for automatic diagnosing and displaying of the result in a user friendly manner. The algorithm was tested with a separate set of 25 fundus images. From this, the result obtained for microaneurysms and haemorrhages diagnosis shows the appropriateness of the method.
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| 3. |
- Iqbal, Muhammad Imran, et al.
(författare)
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Detection of Vascular Intersection in Retina Fundus Image Using Modified Cross Point Number and Neural Network Technique
- 2008
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Konferensbidrag (refereegranskat)abstract
- Vascular intersection can be used as one of the symptoms for monitoring and diagnosis of diabetic retinopathy from fundus images. In this work we apply the knowledge of digital image processing, fuzzy logic and neural network technique to detect bifurcation and vein-artery cross-over points in fundus images. The acquired images undergo preprocessing stage for illumination equalization and noise removal. Segmentation stage clusters the image into two distinct classes by the use of fuzzy c-means technique, neural network technique and modified cross-point number (MCN) methods were employed for the detection of bifurcation and cross-over points. MCN uses a 5x5 window with 16 neighboring pixels for efficient detection of bifurcation and cross over points in fundus images. Result obtained from applying this hybrid method on both real and simulated vascular points shows that this method perform better than the existing simple cross-point number (SCN) method, thus an improvement to the vascular point detection and a good tool in the monitoring and diagnosis of diabetic retinopathy. ©2008 IEEE.
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| 4. |
- Iqbal, Muhammad Imran, et al.
(författare)
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Error Sensitivity Analysis for Wireless JPEG2000 Using Perceptual Quality Metrics
- 2008
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Konferensbidrag (refereegranskat)abstract
- Quality assessment of mobile and wireless multimedia services including image and video applications has gained increased attention in recent years as a means of facilitating efficient radio resource management. In particular, approaches that utilize perceptual-based metrics are becoming more dominant, as conventional fidelity metrics such as the peak signal-to-noise ratio (PSNR) may not correlate well with quality as perceived by the human observer. In this paper, we focus on the error sensitivity analysis for images given in the wireless JPEG2000 (JPWL) format using perceptual quality metrics. Specifically, the perceptual quality improvements obtained by progressively decoding an increasing number of image packets are examined. It is shown that the considered perceptual quality metrics exploiting structural image features may accompany or replace the PSNR-based error sensitivity description (ESD) marker segment in the wireless JPEG2000 standard. This addition will increase the effectiveness of the ESD marker segment as it facilitates the communication of reduced-reference information about the image quality from the transmitter to the receiver. In addition, the proposed approach can be used to guide the design of preferential error control coding schemes, link adaptation techniques, and selective retransmission of packets with respect to their contribution to overall quality as perceived by humans.
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| 5. |
- Iqbal, Muhammad Imran, et al.
(författare)
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On Region of Interest Coding for Wireless Imaging
- 2007
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Konferensbidrag (refereegranskat)abstract
- Numerous studies in the fields of human vision and electronic imaging have revealed that the human visual system (HVS) tends to focus on a few preferred areas for given typical images/scenes. Subjective experiments have also shown a strong correlation for these preferred areas among the involved test subjects provided that the same context is viewed. In light of the limited available and expensive resources in technical systems such as mobile multimedia systems, it would therefore be favorable to explore findings about the operation of the HVS in the design of technical communication systems. This paper aims at stimulating such HVS driven approaches in the context of preferential image coding; the region of interest (ROI) coding and its potential application in wireless imaging. In particular, we will elaborate on the general concepts of ROI coding, propose a framework for ROI coding for wireless imaging, review ROI identification mechanisms, and discuss ROI support by non-standardized techniques and ROI support in the JPEG2000 standard. As this paper is of conceptual nature, the work will be consolidated in a classification of contemporary ROI coding techniques including a discussion of their advantages and disadvantages. As a consequence, a number of application areas of ROI coding are identified with the major focus given to the field of wireless imaging.
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| 6. |
- Iqbal, Muhammad Imran, et al.
(författare)
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Perceptual-based quality assessment of error protection schemes for wireless JPEG2000
- 2009
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Konferensbidrag (refereegranskat)abstract
- Designing wireless imaging services with acceptable quality imposes great challenges due to the severe impairments induced by wireless channels, high data rate demands and limited transmission bandwidth. In this paper, we examine different error protection schemes for the JPEG2000 codestream using the error control codes offered by the wireless JPEG2000 (JPWL) standard. In particular, two unequal error protection (UEP) schemes are considered. In the first scheme, only the initial and more important packets of the JPWL codestream are protected while the remaining packets are left without protection. In contrast, the second scheme uses a strong code for the initial packets while a weaker code is used for the tail packets. As quality of visual services may not be captured adequately with traditional link layer metrics, code selection and their performance assessment is based on perceptual quality metrics. Specifically, the LP -norm, structural similarity (SSIM) index and visual information fidelity (VIF) criterion are utilized. Numerical results are provided for a range of system conditions under which UEP outperforms conventional equal error protection in terms of perceptual quality metrics.
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