14,216 research outputs found
Improving the Performance of K-Means for Color Quantization
Color quantization is an important operation with many applications in
graphics and image processing. Most quantization methods are essentially based
on data clustering algorithms. However, despite its popularity as a general
purpose clustering algorithm, k-means has not received much respect in the
color quantization literature because of its high computational requirements
and sensitivity to initialization. In this paper, we investigate the
performance of k-means as a color quantizer. We implement fast and exact
variants of k-means with several initialization schemes and then compare the
resulting quantizers to some of the most popular quantizers in the literature.
Experiments on a diverse set of images demonstrate that an efficient
implementation of k-means with an appropriate initialization strategy can in
fact serve as a very effective color quantizer.Comment: 26 pages, 4 figures, 13 table
Using a Second Order Sigma-Delta Control to Improve the Performance of Metal-Oxide Gas Sensors
Controls of surface potential have been proposed to accelerate the time response of MOX gas sensors. These controls use temperature modulations and a feedback loop based on first-order
sigma-delta modulators to keep constant the surface potential. Changes in the surrounding gases,
therefore, must be compensated by average temperature produced by the control loop, which is the
new output signal. The purpose of this paper is to present a second order sigma-delta control of the surface potential for gas sensors. With this new control strategy, it is possible to obtain a second order zero of the quantization noise in the output signal. This provides a less noisy control of the surface potential, while at the same time some undesired effects of first order modulators, such as the presence of plateaus, are avoided. Experiments proving these performance improvements are presented using a gas sensor made of tungsten oxide nanowires. Plateau avoidance and second order noise shaping is shown with ethanol measurements.Postprint (author's final draft
Automatic segmentation of skin cancer images using adaptive color clustering
This paper presents the development of an adaptive image segmentation algorithm designed for the identification of the skin cancer and pigmented lesions in dermoscopy images. The key component of the developed algorithm is the Adaptive Spatial K-Means (A-SKM) clustering technique that is applied to extract the color features from skin cancer images. Adaptive-SKM is a novel technique that includes the primary features that describe the color smoothness and texture complexity in the process of pixel assignment. The A-SKM has been included in the development of a flexible color-texture image segmentation scheme and the experimental data indicates that the developed algorithm is able to produce accurate segmentation when applied to a large number of skin cancer (melanoma) images
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