Livewire Segmentation Technique
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Livewire is a segmentation technique which allows regions of interest to be extracted quickly and accurately, using simple mouse clicks. It is based on the lowest cost path algorithm, by Dijkstra. Firstly the grayscale image is modeled as a rectangular matrix whose pixel values are integers ranging from 0 to 255 (if the image is a color one, it might be converted to a grayscale one and use the algorithm the same way, although it's better to maximize the costs on each color channel). Each pixel of the matrix is a vertex of the graph and has edges going to the 8 pixels around it, as up, down, left, right, upper-right, upper-left, down-right, down-left. The edge costs are defined based on a cost function.
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[edit] Livewire Segmentation
The user sets the starting point clicking on an image’s pixel. Then, as he starts to move the mouse over other points, the smallest cost path is drawn from the starting point to the pixel where the mouse is over, changing itself if the user moves the mouse. If he wants to choose the path that is being displayed, he simply clicks the image again. One can easily see in the right image, that the places where the user clicked to outline the desired region of interest are marked with a small square. It is also easy to see that the livewire has snapped on the image's borders.
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[edit] References
MORTENSEN, E. N.; BARRETT, W. A. Intelligent scissors for image composition. In: SIGGRAPH ’95: Proceedings of the 22nd annual conference on Computer graphics and interactive techniques. New York, NY, USA: ACM Press, 1995. p. 191–198. ISBN 0-89791-701-4.
