optimization routes, dijkstra algorithm, Biograph,

Question

Jesus Luevano 2012-8-10

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Hi, when I try to use the dijkstra algorithm to optimization route, always it asks me the segments from the nodes, what happens if I do not know them, because I trying to get the optmization route of an image.

by the way, I do not understand the CMatrix relationship with the real image on the biograph function.

somebody know how to implement that in simulink???

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Answer 1

Walter Roberson 2012-8-10

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You need to somehow figure out what the node connections are from the image. The difficulty of doing that will depend on how you create your "nodes" out of the image.

http://www.mathworks.com/matlabcentral/answers/7924-where-can-i-upload-images-and-files-for-use-on-matlab-answers

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Walter Roberson 2012-8-13

Show us an image and point out the parts of it that you want to have considered as being nodes.

(My guess is that you are trying to implement robotic navigation with an array of square tiles, but that is speculation on my part.)

Image Analyst 2012-8-14

You can find lots of information if you drill down through the links here: http://en.wikipedia.org/wiki/Pathfinding For example, see the right hand panel on the A* page. I've always wanted to try some of the fancy variants but for most cases A* works so well that I've never needed to.

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Answer 2

Image Analyst 2012-8-13

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I don't know what a biograph is - apparently according to Google images, it's a celebrity, a theater, or a Bob Dylan album. But if you're trying to find some route through an image, like for example you're following a blood vessel in a radiograph, then the nodes are the pixels. You can do something like find the path from one place to another that has the brightest average gray level (I did this using the A* algorithm as part of my Ph.D.). The Djikstra algorithm has been improved upon many many times so you might want to look into better algorithms. Wikipedia has a huge list of them.

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Image Analyst 2012-8-14

Right, good points. If I recall correctly, in my case, each node had an x (column) position, a y (row, line) position, and a value (gray level). And as you traversed the graph (image), each length was either 1 (up, down, left, right) or sqrt(2) (diagonal travel). And yes the cost function can be specified in a number of ways, some of which could get very complicated, depending on what you want to do.