how to select certain shape from different images?
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i have an image of star
and
I want to select a this shape from other different images that content star and other shapes
how to do that
7 个评论
Walter Roberson
2012-5-28
Is the image of the star close enough to show sunspots? oblateness? Is the color fidelity quite good? Is the image available in multiple bands?
Stars usually only show up as dots in images; it is not easy to tell them apart, at least not unless you can capture the picture of some of the planetary nebula near them.
bym
2012-5-28
perhaps aboomnea meant a pentagram or other simple geometric shape
Geoff
2012-5-28
I'm sure Walter realised that. What he's saying is: "ask a good question, get a good answer"
Isee You
2012-5-29
Isee You
2012-5-29
Walter Roberson
2012-5-29
Your sample image is filled. Should only the (small) filled stars be selected, or should the large non-filled stars also be selected?
Some of the hollow stars are different aspect ratios (stretched more vertically); should those be found or only the ones with the same aspect ratio?
Is the task to be able to find portions of the image that match the given input image, or is the task to be able to match stars specifically?
Isee You
2012-5-29
回答（3 个）
Stephen
2012-5-29
0 个投票
haha, Walter :)
You can use the rucklidge algorithm. It relies on the haussdorf distance of a set of points, say the 10 points of your pentagram, and looks for a similar set of distances in all points of the target image. It takes a while sometimes, but it's pretty good.
You can also decompose the image with wavelets and look for similar signatures that way I've heard, but I can't help you build something like that. There may be something in the file exchange, like train a face recognizer to look for pentagrams or satanic faces.
Image Analyst
2012-5-29
0 个投票
I agree that it is a poorly phrased question that is so ambigous and open-ended as to make answering it have a high likelihood of wasting time. About all I can say, unless the poster posts an image or gives other additional information, is that this is a case of pattern recognition and there are thousands of ways to do that. You can go here http://iris.usc.edu/Vision-Notes/bibliography/contentspattern.html#Pattern%20Recognition,%20Clustering,%20Statistics,%20Grammars,%20Learning,%20Neural%20Nets,%20Genetic%20Algorithms for a list of them. The CBIR (content based image retrieval) community is involved heavily in this research right now, so you might look up CBIR methods. You might get your star by using nromxcorr2(), SURF, MSER, looking at the perimeter square to area ratio, or dozens of other ways depending on what your images look like. Sorry I can't explain all or any of them here - it would waste my time unless I know what kind of images you're dealing with.
Image Analyst
2012-5-29
0 个投票
For the images you have now provided, I'd recommend that you look at my image segmentation demo. http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862 Modify it to take the "solidity" - I think that will be enough to pick out just the stars. Basically it comes down to this process:
- extract the red channel: redChannel = rgbImage(:,:,1)
- threshold: binaryImage = redChannel > 128;
- call imfill: binaryImage = imfill(binaryImage , 'holes');
- call bwlabel and regionprops asking for solidity: regionprops(binaryImage, 'Solidity')
- filter out, using ismember, those blobs not having the require solidity values. See my demo.
My demo has everything you need. Give that a shot and let me know if you can't figure it out.
5 个评论
Isee You
2012-5-29
Image Analyst
2012-5-29
Aha, so the truth comes out, which it should have at the beginning, since none of what was said so far applies to livers. Not sure why you sent us on a wild goose chase about stars. Anyway, what is a CRT image? Do you mean CT? But won't the liver have different shapes depending on the slice plane's angle? I suggest you see if anyone else has done it before in section 20.8.2 and 20.8.2.1 here: http://www.visionbib.com/bibliography/contentsmedical.html#KK6863
Isee You
2012-5-30
Walter Roberson
2012-5-30
http://www.mathworks.com/matlabcentral/answers/7924-where-can-i-upload-images-and-files-for-use-on-matlab-answers
Isee You
2012-5-30
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