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jan
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second derivative of an image

Asked by jan
on 9 May 2014
Latest activity Commented on by Image Analyst
on 11 May 2014
Hi every body
The contour of an object in one image is known as the points with second derivative equal to zero. How can i get this characteristic knowing that I have only the image (the pixels intensity)??
Please can any one help me, thanks a lot

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1 Answer

Answer by Nitin
on 10 May 2014

There is a nice explanation on image derivative here . Please check it out, slide 23 onwards.

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Nitin
on 11 May 2014
Did you check the Laplacian second derivative on slide 31?
jan
on 11 May 2014
Hi Nitin In fact, to obtain this characteristic we can apply the laplacien filter and this is what i tested before asking my question and this is the code that i used:
I=imread('image.png');
w=fspecial('laplacian',0);
g=imfilter(I,w,'replicate');
figure(1),imshow(g,[]);
but in g, the contour points aren't only the points with derivative equal to zeros there are other points inside and outside the object with derivative equal to zeros. So what i really need what i have tested is it true? and any explication or other suggested ideas because i need to characterise, in a formal manner the contour points to do a clustering thanks
Image Analyst
on 11 May 2014
Why don't you post your image to help with your explanation about what you want to measure in the image?

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