How do i calculate hessian matrix for an image?

i need to calculate hessian matrix manually.can anyone help?

Answer 1

[David Legland]

Hi, you need to compute second derivatives in each direction, using something like:

 [gx, gy] = gradient(double(img));
 [gxx, gxy] = gradient(gx);
 [gxy, gyy] = gradient(gy);

The coefficients of the hessian matrix for each pixel are given by gxx, gxy and gyy.

regards

[suresh G]

thank you

[sonu Lamba]

Can you please explain me that how to calculate the same(hessian matrix) for videos for key-points detection of moving people?

[Walter Roberson]

Yongkai liu comments to David Legland

important

[Zirui WANG]

Thanks a lot for the answer, but I think there is a small order issue in the last line?

I think the last line should be

[gyx, gyy] = gradient(gx)

instead of

[gxy, gyy] = gradient(gx)

?

[Ismail Zouaoui]

I guess that Gyx = Gxy

Answer 2

[Yongkai liu]

Thanks! It seems that in practice, we use the second derivative of gassian filter convoluted on image to get the hessian matrix feature of image.