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Jun
20
revised Best method to find variation in width along the image of a slit?
added linked image
Jun
13
comment How to do automatic differentiation?
Is there a reason why you want source code transformation instead of operator overloading (which is straightforward to do in MMA, I think)?
Jun
13
answered How to do automatic differentiation?
Jun
5
revised How to build recursive function which only remembers every pth value and the last two values?
added 40 characters in body
Jun
5
answered How to build recursive function which only remembers every pth value and the last two values?
Jun
2
awarded  Enlightened
Jun
2
awarded  Nice Answer
Jun
2
answered Interactive Mandelbrot Zoomer?
May
25
comment What kind of algorithm can be used to map image coordinates to cylinder coordinates
@ChongVera: IIRC, I started with a simple 2nd order polynomial in X direction and 1st order polynomial in Y direction. Then I kept adding terms that didn't break FindMinimum and seemed to improve the result image visually. So, basically, by trial and error.
May
25
answered What kind of algorithm can be used to map image coordinates to cylinder coordinates
May
17
comment Compute a hessian matrix on a image?
@SURF: Of course, just pack the whole thing in a function that takes the scale parameter (second parameter to GaussianFilter) as a parameter and call that with a range of values (using Table or Array). Or use Manipulate to see the effect of scale interactively.
May
16
comment Compute a hessian matrix on a image?
@SURF: Sure, you could use e.g. minEigenvalue = MapThread[Min, imgEigenvalues, 2]; to calculate the per-pixel min of the two eigenvalues, then binarize the result that.
May
16
comment Compute a hessian matrix on a image?
@Histograms: As far as I understand the documentation, GradientFilter basically uses GaussianFilter, and it can only calculate the 1st derivative. You could use DerivativeFilter, of course. I generally start with GaussianFilter, as it's in some sense the most "natural" kernel and has (at least theoretically) certain unique advantages, especially if you calculate multiple scales. (The reasoning is too long for a comment, and honestly, I'd have to look most of it up myself, but I can give references if you're interested.)
May
16
answered Compute a hessian matrix on a image?
May
13
awarded  Nice Question
May
11
comment How to construct a kernel from a function?
Are you looking for Array or Table? Those evaluate a function resp. an expression for every cell in a matrix
May
4
awarded  Nice Answer
Apr
29
awarded  Nice Answer
Apr
29
answered Analyze touching particles with holes in a microscopic image
Apr
17
answered Integrating the second derivative of a 3D curve