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location Munich, Germany
age 36
visits member for 3 years
seen 5 mins ago

I work at a small mechanical engineering company, where I develop software and image processing algorithms for camera-based inspection machines.


Jan
16
comment Plotting y'[x] vs y[x]
ParametricPlot?
Jan
14
comment How can I detect if an image is in or out of focus?
Related: stackoverflow.com/questions/7765810/…
Jan
12
comment How can FactorInteger be so slow if PrimeQ is fast?
@DanielLichtblau: reading an 8th grade math book might lead one to believe that factorizing an integer is the only way to find out if it's prime ;-)
Jan
9
comment Can I force Mathematica to use machine precision?
Thanks @OleksandrR., SystemSetSystemOptions["CatchMachineUnderflow" -> False];` works perfectly. I did look for similar questions, but didn't find the one you linked. It's obviously a duplicate. Should delete it myself or vote to close?
Jan
9
comment Is there a way to characterize a winding object in an image?
+1. If you only want the local maxima of the distance transform, you can use SkeletonTransform. If Mean/Max are not enough, you can use ComponentMeasurements[... "Data" to get the pixel values in the distance transform/skeleton image.
Dec
14
comment ReplaceImageValue and ReplacePixelValue extremely slow
If you just want to highlight pixels, you can use: HighlightImage[image, bin], which is very fast. In general, working with coordinates/indices seems to be much slower than using converting images to arrays with ImageData and using simple arithmetic.
Dec
4
comment Mask outliers in an image
You wrote "I can do the outliner detection" but you didn't give any details: What's the result of your outlier detection? A list of coordinates? A binary image (or 2d array)? Component data from ComponentMeasurements? Also: working with lists of indices is often much slower than working with a 2d array containing 0's and 1's (because of vectorization).
Nov
18
comment What does it mean: “Assuming a matrix | Use a list of lists instead”?
In Mathematica, a matrix is just a list of lists, so don't worry. This just means that the suggestions bar offers suggestions for matrices. If you clicked on "list of lists", you'd see different suggestions.
Nov
13
comment More on performance of Sum[]
I would guess that the resolution of AbsoluteTiming is system dependent. For example, on my Win 7 PC, I never get a value between 0 and 0.0005, so that's probably the resolution of some clock that AbsoluteTiming uses. If you compare only timings large compared to the clock resolution (e.g. t > 0.01), the graphs do look very similar.
Nov
13
comment Finding a specific number of eigenvalues in Mathematica
If m is a square matrix, then Eigenvalues[m,n] gives the first n eigenvalues.
Nov
13
comment FindPeaks does not smooth noise on peak?
MaxDetect[data, 0.01] where 0.01 is a "noise threshold" is also worth a try - the resulting vector is 1 for (possibly extended) maxima, and 0 elsewhere.
Nov
6
comment Best fit equation from a scanned image
Related: mathematica.stackexchange.com/questions/3831/…
Oct
29
comment Usage of @ symbol in Mathematica
Have you seen this? mathematica.stackexchange.com/questions/18393/…
Oct
25
comment how to speedup subpixel registration
The simplest way is to replace (# + {x, y}) & with TranslationTransform[{x, y}] - that makes it about 10x faster on my PC (I'm guessing ImageTransformation is optimized for TransformationFunctions). Replacing NMinimize with FindMinimum makes it 10x faster, again. You can probably make it faster if you carefully think about how ImageTransformation interpolates between pixels (there might even be a closed form solution?), but that's a lot more work for 0.2 seconds.
Sep
29
comment Curve fit based on minimal data
According to the wikipedia link, the polar form is just $r=b+a\cos\theta$ - so maybe you could convert your points to polar coordinates and use Fit?
Sep
22
comment Is there a CDF Player for Mathematica 10?
But you won't tell us where to find it?
Sep
5
comment Compose one image over another
You can use ImageApply to apply a function like Min pixel-wise. Or turn the images to normal arrays using ImageData and use MapThread.
Sep
4
comment Are there ways to create local variables analogous to a local variable in C++ and other languages?
Maybe I'm missing something. Isn't that exactly what Module does?
Aug
31
comment ImageTransformation: polar to cartesian
@paw: The black dot is there because the polar image contains no data for that location. If you use 0 in the DataRange of the inverse transform, but used 1 in the PlotRange of the polar transform, the result will be slightly skewed (by 1 pixel at the center). You can either use 0 for both, or use Padding -> "Fixed" to get rid of the black dot in the center.
Aug
12
comment How to translate and scale an image via ImageTransformation
You could just use Composition[TranslationTransform[...], ScalingTransform[...], RotationTransform[...] ] to create a complex transformation from simple ones