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location Munich, Germany
age 36
visits member for 2 years, 9 months
seen 1 min ago

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


20h
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
Jul
30
comment Automatically lining up two images that have some common elements
@Mr.Wizard: ImageTransformation can wrap. If you have per-pixel offsets (as you would have with many optical flow or non-parametric registration algorithms), this question might be useful: mathematica.stackexchange.com/questions/31274/…
Jul
25
comment Possible bug in Dynamic
@MichaelE2: You're right, this looks like a race condition: If I assign all Mathematica processes to a single CPU core, it doesn't crash anymore (or at least not that often). Maybe the WRI support people can't reproduce it because they have single core CPUs?
Jul
25
comment Possible bug in Dynamic
Yes, putting the ContourPlot inside Module[{x,y}, ... works, too. (I actually included that workaround in my WRI support ticket, but forgot it in the question here...)
Jul
23
comment Is there a way to recreate the typical Red/Blue-Postereffect using Mathematica?
I don't think you should delete the question. There are no close votes, either. But most image processing questions at least contain some img = Import[url of a good source image] code snippet, so everyone can start playing around right away, and the resulting answers are comparable.
Jul
23
comment Plot a perfect looking circle using two functions, always look like an ellipse
@TimHUK: I think the idea is that the axes in Plot often show different quantities (e.g. meters versus seconds), where PlotRange->Automatic would make no sense, and often give extremely stretched results. So WRI chose a fixed ratio that's supposed to be pretty. (But that's really just guessing.)
Jul
15
comment Is it possible to calculate with declarations only?
Any program can be expressed as a Turing machine, without functions or variables, only states and a (potentially) infinite tape. I'm not sure if that's what you want, though.
Jul
13
comment Optimization Algorithm: ideas wanted
If you want to improve your question, show us a function that would "grade" different solutions, i.e. that would add up some distances, values, whatever, and the solution that gets the highest (or lowest) grade is the optimum.
Jul
13
comment Optimization Algorithm: ideas wanted
As it's stated, I think the optimal solution is to move the max in each row to the middle of the row. That way, no value is more than 2 rows away from the maximum.
Jul
13
comment Dynamic with RegionNearest keeps one CPU core at 100% - Is this a bug?
I reported this as a bug to WRI. I also found a reproducible way to crash the kernel using Dynamic, reported that too
Jul
12
comment Swap elements in list without copy
Did you try playing with the numbers? I find it hard to believe that Mathematica can copy a 8 GB list 100.000 times in less than 2 seconds. With a GHz CPU, it should take about a second (order of magnitude) to copy it once.
Jul
12
comment Swap elements in list without copy
But would it also copy the list if no other symbol referenced it? Otherwise, how do you explain @eldo's timing results?
Jul
12
comment Swap elements in list without copy
You could even get rid of the temp write: swap[list_, a_, b_] := {list[[a]], list[[b]]} = {list[[b]], list[[a]]}