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Mar
24
awarded  Nice Answer
Mar
24
revised Extracting road curves from an image
added 3 characters in body
Mar
24
comment Extracting road curves from an image
@Pickett: Weird. The documentation doesn't say that this syntax is new, and I could have sworn I've used it like this since v8. OTOH, the speed difference isn't that large (in this case) so I'll change it to your version.
Mar
24
comment Extracting road curves from an image
@Pickett: Weird. I've just executed the code in a fresh MMA session, and except for the Show-problem Zviovich mentioned, it worked fine. Does whitePixels contain a list of 2d coordinates in your session? Or maybe -> Automatic syntax is newer than your MMA version?
Mar
24
comment Extracting road curves from an image
@Zviovich: I've used bgnd=Image[bgnd], to make my experiments with colorDist faster. I didn't realize this changed the behavior of Show. I've updated my answer. Regarding the title: Maybe something like "Extracting road graphs from an image"?
Mar
24
revised Extracting road curves from an image
added 12 characters in body
Mar
23
answered Extracting road curves from an image
Mar
22
answered How to add a static JPEG into a Manipulate without slowing it down
Mar
19
awarded  Nice Answer
Mar
13
answered Image processing for extracting regions of book pages that are covered by text
Mar
9
comment Can I solve this graph theory problem with Mathematica?
I see. The solution got lost in translation...
Mar
9
comment Can I solve this graph theory problem with Mathematica?
Which number is which? Could you maybe draw one of them in a graph? I thought they were top-to-bottom, left-to-right, but then 4,5 in the first example would be neighbors.
Mar
4
awarded  Popular Question
Feb
20
answered Calculating displacement for a circular disc
Feb
11
comment Using 2D Fourier transform of an image to detect typical wavelengths
@SjoerdC.deVries is right, I didn't notice that. IIRC, this is done to "rotate" the 0 frequencies to the center of the FFT output. If you want to interpret the values numerically (instead of displaying the FT as a picture), you'd want to remove that line.
Feb
11
comment Using 2D Fourier transform of an image to detect typical wavelengths
fw contains the values. I.e. fw[[1,1]] is the value for frequency 0/0, fw[[1,2]] is the value for frequency 0/1...
Feb
7
comment Efficient Lloyd Sampling of Images
Calculating the distance to the nearest seed for each pixel, good idea, I didn't think of that! It might get slower if nx and ny get large (10^4? 10^5?), but for 200, it's pretty fast. I don't have time to update my answer right now, but I think Nearest[seeds -> Range[Length[seeds]], pos][[All, All, 1]] is even faster than your Compiled code.
Feb
7
comment Efficient Lloyd Sampling of Images
@paw: It seems as if Rasterize[Graphics[...]] creates an 8-bit image, and using GrayLevel[index/200] leads to rounding errors. GrayLevel[index/255] seems to work better; If you have more than 255 seeds, you'll have to use RGBColor to encode the seed index. Also, I've noticed that the seed centers seem to be "moving downwards" - I'm guessing Polygon and ComponentMeasurements are rounding in different directions - that's why I've added the (admittedly, ugly) -1 in the PlotRange
Feb
7
revised Efficient Lloyd Sampling of Images
deleted 11 characters in body
Feb
7
revised Efficient Lloyd Sampling of Images
added 1045 characters in body