I have this image:
I would like to separate qualitatively 4 different regions into approximately such an image:
The colors or gray shadings of the regions do not matter.
How can this be achieved with Mathematica?
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2 Answers
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I will rely on the assumption that the noise will blend into different intensities for each desired component.
A Kuwahara filter is good at removing uniform noise from an image while preserving edges. Here the noise is 'locally uniform' and the edges we seek are the boundaries where the noise noticeably changes. So a Kuwahara filter can help, but admittedly might not be the best choice of filter for this task:
im = ColorConvert[RemoveAlphaChannel[Import["https://i.stack.imgur.com/OWfLp.png"]], "Grayscale"];
kuw = KuwaharaFilter[im, 10]
This filter uses a square kernel and therefore looks splotchy. We can do our best to smooth it:
smooth = ImageAdjust[CurvatureFlowFilter[MeanFilter[kuw, 10], 50]];
Before and after:
{im, smooth}
From here we can cluster, but note that my attempt is hand wavy and misses the 4th component:
cov = DominantColors[smooth, Automatic, "CoverageImage"];
HighlightImage[im,
MapIndexed[{ColorData[111] @@ #2,
DeleteSmallComponents[FillingTransform[#]]} &, cov]]
answered Mar 12, 2019 at 19:52
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As an option
image = Import["https://i.stack.imgur.com/OWfLp.png"];
im = ImageData[image];
d = ImageDimensions[image];
f = Interpolation[
Flatten[Table[{i, j, First[im[[i, j]]]}, {i, 1, d[[2]]}, {j, 1,
d[[1]]}], 1]];
ImageReflect[
DensityPlot[f[x, y], {y, d[[1]], 1}, {x, 1, d[[2]]},
ColorFunction -> "Rainbow", AspectRatio -> Automatic,
PlotPoints -> 200, Frame -> False]]
Can also be used
t = Flatten[
Table[{i, j, First[im[[i, j]]]}, {i, 1, d[[2]]}, {j, 1, d[[1]]}],
1];
ListDensityPlot[t, Frame -> False, ColorFunction -> "Rainbow",
AspectRatio -> Automatic]
Clustering gives a less clear result.
ClusteringComponents[image, 6] // Colorize
answered Mar 12, 2019 at 14:49
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1$\begingroup$ I don't see how this answers the OP's question. You did not segment the image into the four requested regions. $\endgroup$– SzabolcsMar 12, 2019 at 15:47
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1$\begingroup$ @Szabolcs I hope that OP understands the criterion by which he identified 4 areas. He himself did not offer any code. $\endgroup$ Mar 12, 2019 at 18:36
ImageFilter[ Module[{m = Mean@Flatten@#}, If[m < .25, .25, If[.5 > m >= .25, .5, If[.75 > m >= .5, .75, If[ m >= .75, 1]]]] ] &, ImageAdjust@i, 10], and changing the tolerances, although I'm sure there are better ways to write that code. $\endgroup$ClusteringComponentscould help, but it has a ton of options and knobs requiring a lot of experimentation. Something likeimage=Import["https://i.stack.imgur.com/OWfLp.png"]; Colorize@ClusteringComponents[image, Method -> {"Spectral", "NeighborhoodRadius" -> 0.2}]but with better parameters and more post-processing. $\endgroup$