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How can I create lines using the center of the circles as a reference?

I created a code, but it generates multiple lines around the circle.

coord=PixelValuePositions[imagem,Red];
coord=Sort@coord;
Graphics[{Line[{{coord[[#,1]],coord[[#,2]]}&/@Range[First[Dimensions[coord]]],{coord[[#,1]],coord[[#,2]]}&/@Range[2,First[Dimensions[coord]]]}]}]

The image used is at the link below:

Image

enter image description here

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  • $\begingroup$ You mean, how do you draw lines between the circles? $\endgroup$
    – Feyre
    Commented Aug 1, 2016 at 21:10
  • $\begingroup$ Exactly what I need. $\endgroup$
    – LCarvalho
    Commented Aug 1, 2016 at 21:25
  • 1
    $\begingroup$ Have you looked at ComponentMeasurements[]? $\endgroup$
    – J. M.'s missing motivation ♦
    Commented Aug 1, 2016 at 21:45

2 Answers 2

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Using FindClusters to group the pixels

coord = FindClusters[ImageValuePositions[imagem, Red], 5];
coord = Table[Mean[coord[[i]]], {i, 1, 5}]
ListPlot[coord]

{{36., 204.}, {347., 184.}, {150., 149.}, {246., 76.}, {71., 39.}}

enter image description here

Show[
 imagem,
 Graphics@Line@Subsets[#, {2}] &@coord]

enter image description here

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  • $\begingroup$ Yes. This is exactly what I need. $\endgroup$
    – LCarvalho
    Commented Aug 2, 2016 at 2:13
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    $\begingroup$ Strictly speaking instead of PixelValuePositions one should use ImageValuePositions here because the latter "assumes the standard image coordinate system." $\endgroup$
    – Alexey Popkov
    Commented Aug 2, 2016 at 4:01
  • $\begingroup$ @AlexeyPopkov Thanks. I thought that might be the better option. $\endgroup$
    – Young
    Commented Aug 2, 2016 at 4:17
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As I mentioned, you can use ComponentMeasurements[], at least for this example:

img = Import["https://i.sstatic.net/3W859.png"];
pts = ComponentMeasurements[SelectComponents[ColorNegate[Binarize[img]],
                                             Small], "Centroid"];

HighlightImage[img, GraphicsComplex[Range[5] /. pts, {Blue, Line[Subsets[Range[5], {2}]]}]]

lines on the image

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  • $\begingroup$ What version and OS are you on? $\endgroup$
    – J. M.'s missing motivation ♦
    Commented Aug 4, 2016 at 21:34
  • $\begingroup$ It shouldn't have problems, then. Try the code in a fresh session. $\endgroup$
    – J. M.'s missing motivation ♦
    Commented Aug 4, 2016 at 21:46
  • $\begingroup$ Try applying Normal[] to the GraphicsComplex[] object before passing it to HighlightImage[]. $\endgroup$
    – J. M.'s missing motivation ♦
    Commented Aug 5, 2016 at 11:23
  • $\begingroup$ Wait... can you give the precise version that you have? ComponentMeasurements[] was introduced in 10.3, you see. $\endgroup$
    – J. M.'s missing motivation ♦
    Commented Aug 5, 2016 at 12:19
  • $\begingroup$ After running the first two lines in a fresh session, what does the output of pts look like? $\endgroup$
    – J. M.'s missing motivation ♦
    Commented Aug 5, 2016 at 12:30

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