How to superimpose contour lines on transformed image

Question

My goal is to

superimpose contours lines or contour plots on distance transformed image.

enter image description here

DistanceTransform[] has a few glitches, but it basically does what you want. What else do you want? — Dr. belisarius, Feb 19 '14 at 16:38
Just use an appropriate colorfunction for the distance transform... no need for ListContourPlot, I think. — rm -rf, Feb 19 '14 at 16:39
@belisarius is anyway I can extract contour from listcontour plot. — user12455, Feb 19 '14 at 17:19
There are lot.For example http://mathematica.stackexchange.com/a/31870/193 — Dr. belisarius, Feb 19 '14 at 17:22

score 3 · Accepted Answer · answered Feb 19 '14 at 21:24

If you use a DistanceFunction where a complete contour always falls on the pixels, like ManhattenDistance you can directly work on the image. The approach is pretty simple, calculate the distance transform

horse = Import["https://i.stack.imgur.com/KCfWy.png"];
dist = DistanceTransform[horse, DistanceFunction -> ManhattanDistance];

And then you set all distances to 1 which have a certain remainder. So if I want to have the contours for distances 1,5,9,... you use

lines = Map[Boole[Mod[#, 4] == 1] &, Round@ImageData[dist], {2} ] // Image

Mathematica graphics

Superimposing is then as easy as laying the images over another, or using different color channels:

ColorCombine[{lines, dist // ImageAdjust, dist // ImageAdjust}]

Mathematica graphics

The big advantage of this method is that you don't need to trace the contour which makes is as fast as an eye-blink. The disadvantage is that it does not work for the natural EuclideanDistance.

@user12455 But this is not what you have asked in your question! — halirutan, Feb 19 '14 at 21:42
@user12455 No, edit your current question. Write up clearly what you try to achieve and what you already tried. — halirutan, Feb 19 '14 at 21:44

Kuba · Answer 2 · 2014-02-19T21:23:42.407

2

Your image is taken from DistanceTransform documentation page.

enter image description here

pic2 = ListContourPlot[ImageData[pic, DataReversed -> True], 
                       ContourShading -> None, Frame -> False, ContourStyle -> Yellow];

Show[ pic, pic2]

enter image description here

edited Feb 19 '14 at 21:23

answered Feb 19 '14 at 21:15

Kuba

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How to superimpose contour lines on transformed image

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