Determining the slope between relevant 2d objects

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Kimo Kalip 2018-6-29

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https://ww2.mathworks.cn/matlabcentral/answers/408141-determining-the-slope-between-relevant-2d-objects

编辑： Kimo Kalip 2018-7-3

Hello all, included I have my post processed image where I've done a lot of things to it, but basically got it to this post watershed state where the edges are quite segmented.

The idea here is I want to take the slope of the objects, then be able to draw some sort of conclusion from it. For example, if I were to draw a slope along the right side set of objects, would I get a regular gradual slope, or something more like a spline curve?

Main questions:

1. How do I extract the x-y coordinates from those identified objects?

2. Is it possible to draw a 'best fit line' of sorts between the right hand objects (ignoring the ones on the left?)

Thanks!

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jonas 2018-6-30

编辑：jonas 2018-6-30

How did you identify the objects? Can you post the code or a sample code?

From the name of the file I assume you used CC=BwConncomp. The output of that function includes a field CC.PixelIdxList, where the connected pixels for each object are stored.

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Answer 1

Image Analyst 2018-6-30

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Why not take the points and use poly2mask() to create a solid binary image mask from them?

Then you can call bwperim() or bwboundaries() to get the boundary/outline coordinates for every adjacent pixel.

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Kimo Kalip 2018-7-3

I'll try this out, thank you!

Kimo Kalip 2018-7-3

编辑：Kimo Kalip 2018-7-3

在 MATLAB Online 中打开

Lets say I wanted to grab four points:

(Smallest x value, corresponding y value)

(Corresponding x value, smallest y value)

(Corresponding x value, highest y value)

(Highest x value, corresponding y value)

First off, how do I extract those particular numbers from the matrix containing the image? Secondly, do you think that would draw a box around my object that I could take the area of, and then try to work from there?

Kinda going off of the image in:

https://blogs.mathworks.com/steve/2006/12/05/poly2mask-and-roipoly-part-1/

Also, is the xi and yi values given in:

BW = poly2mask(xi,yi,m,n)

Are these arrays that I pass in those values that I want?

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