MATLAB Answers

Naresh Naik

How to find out the distance between the inner and outer edge of the image using the Matlab command [x,y]=ginput(1)?

Asked by Naresh Naik
on 2 Jan 2013

Where ever you click on the following link image, matlab code must find out the two edges and find out the distance between the those two points using [x,y]=ginput(1).


3 Answers

Answer by Image Analyst
on 2 Jan 2013
 Accepted answer

I gave you code for calling ginput() in that calculates the distance between two points. Recall where it said:

% Calculate diameters:
outerDiameter = sqrt((xOuter-xCenter)^2+(yOuter-yCenter)^2)
innerDiameter = sqrt((xInner-xCenter)^2+(yInner-yCenter)^2)

Well that's just the Pythagorean theorem. You can replace the two x and y with any any two x and y to get the distance between two points.


But i don't know the center and how can i click mouse point at center in above link image?

I am not interested to find out the center by clicking it.

in this case can you find out the center by automatically?

Also not inttested to click the inner edge and outer edge by mouse pointer.

Just click on the circle (ONLY ONCE) at any point on it, code has take its center and find out the inner and outer dia without selectinig edges.

Whatever you suggested by clicking center,inner and outer edge so could we do the same thing by not selecting the points?

Looking up at the top (your original question here in this post right here), I believe I answered your question of how to find the distance between two points that you specified using ginput(), didn't I?

If you have a follow up to your prior question, where we showed you how to use regionprops(), then post your follow up question in that post, not this one.

Answer by Sean de Wolski
on 2 Jan 2013

I would just use imdistline()


When you showed "Area: 19363" and so on, how did you generate that information? Show the code from the regionprops() call on to the place you display that information.

Here the code how i displayed the Area,FilledArea.....

imshow(I) (I=Inverted of binary image)
>> [L,num]=bwlabel(I);
>> regionprops(L,'Area','FilledArea')
ans = Area: 19363
     FilledArea: 48540
>> sqrt(4*(Filledarea)/pi)

By using the above command i am getting the following error that is

??? Undefined function or variable 'Filledarea'.

How to eliminate above error?

(I mean how to write the code such that the above formula will take the FilledArea as 48540 and display the OD as 248 )

This is my question may be i didn't ask in proper way.

info = regionprops(L,'Area','FilledArea');
OD = sqrt(4*(info.FilledArea)/pi)

Answer by Walter Roberson
on 3 Jan 2013

threshold. Logically negate so the circle becomes the 1's. bwboundaries that. The result for that image would be a 2 x 1 cell array, each entry of which is an array of row and column coordinates that together form one of the boundaries. Find the minimum of the euclidean distances between all points in the first cell and all points in the second cell, and you will have found the minimum distances between the inner and outer boundaries.

You can toss in a ginput(1) if you really want; you would just ignore the value it returns.


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