how to find distance between two points in an image

hello! i have an image something like this.

how to obtain the distance between the dot above i and the line in i? the image of i is attached below.

please help me with the code... thank you!

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Answer 1

[harjeet singh]

try to use this

img=imread('i2.png');
figure(1)
imshow(img)
hold on

[lab,num]=bwlabel(img);
[r,c]=find(lab==1);
[r1,c1]=find(lab==2);

D = pdist2([r c],[r1 c1],'euclidean'); % euclidean distance
[r2,c2]=find(D==min(D(:)));

point_1=[r(r2) c(r2)];
point_2=[r1(c2) c1(c2)];

plot([point_1(2) point_2(2)],[point_1(1) point_2(1)],'r')
hold off

distance=sqrt( (point_1(1)-point_2(1)).^2 + (point_1(2)-point_2(2)).^2)

distance =

   42.1070

[sindhu c]

thank you a lot sir ! it works as expected.

[Meghashree G]

sir,if at all i want to find the position of dot of i in the above image(i.e whether the dot is towards the left/right/straight),how to find it?

[Image Analyst]

One way is to call regionprops() to get the centroids of the two blobs. The dot of the i will have a lower y value of its centroid than the body of the i.

[Meghashree G]

sir,this is what i did to get the centroids,

clc;

BW = imread('i1.png');

s = regionprops(BW,'centroid');

centroids = cat(1, s.Centroid); imshow(BW)

hold on

plot(centroids(:,1),centroids(:,2), 'b*')

hold off

Now what to do?Please help me.. i dint get the last part of your answer

[Image Analyst]

Isn't centroids a 1-D vector?

if centroids(2) < centroids(4)
  % Blob #1 is the dot, so do something.
else
  % Blob #2 is the dot, so do something.
end

[aaditya CHANDEL]

distance unit?

[Walter Roberson]

The distance unit is pixels.

Answer 2

[Walter Roberson]

http://www.mathworks.com/help/images/ref/bwdistgeodesic.html

http://www.mathworks.com/help/images/ref/imdistline.html

[sindhu c]

thank you sir! in both of the above links we need to know column and row vectors, how to find the position vectors for dot and line in the above image attached?