How to represent the value of X and Y Pixels in array of Two Dimensions using Matlab

Hi , Suppose if this is my image

I need to find the x, y coordinates of white pixels in image. I am getting the value of x and y coordinates separately one after the other, i want to represent it in 2 dimensional array matrix like [x,y] ,how can i represent it in 2 D matrix?

Then i need to calculate the farthest distance in that box ? how to solve this?

Answer 1

[Youssef Khmou]

The provided answer is correct, you only need some processing steps, the image contains white borders , you need to crop it using some software, after that, you need to convert into grayscale and then to double instead of unit8 :

   X=rgb2gray(X);
   X=im2double(X);
   % then the command provided above.

[Lakshya]

Thank You Youssef khmou ,

Actually this image i have converted to gray then applied threshold , then edge detection, this image is the output after edge detection .

Using 'find' i am getting x and y coordinates , how to represent it in matrix??

[Youssef Khmou]

Not a square matrix but a very thin matrix :

[y, x] = find(binaryImage);
M=[y,x];

[Lakshya]

Thank you so much....

Now i need to calculate the distance between those coordinates , this can be done by using distance formula. But i need to compare each coordinate with all other coordinate in matrix, then find the farthest distance between them.

like [x1,y1] with [x2,y2],, in next iteration [x1,y1] with [x3,y3] and so on till [xn,yn].

Similarly [x2,y2] with all other coordinates in matrix.

[Youssef Khmou]

Suppose the matrix you obtained is M :

 N=length(M);

The euclidean distances form a matrix of dimensions NxN where the diagonal elements are 0, you can basically use two dimensional loop :

 D=zeros(N);
 for x=1:N
      for y=1:N
  D(x,y)=sqrt((M(x,1)-M(y,1))^2-(M(x,2)-M(y,2))^2);
 end
end

[Lakshya]

Its not working out...

this is my program where a(i,j) is my image

 count=1;

    for(i=1:x)

          for(j=1:y)

             if a(i,j)~=1;

              x(count)=j;

              y(count)=i;

              x(1,:)= x(count);

              y(:,1)= y(count);

              count=count+1;

              a(i,j) = sqrt((y(count)-y(:,1))^2 + (x(count)-x(1,:))^2);

             end;

          end;
     end;

[x,y]=find(a);

xy=[x,y]

My problem is i want to store the value of x(count) and y(count) in some temporary variable. How to assign the value ???

here i have used x(1:,) and y(:,1)

but i am getting error

"Index exceeds matrix dimensions "

[Youssef Khmou]

I tried the the loop i proposed and it is working, try to verify your program .

[Lakshya]

I tried out your program..

i am not getting any answer...

and i have a doubt... why ur using 'zeros', coz i need to find pixel values with ones... and my image is not a square matrix.. its MxN

[Youssef Khmou]

earlier after obtaining the matrix M of coordinates of white pixels, you wanted to calculate the distance between each point M(x,y) and the rest of the points, the two dimensional loop works,zeros is a variable initialization :

 for x=1:N
      for y=1:N
  D(x,y)=sqrt((M(x,1)-M(y,1))^2-(M(x,2)-M(y,2))^2);
 end
end

The diagonal is zero because it is a distance between a point M(x,y) and itself.

[Lakshya]

ok, but i am not getting any result...

can you provide me your code.....

[Lakshya]

And in my code , is this statement correct....??

x(1,:)= x(count);

y(:,1)= y(count);

actually i am getting error at this line...

[Youssef Khmou]

x(1,:) means the x,y coordinates of the 1st point, but y(:,1) is the x coordinates of all points, that is where you get the error, the distance between the x and y points is sqrt((M(x,1)-M(y,1))^2-(M(x,2)-M(y,2))^2)

[Lakshya]

k attach me your complete code ,,, ill just try