Problem with the following.

This is my MATLAB code for the following:

F(m, n) = w0I0 + w1I1 + w2I2
where 
I0 = I2^α0 (m, n)
I1 = I2^α1 (m − 1, n) + I2^α1 (m + 1, n) + I2^α1 (m, n − 1) + I2^α1 (m, n + 1)
I2 = I2^α2 (m − 1, n − 1) + I2^α2 (m + 1, n − 1) + I2^α2 (m + 1, n − 1) + I2^α2 (m + 1, n + 1)

The value of alpha0,alpha1,alpha2,w0,w1,w2 are declared in code. But it shows some error. I dono why?

code:

[file path] = uigetfile ('*.bmp','Select any Image');
if file ~=0
    I = imread (strcat(path,file));
    [m n] = size (I);
    h=1;
    alpha0 = 8*h;
    alpha1 = h;
    alpha2 = h;
    w0 = 2;
    w1 = -0.125;
    w2 = -0.125;
    % Compute I0
    for j = 1 : n
        for i = 1 : m
            I0(i,j) = I(i,j)^(2*alpha0);
        end
    end
    % Compute I1
    for j = 1 : n
        for i = 1 : m
            I1(i,j) = I(i-1,j)^(2*alpha1) + I(i+1,j)^(2*alpha1) + I(i,j-1)^(2*alpha1) + I(i,j+1)^(2*alpha1);
        end
    end
    % Compute I2
    for j = 1 : n
        for i = 1 : m
            I2(i,j) = I(i-1,j-1)^(2*alpha2) + I(i+1,j-1)^(2*alpha2) + I(i+1,j-1)^(2*alpha2) + I(i+1,j+1)^(2*alpha2);
        end
    end

      F(m,n) = (w0*I0(m,n)) + (w1*I1(m,n)) + (w2*I2(m,n));
      figure, imshow(F);
  end

[Oleg Komarov]

What error do you get?

[Sabarinathan Vadivelu]

Index out of bounds

Answer 1

[Jan]

Always provide the complete error message to the forum, when you get one.

I guess at least this fails:

for i = 1 : m
  I1(i,j) = I(i-1,j)^(2*alpha1) + I(i+1,j)^(2*alpha1) ...

This fails for i==1 and i==m, because i-1 and i+1 are no valid indices, respectively. You have to run the loop from 2:m-1, such that I1 has a different size.

Btw.:

• Overwriting the important function path with a local variable is a bad idea. E.g. the debugging might fail.
• This code:

% Compute I0
for j = 1 : n
  for i = 1 : m
    I0(i,j) = I(i,j)^(2*alpha0);
  end
end

can be abbreviated to:

I0 = I .^ (2 * alpha0);

• The comparison of strings should not be done by == or ~=, although this works accidently in your example: "if file ~=0". Better use if ischar(file) or if ~isequal(file, 0).

[Sabarinathan Vadivelu]

But there is a problem that the size of I1, I2 is decreased to 1023*1023. How to rectify this problem?

[Jan]

Yes, the procedure you have shown should decrease the size by two rows and columns. There is no standard solution to "rectify" this, because this is no error. If you want to get the same size as the inputs, a definition of the margins is required. E.g. use the same values as the inputs, or repeat the values of the outputs (and a special trick at the corners).