Data types use in Matlab functions

Question

I am new to Matlab. I have this function which I want to calculate the Euclidean distance between two pixels(RGB).

function[distance]=calc_dist(R1, R2, G1, G2, B1, B2)

    if (R1>R2)
        dR=R1-R2;
    else
        dR=R2-R1;
    end

    if (G1>G2)
        dG=G1-G2;
    else
        dG=G2-G1;
    end

    if (B1>B2)
        dB=B1-B2;
    else
        dB=B2-B1;
    end

  sum=uint64(3*dR*dR+4*dG*dG+2*dB*dB);
  disp(sum);
  distance=(sqrt(double(3*dR*dR+4*dG*dG+2*dB*dB));
end

The problem is the displayed value for sum is 255 each time. This must be happening because the variables are of type uint8. How do I change them? I tried to do some sort of casting

sum=uint64(3*dR*dR+4*dG*dG+2*dB*dB); 

but I get this error: 'Undefined function 'uit64' for input arguments of type 'uint8'. How should I display the right value for the sum? Thanks. '

Answer 1

Consider converting your input of 6 variables to one 2x3 matrix, where the first row is the RGB colours from one pixel, and the second row is the RGB colours from the second pixel:

function[distance]=calc_dist(R1, R2, G1, G2, B1, B2)

rgbPixels = [R1 G1 B1; R2 G2 B2];

% cast as double
rgbPixels = double(rgbPixels);

% compute the difference between the rows
rgbDiffs = diff(rgbPixels);

% compute the Euclidean distance
distance = sqrt(sum(rgbDiffs.^2));

This way, you don't have to change your signature and all casting can be done in one line. Try the above and see what happens!