Image into grayscale without using toolbox

This is my current code:

function out = luminance(current_img )
  R=current_img(:,:,1);
  G=current_img(:,:,2);
  B=current_img(:,:,3);
  I=.299*R + 0.587*G+0.114*B;
  out=I;
  end

I'm trying to make my image grayscale but that's not what's happening, what am I doing wrong?

Answer 1

[Image Analyst]

That should work. What's the problem? Perhaps you want to cast it back to uint8 or something.

 out = uint8(.299*double(R) + 0.587*double(G)+0.114*double(B));

or else just leave it as floating point and use [] in imshow to display it:

imshow(out, []);

[Krish Desai]

The image is coming out in blues, yellows and greens. I tried typecasting but it didn't work.

[Krish Desai]

Update: Using the floating point worked