MATLAB: Why pixels values are unaltered even though after applying double

doubleimage processingImage Processing Toolbox

when i have applied double to my image the pixel values are not changing they are not coming in the range [0,1]?

You need im2double for that.

Try

        a=imread('lena.jpg');
        imshow(a);
        b=double(a);
        imshow(b/255);

How do you convert to double:

In any case, no, you're not losing information. The issue is with how you display it. Try:

imshow(img, []);