How can i modify matrix which i retrieve from image?

I have a gray image, i want to see only the black part ,rest of image i want to replace with value 250, so that gray part will be white.

    f=imread('image1.jpg');
    T = zeros(size(f));  
    for ii = 1:numel(f)
        if f(ii)<50
           T(ii) = f(ii);
        else
           T(ii) = 250;
        end
    end
    imshow(T)

[Matt J]

Yes, the code you've shown would accomplish that, so what is your question?

[Iain]

What, exactly, is your question?

[Umme Tania]

when i want to see the image(T), it's blank or whole image is white.

[Evan]

What's the minimum value of your image?

[Umme Tania]

40

Answer 1

[Iain]

Try:

 %if the problem is just the data type, this should work:
 T = f;
 T(T>50) = 255;

If the problem is that you can't see the very few black pixels, tell us the result from

 sum(f(:) <51)

[Umme Tania]

Thanks.........now it's working