MATLAB: Warning: Integer operands are required for colon operator when used as index, Please help…its emergency

Question

Here are some lines of my code, so as to make it clear

 % --- Executes on button press in levelset.
function levelset_Callback(hObject, eventdata, handles)
global img_gray
global Img
global im3
global img

im3=img;

I=img_gray; figure; imshow(I)

title('Select the region of interest from the whole image')

rect = getrect(gcf);

Img = I(rect(2):rect(2)+rect(4),rect(1):rect(1)+rect(3)); %GIVES WARNING

Img=double(Img);

figure(1);

imshow(uint8(Img));

[nx,ny]=size(Img);

ic=floor(nx/2);

jc=floor(ny/2);

r=ic/3;

Answer 1

Make it integer like it's asking:

rect = getrect(gcf);
% Might be floating point, so round:
rect = int32(rect);
% Make sure it's never zero because an index of 0 is not allowed.
rect(rect == 0) = 1;