warning: Integer operands are required for colon operator when used as index, Please help...its emergency

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

[Image Analyst]

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;

[mal]

still its not working, do you have any alternate solution?

[Image Analyst]

How abourt using rbbox():

k = waitforbuttonpress;
point1 = get(gca,'CurrentPoint');    % button down detected
finalRect = rbbox;                   % return figure units
point2 = get(gca,'CurrentPoint');    % button up detected
p1x = point1(1, 1);
p1y = point1(1, 2);
p2x = point2(1, 1);
p2y = point2(1, 2);
x1 = round(min([p1x, p2x]));
x2 = round(max([p1x, p2x]));
y1 = round(min([p1y, p2y]));
y2 = round(max([p1y, p2y]));

or imrect():

hBox = imrect;
roiPosition = wait(hBox);
roiPosition % Echo coordinates to the command window.

xCoords = [roiPosition(1), roiPosition(1)+roiPosition(3), roiPosition(1)+roiPosition(3), roiPosition(1), roiPosition(1)];
yCoords = [roiPosition(2), roiPosition(2), roiPosition(2)+roiPosition(4), roiPosition(2)+roiPosition(4), roiPosition(2)];

% Plot the mask as an outline over the image.
hold on;
plot(xCoords, yCoords, 'linewidth', 2);