Draggable resizable rectangle in the image to obtain live signal to noise ratio

Hello,

I am trying to design a draggable resizable reactangle in the image to display live signal to noise ratio (SNR). I can calculate the SNR for a specific cropped image but I want to let use drag the rectangle to any position of the image and obtain signal to noise ration of that selected rectangular region. However, I did not find any good source code to draw a draggable resizable rectangle that can obtain live position of the rectangle. I found crop_it2 function in Matlab file exchange but it asks user to close the figure first and then it will plot the cropped region. Instead, I want to keep the figure open and let user drag the rectangle with mouse and it will display SNR value of that rectangular region in the image. This is the source code I found here: https://www.mathworks.com/matlabcentral/fileexchange/21178-cropping-an-image-with-resizable-and-draggable-rectangle

 function [rect_pos] = Crop_it2(I)
%
%
% Crops the Image from a resizable & draggable rectangle 
% & displays it (after the figure is closed)
%
% I is the Image to be cropped, assumed to be in the 
% matlab workspace
%
% EXAMPLES
%
% I = imread('liftingbody.png');
% [rect_pos] = Crop_it(I);
%
% RGB = imread('peppers.png');
% [rect_pos] = Crop_it(RGB);
%
% See also IMPIXEL, IMPROFILE, ANNOTATION, IMCROP.

% $author Shripad Kondra, SISSA, Trieste, Italy
% $acknowledgments Diana Bedolla (SISSA),  Erion Hasanbelliu (UFL)
% $date 21-Aug-2008
%
%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
r=size(I,1);
c=size(I,2);

% 1) get the screensize 
Screen_size = get(0,'ScreenSize');
min_Screen_size = min(Screen_size(3:4));
% 2) imagine the screen as a aquare with this size
% 3) find the length of diagonal
diag_Screen_size =  round(sqrt(2*min_Screen_size.^2));
% 3) Lets say you have to fit a figure which is half the screen size
scale_screen = diag_Screen_size/4;
d=sqrt(r.^2+c.^2);  % find the size of the diagonal of the image 
scale_fig = (scale_screen/d); 

%% Figure resizing
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Don't use IMSHOW as it doesn't strecth the image in same proportion     % 
% as the figure when the figure is strecthed.                             %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

figure, imshow(I); %colormap gray;
rect_pos_fig = get(gcf,'position');
rect_pos_fig(3) = round(c*scale_fig);
rect_pos_fig(4) = round(r*scale_fig);
% set the figure position so that it is proportional to the image
set(gcf,'Units','pixels')
set(gcf,'position',rect_pos_fig);
% set axis to fill the figure. 
set(gca,'position',[0 0 1 1]);

%% Creating the rectangle
% create the rectangle
plotedit on

h1=annotation('rectangle',[0  0 0.4 0.4]);
set(h1,'EdgeColor','r','LineStyle','-','LineWidth',2);
% fancy stuff -> slower if image is gray or is too big
if(size(I,3)>1 && scale_fig>1) 
set(h1,'FaceAlpha',.2,'FaceColor','yellow'); 
end
 
% here is the key for resizable rectangle

% set the delete callback
set(gcf,'DeleteFcn',{@myCallback,I,h1});
waitfor(h1);

% recover the value of the position of rectangle from root.
rect_pos=get(0,'UserData');
return;



%% Callback subfunction 
function myCallback(src,eventdata,I,h1)
r=size(I,1);
c=size(I,2);

rect_pos = get(h1,'position');
rect_pos = (floor(rect_pos.*[c r c r]))+1;
rect_pos(2) = r - (rect_pos(2) + rect_pos(4));

rect_pos 

try
I2=imcrop(I,rect_pos); % uses imageprocessing toolbox
catch
I2=myCrop(I,rect_pos);    
end    

figure, imshow(I2); colormap gray; % remove this line if you don't want
set(gca,'position',[0 0 1 1]);

% save the position of rectangle in root.
set(0,'UserData',rect_pos);

% or put imwrite function to save the
% cropped image
% e.g. 
% imwrite(I2,'temp','png');
% see imwrite

%% croping function
function I2 = myCrop(I,rect)
% copied from imcrop -> see IMCROP
m = size(I,1);
n = size(I,2);
pixelHeight = rect(4);
pixelWidth = rect(3);

r1 = round(rect(2) + 1 );
c1 = round(rect(1) + 1 );
r2 = round(rect(4) + r1);
c2 = round(rect(3) + c1);

% Check for selected rectangle completely outside the image
if ((r1 > m) || (r2 < 1) || (c1 > n) || (c2 < 1))
    b = [];
else
    r1 = max(r1, 1);
    r2 = min(r2, m);
    c1 = max(c1, 1);
    c2 = min(c2, n);
    I2 = I(r1:r2, c1:c2, :);

end

return;

Answer 1

[Image Analyst]

Try this:

imshow('cameraman.tif')
% Maximize the window.
g = gcf;
g.WindowState = 'maximized'
uiwait(msgbox('After you click OK, and when you see the crosshairs, drag out a rectangle'));
title('Double Click or type Enter when ready', 'FontSize', 20);
% roi = drawrectangle('Color','r')
% position = roi.Position;
roi = imrect();
position = wait(roi)
% Delete the draggable roi
delete(roi);
% Create a new rectangle
rectangle('Position', position, 'EdgeColor', 'r', 'LineWidth', 2);
row1 = position(2)
row2 = row1 + position(4) - 1
col1 = position(1)
col2 = col1 + position(3) - 1
caption = sprintf('y Row 1 = %.1f, y Row 2 = %.1f, x Col 1 = %.1f, x Col 2 = %.1f', row1, row2, col1, col2);
title(caption, 'FontSize', 20);

[Muhammad Abir]

Thanks for your response. Actually this is not what I wanted. This is similar to imcrop. What I wanted is I wanted to get the coordinate of each positions when I move the rectangle. It does not give me each x, y, width and height position when I slide the rectangle to different positions

[Image Analyst]

Do you need it "live"? What's wrong with just getting it once the user has finalized the size and position?

[Muhammad Abir]

Yes, I would like to do it live. This is the requirement for my project. I am still struggling with this

[Image Analyst]

You'd have to look into that listener capability. I've not done that before so I'd be fumbling around just like you'll have to. Good luck.

[Muhammad Abir]

I think I found the solution. Thanks for you suggestion. Appreciate it.

I = imread('cameraman.tif');

% plot image 1 & draw a rectangular ROI on images
figure,  imshow(I);
roi = drawrectangle('LineWidth',2,'Color','white');

% set up listeners for ROI moving events
addlistener(roi,'MovingROI',@(r1,evt) allevents(r1,evt));
% allevents callback function displays the previous position & the current position of the ROI
function allevents(r1,evt)
            disp(['ROI moving current position: ' mat2str(evt.CurrentPosition)]);
end

Answer 2

[Image Analyst]

I'd just use drawrectangle() or imrect().

[Muhammad Abir]

The program also uses imrect but that is not draggable

[Image Analyst]

So...did you try to implement the example for drawrectangle()?

[Muhammad Abir]

I tried to use imrect like this but I cannot be the postion of the rectangle. I just need the postion of the rectangle so I can calculate SNR

imshow('cameraman.tif')
h = imrect(gca, [10 10 100 100]);
addNewPositionCallback(h,@(p) getPosition(h))