draw 2 pairs of resizable rectangles in matlab - matlab

Question

I have a program that should draw 2 re sizable rectangle in matlab. drawing two resizable is ok, but I want to change size in the same time, I mean when I change size of the first one, the second'size change too. but I don know haw to connect them together. can any body help me?!
thanks.
here is my code:
figure,imshow('image.jpg');
h1 = imrect(gca, [10 10 300 500]);
h2 = imrect(gca, [200 200 400 300]);

Answer 1

To solve this you have to use the addNewPositionCallback.
Write your own function implementing the logic you need. This example sets all rectangles to the same size:
function myPositionFunction(allRects,changed,position)
%iterate over all rectangles
for idx=1:numel(allRects)
%skip the currently changed one
if idx~=changed
%get position, modify it and set it
thisP=allRects(idx).getPosition();
thisP(3:4)=position(3:4);
allRects(idx).setPosition(thisP);
end
end
end
Now the tricky part, how make practical usable callback:
figure
imshow('board.tif')
h1 = imrect(gca, [10 10 20 20]);
h2 = imrect(gca, [20 20 30 30]);
addNewPositionCallback(h1,#(p)myPositionFunction([h1,h2],1,p))
addNewPositionCallback(h2,#(p)myPositionFunction([h1,h2],2,p))
This way your callback is called with:
-first parameter a list of all rectangles (could be extended to more than two)
-second parameter the index of the changed rectangle
-third parameter the new boundaries of the changed rectangle

Answer 2

I see #Daniel has just posted an answer, but here is an alternative solution using addNewPositionCallback as well.
1) First create a function in which you draw a first rectangle, and add the callback:
function Draw2Rect(~)
global h1
A = imread('peppers.png');
imshow(A);
h1 = imrect(gca,[20 20 200 150]);
addNewPositionCallback(h1,#UpdateRect)
2) Then define the anonymous function called by the callback, in which you 1st use findobj in order to find rectangles drawn in the current axes. imrect objects are of the type 'hggroup'. Basically you look for all the rectangles present and as you move the first rectangle previous ones are deleted and a new rectangle is drawn. Here I used a dummy relation between the positions but you get the idea.
function UpdateRect(~)
global h1 % Simpler to use global variables but there are more robust alternatives!
Rect1Pos = getPosition(h1); % Get the position of your rectangle of interest
hRect = findobj(gca,'Type','hggroup'); % Find all rectangle objects
if numel(hRect>1) Once you start changing the first rectangle position, delete others.
delete(hRect(1:end-1))
h2 = imrect(gca,round(Rect1Pos/2));
end
I don't know how to post animated gifs in answers, but here are 2 images showing the 1st rectangle and then the 2 rectangles after moving the first one:
1:
2:
Hope that helps! As noted I used h1 as a global variable to easily pass data between functions, but there are more robust alternatives you can use.