Draw a rectangle on an image in gui with mouse hover

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Abdulllah
Abdulllah on 11 Jan 2019
Commented: Abdulllah on 14 Jan 2019
This question has two parts.
First I want to draw a rectangle on an image in gui only when the mouse hovers on the image. Secondly, if the user clicks the image execute some statements. Right now, I can only draw the rectangle on the image in following manner,
axes(handles.axes1);
[r,c,~]=size(Image);
rectangle('Position', [-2,-2,c+4,r+4],'EdgeColor','r');
  3 Comments
Abdulllah
Abdulllah on 11 Jan 2019
I am sorry, I forget to reply second question. These statemens drawing the rectangle on image ver well.
[r,c,~]=size(Image);
rectangle('Position', [-2,-2,c+4,r+4],'EdgeColor','r');
New Bitmap Image.bmp

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Accepted Answer

Kevin Phung
Kevin Phung on 11 Jan 2019
Edited: Kevin Phung on 11 Jan 2019
Hello,
You can use the 'WindowButtonMotionFcn' property of your figure,
f = figure;
set(f,'WindowButtonMotionFcn',@cursorPos)
with the callback function retrieving the position of your cursor:
function cursorPos(my_fig,event)
pos = get(my_fig,'CurrentPoint');
You know the position of your image with:
image_pos = get(image_handle,'Position')
so you can add the logic where if the position is within the bounds of the image: draw a rectangle; else, delete existing rectangle.
If you call the handle of your figure and see all the properties, you can see the various types of callbacks your function can trigger, for example:
WindowButtonDownFcn: ''
WindowButtonMotionFcn: ''
WindowButtonUpFcn: ''
WindowKeyPressFcn: ''
WindowKeyReleaseFcn: ''
WindowScrollWheelFcn: ''
------
The 'WindowButtonDownFcn' should be used for:
set(f,'WindowButtonDownFcn',@call_when_image_clicked)
Hope this helps!
  1 Comment
Abdulllah
Abdulllah on 14 Jan 2019
Hello, Thank you for your reply. I can now WindowButtonMotionFcn and can draw the rectangle. but I am I unable to find the postions of the image. If I find position of the image using
get(eventdata.axes1,'Position')
I get values in points (). and if I use
image_pos = get(eventdata.figure1,'Position')
I get value in even -ve (1084.2 -55.8 2033.6 1115.2). I dont know why negative,
I am using this logic now to draw the rectangle under the WindowButtonMotionFcn.
pos1 = getpixelposition(eventdata.axes1,true)
currentp=src.CurrentPoint
image_pos = get(eventdata.figure1,'Position')
x1=680;
y1=1046;
matlabImage = imread(strcat(num2str(randArr(3)),'.tif'));
[r,c,~]=size(matlabImage);
x2=1397;
y2=512;
if ((currentp(1)<x2&&currentp(1)>x1)&&currentp(2)>y2&&currentp(2)<y1)
% axes(hObject.figure1);
rectangle('Position', [-2,-2,c+4,r+4],'EdgeColor','r','LineWidth',3);
else
rectangle('Position', [-2,-2,c+4,r+4],'EdgeColor',[0,0,0]','LineWidth',3);
end
I need to determine the values of x1,y1,x2,y2.

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