How to draw rectangle on a figure, based on mouse location?

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Hello, I'd like to "live-draw" a rectangle on my figure, based on mouse location.
I'm using the following:
set (gcf, 'WindowButtonMotionFcn', @mg_BPP_mouseMove);
function mg_BPP_mouseMove(object,eventdata)
windowSize = 64;
C = get (gca, 'CurrentPoint');
topLeftCornerX = round(C(1,1)) - windowSize/2;
topLeftCornerY = round(C(1,2)) - windowSize/2;
width = windowSize;
height = windowSize;
imrect(gca, [topLeftCornerX, topLeftCornerY, width, height]);
end
Two questions:
1. How can I make the windowSize be an input variable of mg_BPP_mouseMove? I don't want explicitly define it within the function itself.
2. At the moment it draws lots of rectangles (like a "snake") as my mouse moves across the figure. I'd like to display only the last one. I mean, I would like to have one rectangle that "flows" with my mouse cursor.

Accepted Answer

Guillaume
Guillaume on 19 Jul 2016
For 1, create an anonymous function that binds the window size to BPP_mouseMove (with an added input argument).
For 2, keep track of the previously drawn rectangle and delete it.
windowsize = 40;
set(gcf, 'WindowButtonMotionFcn', @(source, eventarg) mg_BPP_mouseMove(source, eventarg, windowsize));
function mg_BPP_mouseMove(object, eventdata, windowSize)
persistent lastrect;
C = get (gca, 'CurrentPoint');
topLeftCornerX = round(C(1,1)) - windowSize/2;
topLeftCornerY = round(C(1,2)) - windowSize/2;
width = windowSize;
height = windowSize;
if ~isempty(lastrect) && lastrect.isvalid
delete(lastrect);
end
lastrect = imrect(gca, [topLeftCornerX, topLeftCornerY, width, height]);
end

More Answers (1)

Walter Roberson
Walter Roberson on 19 Jul 2016
  1 Comment
Mark Golberg
Mark Golberg on 19 Jul 2016
Edited: Mark Golberg on 19 Jul 2016
Thank you Walter.
A) could you help me with my first question also please?
B) getrect is not my intention. Please note, I'm using WindowButtonMotionFcn in order for the rectangle to appear without me pressing the mouse.

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