Detecting cursor position inside or outside an object.

Hi Everyone,

I have a problem and can not think of a how to approach it? Here it goes. I have an binary image containing a random line object inside a rectangle. Using the bwboundaries, i know the boundary points of the rectangle and random object. Now when i move the cursor, i get its current position as shown below.

[B,L,N,A] = bwboundaries(BW);

%Determine the screen size
SS = get(0,'ScreenSize');sh=SS(4); sw=SS(3);

%Determine current location of cursor
PL = get(0,'PointerLocation');
Yc=PL(1); Xc=sh-PL(2);

How can i know, if my current cursor location (Xc,Yc) is: 1) Outside the rectangle? Then perform single "beep" 2) inside the rectangle but outside the random object? perform "beep; pause(0.5); beep" 3) inside the object? Perform "beep; pause(0.5); beep; pause(0.5); beep"

Thanks RR

Answer 1

[Jan]

The is the pointer location relative to the screen:

PL = get(0,'PointerLocation');

But I assume you want it either relative to the figure or an axes:

PLfig = get(gcf, 'CurrentPoint');
PLaxes = get(gca, 'CurrentPoint');

For live updates of the figure's current point value an WindowButtonMotionFcn must be defined.

For the in-polygon test see Walter's answer.

[Ravi Rastogi]

The position of the cursor is with respect to the screen, which is changes to match it with image matrix. Your suggestion is a cool way though!! thanks

Answer 2

[Walter Roberson]

http://www.mathworks.com/help/techdoc/ref/inpolygon.html

There are also MATLAB File Exchange (FEX) for this, such as inpoly()

[Ravi Rastogi]

hi walter, thanks for your suggestion. For my application i just ended up using colors to distinguish different parts. Thanks for your advice. Great help!!