Using current points instead of ginput to get locations on axes

Question

Jason 2017-10-3

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https://ww2.mathworks.cn/matlabcentral/answers/359441-using-current-points-instead-of-ginput-to-get-locations-on-axes

评论： Jason 2017-10-3

Hi. I am currently using ginput to select two points on an image to then draw a line. The problem is that my image is mainly black with white spots and the cross hairs for ginput are black, so its hard to use.

So after investigating I thought I could use the following

    axes(handles.axes4);    %my image is on axes4
    cp = get(handles.axes4,'CurrentPoint') 
    x = cp(1,1)
    y = cp(1,2)
    plot(x,y,'ro'); drawnow;

The point I selected on is the red circle below at coordiantes 244, 605 on that axes. However, the returned values of cp are

cp =
     1.0e+03 *
     -1.2142    1.3601    5.6639
     -1.2142    1.3601    0.0000

What do these cp values correspond to, I thought x = cp(1,1) and y = cp(1,2), but they don't seem to be.

Also is this the best way or is there another way?

Thanks Jason

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Answer 1

Walter Roberson 2017-10-3

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https://ww2.mathworks.cn/matlabcentral/answers/359441-using-current-points-instead-of-ginput-to-get-locations-on-axes#answer_284076

http://www.mathworks.com/help/matlab/ref/matlab.graphics.axis.axes-properties.html#property_d119e58735

cp(2,:) is for the back points, which is more meaningful for 3D.

The values are in axes data units.

"The two points indicate the location of the last mouse click, unless there is a WindowButtonMotionFcn callback defined for the figure. If the WindowButtonMotionFcn callback is defined, then the points indicate the last location of the mouse pointer."

My speculation is that you do not have WindowButtonMotionFcn active and that your last click was to the left of the current mouse position.

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Jason 2017-10-3

So I would use something like this:

axes(handles.axes4)('WindowButtonDownFcn',@myMouseclickFunction)

Jason 2017-10-3

在 MATLAB Online 中打开

I think I've done it, I just put a waitforbuttonpress!!

 w = waitforbuttonpress
  if w == 0     %0 for mouse click, 1 for button press
    disp('Button click')
    cp = get(gca,'CurrentPoint') 
    x = cp(1,1)
    y = cp(1,2)
    plot(x,y,'ro'); drawnow;
  end