Getting no results from a mouse click when using ButtonDownFcn with imshow

I'm unable to obtain (x,y) coordinates of an image using a mouse click with "imshow". I can do it with "image" but not with "imshow", and I need "imshow". I've seen lots of other posts on this issue, but none of their solutions seem to work, or the discussion is too technical for me.

I have 4 images arranged two by two, and I'm interested in clicking only on the image in subplot (2,2,3). But when I click nothing happens. Apparantly my function "clicky4" is not being called. Here's the relevant section of code:

global x y
.........
Image = single(rgb2gray(FilterRGBImage));
subplot(2, 2, 3);
vv = imshow(Image,'InitialMagnification', 'Fit');
set(vv, 'HitTest','off','PickableParts','none');
% Try to use the mouse to select a pixel
 set(gca,'ButtonDownFcn', @clicky4)

And here is my function "clicky4":

function clicky4(gcbo,eventdata,handles)
%This function is supposed to grab the position (x,y) of the mouse upon a click
global x y
v = get(gca,'Currentpoint');
hold on
x = v(1,1);
y = v(1,2);
end

Any suggestions will be much appreciated. I'm a relative beginner at this stuff....

Answer 1

[Image Analyst]

Would ginput(1) or impixelinfo help you?

[jack feinberg]

Thank you for your suggestion.

ginput(1) pauses execution until a button is pressed. Unfortunately, I want to watch the images be rapidly displayed (they are frames of a movie), and then click on a spot in a particular frame. Using ginput(1) will just make the first frame of the movie pause until I click. So I don't see how I can make ginput(1) work.

impixelinfo displays the [x,y] coordinates of the mouse if my window doesn't fill up the screeen, but if my window does fill up the screen then that display is gone. Also, as mentioned above, I want to click on a particular frame of the movie and then have that [x,y] remembered for all future frames, irrespective of how I move the mouse after the click.

Perhaps Walter Roberson, the grand wizard of such dilemnas, can weigh in on this probelm?

[Walter Roberson]

Try using image() instead of imshow() as imshow() tends to clear the axes.

[jack feinberg]

Thanks for your reply. As mentioned in the preamble to my question, using image() does not seem to work. Using image() all I get displayed is a purple rectangle instead of my image, nor can I set the 'InitialMagnification' to 'Fit' when using image(). There must be a way to solve this problem using imshow(). I think the problem has to do with the statements

vv = imshow(Image,'InitialMagnification', 'Fit');
set(vv, 'HitTest','off','PickableParts','none');

but I've tried lots of different values for HitTest and PickableParts, and none seem to work.

[Walter Roberson]

colormap(gray) after you image()

Are you wanting initial magnification to be 'fit' because your array is larger or smaller than the axes area?

[jack feinberg]

1) OK. We are getting there. Colormap(gray) helped. The purple is gone.

But the program still doesn't pay attention to my mouse clicks. It won't call my function "clicky4". (See above.) Instead I get the error message:

"Undefined function 'clicky4' for input arguments of type 'matlab.graphics.axis.Axes'.

Error while evaluating Axes ButtonDownFcn."

2) And yes, I've shrunk (blurred, actually) my original image by a known amount so that my array is now smaller, but for display I want it to enlarge to fill the axes area.

[Walter Roberson]

Is clicky4 stored in the same .m file as the other code, or in a separate clicky4.m file? Is it possibly defined as a nested function?

[jack feinberg]

Yup. That was the problem; my @function was stored inthe wrong location. A beginner's mistake! Thanks. It all works now!

[Jan]

@jack feinberg: Please use flags only to inform admins and editors about contents, which might conflict with the terms of use, but not to post a comment. Thanks.