The reason why uicontextmenu is not working with imshow()

When you ask why the uicontextmenu is not working in an axes plotted with an image, most people will say that it is the hittest property of the image object. If the hittest property of the image object is set to 'on', any time you click the mouse within the axes, the image object, which covers the entire axes, will take over the click action and deal with it. Since you probably don't have anything associate with the image object, it will appear doing nothing at all. But at the same time you are expecting the uicontextmenu from the axes to do something. I know, drives you crazy.

If you create the image with the image() or imagesc() function, setting the hittest property of the image object to 'off' should fix the problem. Effectively, it allows you to click through the image and get to the axes.

However, if you create the image with the imshow() function, you are faced with the same problem, the uicontextmenu on the axes doesn't do anything. You can spend hours searching for a logical explanation on the Internet, and yet nothing turns up.

Well, hopefully the few hours I wasted can save you some time.

The reason is actually quite simple. One obvious differences between the images created from image() and imshow() is the ticks on the axes, while image() shows it, imshow() hides it. Now, think of the ways you can use to get rid of the ticks, you can set xtick and ytick to '[]' using set function, or you can just set the entire axes to invisible. Guess what MATHWORKS did? THEY SET THE ENTIRE AXES TO INVISIBLE, so even if you click through the image object, you won't be able to click on the axes BECAUSE IT IS INVISIBLE.

So here is the fix.
Besides setting the hittest property of the image object to 'off', you need to set 'visible' property of the axes to 'on'. Once you do that, the xticks and yticks will appear, but you can easily make them disappear by setting them to [].