How to prevent "save image" popup on Android when taphold?

If I taphold on an image in Chrome Android I get a popup saying if I want to “save image” “Share image” and “Open in Crome” etc. How can I prevent that ?

I have set this on the image, but it still shows the popup.

    -webkit-user-select: none;
    -ms-user-select: none;
    -moz-user-select: none;
    -o-user-select: none;
     user-select: none; 


    -webkit-touch-callout: none !important;
    -ms-touch-callout: none !important;
    -moz-touch-callout: none !important;
    -o-touch-callout: none !important;
    touch-callout: none !important;

Any input appreciated, thanks.

SOLVED with this code:

window.oncontextmenu = function(event) {
     event.preventDefault();
     event.stopPropagation();
     return false;
};