How show icon in BO with ZUL file

Question

I must show an icon (icon.png) on Backoffice. I have a controller class java where I choose where icon must appear (I have a folder "icons" and put a file "icon.png" into definition.xml). in zul file the tag is this :

<image src="icons/info.png" sclass="info-box-class" id="image"  />

Java class:

image.setTooltip("This is my tooltip");
        this.image.addEventListener(Events.ON_MOUSE_OVER, (event) -> {
            Popup p = new Popup();
            p.appendChild(new Label("Tooltip"));
            p.appendChild(new Label("Tooltip 2"));