How to get the selected image from <p:galleria

Question

In this code,

<p:galleria value="#{Bean.images}" var="image" panelWidth="500" panelHeight="313" showCaption="true"
<p:graphicImage value="/images/galleria/#{image}" alt="Image Description for #{image}" title="#{image}"/ 
</p:galleria>

how do you get selectedImage? as expressed in

<p:carousel id="carousel" value="#{tableBean.carsSmall}" var="car" itemStyleClass="carItem" headerText="Cars"> 
    <p:graphicImage id="image" value="/images/cars/#{car.manufacturer}.jpg"/>   

    <h:panelGrid columns="2" style="width:100%" cellpadding="5"> 
        <h:outputText value="Model: " /><h:outputText id="model" value="#{car.model}" /> 
    </h:panelGrid> 

    <p:commandLink id="view" update=":form:carDetail" oncomplete="carDialog.show()" title="View Detail"> 
        <h:outputText styleClass="ui-icon ui-icon-search" style="margin:0 auto;" />   
        <f:setPropertyActionListener value="#{car}"   
                target="#{tableBean.selectedCar}" /> 
    </p:commandLink> 
</p:carousel>  

Answer 1

Supposing you have a details button on each current displayed picture (with alt attribute set to image filename)

<p:galleria value="#{Bean.images}" var="image">
  <p:graphicImage value="/images/galleria/#{image}"/>

  <f:facet name="content"> 
    <p:graphicImage value="/images/galleria/#{image}" alt="#{image}" />
    <span style="position:absolute;right:0;top:0;">
      <p:commandButton styleClass="ui-icon ui-icon-search" onclick="jsCallRemote(this);" />
    </span>
 </f:facet>
</p:galleria>

Search button could call a js function passing the button himself as a hint to find the current image filename, and then call a remote command passing it the filename as a request parameter:

<script>
function jsCallRemote(btn) {
    var imageFileName = btn.parentNode.parentNode.getElementsByTagName('img')[0].alt;
    selectImage([{name:'imageFileName', value:imageFileName}]);
}
</script>

<p:remoteCommand name="selectImage" actionListener="#{tableBean.selectImage}" />

And the bean's method makes the actual selection through the request parameter imageFileName:

public void selectImage() {
  String fileName = FacesContext.getCurrentInstance().getExternalContext().getRequestParameterMap().get("imageFileName");
  // find image by filename...
}

Answer 2

In case you do not intend to have a button for each image you can take advantage of the galleria caption to catch the selected image title. This solution is based on the answer of andreea m.

        <p:commandButton action="#{controller.preview}" value="Preview" onclick="checkSelectedImage();" oncomplete="PF('previewDialog').show();"/>

JS function

      function checkSelectedImage() {
            var caption = document.getElementsByClassName("ui-galleria-caption");
            selectImage([{name:'imageFileName', value:caption[0].getElementsByTagName("h4")[0].innerHTML}]);
        }

Remote command

    <p:remoteCommand name="selectImage" actionListener="#{controller.selectImage}"/>