Bulk Generate page Thumbnails

Hi,

Not sure if it can be done from backend as there is no API(I am not aware of any)

But the logic is at client side - http://localhost:4502/libs/cq/gui/components/common/wcm/clientlibs/wcm.js

function generate(component) {
        var activator = component.find(".cq-wcm-pagethumbnail-activator").prop("disabled", true);
        wait(component);

        var path = component.data("cqWcmPagethumbnailPath");
        var isTemplate = component.data("isTemplate") || false;
        var dest = isTemplate ? "thumbnail.png.sftmp" : "file.sftmp";

        var pgen = new CQ.Siteadmin.PagePreview();
        pgen.generatePreview(path, dest, isTemplate, function(data) {
            // use attr() instead of prop() for action, so that no domain is appended
            if(isTemplate) {
                setValue(component, "./thumbnail.png@MoveFrom", component.closest("form").attr("action") + "/" + dest);
            } else {
                setValue(component, "./image/file@MoveFrom", component.closest("form").attr("action") + "/image/" + dest);
            }
            clearWait(component, data);
            activator.prop("disabled", false);
        });
    }

Do you want to apply some specific image as thumbnail ? If yes, you can write custom script for this.