camanjs and openseadragon: filters are loading delayed

Question

I want to use some caman filters in a OpenSeaDragon viewer. Whenever I try to load multiple filters synchronously, the filters load delayed and become visible only after zooming the image.

I used the following filter options. Does anybody struggle with a similar problem or are there any ideas how to force the viewer into sync mode?

viewer.setFilterOptions({
  filters: {
    processors: function (context, callback) {
      Caman(context.canvas, function () {
        this.brightness(value);
        this.render(callback);
      });
    },
  },
  sync: true,
  loadMode: true ? "sync" : "async",
});

Answer 1

I assume you're using https://github.com/usnistgov/OpenSeadragonFiltering? I believe Caman filters have to be asynchronous by their very nature, so I think the effect you're seeing (of them not working until you zoom) is because you're trying to make them synchronous. Stick with async and they should work.