The animator is the work-horse function of SeuratJS. The elm is the Raphaël element generated and filled with the color from (x,y). step is the grid spacing used to collect the color samples. You can see more great animation examples and code on the SeuratJS Website.
paper.seurat({ imageSource: 'imgs/circus-sideshow.png', animator: function(elm, x,y,step){ var anim = Raphael.animation({r: 7}, 350) .delay(35*(x+y)); elm.animate(anim);}});
Note paper is a Raphaël canvas object as defined here.
Chrome Users Because SeuratJS uses the HTML5 canvas element if you are attempting to debug from file:// as opposed to a local webserver you will need to run Chrome using the --allow-file-access-from-files flag. More info here.