stroke-svg-image.js

var filter = vis.append("defs")
  .append("filter")
  .attr("id", "stroke")

filter
  .append("feFlood")
  .attr("flood-color", "blue")
  .attr("result", "strokeColor")
  ;

filter
  .append("feMorphology")
  .attr("in", "SourceAlpha")
  .attr("operator", "dilate")
  .attr("radius", "2"),

filter
  .append("feComposite")
  .attr("in", "strokeColor")
  .attr("operator", "in")
  .attr("result", "outsideStroke")

filter
  .append("feMorphology")
  .attr("in", "sourceAlpha")
  .attr("operator", "erode")
  .attr("radius", "2"),

filter
  .append("feComposite")
  .attr("in", "SourceGraphic")
  .attr("operator", "in")
  .attr("result", "fill")

var merge = filter
  .append("feMerge")

merge.append("feMergeNode")
  .attr("in", "outsideStroke")
merge.append("feMergeNode")
  .attr("in", "fill")

// apply

vis.append('svg:image').attr({
  filter: 'url(#stroke)'
})