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A little alternative way to use the SVG
D3 code creates a layout-based mask, where each node is a circle + circle-clipped 'silhouette' image, which is, of course, included in the generated mask.
WARNING: clip-mask
applied to elements inside a SVG mask
don't work in Safari/Win; Chrome works okay, so this result is best viewed in bleeding edge Chrome.
Modified http://d3js.org/d3.v2.js to a secure url
Modified http://gerhobbelt.github.com/bl.ocks.org-hack/fixit.js to a secure url
https://d3js.org/d3.v2.js
https://gerhobbelt.github.com/bl.ocks.org-hack/fixit.js