How to convert from D3 svg to topojson/geojson?

问题

D3 allows to convert geojson/topojson arrays of points' coordinates

[ [x,y],[x,y],[x,y],...]    // aka, a geojson arc.

And, via a projection, into svg paths

<path d="M x,y x,y x,y ..."></path>  // aka, an svg-xml path

Note: the values actually change. Points [x,y] in topojson, get new valued via projection([x,y]) for svg's path.

So, if we store in the svg:

1. the projection name

2. the points absolute coordonates relative to the svg origine 0,0 (already stored in the path).

3. Use projection.invert()

We could convert from xml back into topojson/shp, including hand added shapes.

I am unaware so far of any open source tool doing so.

Question become: What minimal requirements should i store in my svg so it keep the potential to be converted back into gis formats ? (i may have missed some points)

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Edit: While aware about it, the complexity of handling Point, LineString, Polygon, MultiPoints, MultiLineStrings, MultiPolygons is not the issue right now. Just the minimal requirements so backward conversion stays possible.

Edit2: convert back to geojson would likely be easier, since the svg and geojson data structures are more similar.

来源：https://stackoverflow.com/questions/28266721/how-to-convert-from-d3-svg-to-topojson-geojson