simplify

[morganherlocker]

Takes a collection of detailed polygons and smooths out the edges to a given tolerance. It will probably use a Ramer Douglas Peucker algorithm or something similar. This will probably require the use of topojson to maintain edge integrity of geographies.

g.simplify(polys, 2000, function(err, smoothed){
  console.log(smoothed)
})

[morganherlocker]

This is being changed to "simplify", since that is what douglas peucker really does. mapshaper will be used for this.

[morganherlocker]

stubbed out, but need to figure out how to properly use topojson from node.

[calvinmetcalf]

You need to figure out quantization and simplification, if you have them as q and s with geojson geojson

function(q,s,geojson){
    var options = {
        "quantization" : q,
        "minimum-area" : s,
        "property-transform": function (properties, key, value) {
             //keeps all
             properties[key] = value;
             return true;
         }
    }
    var topo =topojson.topology({name:geojson}, options);
    topojson.simplify(topo,options);
    return topojson.feature(topo, topo.objects.name);
}

[morganherlocker]

Perfect, that is great. I will implement this in the next couple days.

Thanks!

[morganherlocker]

This feature has been implemented. I will add an example to the docs shortly.

[LarsBuur]

Hi Morgan,

It great to be able to do this on Polygons. I would very much like the ability to apply simplification on LineString. While at it - it would also be nice to be able to apply simplification on a single polygon or LineString.

Cheers, Lars

[calvinmetcalf]

might look into simplify-js for stuff where topojson is overkill

[morganherlocker]

Hey Lars,

It will currently work on a feature collection of polygons. I think it will work on a feature collection of linestrings too. I will write a test for the lines. As far as the single features go, I think that is a great idea and will be simple to add in. I will reopen this issue until I have both of these things resolved.

[calvinmetcalf]

topojson (and the snippit I wrote) should work fine for any sort of feature collection of any of the 7 types in any combination (obviously points don't get simplified)

On Thu, Dec 5, 2013 at 8:44 AM, Morgan Herlocker notifications@github.comwrote:

Hey Lars,

It will currently work on a feature collection of polygons. I think it will work on a feature collection of linestrings too. I will write a test for the lines. As far as the single features go, I think that is a great idea and will be simple to add in. I will reopen this issue until I have both of these things resolved.

— Reply to this email directly or view it on GitHubhttps://github.com/morganherlocker/turf/issues/17#issuecomment-29898149 .

-Calvin W. Metcalf

[morganherlocker]

@calvinmetcalf @LarsBuur I added tests for for the various feature types and everything is passing https://github.com/morganherlocker/turf/blob/master/test/simplify.js

[LarsBuur]

Great! - thank you very much. I will look into the simplification and report back.