AGSPolygon Border or Buffer

JaiByron

I'm developing an app in Swift where I need to draw an outline around a Polygon.

At the moment I'm using the following API

https://developers.arcgis.com/ios/latest/api-reference/interface_a_g_s_geometry_engine.html#af776cf76190e456bebc501e13cfba37a

+ (nullable AGSPolygon*) geodeticBufferGeometryAGSGeometry *) geometrydistance:(double) distancedistanceUnit:(AGSLinearUnit *) distanceUnitmaxDeviation:(double) maxDeviationcurveType:(AGSGeodeticCurveType) curveType 

The problem for me is that it produces a buffer of constant distance around my original AGSGeometry (which in this case happens to be an AGSPolygon) rather than an outline. This manifests as an issue in the following situation:

1. Original polygon outlining an area.

2. After running the geodeticBufferGeometry function to get a new AGSPolygon and drawing them I see the following:

Rounded corners on the edges of the shape where you have right-angles. Which is to be expected when calculating buffer points at a corner.

Is there an API within the SDK I can call that would give me a border rather than a buffer as shown here :

Thanks

Nicholas-Furness

Hi Jai.

We just got this moved to the right place. Sorry we didn't see the question sooner.

You should use the AGSGeometryEngine.offset() method.‌

I used:

<SPAN class="keyword token">let</SPAN> newPolygon <SPAN class="operator token">=</SPAN> AGSGeometryEngine<SPAN class="punctuation token">.</SPAN><SPAN class="token function">offsetGeometry</SPAN><SPAN class="punctuation token">(</SPAN>geom<SPAN class="punctuation token">,</SPAN> distance<SPAN class="punctuation token">:</SPAN> <SPAN class="operator token">-</SPAN><SPAN class="number token">50</SPAN><SPAN class="punctuation token">,</SPAN>
                                                  offsetType<SPAN class="punctuation token">:</SPAN> <SPAN class="punctuation token">.</SPAN>squared<SPAN class="punctuation token">,</SPAN>
                                                  bevelRatio<SPAN class="punctuation token">:</SPAN> <SPAN class="number token">1</SPAN><SPAN class="punctuation token">,</SPAN>
                                                  flattenError<SPAN class="punctuation token">:</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="keyword token">as</SPAN><SPAN class="operator token">?</SPAN> AGSPolygon‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

 

and got the following result (the cyan polygon was the original input):

See the documentation to understand why the distance is -ve in this case.

Hope this helps!