The polygon to calculate the offset for.
The final result: all valid split-polygons. These are making up the actual polygon inset. Note: list may be empty. Depending on the offset amount there is not a guaranteed offset polygon existing.
The simple inset lines, directly generated by offsetting the original polygon lines by the given amount.
The inset polygon lines resembling an actual polygon instance (not just a sequence of lines).
The cropped inset lines that makes up the first direct iteration of the inset polygon. This one will probably be self-intersecting.
Each polygon line and it's offsetted inset-line resemble a rectangular polygon.
Array
The input polygon, but without ear edges.
The original polygon as a sequence of line objects. This is easier to use than a list of points.
Readonly polygonThe polygon to work with.
The inset polygon split up into simple non-self-intersecting polygons. Represented as a list of vertex-lists. Each sub-list represents a single polygon.
Private _collectThis method transforms each polygon line into a new line
by moving it to the inside direction of the polygon (by the given insetAmount).
The transformed lines. The result array has the same length and order as the input array.
Private _collectFor a sequence of inset polygon lines get the inset polygon by detecting useful intersections (by cropping or extending them).
The returned lines resemble a new polygon.
Please note that the returned polygon can be self-intersecting!
The cropped or exented inset polygon lines.
Private _collectConverts two lists (same length) of original polygon lines and inset lines (interpreted as pairs) to a list of rectangular polyons.
A list of rectangular polygons; each returned polyon has exactly four vertices.
This is the main method.
Call this with the required option params to compute your desired offset polygon(s).
A list of vertex-lists, each one representing a simple polygon from the offset-polygons.
Static Private _assertThis private method will reverse each polygon's vertex order that's not clockwise.
Static Private _assertThis private method will revert the vertex order if the polygon is not clockwise.
Static Private _filterStatic Private _filterFilter split polygons: only keep those whose vertices are all contained inside the original polygon. Reason: scaling too much will result in excessive translation beyond the opposite bounds of the polygon (like more than 200% of possible insetting).
The filtered polygon list.
Static Private _hasFor simplification I'm using a callback generator function here.
The callback for an Array.some parameter.
Static Private _locateStatic Private _optimizeOptimize the inset polygon by removing critical ear edges.
Such an is identified by: the edge itself is completely located inside its neighbours inset rectangle.
In this process multiple edges from the ear might be dropped and two adjacent edges get a new common intersection point.
Note: this method is not working as expected in all cases and quite experimental.
Static Private _rectangleStatic Private convert
Constructs a new PolygonInset instance with the underlying given polygon to work with.
Please note that the algorithm will reverse the vertex order if the given polygon is not clockwise.