About
Library polyclip-go is a pure Go, MIT-licensed implementation of an algorithm for Boolean operations on 2D polygons (invented by F. Martínez, A.J. Rueda, F.R. Feito) -- that is, for calculation of polygon intersection, union, difference and xor.
The original paper describes the algorithm as performing in time O((n+k) log n), where n is number of all edges of all polygons in operation, and k is number of intersections of all polygon edges.
Limitations
- Although the algorithm will not produce self-intersecting polygons, it is not designed
to handle them either. To remove self-intersections from polygons, use
Simplify().
Example
Simplest Go program using polyclip-go for calculating intersection of a square and triangle:
// example.go
package main
import (
"fmt"
"github.com/ctessum/polyclip-go"
)
func main() {
subject := polyclip.Polygon{{{1, 1}, {1, 2}, {2, 2}, {2, 1}}} // small square
clipping := polyclip.Polygon{{{0, 0}, {0, 3}, {3, 0}}} // overlapping triangle
result := subject.Construct(polyclip.INTERSECTION, clipping)
// will print triangle: [[{1 1} {1 2} {2 1}]]
fmt.Println(result)
}
To compile and run the program above, execute the usual sequence of commands:
go get github.com/akavel/polyclip-go # or: bitbucket.org/...
go build example.go
./example # Windows: example.exe
For full package documentation, run locally godoc github.com/akavel/polyclip-go, or visit online documentation for polyclip-go.
See also
- Online docs for polyclip-go.
- Microsite about the original algorithm, from its authors (with PDF, and public-domain code in C++).
- The as3polyclip library -- a MIT-licensed ActionScript3 library implementing this same algorithm (it actually served as a base for polyclip-go). The page also contains some thoughts with regards to speed of the algorithm.