예제 #1
0
파일: limit.go 프로젝트: Rachine/imposm3
func splitPolygonAtGrid(g *geos.Geos, geom *geos.Geom, gridWidth, currentGridWidth float64) ([]*geos.Geom, error) {
	var result []*geos.Geom
	geomBounds := geom.Bounds()
	if geomBounds == geos.NilBounds {
		return nil, errors.New("couldn't create bounds for geom")
	}
	for _, bounds := range tileBounds(geom.Bounds(), currentGridWidth) {
		clipGeom := g.BoundsPolygon(bounds)
		if clipGeom == nil {
			return nil, errors.New("couldn't create bounds polygon")
		}
		part := g.Intersection(geom, clipGeom)
		g.Destroy(clipGeom)
		if part == nil {
			return nil, errors.New("couldn't create intersection")
		}
		if !g.IsEmpty(part) && strings.HasSuffix(g.Type(part), "Polygon") {
			if gridWidth >= currentGridWidth {
				result = append(result, part)
			} else {
				moreParts, err := splitPolygonAtGrid(g, part, gridWidth, currentGridWidth/2.0)
				g.Destroy(part)
				if err != nil {
					return nil, err
				}
				result = append(result, moreParts...)
			}
		}
	}
	return result, nil
}