Module offset 

Line offset (parallel curve) generation for cartographic styling

This module implements open-curve parallel offset — shifting a polyline laterally to produce a parallel polyline — distinct from the filled-polygon buffer in buffer.rs.

Conventions

A positive distance places the offset curve on the left of the direction of travel (right-hand coordinate system). A negative distance places it on the right.

Join styles

At interior vertices the two adjacent offset segment directions differ. Three strategies reconcile them:

• Miter – extend both segments to their intersection point. If the resulting extension ratio exceeds miter_limit, fall back to Bevel.
• Bevel – insert two points (one per segment), slicing off the sharp corner.
• Round – interpolate a circular arc between the two offset directions. Arc resolution adapts to the turn angle at approximately 8 segments per π.

Example

use oxigdal_algorithms::vector::{JoinStyle, OffsetOptions, offset_linestring};

let coords = vec![(0.0_f64, 0.0_f64), (10.0, 0.0)];
let opts = OffsetOptions::default();
let result = offset_linestring(&coords, 1.0, &opts)?;
assert_eq!(result.coords.len(), 2);
assert!((result.coords[0].1 - 1.0).abs() < 1e-10);

Structs

OffsetOptions

Options controlling how the offset curve is generated.

OffsetResult

Result returned by offset_linestring and its variants.

Enums

JoinStyle

Join style used when constructing the offset curve at interior vertices.

Functions

offset_linestring

Compute a parallel offset of an open polyline.

offset_polygon_rings

Compute parallel offset for each ring of a polygon independently.