# Struct kurbo::BezPath[−][src]

pub struct BezPath(_);

A Bézier path.

These docs assume basic familiarity with Bézier curves; for an introduction, see Pomax’s wonderful A Primer on Bézier Curves.

This path can contain lines, quadratics (QuadBez) and cubics (CubicBez), and may contain multiple subpaths.

# Elements and Segments

A Bézier path can be represented in terms of either ‘elements’ (PathEl) or ‘segments’ (PathSeg). Elements map closely to how Béziers are generally used in PostScript-style drawing APIs; they can be thought of as instructions for drawing the path. Segments more directly describe the path itself, with each segment being an independent line or curve.

These different representations are useful in different contexts. For tasks like drawing, elements are a natural fit, but when doing hit-testing or subdividing, we need to have access to the segments.

Internally, a BezPath is a list of PathEls; as such it implements FromIterator<PathEl> and Extend<PathEl>:

use kurbo::{BezPath, Rect, Shape, Vec2};
let accuracy = 0.1;
let rect = Rect::from_origin_size((0., 0.,), (10., 10.));
// these are equivalent
let path1 = rect.to_path(accuracy);
let path2: BezPath = rect.path_elements(accuracy).collect();

// extend a path with another path:
let mut path = rect.to_path(accuracy);
let shifted_rect = rect + Vec2::new(5.0, 10.0);
path.extend(shifted_rect.to_path(accuracy));

You can iterate the elements of a BezPath with the iter method, and the segments with the segments method:

use kurbo::{BezPath, Line, PathEl, PathSeg, Point, Rect, Shape};
let accuracy = 0.1;
let rect = Rect::from_origin_size((0., 0.,), (10., 10.));
// these are equivalent
let path = rect.to_path(accuracy);
let first_el = PathEl::MoveTo(Point::ZERO);
let first_seg = PathSeg::Line(Line::new((0., 0.), (10., 0.)));
assert_eq!(path.iter().next(), Some(first_el));
assert_eq!(path.segments().next(), Some(first_seg));

In addition, if you have some other type that implements Iterator<Item=PathEl>, you can adapt that to an iterator of segments with the segments free function.

In addition to the basic API, there are several useful pieces of advanced functionality available on BezPath:

• flatten does Bézier flattening, converting a curve to a series of line segments
• intersect_line computes intersections of a path with a line, useful for things like subdividing

## Implementations

### impl BezPath[src]

#### pub fn new() -> BezPath[src]

Create a new path.

#### pub fn from_vec(v: Vec<PathEl>) -> BezPath[src]

Create a path from a vector of path elements.

BezPath also implements FromIterator<PathEl>, so it works with collect:

// a very contrived example:
use kurbo::{BezPath, PathEl};

let path = BezPath::new();
let as_vec: Vec<PathEl> = path.into_iter().collect();
let back_to_path: BezPath = as_vec.into_iter().collect();

#### pub fn push(&mut self, el: PathEl)[src]

Push a generic path element onto the path.

#### pub fn move_to<P: Into<Point>>(&mut self, p: P)[src]

Push a “move to” element onto the path.

#### pub fn line_to<P: Into<Point>>(&mut self, p: P)[src]

Push a “line to” element onto the path.

#### pub fn quad_to<P: Into<Point>>(&mut self, p1: P, p2: P)[src]

Push a “quad to” element onto the path.

#### pub fn curve_to<P: Into<Point>>(&mut self, p1: P, p2: P, p3: P)[src]

Push a “curve to” element onto the path.

#### pub fn close_path(&mut self)[src]

Push a “close path” element onto the path.

#### pub fn elements(&self) -> &[PathEl][src]

Get the path elements.

#### pub fn iter(&self) -> impl Iterator<Item = PathEl> + '_[src]

Returns an iterator over the path’s elements.

#### pub fn segments(&self) -> impl Iterator<Item = PathSeg> + '_[src]

Iterate over the path segments.

#### pub fn flatten(&self, tolerance: f64, callback: impl FnMut(PathEl))[src]

Flatten the path, invoking the callback repeatedly.

Flattening is the action of approximating a curve with a succession of line segments.

The tolerance value controls the maximum distance between the curved input segments and their polyline approximations. (In technical terms, this is the Hausdorff distance). The algorithm attempts to bound this distance between by tolerance but this is not absolutely guaranteed. The appropriate value depends on the use, but for antialiasted rendering, a value of 0.25 has been determined to give good results. The number of segments tends to scale as the inverse square root of tolerance.

The callback will be called in order with each element of the generated path. Because the result is made of polylines, these will be straight-line path elements only, no curves.

This algorithm is based on the blog post Flattening quadratic Béziers but with some refinements. For one, there is a more careful approximation at cusps. For two, the algorithm is extended to work with cubic Béziers as well, by first subdividing into quadratics and then computing the subdivision of each quadratic. However, as a clever trick, these quadratics are subdivided fractionally, and their endpoints are not included.

TODO: write a paper explaining this in more detail.

Note: the flatten function provides the same functionality but works with slices and other PathEl iterators.

#### pub fn get_seg(&self, ix: usize) -> Option<PathSeg>[src]

Get the segment at the given element index.

The element index counts PathEl elements, so for example includes an initial Moveto.

#### pub fn is_empty(&self) -> bool[src]

Returns true if the path contains no segments.

#### pub fn apply_affine(&mut self, affine: Affine)[src]

Apply an affine transform to the path.

#### pub fn is_finite(&self) -> bool[src]

Is this path finite?

#### pub fn is_nan(&self) -> bool[src]

Is this path NaN?

### impl BezPath[src]

#### pub fn from_path_segments(segments: impl Iterator<Item = PathSeg>) -> BezPath[src]

Create a BezPath with segments corresponding to the sequence of PathSegs

#### pub fn to_svg(&self) -> String[src]

Convert the path to an SVG path string representation.

The current implementation doesn’t take any special care to produce a short string (reducing precision, using relative movement).

#### pub fn write_to<W: Write>(&self, writer: W) -> Result<()>[src]

Write the SVG representation of this path to the provided buffer.

#### pub fn from_svg(data: &str) -> Result<BezPath, SvgParseError>[src]

Try to parse a bezier path from an SVG path element.

This is implemented on a best-effort basis, intended for cases where the user controls the source of paths, and is not intended as a replacement for a general, robust SVG parser.

## Trait Implementations

### impl<'a> IntoIterator for &'a BezPath[src]

Allow iteration over references to BezPath.

Note: the semantics are slightly different than simply iterating over the slice, as it returns PathEl items, rather than references.

#### type Item = PathEl

The type of the elements being iterated over.

#### type IntoIter = Cloned<Iter<'a, PathEl>>

Which kind of iterator are we turning this into?

### impl IntoIterator for BezPath[src]

#### type Item = PathEl

The type of the elements being iterated over.

#### type IntoIter = IntoIter<PathEl>

Which kind of iterator are we turning this into?

### impl<'a> Mul<&'a BezPath> for Affine[src]

#### type Output = BezPath

The resulting type after applying the * operator.

### impl<'a> Mul<&'a BezPath> for TranslateScale[src]

#### type Output = BezPath

The resulting type after applying the * operator.

### impl Mul<BezPath> for Affine[src]

#### type Output = BezPath

The resulting type after applying the * operator.

### impl Mul<BezPath> for TranslateScale[src]

#### type Output = BezPath

The resulting type after applying the * operator.

### impl Shape for BezPath[src]

#### type PathElementsIter = IntoIter<PathEl>

The iterator returned by the path_elements method. Read more

Signed area.

#### fn winding(&self, pt: Point) -> i32[src]

Winding number of point.

## Blanket Implementations

### impl<T> ToOwned for T where    T: Clone, [src]

#### type Owned = T

The resulting type after obtaining ownership.

### impl<T, U> TryFrom<U> for T where    U: Into<T>, [src]

#### type Error = Infallible

The type returned in the event of a conversion error.

### impl<T, U> TryInto<U> for T where    U: TryFrom<T>, [src]

#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.