397 lines
14 KiB
Rust
397 lines
14 KiB
Rust
//! Bezier shapes for shape layers, masks and text.
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//!
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//! Geometry is kept in [`kurbo::BezPath`]; anti-aliased coverage comes from tiny-skia's scanline
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//! rasteriser (BSD-3) and is converted to our `f32` [`Mask`]. Path operations (trim, round corners,
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//! pucker & bloat, zig zag, twist, wiggle, offset, merge) live in [`ops`]; curve-preserving booleans
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//! (for Merge Paths) in [`boolean`] and curve offsetting in [`offset`].
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pub mod boolean;
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pub mod feather;
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mod fit;
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pub mod interp;
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pub mod offset;
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pub mod ops;
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pub mod trace;
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pub mod varstroke;
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use effectcraft_geom::Mat3;
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use effectcraft_keyframe::ShapePath;
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use effectcraft_raster::Mask;
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pub use kurbo::{BezPath, PathEl, Point};
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use kurbo::{Shape, Vec2 as KVec2};
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/// Convert the AE vertex/tangent model to a kurbo path.
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pub fn to_kurbo(p: &ShapePath) -> BezPath {
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let mut out = BezPath::new();
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let n = p.vertices.len();
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if n == 0 {
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return out;
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}
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let v = |i: usize| Point::new(p.vertices[i][0], p.vertices[i][1]);
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let ot = |i: usize| p.out_tangents.get(i).copied().unwrap_or([0.0; 2]);
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let it = |i: usize| p.in_tangents.get(i).copied().unwrap_or([0.0; 2]);
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out.move_to(v(0));
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let seg = |out: &mut BezPath, a: usize, b: usize| {
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let (o, i) = (ot(a), it(b));
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if o == [0.0; 2] && i == [0.0; 2] {
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out.line_to(v(b));
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} else {
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out.curve_to(v(a) + KVec2::new(o[0], o[1]), v(b) + KVec2::new(i[0], i[1]), v(b));
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}
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};
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for i in 0..n - 1 {
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seg(&mut out, i, i + 1);
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}
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if p.closed && n > 1 {
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seg(&mut out, n - 1, 0);
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out.close_path();
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}
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out
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}
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/// Convert a kurbo path (first subpath) back to the vertex model (quads are elevated).
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pub fn from_kurbo(path: &BezPath) -> Vec<ShapePath> {
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let mut out = Vec::new();
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let mut cur: Option<ShapePath> = None;
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let mut last = Point::ZERO;
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let flush = |cur: &mut Option<ShapePath>, out: &mut Vec<ShapePath>| {
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if let Some(mut c) = cur.take() {
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// A closing segment ending on the first vertex duplicates it.
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if c.closed && c.vertices.len() > 1 {
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let f = c.vertices[0];
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let l = *c.vertices.last().unwrap_or(&f);
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if (f[0] - l[0]).abs() < 1e-9 && (f[1] - l[1]).abs() < 1e-9 {
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let it = c.in_tangents.pop().unwrap_or([0.0; 2]);
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c.vertices.pop();
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c.out_tangents.pop();
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c.in_tangents[0] = it;
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}
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}
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if !c.vertices.is_empty() {
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out.push(c);
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}
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}
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};
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for el in path.elements() {
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match *el {
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PathEl::MoveTo(p) => {
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flush(&mut cur, &mut out);
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cur = Some(ShapePath {
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vertices: vec![[p.x, p.y]],
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in_tangents: vec![[0.0; 2]],
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out_tangents: vec![[0.0; 2]],
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closed: false,
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feather: Vec::new(),
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});
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last = p;
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}
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PathEl::LineTo(p) => {
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if let Some(c) = cur.as_mut() {
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c.vertices.push([p.x, p.y]);
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c.in_tangents.push([0.0; 2]);
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c.out_tangents.push([0.0; 2]);
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}
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last = p;
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}
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PathEl::QuadTo(q, p) => {
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let c1 = last + (q - last) * (2.0 / 3.0);
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let c2 = p + (q - p) * (2.0 / 3.0);
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if let Some(c) = cur.as_mut() {
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if let Some(o) = c.out_tangents.last_mut() {
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*o = [c1.x - last.x, c1.y - last.y];
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}
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c.vertices.push([p.x, p.y]);
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c.in_tangents.push([c2.x - p.x, c2.y - p.y]);
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c.out_tangents.push([0.0; 2]);
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}
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last = p;
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}
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PathEl::CurveTo(c1, c2, p) => {
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if let Some(c) = cur.as_mut() {
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if let Some(o) = c.out_tangents.last_mut() {
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*o = [c1.x - last.x, c1.y - last.y];
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}
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c.vertices.push([p.x, p.y]);
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c.in_tangents.push([c2.x - p.x, c2.y - p.y]);
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c.out_tangents.push([0.0; 2]);
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}
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last = p;
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}
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PathEl::ClosePath => {
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if let Some(c) = cur.as_mut() {
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c.closed = true;
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}
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}
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}
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}
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flush(&mut cur, &mut out);
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out
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}
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/// Rectangle path centred at `pos` with corner `roundness` (AE draws clockwise from the top-right).
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pub fn rect(size: [f64; 2], pos: [f64; 2], roundness: f64) -> BezPath {
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let r = kurbo::Rect::from_center_size(Point::new(pos[0], pos[1]), (size[0].abs(), size[1].abs()));
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let rad = roundness.clamp(0.0, size[0].abs().min(size[1].abs()) / 2.0);
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if rad > 0.0 { r.to_rounded_rect(rad).to_path(0.1) } else { r.to_path(0.1) }
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}
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pub fn ellipse(size: [f64; 2], pos: [f64; 2]) -> BezPath {
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to_kurbo(&ShapePath::ellipse(pos, size[0], size[1]))
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}
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/// Polystar: a star (`inner` radius used) or polygon, rotation in degrees, roundness in percent.
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pub fn polystar(star: bool, points: f64, pos: [f64; 2], rotation: f64, inner: f64, outer: f64, inner_round: f64, outer_round: f64) -> BezPath {
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let n = points.max(3.0).round() as usize;
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let verts = if star { n * 2 } else { n };
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let mut path = BezPath::new();
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let step = std::f64::consts::TAU / verts as f64;
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let start = (rotation - 90.0).to_radians();
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let mut pts = Vec::with_capacity(verts);
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for i in 0..verts {
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let r = if star && i % 2 == 1 { inner } else { outer };
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let a = start + step * i as f64;
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pts.push((Point::new(pos[0] + r * a.cos(), pos[1] + r * a.sin()), a, r, if star && i % 2 == 1 { inner_round } else { outer_round }));
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}
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let tangent = |(p, a, r, round): (Point, f64, f64, f64), sign: f64| -> Point {
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if round == 0.0 {
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return p;
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}
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// Tangent perpendicular to the radius, length proportional to the arc between vertices.
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let len = r * step * 0.25 * round / 100.0 * 4.0 / 3.0 * 0.75;
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let d = KVec2::new(-a.sin(), a.cos()) * len * sign;
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p + d
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};
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path.move_to(pts[0].0);
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for i in 0..verts {
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let a = pts[i];
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let b = pts[(i + 1) % verts];
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if a.3 == 0.0 && b.3 == 0.0 {
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path.line_to(b.0);
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} else {
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path.curve_to(tangent(a, 1.0), tangent(b, -1.0), b.0);
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}
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}
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path.close_path();
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path
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}
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fn to_skia(path: &BezPath) -> Option<tiny_skia::Path> {
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let mut pb = tiny_skia::PathBuilder::new();
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for el in path.elements() {
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match *el {
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PathEl::MoveTo(p) => pb.move_to(p.x as f32, p.y as f32),
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PathEl::LineTo(p) => pb.line_to(p.x as f32, p.y as f32),
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PathEl::QuadTo(a, p) => pb.quad_to(a.x as f32, a.y as f32, p.x as f32, p.y as f32),
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PathEl::CurveTo(a, b, p) => pb.cubic_to(a.x as f32, a.y as f32, b.x as f32, b.y as f32, p.x as f32, p.y as f32),
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PathEl::ClosePath => pb.close(),
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}
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}
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pb.finish()
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}
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fn from_skia(p: &tiny_skia::Path) -> BezPath {
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let mut out = BezPath::new();
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let pt = |p: tiny_skia::Point| Point::new(p.x as f64, p.y as f64);
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for seg in p.segments() {
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match seg {
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tiny_skia::PathSegment::MoveTo(a) => out.move_to(pt(a)),
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tiny_skia::PathSegment::LineTo(a) => out.line_to(pt(a)),
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tiny_skia::PathSegment::QuadTo(a, b) => out.quad_to(pt(a), pt(b)),
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tiny_skia::PathSegment::CubicTo(a, b, c) => out.curve_to(pt(a), pt(b), pt(c)),
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tiny_skia::PathSegment::Close => out.close_path(),
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}
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}
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out
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}
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fn skia_transform(m: &Mat3) -> tiny_skia::Transform {
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let a = &m.0;
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tiny_skia::Transform::from_row(a[0][0] as f32, a[1][0] as f32, a[0][1] as f32, a[1][1] as f32, a[0][2] as f32, a[1][2] as f32)
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}
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#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
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pub enum FillRule {
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#[default]
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NonZero,
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EvenOdd,
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}
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/// Anti-aliased coverage of `paths` (in local space) transformed by `m` into a `w × h` mask.
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pub fn fill_coverage(paths: &[BezPath], m: &Mat3, w: u32, h: u32, rule: FillRule) -> Mask {
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let mut out = Mask::new(w, h, 0.0);
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let Some(mut mask) = tiny_skia::Mask::new(w.max(1), h.max(1)) else { return out };
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let mut all = BezPath::new();
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for p in paths {
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all.extend(p.elements().iter().copied());
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}
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let Some(sp) = to_skia(&all) else { return out };
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let fr = match rule {
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FillRule::NonZero => tiny_skia::FillRule::Winding,
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FillRule::EvenOdd => tiny_skia::FillRule::EvenOdd,
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};
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mask.fill_path(&sp, fr, true, skia_transform(m));
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for (o, &v) in out.data.iter_mut().zip(mask.data()) {
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*o = v as f32 / 255.0;
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}
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out
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}
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#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
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pub enum Cap {
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#[default]
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Butt,
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Round,
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Square,
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}
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#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
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pub enum Join {
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#[default]
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Miter,
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Round,
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Bevel,
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}
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#[derive(Clone, Debug, PartialEq)]
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pub struct StrokeStyle {
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pub width: f64,
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pub cap: Cap,
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pub join: Join,
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pub miter: f64,
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/// Dash pattern (dash, gap, …) and offset.
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pub dash: Option<(Vec<f64>, f64)>,
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/// Stroke Taper (variable width at the ends).
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pub taper: Option<varstroke::Taper>,
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/// Stroke Wave (periodic width).
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pub wave: Option<varstroke::Wave>,
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}
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impl StrokeStyle {
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/// Whether the width varies along the path (Taper or Wave active).
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pub fn is_variable(&self) -> bool {
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self.taper.as_ref().is_some_and(|t| t.is_active()) || self.wave.as_ref().is_some_and(|w| w.is_active())
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}
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}
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impl Default for StrokeStyle {
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fn default() -> Self {
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StrokeStyle { width: 1.0, cap: Cap::Butt, join: Join::Miter, miter: 4.0, dash: None, taper: None, wave: None }
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}
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}
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/// Outline of a stroke as a fillable path (local space). `res_scale` = device/local scale.
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pub fn stroke_outline(paths: &[BezPath], style: &StrokeStyle, res_scale: f64) -> Option<BezPath> {
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if style.width <= 0.0 {
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return None;
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}
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if style.is_variable() {
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return varstroke::outline(paths, style, res_scale);
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}
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let mut all = BezPath::new();
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for p in paths {
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all.extend(p.elements().iter().copied());
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}
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let mut sp = to_skia(&all)?;
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if let Some((d, off)) = &style.dash {
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let arr: Vec<f32> = d.iter().map(|v| v.max(0.0) as f32).collect();
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if arr.len() >= 2 && arr.iter().any(|v| *v > 0.0) {
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let arr = if arr.len() % 2 == 1 { [arr.clone(), arr].concat() } else { arr };
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if let Some(dash) = tiny_skia::StrokeDash::new(arr, *off as f32) {
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sp = sp.dash(&dash, res_scale as f32)?;
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}
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}
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}
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let st = tiny_skia::Stroke {
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width: style.width as f32,
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miter_limit: style.miter.max(1.0) as f32,
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line_cap: match style.cap {
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Cap::Butt => tiny_skia::LineCap::Butt,
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Cap::Round => tiny_skia::LineCap::Round,
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Cap::Square => tiny_skia::LineCap::Square,
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},
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line_join: match style.join {
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Join::Miter => tiny_skia::LineJoin::Miter,
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Join::Round => tiny_skia::LineJoin::Round,
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Join::Bevel => tiny_skia::LineJoin::Bevel,
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},
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dash: None,
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};
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let out = sp.stroke(&st, res_scale.max(0.01) as f32)?;
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Some(from_skia(&out))
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}
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/// Coverage of a stroke.
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pub fn stroke_coverage(paths: &[BezPath], style: &StrokeStyle, m: &Mat3, w: u32, h: u32) -> Mask {
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match stroke_outline(paths, style, m.mean_scale()) {
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Some(o) => fill_coverage(&[o], m, w, h, FillRule::NonZero),
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None => Mask::new(w, h, 0.0),
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}
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}
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/// Bounding box of paths in local space.
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pub fn bounds(paths: &[BezPath]) -> Option<kurbo::Rect> {
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let mut r: Option<kurbo::Rect> = None;
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for p in paths {
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if p.elements().is_empty() {
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continue;
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}
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let b = p.bounding_box();
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r = Some(r.map_or(b, |a| a.union(b)));
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}
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r
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}
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/// Transform paths by an affine Mat3.
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pub fn transform(paths: &[BezPath], m: &Mat3) -> Vec<BezPath> {
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let a = &m.0;
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let k = kurbo::Affine::new([a[0][0], a[1][0], a[0][1], a[1][1], a[0][2], a[1][2]]);
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paths.iter().map(|p| k * p.clone()).collect()
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn roundtrip_vertex_model() {
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let sp = ShapePath::ellipse([10.0, 20.0], 40.0, 30.0);
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let k = to_kurbo(&sp);
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let back = from_kurbo(&k);
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assert_eq!(back.len(), 1);
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let b = &back[0];
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assert!(b.closed);
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assert_eq!(b.vertices.len(), 4);
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for i in 0..4 {
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for c in 0..2 {
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assert!((b.vertices[i][c] - sp.vertices[i][c]).abs() < 1e-9);
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assert!((b.in_tangents[i][c] - sp.in_tangents[i][c]).abs() < 1e-9, "{i} {b:?}");
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assert!((b.out_tangents[i][c] - sp.out_tangents[i][c]).abs() < 1e-9);
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}
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}
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}
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#[test]
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fn rect_coverage_area() {
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let r = rect([20.0, 10.0], [50.0, 50.0], 0.0);
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let m = fill_coverage(&[r], &Mat3::IDENTITY, 100, 100, FillRule::NonZero);
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let area: f32 = m.data.iter().sum();
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assert!((area - 200.0).abs() < 1.0, "{area}");
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}
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#[test]
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fn stroke_has_area() {
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let r = rect([40.0, 40.0], [50.0, 50.0], 0.0);
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let st = StrokeStyle { width: 4.0, ..Default::default() };
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let m = stroke_coverage(&[r], &st, &Mat3::IDENTITY, 100, 100);
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let area: f32 = m.data.iter().sum();
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assert!((area - 4.0 * 160.0).abs() < 40.0, "{area}");
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}
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#[test]
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fn star_has_right_vertex_count() {
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let p = polystar(true, 5.0, [0.0, 0.0], 0.0, 20.0, 50.0, 0.0, 0.0);
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let v = from_kurbo(&p);
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assert_eq!(v[0].vertices.len(), 10);
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}
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}
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