vectorcraft/crates/effects/src/warp.rs

//! Warp effects: 15 envelope styles plus horizontal/vertical perspective distortion.
//!
//! Each style is a map on normalised box coordinates (x, y) ∈ [-1, 1]² (y down). The path is
//! split into short pieces whose control points are mapped (see `map_nonlinear`).

use serde_json::Value;
use vectorcraft_geom::{PathData, Point, Rect};

use crate::util::*;

pub use vectorcraft_doc::live::{WarpStyle, warp_point};

/// Apply a warp to `path` using box `b`.
pub fn warp(path: &PathData, b: Rect, style: WarpStyle, p: &Value) -> PathData {
    let bend = num(p, "bend", 50.0).clamp(-100.0, 100.0) / 100.0;
    let dh = num(p, "horizontal", 0.0).clamp(-100.0, 100.0) / 100.0;
    let dv = num(p, "vertical", 0.0).clamp(-100.0, 100.0) / 100.0;
    let vertical = text(p, "orientation", "horizontal").eq_ignore_ascii_case("vertical");
    let c = b.center();
    let hw = (b.width() / 2.0).max(1e-9);
    let hh = (b.height() / 2.0).max(1e-9);
    let f = |q: Point| {
        let (x, y) = ((q.x - c.x) / hw, (q.y - c.y) / hh);
        let (x2, y2) = if vertical {
            let (a, b2) = warp_point(style, bend, dh, dv, y, x);
            (b2, a)
        } else {
            warp_point(style, bend, dh, dv, x, y)
        };
        Point::new(c.x + x2 * hw, c.y + y2 * hh)
    };
    let piece = b.width().hypot(b.height()) / 24.0;
    map_nonlinear(path, piece, f)
}