From 1f63516bf4bbdc8f2075b6737af43e077409f5a1 Mon Sep 17 00:00:00 2001
From: Preet Shihn <preetshihn@gmail.com>
Date: Mon, 6 Apr 2020 15:53:49 -0700
Subject: [PATCH] support filling of curves

---
 src/generator.ts | 24 ++++++++++++---
 src/geometry.ts  | 80 ++++++++++++++++++++++++++++++++++++++++++++++--
 src/renderer.ts  | 18 +++++++++++
 3 files changed, 115 insertions(+), 7 deletions(-)

diff --git a/src/generator.ts b/src/generator.ts
index 88684d4..310589e 100644
--- a/src/generator.ts
+++ b/src/generator.ts
@@ -1,6 +1,6 @@
 import { Config, DrawingSurface, Options, Drawable, OpSet, ResolvedOptions, PathInfo, PatternInfo, SVGNS } from './core';
-import { Point } from './geometry.js';
-import { line, solidFillPolygon, patternFillPolygon, rectangle, ellipseWithParams, generateEllipseParams, linearPath, arc, patternFillArc, curve, svgPath } from './renderer.js';
+import { Point, getPointsOnBezierCurves } from './geometry.js';
+import { line, solidFillPolygon, patternFillPolygon, rectangle, ellipseWithParams, generateEllipseParams, linearPath, arc, patternFillArc, curve, svgPath, curveAsBezierPoints } from './renderer.js';
 import { randomSeed } from './math';
 
 const hasSelf = typeof self !== 'undefined';
@@ -125,12 +125,28 @@ export class RoughGenerator {
 
   curve(points: Point[], options?: Options): Drawable {
     const o = this._options(options);
-    return this._drawable('curve', [curve(points, o)], o);
+    const paths: OpSet[] = [];
+    const outline = curve(points, o);
+    if (o.fill && o.fill !== NOS) {
+      const bezPoints = curveAsBezierPoints(points, o);
+      if (bezPoints.length >= 4) {
+        const polyPoints = getPointsOnBezierCurves(bezPoints, Math.min(50, 50 * o.roughness));
+        if (o.fillStyle === 'solid') {
+          paths.push(solidFillPolygon(polyPoints, o));
+        } else {
+          paths.push(patternFillPolygon(polyPoints, o));
+        }
+      }
+    }
+    if (o.stroke !== NOS) {
+      paths.push(outline);
+    }
+    return this._drawable('curve', paths, o);
   }
 
   polygon(points: Point[], options?: Options): Drawable {
     const o = this._options(options);
-    const paths = [];
+    const paths: OpSet[] = [];
     const outline = linearPath(points, true, o);
     if (o.fill) {
       if (o.fillStyle === 'solid') {
diff --git a/src/geometry.ts b/src/geometry.ts
index e845f33..1cebd4e 100644
--- a/src/geometry.ts
+++ b/src/geometry.ts
@@ -1,6 +1,5 @@
-export declare type Point = [number, number];
-
-export declare type Line = [Point, Point];
+export type Point = [number, number];
+export type Line = [Point, Point];
 
 export interface Rectangle {
   x: number;
@@ -33,4 +32,79 @@ export function lineLength(line: Line): number {
   const p1 = line[0];
   const p2 = line[1];
   return Math.sqrt(Math.pow(p1[0] - p2[0], 2) + Math.pow(p1[1] - p2[1], 2));
+}
+
+export function getPointsOnBezierCurves(points: Point[], tolerance: number): Point[] {
+  const newPoints: Point[] = [];
+  const numSegments = (points.length - 1) / 3;
+  for (let i = 0; i < numSegments; i++) {
+    const offset = i * 3;
+    getPointsOnBezierCurveWithSplitting(points, offset, tolerance, newPoints);
+  }
+  return newPoints;
+}
+
+function lerp(a: Point, b: Point, t: number): Point {
+  return [
+    a[0] + (b[0] - a[0]) * t,
+    a[1] + (b[1] - a[1]) * t,
+  ];
+}
+
+function flatness(points: Point[], offset: number): number {
+  const p1 = points[offset + 0];
+  const p2 = points[offset + 1];
+  const p3 = points[offset + 2];
+  const p4 = points[offset + 3];
+
+  let ux = 3 * p2[0] - 2 * p1[0] - p4[0]; ux *= ux;
+  let uy = 3 * p2[1] - 2 * p1[1] - p4[1]; uy *= uy;
+  let vx = 3 * p3[0] - 2 * p4[0] - p1[0]; vx *= vx;
+  let vy = 3 * p3[1] - 2 * p4[1] - p1[1]; vy *= vy;
+
+  if (ux < vx) {
+    ux = vx;
+  }
+
+  if (uy < vy) {
+    uy = vy;
+  }
+
+  return ux + uy;
+}
+
+function getPointsOnBezierCurveWithSplitting(points: Point[], offset: number, tolerance: number, newPoints: Point[]) {
+  const outPoints = newPoints || [];
+  if (flatness(points, offset) < tolerance) {
+    const p0 = points[offset + 0];
+    if (outPoints.length) {
+      const d = lineLength([outPoints[outPoints.length - 1], p0]);
+      if (d > 1) {
+        outPoints.push(p0);
+      }
+    } else {
+      outPoints.push(p0);
+    }
+    outPoints.push(points[offset + 3]);
+  } else {
+    // subdivide
+    const t = .5;
+    const p1 = points[offset + 0];
+    const p2 = points[offset + 1];
+    const p3 = points[offset + 2];
+    const p4 = points[offset + 3];
+
+    const q1 = lerp(p1, p2, t);
+    const q2 = lerp(p2, p3, t);
+    const q3 = lerp(p3, p4, t);
+
+    const r1 = lerp(q1, q2, t);
+    const r2 = lerp(q2, q3, t);
+
+    const red = lerp(r1, r2, t);
+
+    getPointsOnBezierCurveWithSplitting([p1, q1, r1, red], 0, tolerance, outPoints);
+    getPointsOnBezierCurveWithSplitting([red, r2, q3, p4], 0, tolerance, outPoints);
+  }
+  return outPoints;
 }
\ No newline at end of file
diff --git a/src/renderer.ts b/src/renderer.ts
index 0955b6e..155dfc5 100644
--- a/src/renderer.ts
+++ b/src/renderer.ts
@@ -56,6 +56,24 @@ export function curve(points: Point[], o: ResolvedOptions): OpSet {
   return { type: 'path', ops: o1.concat(o2) };
 }
 
+export function curveAsBezierPoints(points: Point[], o: ResolvedOptions): Point[] {
+  const ops = _curveWithOffset(points, 1 * (1 + o.roughness * 0.2), o);
+  const bez: Point[] = [];
+  ops.forEach((op) => {
+    switch (op.op) {
+      case 'move':
+        bez.push([op.data[0], op.data[1]]);
+        break;
+      case 'bcurveTo':
+        bez.push([op.data[0], op.data[1]]);
+        bez.push([op.data[2], op.data[3]]);
+        bez.push([op.data[4], op.data[5]]);
+        break;
+    }
+  });
+  return bez;
+}
+
 export interface EllipseResult {
   opset: OpSet;
   estimatedPoints: Point[];