Fix errors in simplifyThreshold in textToPoints

src/type/p5.Font.js

@@ -234,15 +234,15 @@ export class Font {
    * path and are more precise.
    *
    * `simplifyThreshold` removes collinear points if it's set to a number other
-   * than 0. The value represents the threshold angle to use when determining
+   * than 0. The value represents the threshold angle in radians to use when determining
    * whether two edges are collinear.
    *
    * @param  {String} str        string of text.
    * @param  {Number} x          x-coordinate of the text.
    * @param  {Number} y          y-coordinate of the text.
    * @param  {Object} [options]  Configuration:
    * @param  {Number} [options.sampleFactor=0.1] The ratio of the text's path length to the number of samples.
-   * @param  {Number} [options.simplifyThreshold=0] A minmum angle between two segments. Segments with a shallower angle will be merged.
+   * @param  {Number} [options.simplifyThreshold=0] A minmum angle in radian sbetween two segments. Segments with a shallower angle will be merged.
    * @return {Array<Object>} array of point objects, each with `x`, `y`, and `alpha` (path angle) properties.
    *
    * @example
@@ -306,15 +306,15 @@ export class Font {
    * path and are more precise.
    *
    * `simplifyThreshold` removes collinear points if it's set to a number other
-   * than 0. The value represents the threshold angle to use when determining
+   * than 0. The value represents the threshold angle in radians to use when determining
    * whether two edges are collinear.
    *
    * @param  {String} str        string of text.
    * @param  {Number} x          x-coordinate of the text.
    * @param  {Number} y          y-coordinate of the text.
    * @param  {Object} [options]  Configuration options:
    * @param  {Number} [options.sampleFactor=0.1] The ratio of the text's path length to the number of samples.
-   * @param  {Number} [options.simplifyThreshold=0] A minmum angle between two segments. Segments with a shallower angle will be merged.
+   * @param  {Number} [options.simplifyThreshold=0] A minmum angle in radians between two segments. Segments with a shallower angle will be merged.
    * @return {Array<Array<Object>>} array of point objects, each with `x`, `y`, and `alpha` (path angle) properties.
    *
    * @example
@@ -1092,6 +1092,35 @@ function pathToPoints(cmds, options, font) {
     return num;
   };
 
+  const collinear = (a, b, c, thresholdAngle) => {
+    if (!thresholdAngle) {
+      return areaTriangle(a, b, c) === 0;
+    }
+
+    if (typeof collinear.tmpPoint1 === 'undefined') {
+      collinear.tmpPoint1 = [];
+      collinear.tmpPoint2 = [];
+    }
+
+    const ab = collinear.tmpPoint1,
+      bc = collinear.tmpPoint2;
+    ab.x = b.x - a.x;
+    ab.y = b.y - a.y;
+    bc.x = c.x - b.x;
+    bc.y = c.y - b.y;
+
+    const dot = ab.x * bc.x + ab.y * bc.y,
+      magA = Math.sqrt(ab.x * ab.x + ab.y * ab.y),
+      magB = Math.sqrt(bc.x * bc.x + bc.y * bc.y),
+      angle = Math.acos(dot / (magA * magB));
+
+    return angle < thresholdAngle;
+  };
+
+  const areaTriangle = (a, b, c) => {
+    return (b[0] - a[0]) * (c[1] - a[1]) - (c[0] - a[0]) * (b[1] - a[1]);
+  };
+
   const path = createFromCommands(arrayCommandsToObjects(cmds));
   let opts = parseOpts(options, {
     sampleFactor: 0.1,

test/unit/type/p5.Font.js

@@ -60,6 +60,14 @@ suite('p5.Font', function () {
         expect(pt.y).not.toBeNaN();
       }
     });
+
+    test('simplifies collinear points', async () => {
+      const font = await myp5.loadFont(fontFile);
+      myp5.textSize(50);
+      const pts = font.textToPoints('T', 0, 0);
+      const simplifiedPts = font.textToPoints('T', 0, 0, { simplifyThreshold: Math.PI * 0.01 });
+      expect(pts.length).toBeGreaterThan(simplifiedPts.length);
+    });
   });
 });