feat: implement getMathAngle

Author: opatiny

src/maskAnalysis/utils/__tests__/getAngle.test.ts

@@ -1,6 +1,6 @@
 import { toBeDeepCloseTo } from 'jest-matcher-deep-close-to';
 
-import { getAngle } from '../getAngle';
+import { getAngle, getMathAngle } from '../getAngle';
 
 expect.extend({ toBeDeepCloseTo });
 
@@ -38,3 +38,50 @@ test.each([
   const result = getAngle(point1, point2);
   expect(result).toBeCloseTo(expectedAngle);
 });
+
+test.each([
+  [
+    '60 degrees',
+    { column: 0, row: 0 },
+    { column: 1, row: -Math.sqrt(3) },
+    Math.PI / 3,
+  ],
+  ['45 degrees', { column: 0, row: 0 }, { column: 1, row: -1 }, Math.PI / 4],
+  [
+    '30 degrees',
+    { column: 0, row: 0 },
+    { column: Math.sqrt(3), row: -1 },
+    Math.PI / 6,
+  ],
+  [
+    '-60 degrees',
+    { column: 0, row: 0 },
+    { column: 1, row: Math.sqrt(3) },
+    -Math.PI / 3,
+  ],
+  ['-45 degrees', { column: 0, row: 0 }, { column: 1, row: 1 }, -Math.PI / 4],
+  [
+    '-30 degrees',
+    { column: 0, row: 0 },
+    { column: Math.sqrt(3), row: 1 },
+    -Math.PI / 6,
+  ],
+  ['180 degrees', { column: 0, row: 0 }, { column: -1, row: 0 }, Math.PI],
+  ['270 degrees', { column: 0, row: 0 }, { column: 0, row: 1 }, -Math.PI / 2],
+  ['90 degrees', { column: 0, row: 0 }, { column: 0, row: -1 }, Math.PI / 2],
+  [
+    '90 degrees, origin not zero',
+    { column: 1, row: 4 },
+    { column: 1, row: 3 },
+    Math.PI / 2,
+  ],
+  [
+    '45 degrees, origin not zero',
+    { column: 4, row: 5 },
+    { column: 5, row: 4 },
+    Math.PI / 4,
+  ],
+])('getMathAngle (%s)', (_, point1, point2, expectedAngle) => {
+  const result = getMathAngle(point1, point2);
+  expect(result).toBeCloseTo(expectedAngle);
+});

src/maskAnalysis/utils/getAngle.ts

@@ -11,9 +11,31 @@ import { difference, normalize, Point } from '../../utils/geometry/points';
  * @returns Rotation angle in radians to make the line horizontal.
  */
 export function getAngle(p1: Point, p2: Point): number {
-  let diff = difference(p2, p1);
-  let vector = normalize(diff);
-  let angle = Math.acos(vector.column);
+  const diff = difference(p2, p1);
+  const vector = normalize(diff);
+  const angle = Math.acos(vector.column);
   if (vector.row < 0) return -angle;
   return angle;
 }
+
+/**
+ * Compute the mathematical angle in radians of the segment p1-p2.
+ *
+ * @param p1 - First point.
+ * @param p2 - Second point.
+ * @returns The angle of the segment in radians.
+ */
+export function getMathAngle(p1: Point, p2: Point): number {
+  const diff = difference(p2, p1);
+  const vector = normalize(diff);
+  const atan = -Math.atan(vector.row / vector.column);
+  if (vector.column < 0) {
+    if (vector.row < 0) {
+      return atan - Math.PI;
+    } else {
+      return atan + Math.PI;
+    }
+  } else {
+    return atan;
+  }
+}