chore: add centroid property to toJSON function (#293)

Author: EscapedGibbon

src/roi/Roi.ts

@@ -326,6 +326,7 @@ export class Roi {
       perimeter: this.perimeter,
       convexHull: this.convexHull,
       mbr: this.mbr,
+      centroid: this.centroid,
     };
   }
 

src/roi/__tests__/__snapshots__/computeRois.test.ts.snap

@@ -3,6 +3,10 @@
 exports[`3x3 mask 1`] = `
 [
   {
+    "centroid": {
+      "column": 0.75,
+      "row": 0.25,
+    },
     "convexHull": {
       "perimeter": 9.23606797749979,
       "points": [
@@ -102,6 +106,10 @@ exports[`3x3 mask 1`] = `
     "width": 3,
   },
   {
+    "centroid": {
+      "column": 2,
+      "row": 2,
+    },
     "convexHull": {
       "perimeter": 4,
       "points": [
@@ -202,6 +210,10 @@ exports[`3x3 mask 1`] = `
 exports[`3x3 mask 2`] = `
 [
   {
+    "centroid": {
+      "column": 1,
+      "row": 1.5,
+    },
     "convexHull": {
       "perimeter": 8.82842712474619,
       "points": [