Fix center coordinates calculation for point and polygon annotations (#851)

Author: stockiNail

src/helpers/helpers.chart.js

@@ -137,13 +137,15 @@ export function resolvePointProperties(chart, options) {
       options.radius = radius;
     }
     const size = radius * 2;
+    const adjustCenterX = box.centerX + options.xAdjust;
+    const adjustCenterY = box.centerY + options.yAdjust;
     return {
-      x: box.x + options.xAdjust,
-      y: box.y + options.yAdjust,
-      x2: box.x + size + options.xAdjust,
-      y2: box.y + size + options.yAdjust,
-      centerX: box.centerX + options.xAdjust,
-      centerY: box.centerY + options.yAdjust,
+      x: adjustCenterX - radius,
+      y: adjustCenterY - radius,
+      x2: adjustCenterX + radius,
+      y2: adjustCenterY + radius,
+      centerX: adjustCenterX,
+      centerY: adjustCenterY,
       width: size,
       height: size
     };