From 2dcd40afc63ae3975f6cc36e08f45181fe95cab9 Mon Sep 17 00:00:00 2001
From: Antoine Vandecreme <ant.vand@gmail.com>
Date: Sun, 13 Dec 2015 11:49:58 -0500
Subject: [PATCH] Fix flickering issue at certain rotation angles.
---
src/point.js | 34 +++++++++++++++++++++++++++++++---
1 file changed, 31 insertions(+), 3 deletions(-)
diff --git a/src/point.js b/src/point.js
index cf31c44a..ebddfffe 100644
--- a/src/point.js
+++ b/src/point.js
@@ -185,9 +185,37 @@ $.Point.prototype = /** @lends OpenSeadragon.Point.prototype */{
*/
rotate: function (degrees, pivot) {
pivot = pivot || new $.Point(0, 0);
- var angle = degrees * Math.PI / 180.0;
- var cos = Math.cos(angle);
- var sin = Math.sin(angle);
+ var cos;
+ var sin;
+ // Avoid float computations when possible
+ if (degrees % 90 === 0) {
+ var d = degrees % 360;
+ if (d < 0) {
+ d += 360;
+ }
+ switch (d) {
+ case 0:
+ cos = 1;
+ sin = 0;
+ break;
+ case 90:
+ cos = 0;
+ sin = 1;
+ break;
+ case 180:
+ cos = -1;
+ sin = 0;
+ break;
+ case 270:
+ cos = 0;
+ sin = -1;
+ break;
+ }
+ } else {
+ var angle = degrees * Math.PI / 180.0;
+ cos = Math.cos(angle);
+ sin = Math.sin(angle);
+ }
var x = cos * (this.x - pivot.x) - sin * (this.y - pivot.y) + pivot.x;
var y = sin * (this.x - pivot.x) + cos * (this.y - pivot.y) + pivot.y;
return new $.Point(x, y);