diff --git a/simpleheat.js b/simpleheat.js
index dc06eb9..7372165 100644
--- a/simpleheat.js
+++ b/simpleheat.js
@@ -111,6 +111,10 @@ simpleheat.prototype = {
         }
 
         // colorize the heatmap, using opacity value of each pixel to get the right color from our gradient
+        //some time,the canvas's width and height may be zero
+        if(this._width==0||this._height==0){
+            this.resize();
+        }
         var colored = ctx.getImageData(0, 0, this._width, this._height);
         this._colorize(colored.data, this._grad);
         ctx.putImageData(colored, 0, 0);