Update index.html

index.html

@@ -20,7 +20,7 @@
     <section class="page-header">
       <h1 class="project-name">Picasso</h1>
       <h2 class="project-tagline">Picasso is a high quality vector graphic rendering library. It support path , matrix , gradient , pattern , image and truetype font. </h2>
-      <a href="https://github.com/sponsors/onecoolx" target="_blank"><img src="https://github.com/onecoolx/picasso/blob/gh-pages/res/sponsor.png"></a>
+      <a href="https://github.com/sponsors/onecoolx" target="_blank"><img src="res/sponsor.png"></a>
       <a href="https://github.com/onecoolx/picasso" class="btn">View on GitHub</a>
       <a href="http://onecoolx.github.io/picasso/html/index.html" class="btn">Document</a>
       <a href="https://github.com/onecoolx/picasso/zipball/master" class="btn">Download .zip</a>