Add margin param for image preview.

boards/static/js/image.js

@@ -1,4 +1,6 b''
 function addImgPreview() {
+    var margin = 20;
+
     //keybind
     $(document).on('keyup.removepic', function(e) {
         if(e.which === 27) {
@@ -18,12 +20,12 b' function addImgPreview() {'
             var win_h = $(window).height();
             //new image size
             if (img_w > win_w) {
-                img_h = img_h * (win_w/img_w);
-                img_w = win_w;
+                img_h = img_h * (win_w/img_w) - margin;
+                img_w = win_w - margin;
             }
             if (img_h > win_h) {
-                img_w = img_w * (win_h/img_h);
-                img_h = win_h;
+                img_w = img_w * (win_h/img_h) - margin;
+                img_h = win_h - margin;
             }
 
             var img_pv = new Image();