add type property to drawers. only add extra padding to tiles for drawers that need it.

src/canvasdrawer.js

@@ -85,6 +85,10 @@ class CanvasDrawer extends $.DrawerBase{
         return $.supportsCanvas;
     }
 
+    get type(){
+        return 'canvas';
+    }
+
     /**
      * create the HTML element (e.g. canvas, div) that the image will be drawn into
      * @returns {Element} the canvas to draw into
@@ -129,6 +133,14 @@ class CanvasDrawer extends $.DrawerBase{
         this.sketchContext = null;
     }
 
+    /**
+     * @returns {Boolean} Whether this drawer requires enforcing minimum tile overlap to avoid showing seams.
+     */
+    minimumOverlapRequired() {
+       return true;
+    }
+
+
     /**
      * Turns image smoothing on or off for this viewer. Note: Ignored in some (especially older) browsers that do not support this property.
      *

src/drawerbase.js

@@ -122,6 +122,13 @@ $.DrawerBase = class DrawerBase{
         return this.container;
     }
 
+    /**
+     * @property {String|undefined} type What type of drawer this is. Implementations should override this property.
+     */
+    get type(){
+        return undefined;
+    }
+
     /**
      * @returns {Boolean} whether the drawer implementation is supported by the browser
      */
@@ -139,9 +146,9 @@ $.DrawerBase = class DrawerBase{
     }
 
     /**
-     * @param tiledImage the TiledImage that is ready to be drawn
+     * @param {Array} tiledImages - An array of TiledImages that are ready to be drawn
      */
-    draw(tiledImage) {
+    draw(tiledImages) {
         $.console.error('Drawer.draw must be implemented by child class');
     }
 
@@ -159,6 +166,14 @@ $.DrawerBase = class DrawerBase{
         $.console.error('Drawer.destroy must be implemented by child class');
     }
 
+    /**
+     * @returns {Boolean} Whether this drawer requires enforcing minimum tile overlap to avoid showing seams.
+     */
+    minimumOverlapRequired() {
+        return false;
+     }
+
+
     /**
      * Turns image smoothing on or off for this viewer. Note: Ignored in some (especially older) browsers that do not support this property.
      *

src/htmldrawer.js

@@ -65,6 +65,17 @@ class HTMLDrawer extends $.DrawerBase{
         return true;
     }
 
+    get type(){
+        return 'html';
+    }
+
+    /**
+     * @returns {Boolean} Whether this drawer requires enforcing minimum tile overlap to avoid showing seams.
+     */
+    minimumOverlapRequired() {
+        return true;
+     }
+
     /**
      * create the HTML element (e.g. canvas, div) that the image will be drawn into
      * @returns {Element} the div to draw into

src/tiledimage.js

@@ -1657,16 +1657,18 @@ $.extend($.TiledImage.prototype, $.EventSource.prototype, /** @lends OpenSeadrag
             tileCenter = positionT.plus( sizeT.divide( 2 ) ),
             tileSquaredDistance = viewportCenter.squaredDistanceTo( tileCenter );
 
-        if ( !overlap ) {
+        if(this.viewer.drawer.minimumOverlapRequired()){
-            sizeC = sizeC.plus( new $.Point( 1, 1 ) );
+            if ( !overlap ) {
-        }
+                sizeC = sizeC.plus( new $.Point(1, 1));
+            }
 
-        if (tile.isRightMost && this.wrapHorizontal) {
+            if (tile.isRightMost && this.wrapHorizontal) {
-            sizeC.x += 0.75; // Otherwise Firefox and Safari show seams
+                sizeC.x += 0.75; // Otherwise Firefox and Safari show seams
-        }
+            }
 
-        if (tile.isBottomMost && this.wrapVertical) {
+            if (tile.isBottomMost && this.wrapVertical) {
-            sizeC.y += 0.75; // Otherwise Firefox and Safari show seams
+                sizeC.y += 0.75; // Otherwise Firefox and Safari show seams
+            }
         }
 
         tile.position   = positionC;

src/webgldrawer.js

@@ -248,6 +248,10 @@
             return !!( webglContext );
         }
 
+        get type(){
+            return 'webgl';
+        }
+
         /**
             * create the HTML element (canvas in this case) that the image will be drawn into
             * @returns {Element} the canvas to draw into