added 'desharpen' enhancement, auto run it before 'sharpen' so that sharpening effects are not always applied over themselves (although this is quite unperformant)

lib/ComicBook.js

@@ -593,6 +593,8 @@ function ComicBook(id, srcs, opts) {
 		 */
 		sharpen: function (params) {
 			
+			this.desharpen();
+			
 			var opts = merge({ amount: 0 }, params);
 			
 			options.enhance.sharpen = opts;
@@ -602,6 +604,11 @@ function ComicBook(id, srcs, opts) {
 			});
 			
 			init();
+		},
+		
+		desharpen: function() {
+			delete options.enhance.sharpen;
+			ComicBook.prototype.drawPage();
 		}
 	};