ApplyFilters updates dirty flag in orde to refresh groups

src/shapes/image.class.js

@@ -389,6 +389,9 @@
           scaleX = this.scaleX * retinaScaling,
           scaleY = this.scaleY * retinaScaling,
           elementToFilter = this._filteredEl || this._originalElement;
+      if (this.group) {
+        this.set('dirty', true);
+      }
       if (!filter || (scaleX > minimumScale && scaleY > minimumScale)) {
         this._element = elementToFilter;
         this._filterScalingX = 1;
@@ -424,6 +427,9 @@
 
       filters = filters || this.filters || [];
       filters = filters.filter(function(filter) { return filter; });
+      if (this.group) {
+        this.set('dirty', true);
+      }
       if (filters.length === 0) {
         this._element = this._originalElement;
         this._filteredEl = null;

test/unit/image.js

@@ -645,4 +645,30 @@
       done();
     });
   });
+
+  QUnit.test('apply filters do not set the image dirty if not in group', function(assert) {
+    var done = assert.async();
+    createImageObject(function(image) {
+      image.dirty = false;
+      assert.equal(image.dirty, false, 'false apply filter dirty is false');
+      image.applyFilters();
+      assert.equal(image.dirty, false, 'After apply filter dirty is true');
+      done();
+    });
+  });
+
+  QUnit.test('apply filters set the image dirty and also the group', function(assert) {
+    var done = assert.async();
+    createImageObject(function(image) {
+      var group = new fabric.Group([image]);
+      image.dirty = false;
+      group.dirty = false;
+      assert.equal(image.dirty, false, 'false apply filter dirty is false');
+      assert.equal(group.dirty, false, 'false apply filter dirty is false');
+      image.applyFilters();
+      assert.equal(image.dirty, true, 'After apply filter dirty is true');
+      assert.equal(group.dirty, true, 'After apply filter dirty is true');
+      done();
+    });
+  });
 })();