diff --git a/jsk_perception/node_scripts/solidity_rag_merge.py b/jsk_perception/node_scripts/solidity_rag_merge.py
index ba5e2a2b38..d72ef3f07f 100755
--- a/jsk_perception/node_scripts/solidity_rag_merge.py
+++ b/jsk_perception/node_scripts/solidity_rag_merge.py
@@ -165,39 +165,63 @@ def __init__(self):
                                             queue_size=5)
 
     def subscribe(self):
-        self.sub = message_filters.Subscriber('~input', Image)
-        self.sub_mask = message_filters.Subscriber('~input/mask', Image)
-        self.use_async = rospy.get_param('~approximate_sync', False)
-        rospy.loginfo('~approximate_sync: {}'.format(self.use_async))
-        if self.use_async:
-            sync = message_filters.ApproximateTimeSynchronizer(
-                [self.sub, self.sub_mask], queue_size=1000, slop=0.1)
+        self.use_mask = rospy.get_param('~use_mask', True)
+        if self.use_mask:
+            self.sub = message_filters.Subscriber('~input', Image)
+            self.sub_mask = message_filters.Subscriber('~input/mask', Image)
+            self.use_async = rospy.get_param('~approximate_sync', False)
+            rospy.loginfo('~approximate_sync: {}'.format(self.use_async))
+            if self.use_async:
+                sync = message_filters.ApproximateTimeSynchronizer(
+                    [self.sub, self.sub_mask], queue_size=1000, slop=0.1)
+            else:
+                sync = message_filters.TimeSynchronizer(
+                    [self.sub, self.sub_mask], queue_size=1000)
+            sync.registerCallback(self.sub_cb)
+            warn_no_remap('~input', '~input/mask')
         else:
-            sync = message_filters.TimeSynchronizer(
-                [self.sub, self.sub_mask], queue_size=1000)
-        sync.registerCallback(self._apply)
-        warn_no_remap('~input', '~input/mask')
+            self.sub = rospy.Subscriber('~input', Image, self.sub_img_cb,
+                                        queue_size=1)
+            warn_no_remap('~input')
 
     def unsubscribe(self):
         self.sub.unregister()
-        self.sub_mask.unregister()
+        if self.use_mask:
+            self.sub_mask.unregister()
+
+    def sub_cb(self, imgmsg, maskmsg):
+        self._apply(imgmsg, maskmsg)
+
+    def sub_img_cb(self, imgmsg):
+        self._apply(imgmsg, None)
 
-    def _apply(self, imgmsg, maskmsg):
+    def _apply(self, imgmsg, maskmsg=None):
         bridge = cv_bridge.CvBridge()
         img = bridge.imgmsg_to_cv2(imgmsg)
         if img.ndim == 2:
             img = gray2rgb(img)
-        mask = bridge.imgmsg_to_cv2(maskmsg, desired_encoding='mono8')
-        mask = mask.reshape(mask.shape[:2])
-        # compute label
-        roi = closed_mask_roi(mask)
-        roi_labels = masked_slic(img=img[roi], mask=mask[roi],
+
+        if maskmsg is None:
+            # compute label
+            mask = np.ones(img.shape[:2], dtype=np.uint8)
+            labels = masked_slic(img=img, mask=mask,
                                  n_segments=20, compactness=30)
-        if roi_labels is None:
-            return
-        labels = np.zeros(mask.shape, dtype=np.int32)
+            if labels is None:
+                return
+            labels = labels.astype(np.int32)
+        else:
+            mask = bridge.imgmsg_to_cv2(maskmsg, desired_encoding='mono8')
+            mask = mask.reshape(mask.shape[:2])
+            # compute label
+            roi = closed_mask_roi(mask)
+            roi_labels = masked_slic(img=img[roi], mask=mask[roi],
+                                     n_segments=20, compactness=30)
+            if roi_labels is None:
+                return
+            labels = np.zeros(mask.shape, dtype=np.int32)
+            labels[roi] = roi_labels
+
         # labels.fill(-1)  # set bg_label
-        labels[roi] = roi_labels
         if self.is_debugging:
             # publish debug slic label
             slic_labelmsg = bridge.cv2_to_imgmsg(labels)