add ng layer

Author: donglaiw

emu/ng/__init__.py

@@ -1 +1,2 @@
 from .ngDataset import *
+from .ngLayer import *

emu/ng/ngLayer.py

@@ -0,0 +1,8 @@
+import neuroglancer
+
+def ngLayer(data,res,oo=[0,0,0],tt='segmentation'):
+    # input zyx -> display xyz
+    dim = neuroglancer.CoordinateSpace(names=['x', 'y', 'z'],
+                                              units='nm',
+                                              scales=res)
+    return neuroglancer.LocalVolume(data.transpose([2,1,0]),volume_type=tt,dimensions=dim,voxel_offset=oo)