add channel support

server/visualdl/lib_test.py

@@ -21,6 +21,9 @@ class LibTest(unittest.TestCase):
         add_image(writer, "train", "layer/image0", 7, 10, 1)
         add_image(writer, "test", "layer/image0", 7, 10, 3)
 
+        add_image(writer, "train", "layer/image1", 7, 10, 1, shape=[30,30,2])
+        add_image(writer, "test", "layer/image1", 7, 10, 1, shape=[30,30,2])
+
         self.reader = storage.StorageReader(dir)
 
     def test_modes(self):

visualdl/logic/sdk.cc

@@ -103,6 +103,10 @@ void Image::SetSample(int index,
   int size = std::accumulate(
       shape.begin(), shape.end(), 1., [](float a, float b) { return a * b; });
   CHECK_GT(size, 0);
+  CHECK_EQ(shape.size(), 3)
+      << "shape should be something like (width, height, num_channel)";
+  CHECK_LE(shape.back(), 3);
+  CHECK_GE(shape.back(), 2);
   CHECK_EQ(size, data.size()) << "image's shape not match data";
   CHECK_LT(index, num_samples_);
   CHECK_LE(index, num_records_);