Add support for Explicit padding (#1458)

Signed-off-by: Tom Wildenhain <[email protected]>

Author: TomWildenhain-Microsoft

tests/test_backend.py

@@ -438,6 +438,16 @@ def test_conv2d_6(self):
         kernel_val = np.arange(1, 1 + np.prod(kernel_shape)).astype("float32").reshape(kernel_shape)
         self._conv_test(x_val, kernel_val, strides=strides, padding="VALID", rtol=1e-05)
 
+    @check_tf_min_version("1.14", "tf 1.14 needed for explicit padding")
+    def test_conv2d_explicit_padding(self):
+        x_shape = [1, 35, 35, 288]
+        kernel_shape = [3, 3, 288, 384]
+        pads = [[0, 0], [1, 2], [3, 4], [0, 0]]
+        strides = [1, 1, 1, 1]
+        x_val = np.arange(1, 1 + np.prod(x_shape)).astype("float32").reshape(x_shape)
+        kernel_val = np.arange(1, 1 + np.prod(kernel_shape)).astype("float32").reshape(kernel_shape)
+        self._conv_test(x_val, kernel_val, strides=strides, padding=pads, rtol=1e-05)
+
     def test_conv2d_dilation_same(self):
         x_shape = [1, 35, 35, 288]  # NHWC
         kernel_shape = [3, 3, 288, 384]  # [filter_height, filter_width, in_channels, out_channels]

tf2onnx/onnx_opset/nn.py

@@ -249,6 +249,15 @@ def add_padding(ctx, node, kernel_shape, strides, dilations=None, spatial=2):
         node.set_attr("pads", pads)
     elif padding == "VALID":
         pass
+    elif padding == "EXPLICIT":
+        pads = node.get_attr_value("explicit_paddings")
+        start_pads = []
+        end_pads = []
+        d = 1 if is_channels_last(node) else 2
+        for i in range(spatial):
+            start_pads.append(pads[(d + i) * 2])
+            end_pads.append(pads[(d + i) * 2 + 1])
+        node.set_attr("pads", start_pads + end_pads)
     else:
         raise ValueError("invalid padding value: {}".format(padding))