Add C++ gradients for some image operators.

Added gradients and tests for
- ResizeBilinear
- ResizeBicubic
- ResizeNearestNeighbor

Note: Some of the tests are for the operator itself rather than
the gradient, paralleling existing tests in image_grad.py

See https://github.com/tensorflow/tensorflow/issues/21019

4 files changed, 262 insertions, 0 deletions

diff --git a/tensorflow/cc/BUILD b/tensorflow/cc/BUILD
index a98f0b00b2..d686ccfe29 100644
--- a/tensorflow/cc/BUILD
+++ b/tensorflow/cc/BUILD
@@ -121,6 +121,7 @@ cc_library(
     deps = [
         ":array_grad",
         ":data_flow_grad",
+        ":image_grad",
         ":math_grad",
         ":nn_grad",
     ],
@@ -332,6 +333,35 @@ tf_cc_test(
 )
 
 cc_library(
+    name = "image_grad",
+    srcs = ["gradients/image_grad.cc"],
+    deps = [
+        ":cc_ops",
+        ":cc_ops_internal",
+        ":grad_op_registry",
+        ":gradients",
+    ],
+    alwayslink = 1,
+)
+
+tf_cc_test(
+    name = "gradients_image_grad_test",
+    srcs = ["gradients/image_grad_test.cc"],
+    deps = [
+        ":cc_ops",
+        ":grad_op_registry",
+        ":grad_testutil",
+        ":gradient_checker",
+        ":image_grad",
+        ":testutil",
+        "//tensorflow/core:lib_internal",
+        "//tensorflow/core:test",
+        "//tensorflow/core:test_main",
+        "//tensorflow/core:testlib",
+    ],
+)
+
+cc_library(
     name = "math_grad",
     srcs = ["gradients/math_grad.cc"],
     deps = [
diff --git a/tensorflow/cc/framework/gradient_checker.cc b/tensorflow/cc/framework/gradient_checker.cc
index de2645cb44..695180c23b 100644
--- a/tensorflow/cc/framework/gradient_checker.cc
+++ b/tensorflow/cc/framework/gradient_checker.cc
@@ -409,6 +409,7 @@ Status ComputeGradientError(const Scope& scope, const Output& x,
       const Output& y, const TensorShape& y_shape, JAC_T* max_error);
 
 INSTANTIATE_GRAD_ERR_TYPE(float, float, float);
+INSTANTIATE_GRAD_ERR_TYPE(double, float, double);
 INSTANTIATE_GRAD_ERR_TYPE(double, double, double);
 INSTANTIATE_GRAD_ERR_TYPE(complex64, float, float);
 INSTANTIATE_GRAD_ERR_TYPE(float, complex64, float);
diff --git a/tensorflow/cc/gradients/image_grad.cc b/tensorflow/cc/gradients/image_grad.cc
new file mode 100644
index 0000000000..882709e1e2
--- /dev/null
+++ b/tensorflow/cc/gradients/image_grad.cc
@@ -0,0 +1,74 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#include <vector>
+#include "tensorflow/cc/framework/grad_op_registry.h"
+#include "tensorflow/cc/framework/gradients.h"
+#include "tensorflow/cc/ops/image_ops_internal.h"
+#include "tensorflow/cc/ops/standard_ops.h"
+
+namespace tensorflow {
+namespace ops {
+namespace {
+
+Status ResizeNearestNeighborGradHelper(const Scope& scope, const Operation& op,
+                                       const std::vector<Output>& grad_inputs,
+                                       std::vector<Output>* grad_outputs) {
+  bool align_corners;
+  TF_RETURN_IF_ERROR(
+      GetNodeAttr(op.node()->attrs(), "align_corners", &align_corners));
+  // The internal gradient implementation needs the shape of the input image.
+  // x_shape = shape(x)[1:3]
+  //         = slice(shape(x), {1}, {3 - 1})
+  auto x_shape = Slice(scope, Shape(scope, op.input(0)), {1}, {2});
+  grad_outputs->push_back(internal::ResizeNearestNeighborGrad(
+      scope, grad_inputs[0], x_shape,
+      internal::ResizeNearestNeighborGrad::AlignCorners(align_corners)));
+  grad_outputs->push_back(NoGradient());
+  return scope.status();
+}
+REGISTER_GRADIENT_OP("ResizeNearestNeighbor", ResizeNearestNeighborGradHelper);
+
+Status ResizeBilinearGradHelper(const Scope& scope, const Operation& op,
+                                const std::vector<Output>& grad_inputs,
+                                std::vector<Output>* grad_outputs) {
+  bool align_corners;
+  TF_RETURN_IF_ERROR(
+      GetNodeAttr(op.node()->attrs(), "align_corners", &align_corners));
+  grad_outputs->push_back(internal::ResizeBilinearGrad(
+      scope, grad_inputs[0], op.input(0),
+      internal::ResizeBilinearGrad::AlignCorners(align_corners)));
+  grad_outputs->push_back(NoGradient());
+  return scope.status();
+}
+REGISTER_GRADIENT_OP("ResizeBilinear", ResizeBilinearGradHelper);
+
+Status ResizeBicubicGradHelper(const Scope& scope, const Operation& op,
+                               const std::vector<Output>& grad_inputs,
+                               std::vector<Output>* grad_outputs) {
+  bool align_corners;
+  TF_RETURN_IF_ERROR(
+      GetNodeAttr(op.node()->attrs(), "align_corners", &align_corners));
+  grad_outputs->push_back(internal::ResizeBicubicGrad(
+      scope, grad_inputs[0], op.input(0),
+      internal::ResizeBicubicGrad::AlignCorners(align_corners)));
+  grad_outputs->push_back(NoGradient());
+  return scope.status();
+}
+REGISTER_GRADIENT_OP("ResizeBicubic", ResizeBicubicGradHelper);
+
+}  // anonymous namespace
+}  // namespace ops
+}  // namespace tensorflow
diff --git a/tensorflow/cc/gradients/image_grad_test.cc b/tensorflow/cc/gradients/image_grad_test.cc
new file mode 100644
index 0000000000..b9271522ed
--- /dev/null
+++ b/tensorflow/cc/gradients/image_grad_test.cc
@@ -0,0 +1,157 @@
+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#include "tensorflow/cc/client/client_session.h"
+#include "tensorflow/cc/framework/grad_op_registry.h"
+#include "tensorflow/cc/framework/gradient_checker.h"
+#include "tensorflow/cc/framework/testutil.h"
+#include "tensorflow/cc/gradients/grad_testutil.h"
+#include "tensorflow/cc/ops/image_ops_internal.h"
+#include "tensorflow/cc/ops/standard_ops.h"
+#include "tensorflow/core/framework/tensor_testutil.h"
+#include "tensorflow/core/lib/core/status_test_util.h"
+
+namespace tensorflow {
+namespace {
+
+using ops::Const;
+using ops::ResizeBilinear;
+using ops::ResizeBicubic;
+using ops::ResizeNearestNeighbor;
+
+class ImageGradTest : public ::testing::Test {
+ protected:
+  ImageGradTest() : scope_(Scope::NewRootScope()) {}
+
+  enum OpType { RESIZE_NEAREST, RESIZE_BILINEAR, RESIZE_BICUBIC };
+
+  template <typename T>
+  Tensor MakeData(TensorShape& data_shape) {
+    DataType data_type = DataTypeToEnum<T>::v();
+    Tensor data(data_type, data_shape);
+    auto data_flat = data.flat<T>();
+    for (int i = 0; i < data_flat.size(); ++i) {
+      data_flat(i) = T(i);
+    }
+    return data;
+  }
+
+  template <typename T>
+  void MakeOp(const OpType op_type, const Tensor& x_data, const Input& y_shape,
+              const bool align_corners, Output* x, Output* y) {
+    *x = Const<T>(scope_, x_data);
+    switch (op_type) {
+      case RESIZE_NEAREST:
+        *y = ResizeNearestNeighbor(
+            scope_, *x, y_shape,
+            ResizeNearestNeighbor::AlignCorners(align_corners));
+        break;
+      case RESIZE_BILINEAR:
+        *y = ResizeBilinear(scope_, *x, y_shape,
+                            ResizeBilinear::AlignCorners(align_corners));
+        break;
+      case RESIZE_BICUBIC:
+        *y = ResizeBicubic(scope_, *x, y_shape,
+                           ResizeBicubic::AlignCorners(align_corners));
+        break;
+    }
+    assert(false);
+  }
+
+  template <typename T>
+  void TestResizedShapeForType(const OpType op_type, const bool align_corners) {
+    TensorShape x_shape({1, 2, 2, 1});
+    Tensor x_data = MakeData<T>(x_shape);
+    Output x, y;
+    MakeOp<T>(op_type, x_data, {4, 6}, align_corners, &x, &y);
+
+    ClientSession session(scope_);
+    std::vector<Tensor> outputs;
+    TF_ASSERT_OK(session.Run({}, {y}, &outputs));
+    EXPECT_EQ(outputs.size(), 1);
+    EXPECT_EQ(outputs[0].shape(), TensorShape({1, 4, 6, 1}));
+  }
+
+  void TestResizedShape(OpType op_type) {
+    for (const bool align_corners : {true, false}) {
+      TestResizedShapeForType<Eigen::half>(op_type, align_corners);
+      TestResizedShapeForType<float>(op_type, align_corners);
+      TestResizedShapeForType<double>(op_type, align_corners);
+    }
+  }
+
+  template <typename X_T, typename Y_T, typename JAC_T>
+  void TestResizeToSmallerAndAlign(const OpType op_type,
+                                   const bool align_corners) {
+    TensorShape x_shape({1, 4, 6, 1});
+    Tensor x_data = MakeData<X_T>(x_shape);
+    Output x, y;
+    MakeOp<X_T>(op_type, x_data, {2, 3}, align_corners, &x, &y);
+    JAC_T max_error;
+    TF_ASSERT_OK((ComputeGradientError<X_T, Y_T, JAC_T>(
+        scope_, x, x_data, y, {1, 2, 3, 1}, &max_error)));
+    EXPECT_LT(max_error, 1e-3);
+  }
+
+  template <typename X_T, typename Y_T, typename JAC_T>
+  void TestResizeToLargerAndAlign(const OpType op_type,
+                                  const bool align_corners) {
+    TensorShape x_shape({1, 2, 3, 1});
+    Tensor x_data = MakeData<X_T>(x_shape);
+    Output x, y;
+    MakeOp<X_T>(op_type, x_data, {4, 6}, align_corners, &x, &y);
+    JAC_T max_error;
+    TF_ASSERT_OK((ComputeGradientError<X_T, Y_T, JAC_T>(
+        scope_, x, x_data, y, {1, 4, 6, 1}, &max_error)));
+    EXPECT_LT(max_error, 1e-3);
+  }
+
+  template <typename X_T, typename Y_T, typename JAC_T>
+  void TestResize(OpType op_type) {
+    for (const bool align_corners : {true, false}) {
+      TestResizeToSmallerAndAlign<X_T, Y_T, JAC_T>(op_type, align_corners);
+      TestResizeToLargerAndAlign<X_T, Y_T, JAC_T>(op_type, align_corners);
+    }
+  }
+
+  Scope scope_;
+};
+
+TEST_F(ImageGradTest, TestNearestNeighbor) {
+  TestResizedShape(RESIZE_NEAREST);
+  TestResize<float, float, float>(RESIZE_NEAREST);
+  TestResize<double, double, double>(RESIZE_NEAREST);
+}
+
+TEST_F(ImageGradTest, TestBilinear) {
+  TestResizedShape(RESIZE_BILINEAR);
+  TestResize<float, float, float>(RESIZE_BILINEAR);
+  // Note that Y_T is always float for this op. We choose
+  // double for the jacobian to capture the higher precision
+  // between X_T and Y_T.
+  TestResize<double, float, double>(RESIZE_BILINEAR);
+}
+
+TEST_F(ImageGradTest, TestBicubic) {
+  TestResizedShape(RESIZE_BICUBIC);
+  TestResize<float, float, float>(RESIZE_BICUBIC);
+  // Note that Y_T is always float for this op. We choose
+  // double for the jacobian to capture the higher precision
+  // between X_T and Y_T.
+  TestResize<double, float, double>(RESIZE_BICUBIC);
+}
+
+}  // namespace
+}  // namespace tensorflow