127 lines
4.1 KiB
Python
127 lines
4.1 KiB
Python
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# Copyright 2015 The TensorFlow Authors. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# ==============================================================================
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"""Contains Gradient functions for image ops."""
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from __future__ import absolute_import
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from __future__ import division
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from __future__ import print_function
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from tensorflow.python.framework import dtypes
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from tensorflow.python.framework import ops
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from tensorflow.python.ops import array_ops
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from tensorflow.python.ops import gen_image_ops
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@ops.RegisterGradient("ResizeNearestNeighbor")
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def _ResizeNearestNeighborGrad(op, grad):
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"""The derivatives for nearest neighbor resizing.
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Args:
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op: The ResizeNearestNeighbor op.
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grad: The tensor representing the gradient w.r.t. the output.
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Returns:
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The gradients w.r.t. the input and the output.
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"""
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image = op.inputs[0]
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if image.get_shape()[1:3].is_fully_defined():
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image_shape = image.get_shape()[1:3]
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else:
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image_shape = array_ops.shape(image)[1:3]
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grads = gen_image_ops.resize_nearest_neighbor_grad(
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grad,
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image_shape,
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align_corners=op.get_attr("align_corners"))
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return [grads, None]
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@ops.RegisterGradient("ResizeBilinear")
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def _ResizeBilinearGrad(op, grad):
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"""The derivatives for bilinear resizing.
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Args:
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op: The ResizeBilinear op.
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grad: The tensor representing the gradient w.r.t. the output.
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Returns:
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The gradients w.r.t. the input.
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"""
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grad0 = gen_image_ops.resize_bilinear_grad(
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grad, op.inputs[0], align_corners=op.get_attr("align_corners"))
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return [grad0, None]
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@ops.RegisterGradient("ResizeBicubic")
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def _ResizeBicubicGrad(op, grad):
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"""The derivatives for bicubic resizing.
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Args:
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op: The ResizeBicubic op.
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grad: The tensor representing the gradient w.r.t. the output.
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Returns:
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The gradients w.r.t. the input.
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"""
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allowed_types = [dtypes.float32, dtypes.float64]
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grad0 = None
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if op.inputs[0].dtype in allowed_types:
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grad0 = gen_image_ops.resize_bicubic_grad(
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grad, op.inputs[0], align_corners=op.get_attr("align_corners"))
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return [grad0, None]
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@ops.RegisterGradient("CropAndResize")
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def _CropAndResizeGrad(op, grad):
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"""The derivatives for crop_and_resize.
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We back-propagate to the image only when the input image tensor has floating
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point dtype but we always back-propagate to the input boxes tensor.
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Args:
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op: The CropAndResize op.
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grad: The tensor representing the gradient w.r.t. the output.
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Returns:
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The gradients w.r.t. the input image, boxes, as well as the always-None
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gradients w.r.t. box_ind and crop_size.
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"""
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image = op.inputs[0]
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if image.get_shape().is_fully_defined():
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image_shape = image.get_shape().as_list()
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else:
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image_shape = array_ops.shape(image)
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allowed_types = [dtypes.float16, dtypes.float32, dtypes.float64]
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if op.inputs[0].dtype in allowed_types:
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# pylint: disable=protected-access
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grad0 = gen_image_ops.crop_and_resize_grad_image(
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grad, op.inputs[1], op.inputs[2], image_shape, T=op.get_attr("T"),
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method=op.get_attr("method"))
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# pylint: enable=protected-access
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else:
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grad0 = None
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# `grad0` is the gradient to the input image pixels and it
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# has been implemented for nearest neighbor and bilinear sampling
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# respectively. `grad1` is the gradient to the input crop boxes' coordinates.
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# When using nearest neighbor sampling, the gradient to crop boxes'
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# coordinates are not well defined. In practice, we still approximate
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# grad1 using the gradient derived from bilinear sampling.
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grad1 = gen_image_ops.crop_and_resize_grad_boxes(
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grad, op.inputs[0], op.inputs[1], op.inputs[2])
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return [grad0, grad1, None, None]
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