# Copyright 2017 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.
# ==============================================================================
"""Operations for np_box_mask_list.BoxMaskList.
Example box operations that are supported:
* Areas: compute bounding box areas
* IOU: pairwise intersection-over-union scores
"""
import numpy as np
import ava.np_box_list_ops as np_box_list_ops
import ava.np_box_mask_list as np_box_mask_list
import ava.np_mask_ops as np_mask_ops
def box_list_to_box_mask_list(boxlist):
"""Converts a BoxList containing 'masks' into a BoxMaskList.
Args:
boxlist: An np_box_list.BoxList object.
Returns:
An np_box_mask_list.BoxMaskList object.
Raises:
ValueError: If boxlist does not contain `masks` as a field.
"""
if not boxlist.has_field('masks'):
raise ValueError('boxlist does not contain mask field.')
box_mask_list = np_box_mask_list.BoxMaskList(
box_data=boxlist.get(),
mask_data=boxlist.get_field('masks'))
extra_fields = boxlist.get_extra_fields()
for key in extra_fields:
if key != 'masks':
box_mask_list.data[key] = boxlist.get_field(key)
return box_mask_list
def area(box_mask_list):
"""Computes area of masks.
Args:
box_mask_list: np_box_mask_list.BoxMaskList holding N boxes and masks
Returns:
a numpy array with shape [N*1] representing mask areas
"""
return np_mask_ops.area(box_mask_list.get_masks())
def intersection(box_mask_list1, box_mask_list2):
"""Compute pairwise intersection areas between masks.
Args:
box_mask_list1: BoxMaskList holding N boxes and masks
box_mask_list2: BoxMaskList holding M boxes and masks
Returns:
a numpy array with shape [N*M] representing pairwise intersection area
"""
return np_mask_ops.intersection(box_mask_list1.get_masks(),
box_mask_list2.get_masks())
def iou(box_mask_list1, box_mask_list2):
"""Computes pairwise intersection-over-union between box and mask collections.
Args:
box_mask_list1: BoxMaskList holding N boxes and masks
box_mask_list2: BoxMaskList holding M boxes and masks
Returns:
a numpy array with shape [N, M] representing pairwise iou scores.
"""
return np_mask_ops.iou(box_mask_list1.get_masks(),
box_mask_list2.get_masks())
def ioa(box_mask_list1, box_mask_list2):
"""Computes pairwise intersection-over-area between box and mask collections.
Intersection-over-area (ioa) between two masks mask1 and mask2 is defined as
their intersection area over mask2's area. Note that ioa is not symmetric,
that is, IOA(mask1, mask2) != IOA(mask2, mask1).
Args:
box_mask_list1: np_box_mask_list.BoxMaskList holding N boxes and masks
box_mask_list2: np_box_mask_list.BoxMaskList holding M boxes and masks
Returns:
a numpy array with shape [N, M] representing pairwise ioa scores.
"""
return np_mask_ops.ioa(box_mask_list1.get_masks(), box_mask_list2.get_masks())
def gather(box_mask_list, indices, fields=None):
"""Gather boxes from np_box_mask_list.BoxMaskList according to indices.
By default, gather returns boxes corresponding to the input index list, as
well as all additional fields stored in the box_mask_list (indexing into the
first dimension). However one can optionally only gather from a
subset of fields.
Args:
box_mask_list: np_box_mask_list.BoxMaskList holding N boxes
indices: a 1-d numpy array of type int_
fields: (optional) list of fields to also gather from. If None (default),
all fields are gathered from. Pass an empty fields list to only gather
the box coordinates.
Returns:
subbox_mask_list: a np_box_mask_list.BoxMaskList corresponding to the subset
of the input box_mask_list specified by indices
Raises:
ValueError: if specified field is not contained in box_mask_list or if the
indices are not of type int_
"""
if fields is not None:
if 'masks' not in fields:
fields.append('masks')
return box_list_to_box_mask_list(
np_box_list_ops.gather(
boxlist=box_mask_list, indices=indices, fields=fields))
def sort_by_field(box_mask_list, field,
order=np_box_list_ops.SortOrder.DESCEND):
"""Sort boxes and associated fields according to a scalar field.
A common use case is reordering the boxes according to descending scores.
Args:
box_mask_list: BoxMaskList holding N boxes.
field: A BoxMaskList field for sorting and reordering the BoxMaskList.
order: (Optional) 'descend' or 'ascend'. Default is descend.
Returns:
sorted_box_mask_list: A sorted BoxMaskList with the field in the specified
order.
"""
return box_list_to_box_mask_list(
np_box_list_ops.sort_by_field(
boxlist=box_mask_list, field=field, order=order))
def non_max_suppression(box_mask_list,
max_output_size=10000,
iou_threshold=1.0,
score_threshold=-10.0):
"""Non maximum suppression.
This op greedily selects a subset of detection bounding boxes, pruning
away boxes that have high IOU (intersection over union) overlap (> thresh)
with already selected boxes. In each iteration, the detected bounding box with
highest score in the available pool is selected.
Args:
box_mask_list: np_box_mask_list.BoxMaskList holding N boxes. Must contain
a 'scores' field representing detection scores. All scores belong to the
same class.
max_output_size: maximum number of retained boxes
iou_threshold: intersection over union threshold.
score_threshold: minimum score threshold. Remove the boxes with scores
less than this value. Default value is set to -10. A very
low threshold to pass pretty much all the boxes, unless
the user sets a different score threshold.
Returns:
an np_box_mask_list.BoxMaskList holding M boxes where M <= max_output_size
Raises:
ValueError: if 'scores' field does not exist
ValueError: if threshold is not in [0, 1]
ValueError: if max_output_size < 0
"""
if not box_mask_list.has_field('scores'):
raise ValueError('Field scores does not exist')
if iou_threshold < 0. or iou_threshold > 1.0:
raise ValueError('IOU threshold must be in [0, 1]')
if max_output_size < 0:
raise ValueError('max_output_size must be bigger than 0.')
box_mask_list = filter_scores_greater_than(box_mask_list, score_threshold)
if box_mask_list.num_boxes() == 0:
return box_mask_list
box_mask_list = sort_by_field(box_mask_list, 'scores')
# Prevent further computation if NMS is disabled.
if iou_threshold == 1.0:
if box_mask_list.num_boxes() > max_output_size:
selected_indices = np.arange(max_output_size)
return gather(box_mask_list, selected_indices)
else:
return box_mask_list
masks = box_mask_list.get_masks()
num_masks = box_mask_list.num_boxes()
# is_index_valid is True only for all remaining valid boxes,
is_index_valid = np.full(num_masks, 1, dtype=bool)
selected_indices = []
num_output = 0
for i in range(num_masks):
if num_output < max_output_size:
if is_index_valid[i]:
num_output += 1
selected_indices.append(i)
is_index_valid[i] = False
valid_indices = np.where(is_index_valid)[0]
if valid_indices.size == 0:
break
intersect_over_union = np_mask_ops.iou(
np.expand_dims(masks[i], axis=0), masks[valid_indices])
intersect_over_union = np.squeeze(intersect_over_union, axis=0)
is_index_valid[valid_indices] = np.logical_and(
is_index_valid[valid_indices],
intersect_over_union <= iou_threshold)
return gather(box_mask_list, np.array(selected_indices))
def multi_class_non_max_suppression(box_mask_list, score_thresh, iou_thresh,
max_output_size):
"""Multi-class version of non maximum suppression.
This op greedily selects a subset of detection bounding boxes, pruning
away boxes that have high IOU (intersection over union) overlap (> thresh)
with already selected boxes. It operates independently for each class for
which scores are provided (via the scores field of the input box_list),
pruning boxes with score less than a provided threshold prior to
applying NMS.
Args:
box_mask_list: np_box_mask_list.BoxMaskList holding N boxes. Must contain a
'scores' field representing detection scores. This scores field is a
tensor that can be 1 dimensional (in the case of a single class) or
2-dimensional, in which case we assume that it takes the
shape [num_boxes, num_classes]. We further assume that this rank is known
statically and that scores.shape[1] is also known (i.e., the number of
classes is fixed and known at graph construction time).
score_thresh: scalar threshold for score (low scoring boxes are removed).
iou_thresh: scalar threshold for IOU (boxes that that high IOU overlap
with previously selected boxes are removed).
max_output_size: maximum number of retained boxes per class.
Returns:
a box_mask_list holding M boxes with a rank-1 scores field representing
corresponding scores for each box with scores sorted in decreasing order
and a rank-1 classes field representing a class label for each box.
Raises:
ValueError: if iou_thresh is not in [0, 1] or if input box_mask_list does
not have a valid scores field.
"""
if not 0 <= iou_thresh <= 1.0:
raise ValueError('thresh must be between 0 and 1')
if not isinstance(box_mask_list, np_box_mask_list.BoxMaskList):
raise ValueError('box_mask_list must be a box_mask_list')
if not box_mask_list.has_field('scores'):
raise ValueError('input box_mask_list must have \'scores\' field')
scores = box_mask_list.get_field('scores')
if len(scores.shape) == 1:
scores = np.reshape(scores, [-1, 1])
elif len(scores.shape) == 2:
if scores.shape[1] is None:
raise ValueError('scores field must have statically defined second '
'dimension')
else:
raise ValueError('scores field must be of rank 1 or 2')
num_boxes = box_mask_list.num_boxes()
num_scores = scores.shape[0]
num_classes = scores.shape[1]
if num_boxes != num_scores:
raise ValueError('Incorrect scores field length: actual vs expected.')
selected_boxes_list = []
for class_idx in range(num_classes):
box_mask_list_and_class_scores = np_box_mask_list.BoxMaskList(
box_data=box_mask_list.get(),
mask_data=box_mask_list.get_masks())
class_scores = np.reshape(scores[0:num_scores, class_idx], [-1])
box_mask_list_and_class_scores.add_field('scores', class_scores)
box_mask_list_filt = filter_scores_greater_than(
box_mask_list_and_class_scores, score_thresh)
nms_result = non_max_suppression(
box_mask_list_filt,
max_output_size=max_output_size,
iou_threshold=iou_thresh,
score_threshold=score_thresh)
nms_result.add_field(
'classes',
np.zeros_like(nms_result.get_field('scores')) + class_idx)
selected_boxes_list.append(nms_result)
selected_boxes = np_box_list_ops.concatenate(selected_boxes_list)
sorted_boxes = np_box_list_ops.sort_by_field(selected_boxes, 'scores')
return box_list_to_box_mask_list(boxlist=sorted_boxes)
def prune_non_overlapping_masks(box_mask_list1, box_mask_list2, minoverlap=0.0):
"""Prunes the boxes in list1 that overlap less than thresh with list2.
For each mask in box_mask_list1, we want its IOA to be more than minoverlap
with at least one of the masks in box_mask_list2. If it does not, we remove
it. If the masks are not full size image, we do the pruning based on boxes.
Args:
box_mask_list1: np_box_mask_list.BoxMaskList holding N boxes and masks.
box_mask_list2: np_box_mask_list.BoxMaskList holding M boxes and masks.
minoverlap: Minimum required overlap between boxes, to count them as
overlapping.
Returns:
A pruned box_mask_list with size [N', 4].
"""
intersection_over_area = ioa(box_mask_list2, box_mask_list1) # [M, N] tensor
intersection_over_area = np.amax(intersection_over_area, axis=0) # [N] tensor
keep_bool = np.greater_equal(intersection_over_area, np.array(minoverlap))
keep_inds = np.nonzero(keep_bool)[0]
new_box_mask_list1 = gather(box_mask_list1, keep_inds)
return new_box_mask_list1
def concatenate(box_mask_lists, fields=None):
"""Concatenate list of box_mask_lists.
This op concatenates a list of input box_mask_lists into a larger
box_mask_list. It also
handles concatenation of box_mask_list fields as long as the field tensor
shapes are equal except for the first dimension.
Args:
box_mask_lists: list of np_box_mask_list.BoxMaskList objects
fields: optional list of fields to also concatenate. By default, all
fields from the first BoxMaskList in the list are included in the
concatenation.
Returns:
a box_mask_list with number of boxes equal to
sum([box_mask_list.num_boxes() for box_mask_list in box_mask_list])
Raises:
ValueError: if box_mask_lists is invalid (i.e., is not a list, is empty, or
contains non box_mask_list objects), or if requested fields are not
contained in all box_mask_lists
"""
if fields is not None:
if 'masks' not in fields:
fields.append('masks')
return box_list_to_box_mask_list(
np_box_list_ops.concatenate(boxlists=box_mask_lists, fields=fields))
def filter_scores_greater_than(box_mask_list, thresh):
"""Filter to keep only boxes and masks with score exceeding a given threshold.
This op keeps the collection of boxes and masks whose corresponding scores are
greater than the input threshold.
Args:
box_mask_list: BoxMaskList holding N boxes and masks. Must contain a
'scores' field representing detection scores.
thresh: scalar threshold
Returns:
a BoxMaskList holding M boxes and masks where M <= N
Raises:
ValueError: if box_mask_list not a np_box_mask_list.BoxMaskList object or
if it does not have a scores field
"""
if not isinstance(box_mask_list, np_box_mask_list.BoxMaskList):
raise ValueError('box_mask_list must be a BoxMaskList')
if not box_mask_list.has_field('scores'):
raise ValueError('input box_mask_list must have \'scores\' field')
scores = box_mask_list.get_field('scores')
if len(scores.shape) > 2:
raise ValueError('Scores should have rank 1 or 2')
if len(scores.shape) == 2 and scores.shape[1] != 1:
raise ValueError('Scores should have rank 1 or have shape '
'consistent with [None, 1]')
high_score_indices = np.reshape(np.where(np.greater(scores, thresh)),
[-1]).astype(np.int32)
return gather(box_mask_list, high_score_indices)
