official/legacy/detection/utils/box_utils.py
# Copyright 2024 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,
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"""Utility functions for bounding box processing."""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import numpy as np
import tensorflow as tf, tf_keras
EPSILON = 1e-8
BBOX_XFORM_CLIP = np.log(1000. / 16.)
def visualize_images_with_bounding_boxes(images, box_outputs, step,
summary_writer):
"""Records subset of evaluation images with bounding boxes."""
image_shape = tf.shape(images[0])
image_height = tf.cast(image_shape[0], tf.float32)
image_width = tf.cast(image_shape[1], tf.float32)
normalized_boxes = normalize_boxes(box_outputs, [image_height, image_width])
bounding_box_color = tf.constant([[1.0, 1.0, 0.0, 1.0]])
image_summary = tf.image.draw_bounding_boxes(images, normalized_boxes,
bounding_box_color)
with summary_writer.as_default():
tf.summary.image('bounding_box_summary', image_summary, step=step)
summary_writer.flush()
def yxyx_to_xywh(boxes):
"""Converts boxes from ymin, xmin, ymax, xmax to xmin, ymin, width, height.
Args:
boxes: a numpy array whose last dimension is 4 representing the coordinates
of boxes in ymin, xmin, ymax, xmax order.
Returns:
boxes: a numpy array whose shape is the same as `boxes` in new format.
Raises:
ValueError: If the last dimension of boxes is not 4.
"""
if boxes.shape[-1] != 4:
raise ValueError('boxes.shape[-1] is {:d}, but must be 4.'.format(
boxes.shape[-1]))
boxes_ymin = boxes[..., 0]
boxes_xmin = boxes[..., 1]
boxes_width = boxes[..., 3] - boxes[..., 1]
boxes_height = boxes[..., 2] - boxes[..., 0]
new_boxes = np.stack([boxes_xmin, boxes_ymin, boxes_width, boxes_height],
axis=-1)
return new_boxes
def jitter_boxes(boxes, noise_scale=0.025):
"""Jitter the box coordinates by some noise distribution.
Args:
boxes: a tensor whose last dimension is 4 representing the coordinates of
boxes in ymin, xmin, ymax, xmax order.
noise_scale: a python float which specifies the magnitude of noise. The rule
of thumb is to set this between (0, 0.1]. The default value is found to
mimic the noisy detections best empirically.
Returns:
jittered_boxes: a tensor whose shape is the same as `boxes` representing
the jittered boxes.
Raises:
ValueError: If the last dimension of boxes is not 4.
"""
if boxes.shape[-1] != 4:
raise ValueError('boxes.shape[-1] is {:d}, but must be 4.'.format(
boxes.shape[-1]))
with tf.name_scope('jitter_boxes'):
bbox_jitters = tf.random.normal(boxes.get_shape(), stddev=noise_scale)
ymin = boxes[..., 0:1]
xmin = boxes[..., 1:2]
ymax = boxes[..., 2:3]
xmax = boxes[..., 3:4]
width = xmax - xmin
height = ymax - ymin
new_center_x = (xmin + xmax) / 2.0 + bbox_jitters[..., 0:1] * width
new_center_y = (ymin + ymax) / 2.0 + bbox_jitters[..., 1:2] * height
new_width = width * tf.math.exp(bbox_jitters[..., 2:3])
new_height = height * tf.math.exp(bbox_jitters[..., 3:4])
jittered_boxes = tf.concat([
new_center_y - new_height * 0.5, new_center_x - new_width * 0.5,
new_center_y + new_height * 0.5, new_center_x + new_width * 0.5
],
axis=-1)
return jittered_boxes
def normalize_boxes(boxes, image_shape):
"""Converts boxes to the normalized coordinates.
Args:
boxes: a tensor whose last dimension is 4 representing the coordinates of
boxes in ymin, xmin, ymax, xmax order.
image_shape: a list of two integers, a two-element vector or a tensor such
that all but the last dimensions are `broadcastable` to `boxes`. The last
dimension is 2, which represents [height, width].
Returns:
normalized_boxes: a tensor whose shape is the same as `boxes` representing
the normalized boxes.
Raises:
ValueError: If the last dimension of boxes is not 4.
"""
if boxes.shape[-1] != 4:
raise ValueError('boxes.shape[-1] is {:d}, but must be 4.'.format(
boxes.shape[-1]))
with tf.name_scope('normalize_boxes'):
if isinstance(image_shape, list) or isinstance(image_shape, tuple):
height, width = image_shape
else:
image_shape = tf.cast(image_shape, dtype=boxes.dtype)
height = image_shape[..., 0:1]
width = image_shape[..., 1:2]
ymin = boxes[..., 0:1] / height
xmin = boxes[..., 1:2] / width
ymax = boxes[..., 2:3] / height
xmax = boxes[..., 3:4] / width
normalized_boxes = tf.concat([ymin, xmin, ymax, xmax], axis=-1)
return normalized_boxes
def denormalize_boxes(boxes, image_shape):
"""Converts boxes normalized by [height, width] to pixel coordinates.
Args:
boxes: a tensor whose last dimension is 4 representing the coordinates of
boxes in ymin, xmin, ymax, xmax order.
image_shape: a list of two integers, a two-element vector or a tensor such
that all but the last dimensions are `broadcastable` to `boxes`. The last
dimension is 2, which represents [height, width].
Returns:
denormalized_boxes: a tensor whose shape is the same as `boxes` representing
the denormalized boxes.
Raises:
ValueError: If the last dimension of boxes is not 4.
"""
with tf.name_scope('denormalize_boxes'):
if isinstance(image_shape, list) or isinstance(image_shape, tuple):
height, width = image_shape
else:
image_shape = tf.cast(image_shape, dtype=boxes.dtype)
height, width = tf.split(image_shape, 2, axis=-1)
ymin, xmin, ymax, xmax = tf.split(boxes, 4, axis=-1)
ymin = ymin * height
xmin = xmin * width
ymax = ymax * height
xmax = xmax * width
denormalized_boxes = tf.concat([ymin, xmin, ymax, xmax], axis=-1)
return denormalized_boxes
def clip_boxes(boxes, image_shape):
"""Clips boxes to image boundaries.
Args:
boxes: a tensor whose last dimension is 4 representing the coordinates of
boxes in ymin, xmin, ymax, xmax order.
image_shape: a list of two integers, a two-element vector or a tensor such
that all but the last dimensions are `broadcastable` to `boxes`. The last
dimension is 2, which represents [height, width].
Returns:
clipped_boxes: a tensor whose shape is the same as `boxes` representing the
clipped boxes.
Raises:
ValueError: If the last dimension of boxes is not 4.
"""
if boxes.shape[-1] != 4:
raise ValueError('boxes.shape[-1] is {:d}, but must be 4.'.format(
boxes.shape[-1]))
with tf.name_scope('clip_boxes'):
if isinstance(image_shape, list) or isinstance(image_shape, tuple):
height, width = image_shape
max_length = [height - 1.0, width - 1.0, height - 1.0, width - 1.0]
else:
image_shape = tf.cast(image_shape, dtype=boxes.dtype)
height, width = tf.unstack(image_shape, axis=-1)
max_length = tf.stack(
[height - 1.0, width - 1.0, height - 1.0, width - 1.0], axis=-1)
clipped_boxes = tf.math.maximum(tf.math.minimum(boxes, max_length), 0.0)
return clipped_boxes
def compute_outer_boxes(boxes, image_shape, scale=1.0):
"""Compute outer box encloses an object with a margin.
Args:
boxes: a tensor whose last dimension is 4 representing the coordinates of
boxes in ymin, xmin, ymax, xmax order.
image_shape: a list of two integers, a two-element vector or a tensor such
that all but the last dimensions are `broadcastable` to `boxes`. The last
dimension is 2, which represents [height, width].
scale: a float number specifying the scale of output outer boxes to input
`boxes`.
Returns:
outer_boxes: a tensor whose shape is the same as `boxes` representing the
outer boxes.
"""
if scale < 1.0:
raise ValueError(
'scale is {}, but outer box scale must be greater than 1.0.'.format(
scale))
centers_y = (boxes[..., 0] + boxes[..., 2]) / 2.0
centers_x = (boxes[..., 1] + boxes[..., 3]) / 2.0
box_height = (boxes[..., 2] - boxes[..., 0]) * scale
box_width = (boxes[..., 3] - boxes[..., 1]) * scale
outer_boxes = tf.stack([
centers_y - box_height / 2.0, centers_x - box_width / 2.0,
centers_y + box_height / 2.0, centers_x + box_width / 2.0
],
axis=1)
outer_boxes = clip_boxes(outer_boxes, image_shape)
return outer_boxes
def encode_boxes(boxes, anchors, weights=None):
"""Encode boxes to targets.
Args:
boxes: a tensor whose last dimension is 4 representing the coordinates of
boxes in ymin, xmin, ymax, xmax order.
anchors: a tensor whose shape is the same as, or `broadcastable` to `boxes`,
representing the coordinates of anchors in ymin, xmin, ymax, xmax order.
weights: None or a list of four float numbers used to scale coordinates.
Returns:
encoded_boxes: a tensor whose shape is the same as `boxes` representing the
encoded box targets.
Raises:
ValueError: If the last dimension of boxes is not 4.
"""
if boxes.shape[-1] != 4:
raise ValueError('boxes.shape[-1] is {:d}, but must be 4.'.format(
boxes.shape[-1]))
with tf.name_scope('encode_boxes'):
boxes = tf.cast(boxes, dtype=anchors.dtype)
ymin = boxes[..., 0:1]
xmin = boxes[..., 1:2]
ymax = boxes[..., 2:3]
xmax = boxes[..., 3:4]
box_h = ymax - ymin + 1.0
box_w = xmax - xmin + 1.0
box_yc = ymin + 0.5 * box_h
box_xc = xmin + 0.5 * box_w
anchor_ymin = anchors[..., 0:1]
anchor_xmin = anchors[..., 1:2]
anchor_ymax = anchors[..., 2:3]
anchor_xmax = anchors[..., 3:4]
anchor_h = anchor_ymax - anchor_ymin + 1.0
anchor_w = anchor_xmax - anchor_xmin + 1.0
anchor_yc = anchor_ymin + 0.5 * anchor_h
anchor_xc = anchor_xmin + 0.5 * anchor_w
encoded_dy = (box_yc - anchor_yc) / anchor_h
encoded_dx = (box_xc - anchor_xc) / anchor_w
encoded_dh = tf.math.log(box_h / anchor_h)
encoded_dw = tf.math.log(box_w / anchor_w)
if weights:
encoded_dy *= weights[0]
encoded_dx *= weights[1]
encoded_dh *= weights[2]
encoded_dw *= weights[3]
encoded_boxes = tf.concat([encoded_dy, encoded_dx, encoded_dh, encoded_dw],
axis=-1)
return encoded_boxes
def decode_boxes(encoded_boxes, anchors, weights=None):
"""Decode boxes.
Args:
encoded_boxes: a tensor whose last dimension is 4 representing the
coordinates of encoded boxes in ymin, xmin, ymax, xmax order.
anchors: a tensor whose shape is the same as, or `broadcastable` to `boxes`,
representing the coordinates of anchors in ymin, xmin, ymax, xmax order.
weights: None or a list of four float numbers used to scale coordinates.
Returns:
encoded_boxes: a tensor whose shape is the same as `boxes` representing the
decoded box targets.
"""
if encoded_boxes.shape[-1] != 4:
raise ValueError('encoded_boxes.shape[-1] is {:d}, but must be 4.'.format(
encoded_boxes.shape[-1]))
with tf.name_scope('decode_boxes'):
encoded_boxes = tf.cast(encoded_boxes, dtype=anchors.dtype)
dy = encoded_boxes[..., 0:1]
dx = encoded_boxes[..., 1:2]
dh = encoded_boxes[..., 2:3]
dw = encoded_boxes[..., 3:4]
if weights:
dy /= weights[0]
dx /= weights[1]
dh /= weights[2]
dw /= weights[3]
dh = tf.math.minimum(dh, BBOX_XFORM_CLIP)
dw = tf.math.minimum(dw, BBOX_XFORM_CLIP)
anchor_ymin = anchors[..., 0:1]
anchor_xmin = anchors[..., 1:2]
anchor_ymax = anchors[..., 2:3]
anchor_xmax = anchors[..., 3:4]
anchor_h = anchor_ymax - anchor_ymin + 1.0
anchor_w = anchor_xmax - anchor_xmin + 1.0
anchor_yc = anchor_ymin + 0.5 * anchor_h
anchor_xc = anchor_xmin + 0.5 * anchor_w
decoded_boxes_yc = dy * anchor_h + anchor_yc
decoded_boxes_xc = dx * anchor_w + anchor_xc
decoded_boxes_h = tf.math.exp(dh) * anchor_h
decoded_boxes_w = tf.math.exp(dw) * anchor_w
decoded_boxes_ymin = decoded_boxes_yc - 0.5 * decoded_boxes_h
decoded_boxes_xmin = decoded_boxes_xc - 0.5 * decoded_boxes_w
decoded_boxes_ymax = decoded_boxes_ymin + decoded_boxes_h - 1.0
decoded_boxes_xmax = decoded_boxes_xmin + decoded_boxes_w - 1.0
decoded_boxes = tf.concat([
decoded_boxes_ymin, decoded_boxes_xmin, decoded_boxes_ymax,
decoded_boxes_xmax
],
axis=-1)
return decoded_boxes
def encode_boxes_lrtb(boxes, anchors, weights=None):
"""Encode boxes to targets on lrtb (=left,right,top,bottom) format.
Args:
boxes: a tensor whose last dimension is 4 representing the coordinates
of boxes in ymin, xmin, ymax, xmax order.
anchors: a tensor whose shape is the same as, or `broadcastable` to `boxes`,
representing the coordinates of anchors in ymin, xmin, ymax, xmax order.
weights: None or a list of four float numbers used to scale coordinates.
Returns:
encoded_boxes_lrtb: a tensor whose shape is the same as `boxes` representing
the encoded box targets. The box targets encode the left, right, top,
bottom distances from an anchor location to the four borders of the
matched groundtruth bounding box.
center_targets: centerness targets defined by the left, right, top, and
bottom distance targets. The centerness is defined as the deviation of the
anchor location from the groundtruth object center. Formally, centerness =
sqrt(min(left, right)/max(left, right)*min(top, bottom)/max(top, bottom)).
Raises:
ValueError: If the last dimension of boxes is not 4.
"""
if boxes.shape[-1] != 4:
raise ValueError(
'boxes.shape[-1] is {:d}, but must be 4.'.format(boxes.shape[-1]))
with tf.name_scope('encode_boxes_lrtb'):
boxes = tf.cast(boxes, dtype=anchors.dtype)
ymin = boxes[..., 0:1]
xmin = boxes[..., 1:2]
ymax = boxes[..., 2:3]
xmax = boxes[..., 3:4]
# box_h = ymax - ymin + 1.0
# box_w = xmax - xmin + 1.0
box_h = ymax - ymin
box_w = xmax - xmin
anchor_ymin = anchors[..., 0:1]
anchor_xmin = anchors[..., 1:2]
anchor_ymax = anchors[..., 2:3]
anchor_xmax = anchors[..., 3:4]
# anchor_h = anchor_ymax - anchor_ymin + 1.0
# anchor_w = anchor_xmax - anchor_xmin + 1.0
anchor_h = anchor_ymax - anchor_ymin
anchor_w = anchor_xmax - anchor_xmin
anchor_yc = anchor_ymin + 0.5 * anchor_h
anchor_xc = anchor_xmin + 0.5 * anchor_w
box_h += EPSILON
box_w += EPSILON
anchor_h += EPSILON
anchor_w += EPSILON
left = (anchor_xc - xmin) / anchor_w
right = (xmax - anchor_xc) / anchor_w
top = (anchor_yc - ymin) / anchor_h
bottom = (ymax - anchor_yc) / anchor_h
# Create centerness target. {
lrtb_targets = tf.concat([left, right, top, bottom], axis=-1)
valid_match = tf.greater(tf.reduce_min(lrtb_targets, -1), 0.0)
# Centerness score.
left_right = tf.concat([left, right], axis=-1)
left_right = tf.where(tf.stack([valid_match, valid_match], -1),
left_right, tf.zeros_like(left_right))
top_bottom = tf.concat([top, bottom], axis=-1)
top_bottom = tf.where(tf.stack([valid_match, valid_match], -1),
top_bottom, tf.zeros_like(top_bottom))
center_targets = tf.sqrt(
(tf.reduce_min(left_right, -1) /
(tf.reduce_max(left_right, -1) + EPSILON)) *
(tf.reduce_min(top_bottom, -1) /
(tf.reduce_max(top_bottom, -1) + EPSILON)))
center_targets = tf.where(valid_match,
center_targets,
tf.zeros_like(center_targets))
if weights:
left *= weights[0]
right *= weights[1]
top *= weights[2]
bottom *= weights[3]
encoded_boxes_lrtb = tf.concat(
[left, right, top, bottom],
axis=-1)
return encoded_boxes_lrtb, center_targets
def decode_boxes_lrtb(encoded_boxes_lrtb, anchors, weights=None):
"""Decode boxes.
Args:
encoded_boxes_lrtb: a tensor whose last dimension is 4 representing the
coordinates of encoded boxes in left, right, top, bottom order.
anchors: a tensor whose shape is the same as, or `broadcastable` to `boxes`,
representing the coordinates of anchors in ymin, xmin, ymax, xmax order.
weights: None or a list of four float numbers used to scale coordinates.
Returns:
decoded_boxes_lrtb: a tensor whose shape is the same as `boxes` representing
the decoded box targets in lrtb (=left,right,top,bottom) format. The box
decoded box coordinates represent the left, right, top, and bottom
distances from an anchor location to the four borders of the matched
groundtruth bounding box.
"""
if encoded_boxes_lrtb.shape[-1] != 4:
raise ValueError(
'encoded_boxes_lrtb.shape[-1] is {:d}, but must be 4.'
.format(encoded_boxes_lrtb.shape[-1]))
with tf.name_scope('decode_boxes_lrtb'):
encoded_boxes_lrtb = tf.cast(encoded_boxes_lrtb, dtype=anchors.dtype)
left = encoded_boxes_lrtb[..., 0:1]
right = encoded_boxes_lrtb[..., 1:2]
top = encoded_boxes_lrtb[..., 2:3]
bottom = encoded_boxes_lrtb[..., 3:4]
if weights:
left /= weights[0]
right /= weights[1]
top /= weights[2]
bottom /= weights[3]
anchor_ymin = anchors[..., 0:1]
anchor_xmin = anchors[..., 1:2]
anchor_ymax = anchors[..., 2:3]
anchor_xmax = anchors[..., 3:4]
anchor_h = anchor_ymax - anchor_ymin
anchor_w = anchor_xmax - anchor_xmin
anchor_yc = anchor_ymin + 0.5 * anchor_h
anchor_xc = anchor_xmin + 0.5 * anchor_w
anchor_h += EPSILON
anchor_w += EPSILON
decoded_boxes_ymin = anchor_yc - top * anchor_h
decoded_boxes_xmin = anchor_xc - left * anchor_w
decoded_boxes_ymax = anchor_yc + bottom * anchor_h
decoded_boxes_xmax = anchor_xc + right * anchor_w
decoded_boxes_lrtb = tf.concat(
[decoded_boxes_ymin, decoded_boxes_xmin,
decoded_boxes_ymax, decoded_boxes_xmax],
axis=-1)
return decoded_boxes_lrtb
def filter_boxes(boxes, scores, image_shape, min_size_threshold):
"""Filter and remove boxes that are too small or fall outside the image.
Args:
boxes: a tensor whose last dimension is 4 representing the coordinates of
boxes in ymin, xmin, ymax, xmax order.
scores: a tensor whose shape is the same as tf.shape(boxes)[:-1]
representing the original scores of the boxes.
image_shape: a tensor whose shape is the same as, or `broadcastable` to
`boxes` except the last dimension, which is 2, representing [height,
width] of the scaled image.
min_size_threshold: a float representing the minimal box size in each side
(w.r.t. the scaled image). Boxes whose sides are smaller than it will be
filtered out.
Returns:
filtered_boxes: a tensor whose shape is the same as `boxes` but with
the position of the filtered boxes are filled with 0.
filtered_scores: a tensor whose shape is the same as 'scores' but with
the positinon of the filtered boxes filled with 0.
"""
if boxes.shape[-1] != 4:
raise ValueError('boxes.shape[1] is {:d}, but must be 4.'.format(
boxes.shape[-1]))
with tf.name_scope('filter_boxes'):
if isinstance(image_shape, list) or isinstance(image_shape, tuple):
height, width = image_shape
else:
image_shape = tf.cast(image_shape, dtype=boxes.dtype)
height = image_shape[..., 0]
width = image_shape[..., 1]
ymin = boxes[..., 0]
xmin = boxes[..., 1]
ymax = boxes[..., 2]
xmax = boxes[..., 3]
h = ymax - ymin + 1.0
w = xmax - xmin + 1.0
yc = ymin + 0.5 * h
xc = xmin + 0.5 * w
min_size = tf.cast(
tf.math.maximum(min_size_threshold, 1.0), dtype=boxes.dtype)
filtered_size_mask = tf.math.logical_and(
tf.math.greater(h, min_size), tf.math.greater(w, min_size))
filtered_center_mask = tf.logical_and(
tf.math.logical_and(tf.math.greater(yc, 0.0), tf.math.less(yc, height)),
tf.math.logical_and(tf.math.greater(xc, 0.0), tf.math.less(xc, width)))
filtered_mask = tf.math.logical_and(filtered_size_mask,
filtered_center_mask)
filtered_scores = tf.where(filtered_mask, scores, tf.zeros_like(scores))
filtered_boxes = tf.cast(
tf.expand_dims(filtered_mask, axis=-1), dtype=boxes.dtype) * boxes
return filtered_boxes, filtered_scores
def filter_boxes_by_scores(boxes, scores, min_score_threshold):
"""Filter and remove boxes whose scores are smaller than the threshold.
Args:
boxes: a tensor whose last dimension is 4 representing the coordinates of
boxes in ymin, xmin, ymax, xmax order.
scores: a tensor whose shape is the same as tf.shape(boxes)[:-1]
representing the original scores of the boxes.
min_score_threshold: a float representing the minimal box score threshold.
Boxes whose score are smaller than it will be filtered out.
Returns:
filtered_boxes: a tensor whose shape is the same as `boxes` but with
the position of the filtered boxes are filled with -1.
filtered_scores: a tensor whose shape is the same as 'scores' but with
the
"""
if boxes.shape[-1] != 4:
raise ValueError('boxes.shape[1] is {:d}, but must be 4.'.format(
boxes.shape[-1]))
with tf.name_scope('filter_boxes_by_scores'):
filtered_mask = tf.math.greater(scores, min_score_threshold)
filtered_scores = tf.where(filtered_mask, scores, -tf.ones_like(scores))
filtered_boxes = tf.cast(
tf.expand_dims(filtered_mask, axis=-1), dtype=boxes.dtype) * boxes
return filtered_boxes, filtered_scores
def top_k_boxes(boxes, scores, k):
"""Sort and select top k boxes according to the scores.
Args:
boxes: a tensor of shape [batch_size, N, 4] representing the coordiante of
the boxes. N is the number of boxes per image.
scores: a tensor of shsape [batch_size, N] representing the socre of the
boxes.
k: an integer or a tensor indicating the top k number.
Returns:
selected_boxes: a tensor of shape [batch_size, k, 4] representing the
selected top k box coordinates.
selected_scores: a tensor of shape [batch_size, k] representing the selected
top k box scores.
"""
with tf.name_scope('top_k_boxes'):
selected_scores, top_k_indices = tf.nn.top_k(scores, k=k, sorted=True)
batch_size, _ = scores.get_shape().as_list()
if batch_size == 1:
selected_boxes = tf.squeeze(
tf.gather(boxes, top_k_indices, axis=1), axis=1)
else:
top_k_indices_shape = tf.shape(top_k_indices)
batch_indices = (
tf.expand_dims(tf.range(top_k_indices_shape[0]), axis=-1) *
tf.ones([1, top_k_indices_shape[-1]], dtype=tf.int32))
gather_nd_indices = tf.stack([batch_indices, top_k_indices], axis=-1)
selected_boxes = tf.gather_nd(boxes, gather_nd_indices)
return selected_boxes, selected_scores
def bbox_overlap(boxes, gt_boxes):
"""Calculates the overlap between proposal and ground truth boxes.
Some `gt_boxes` may have been padded. The returned `iou` tensor for these
boxes will be -1.
Args:
boxes: a tensor with a shape of [batch_size, N, 4]. N is the number of
proposals before groundtruth assignment (e.g., rpn_post_nms_topn). The
last dimension is the pixel coordinates in [ymin, xmin, ymax, xmax] form.
gt_boxes: a tensor with a shape of [batch_size, MAX_NUM_INSTANCES, 4]. This
tensor might have paddings with a negative value.
Returns:
iou: a tensor with as a shape of [batch_size, N, MAX_NUM_INSTANCES].
"""
with tf.name_scope('bbox_overlap'):
bb_y_min, bb_x_min, bb_y_max, bb_x_max = tf.split(
value=boxes, num_or_size_splits=4, axis=2)
gt_y_min, gt_x_min, gt_y_max, gt_x_max = tf.split(
value=gt_boxes, num_or_size_splits=4, axis=2)
# Calculates the intersection area.
i_xmin = tf.math.maximum(bb_x_min, tf.transpose(gt_x_min, [0, 2, 1]))
i_xmax = tf.math.minimum(bb_x_max, tf.transpose(gt_x_max, [0, 2, 1]))
i_ymin = tf.math.maximum(bb_y_min, tf.transpose(gt_y_min, [0, 2, 1]))
i_ymax = tf.math.minimum(bb_y_max, tf.transpose(gt_y_max, [0, 2, 1]))
i_area = tf.math.maximum((i_xmax - i_xmin), 0) * tf.math.maximum(
(i_ymax - i_ymin), 0)
# Calculates the union area.
bb_area = (bb_y_max - bb_y_min) * (bb_x_max - bb_x_min)
gt_area = (gt_y_max - gt_y_min) * (gt_x_max - gt_x_min)
# Adds a small epsilon to avoid divide-by-zero.
u_area = bb_area + tf.transpose(gt_area, [0, 2, 1]) - i_area + 1e-8
# Calculates IoU.
iou = i_area / u_area
# Fills -1 for IoU entries between the padded ground truth boxes.
gt_invalid_mask = tf.less(
tf.reduce_max(gt_boxes, axis=-1, keepdims=True), 0.0)
padding_mask = tf.logical_or(
tf.zeros_like(bb_x_min, dtype=tf.bool),
tf.transpose(gt_invalid_mask, [0, 2, 1]))
iou = tf.where(padding_mask, -tf.ones_like(iou), iou)
return iou
def get_non_empty_box_indices(boxes):
"""Get indices for non-empty boxes."""
# Selects indices if box height or width is 0.
height = boxes[:, 2] - boxes[:, 0]
width = boxes[:, 3] - boxes[:, 1]
indices = tf.where(
tf.logical_and(tf.greater(height, 0), tf.greater(width, 0)))
return indices[:, 0]