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post_transforms_utils.py
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post_transforms_utils.py
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import numpy as np
import cv2
def flip_back(
output_flipped,
flip_pairs,
target_type='GaussianHeatmap'):
"""Flip the flipped heatmaps back to the original form.
Note:
batch_size: N
num_keypoints: K
heatmap height: H
heatmap width: W
Args:
output_flipped (np.ndarray[N, K, H, W]): The output heatmaps obtained
from the flipped images.
flip_pairs (list[tuple()): Pairs of keypoints which are mirrored
(for example, left ear -- right ear).
target_type (str): GaussianHeatmap or CombinedTarget
Returns:
np.ndarray: heatmaps that flipped back to the original image
"""
assert output_flipped.ndim == 4, \
'output_flipped should be [batch_size, num_keypoints, height, width]'
shape_ori = output_flipped.shape
channels = 1
if target_type.lower() == 'CombinedTarget'.lower():
channels = 3
output_flipped[:, 1::3, ...] = -output_flipped[:, 1::3, ...]
output_flipped = output_flipped.reshape(
shape_ori[0], -1, channels,
shape_ori[2], shape_ori[3])
output_flipped_back = output_flipped.copy()
# Swap left-right parts
for left, right in flip_pairs:
output_flipped_back[:, left, ...] = output_flipped[:, right, ...]
output_flipped_back[:, right, ...] = output_flipped[:, left, ...]
output_flipped_back = output_flipped_back.reshape(shape_ori)
# Flip horizontally
output_flipped_back = output_flipped_back[..., ::-1]
return output_flipped_back
def transform_preds(
coords, center, scale,
output_size,
use_udp=False):
"""Get final keypoint predictions from heatmaps and apply scaling and
translation to map them back to the image.
Note:
num_keypoints: K
Args:
coords (np.ndarray[K, ndims]):
* If ndims=2, corrds are predicted keypoint location.
* If ndims=4, corrds are composed of (x, y, scores, tags)
* If ndims=5, corrds are composed of (x, y, scores, tags,
flipped_tags)
center (np.ndarray[2, ]): Center of the bounding box (x, y).
scale (np.ndarray[2, ]): Scale of the bounding box
wrt [width, height].
output_size (np.ndarray[2, ] | list(2,)): Size of the
destination heatmaps.
use_udp (bool): Use unbiased data processing
Returns:
np.ndarray: Predicted coordinates in the images.
"""
assert coords.shape[1] in (2, 4, 5)
assert len(center) == 2
assert len(scale) == 2
assert len(output_size) == 2
# Recover the scale which is normalized by a factor of 200.
scale = scale * 200.0
if use_udp:
scale_x = scale[0] / (output_size[0] - 1.0)
scale_y = scale[1] / (output_size[1] - 1.0)
else:
scale_x = scale[0] / output_size[0]
scale_y = scale[1] / output_size[1]
target_coords = np.ones_like(coords)
target_coords[:, 0] = coords[:, 0] * scale_x + center[0] - scale[0] * 0.5
target_coords[:, 1] = coords[:, 1] * scale_y + center[1] - scale[1] * 0.5
return target_coords
def get_affine_transform(
center,
scale,
rot,
output_size,
shift=(0., 0.),
inv=False):
"""Get the affine transform matrix, given the center/scale/rot/output_size.
Args:
center (np.ndarray[2, ]): Center of the bounding box (x, y).
scale (np.ndarray[2, ]): Scale of the bounding box
wrt [width, height].
rot (float): Rotation angle (degree).
output_size (np.ndarray[2, ] | list(2,)): Size of the
destination heatmaps.
shift (0-100%): Shift translation ratio wrt the width/height.
Default (0., 0.).
inv (bool): Option to inverse the affine transform direction.
(inv=False: src->dst or inv=True: dst->src)
Returns:
np.ndarray: The transform matrix.
"""
assert len(center) == 2
assert len(scale) == 2
assert len(output_size) == 2
assert len(shift) == 2
# pixel_std is 200.
scale_tmp = scale * 200.0
shift = np.array(shift)
src_w = scale_tmp[0]
dst_w = output_size[0]
dst_h = output_size[1]
rot_rad = np.pi * rot / 180
src_dir = rotate_point([0., src_w * -0.5], rot_rad)
dst_dir = np.array([0., dst_w * -0.5])
src = np.zeros((3, 2), dtype=np.float32)
src[0, :] = center + scale_tmp * shift
src[1, :] = center + src_dir + scale_tmp * shift
src[2, :] = _get_3rd_point(src[0, :], src[1, :])
dst = np.zeros((3, 2), dtype=np.float32)
dst[0, :] = [dst_w * 0.5, dst_h * 0.5]
dst[1, :] = np.array([dst_w * 0.5, dst_h * 0.5]) + dst_dir
dst[2, :] = _get_3rd_point(dst[0, :], dst[1, :])
if inv:
trans = cv2.getAffineTransform(np.float32(dst), np.float32(src))
else:
trans = cv2.getAffineTransform(np.float32(src), np.float32(dst))
return trans
def _get_3rd_point(a, b):
"""To calculate the affine matrix, three pairs of points are required. This
function is used to get the 3rd point, given 2D points a & b.
The 3rd point is defined by rotating vector `a - b` by 90 degrees
anticlockwise, using b as the rotation center.
Args:
a (np.ndarray): point(x,y)
b (np.ndarray): point(x,y)
Returns:
np.ndarray: The 3rd point.
"""
assert len(a) == 2
assert len(b) == 2
direction = a - b
third_pt = b + np.array([-direction[1], direction[0]], dtype=np.float32)
return third_pt
def rotate_point(pt, angle_rad):
"""Rotate a point by an angle.
Args:
pt (list[float]): 2 dimensional point to be rotated
angle_rad (float): rotation angle by radian
Returns:
list[float]: Rotated point.
"""
assert len(pt) == 2
sn, cs = np.sin(angle_rad), np.cos(angle_rad)
new_x = pt[0] * cs - pt[1] * sn
new_y = pt[0] * sn + pt[1] * cs
rotated_pt = [new_x, new_y]
return rotated_pt