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import numpy as np
import cv2
from PIL import Image
from torchvision.transforms import ColorJitter
class FlowAugmentor:
def __init__(self, crop_size, min_scale=-0.2, max_scale=0.5, do_flip=True,
no_eraser_aug=True,
):
# spatial augmentation params
self.crop_size = crop_size
self.min_scale = min_scale
self.max_scale = max_scale
self.spatial_aug_prob = 0.8
self.stretch_prob = 0.8
self.max_stretch = 0.2
# flip augmentation params
self.do_flip = do_flip
self.h_flip_prob = 0.5
self.v_flip_prob = 0.1
# photometric augmentation params
self.photo_aug = ColorJitter(brightness=0.4, contrast=0.4, saturation=0.4, hue=0.5 / 3.14)
self.asymmetric_color_aug_prob = 0.2
if no_eraser_aug:
# we disable eraser aug since no obvious improvement is observed in our experiments
self.eraser_aug_prob = -1
else:
self.eraser_aug_prob = 0.5
def color_transform(self, img1, img2):
""" Photometric augmentation """
# asymmetric
if np.random.rand() < self.asymmetric_color_aug_prob:
img1 = np.array(self.photo_aug(Image.fromarray(img1)), dtype=np.uint8)
img2 = np.array(self.photo_aug(Image.fromarray(img2)), dtype=np.uint8)
# symmetric
else:
image_stack = np.concatenate([img1, img2], axis=0)
image_stack = np.array(self.photo_aug(Image.fromarray(image_stack)), dtype=np.uint8)
img1, img2 = np.split(image_stack, 2, axis=0)
return img1, img2
def eraser_transform(self, img1, img2, bounds=[50, 100]):
""" Occlusion augmentation """
ht, wd = img1.shape[:2]
if np.random.rand() < self.eraser_aug_prob:
mean_color = np.mean(img2.reshape(-1, 3), axis=0)
for _ in range(np.random.randint(1, 3)):
x0 = np.random.randint(0, wd)
y0 = np.random.randint(0, ht)
dx = np.random.randint(bounds[0], bounds[1])
dy = np.random.randint(bounds[0], bounds[1])
img2[y0:y0 + dy, x0:x0 + dx, :] = mean_color
return img1, img2
def spatial_transform(self, img1, img2, flow, occlusion=None):
# randomly sample scale
ht, wd = img1.shape[:2]
min_scale = np.maximum(
(self.crop_size[0] + 8) / float(ht),
(self.crop_size[1] + 8) / float(wd))
scale = 2 ** np.random.uniform(self.min_scale, self.max_scale)
scale_x = scale
scale_y = scale
if np.random.rand() < self.stretch_prob:
scale_x *= 2 ** np.random.uniform(-self.max_stretch, self.max_stretch)
scale_y *= 2 ** np.random.uniform(-self.max_stretch, self.max_stretch)
scale_x = np.clip(scale_x, min_scale, None)
scale_y = np.clip(scale_y, min_scale, None)
if np.random.rand() < self.spatial_aug_prob:
# rescale the images
img1 = cv2.resize(img1, None, fx=scale_x, fy=scale_y, interpolation=cv2.INTER_LINEAR)
img2 = cv2.resize(img2, None, fx=scale_x, fy=scale_y, interpolation=cv2.INTER_LINEAR)
flow = cv2.resize(flow, None, fx=scale_x, fy=scale_y, interpolation=cv2.INTER_LINEAR)
flow = flow * [scale_x, scale_y]
if occlusion is not None:
occlusion = cv2.resize(occlusion, None, fx=scale_x, fy=scale_y, interpolation=cv2.INTER_LINEAR)
if self.do_flip:
if np.random.rand() < self.h_flip_prob: # h-flip
img1 = img1[:, ::-1]
img2 = img2[:, ::-1]
flow = flow[:, ::-1] * [-1.0, 1.0]
if occlusion is not None:
occlusion = occlusion[:, ::-1]
if np.random.rand() < self.v_flip_prob: # v-flip
img1 = img1[::-1, :]
img2 = img2[::-1, :]
flow = flow[::-1, :] * [1.0, -1.0]
if occlusion is not None:
occlusion = occlusion[::-1, :]
# In case no cropping
if img1.shape[0] - self.crop_size[0] > 0:
y0 = np.random.randint(0, img1.shape[0] - self.crop_size[0])
else:
y0 = 0
if img1.shape[1] - self.crop_size[1] > 0:
x0 = np.random.randint(0, img1.shape[1] - self.crop_size[1])
else:
x0 = 0
img1 = img1[y0:y0 + self.crop_size[0], x0:x0 + self.crop_size[1]]
img2 = img2[y0:y0 + self.crop_size[0], x0:x0 + self.crop_size[1]]
flow = flow[y0:y0 + self.crop_size[0], x0:x0 + self.crop_size[1]]
if occlusion is not None:
occlusion = occlusion[y0:y0 + self.crop_size[0], x0:x0 + self.crop_size[1]]
return img1, img2, flow, occlusion
return img1, img2, flow
def __call__(self, img1, img2, flow, occlusion=None):
img1, img2 = self.color_transform(img1, img2)
img1, img2 = self.eraser_transform(img1, img2)
if occlusion is not None:
img1, img2, flow, occlusion = self.spatial_transform(
img1, img2, flow, occlusion)
else:
img1, img2, flow = self.spatial_transform(img1, img2, flow)
img1 = np.ascontiguousarray(img1)
img2 = np.ascontiguousarray(img2)
flow = np.ascontiguousarray(flow)
if occlusion is not None:
occlusion = np.ascontiguousarray(occlusion)
return img1, img2, flow, occlusion
return img1, img2, flow
class SparseFlowAugmentor:
def __init__(self, crop_size, min_scale=-0.2, max_scale=0.5, do_flip=False,
no_eraser_aug=True,
):
# spatial augmentation params
self.crop_size = crop_size
self.min_scale = min_scale
self.max_scale = max_scale
self.spatial_aug_prob = 0.8
self.stretch_prob = 0.8
self.max_stretch = 0.2
# flip augmentation params
self.do_flip = do_flip
self.h_flip_prob = 0.5
self.v_flip_prob = 0.1
# photometric augmentation params
self.photo_aug = ColorJitter(brightness=0.3, contrast=0.3, saturation=0.3, hue=0.3 / 3.14)
self.asymmetric_color_aug_prob = 0.2
if no_eraser_aug:
# we disable eraser aug since no obvious improvement is observed in our experiments
self.eraser_aug_prob = -1
else:
self.eraser_aug_prob = 0.5
def color_transform(self, img1, img2):
image_stack = np.concatenate([img1, img2], axis=0)
image_stack = np.array(self.photo_aug(Image.fromarray(image_stack)), dtype=np.uint8)
img1, img2 = np.split(image_stack, 2, axis=0)
return img1, img2
def eraser_transform(self, img1, img2):
ht, wd = img1.shape[:2]
if np.random.rand() < self.eraser_aug_prob:
mean_color = np.mean(img2.reshape(-1, 3), axis=0)
for _ in range(np.random.randint(1, 3)):
x0 = np.random.randint(0, wd)
y0 = np.random.randint(0, ht)
dx = np.random.randint(50, 100)
dy = np.random.randint(50, 100)
img2[y0:y0 + dy, x0:x0 + dx, :] = mean_color
return img1, img2
def resize_sparse_flow_map(self, flow, valid, fx=1.0, fy=1.0):
ht, wd = flow.shape[:2]
coords = np.meshgrid(np.arange(wd), np.arange(ht))
coords = np.stack(coords, axis=-1)
coords = coords.reshape(-1, 2).astype(np.float32)
flow = flow.reshape(-1, 2).astype(np.float32)
valid = valid.reshape(-1).astype(np.float32)
coords0 = coords[valid >= 1]
flow0 = flow[valid >= 1]
ht1 = int(round(ht * fy))
wd1 = int(round(wd * fx))
coords1 = coords0 * [fx, fy]
flow1 = flow0 * [fx, fy]
xx = np.round(coords1[:, 0]).astype(np.int32)
yy = np.round(coords1[:, 1]).astype(np.int32)
v = (xx > 0) & (xx < wd1) & (yy > 0) & (yy < ht1)
xx = xx[v]
yy = yy[v]
flow1 = flow1[v]
flow_img = np.zeros([ht1, wd1, 2], dtype=np.float32)
valid_img = np.zeros([ht1, wd1], dtype=np.int32)
flow_img[yy, xx] = flow1
valid_img[yy, xx] = 1
return flow_img, valid_img
def spatial_transform(self, img1, img2, flow, valid):
# randomly sample scale
ht, wd = img1.shape[:2]
min_scale = np.maximum(
(self.crop_size[0] + 1) / float(ht),
(self.crop_size[1] + 1) / float(wd))
scale = 2 ** np.random.uniform(self.min_scale, self.max_scale)
scale_x = np.clip(scale, min_scale, None)
scale_y = np.clip(scale, min_scale, None)
if np.random.rand() < self.spatial_aug_prob:
# rescale the images
img1 = cv2.resize(img1, None, fx=scale_x, fy=scale_y, interpolation=cv2.INTER_LINEAR)
img2 = cv2.resize(img2, None, fx=scale_x, fy=scale_y, interpolation=cv2.INTER_LINEAR)
flow, valid = self.resize_sparse_flow_map(flow, valid, fx=scale_x, fy=scale_y)
if self.do_flip:
if np.random.rand() < 0.5: # h-flip
img1 = img1[:, ::-1]
img2 = img2[:, ::-1]
flow = flow[:, ::-1] * [-1.0, 1.0]
valid = valid[:, ::-1]
margin_y = 20
margin_x = 50
y0 = np.random.randint(0, img1.shape[0] - self.crop_size[0] + margin_y)
x0 = np.random.randint(-margin_x, img1.shape[1] - self.crop_size[1] + margin_x)
y0 = np.clip(y0, 0, img1.shape[0] - self.crop_size[0])
x0 = np.clip(x0, 0, img1.shape[1] - self.crop_size[1])
img1 = img1[y0:y0 + self.crop_size[0], x0:x0 + self.crop_size[1]]
img2 = img2[y0:y0 + self.crop_size[0], x0:x0 + self.crop_size[1]]
flow = flow[y0:y0 + self.crop_size[0], x0:x0 + self.crop_size[1]]
valid = valid[y0:y0 + self.crop_size[0], x0:x0 + self.crop_size[1]]
return img1, img2, flow, valid
def __call__(self, img1, img2, flow, valid):
img1, img2 = self.color_transform(img1, img2)
img1, img2 = self.eraser_transform(img1, img2)
img1, img2, flow, valid = self.spatial_transform(img1, img2, flow, valid)
img1 = np.ascontiguousarray(img1)
img2 = np.ascontiguousarray(img2)
flow = np.ascontiguousarray(flow)
valid = np.ascontiguousarray(valid)
return img1, img2, flow, valid
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