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import matplotlib.pyplot as plt
import numpy as np
import torch
def imshow(ims, ax=None, t=0, vmin=None, vmax=None, title=None, cmap=None, fontsize=20):
if ax is None:
fig, ax = plt.subplots(1,1)
with torch.no_grad():
im = ims[t].float().cpu().numpy().transpose((1,2,0))
if (vmin is not None) and (vmax is not None):
im =ax.imshow(im, vmin=vmin, vmax=vmax, cmap=(cmap or 'viridis'))
else:
im =ax.imshow(im)
if title is not None:
ax.set_title(title, fontsize=fontsize)
return (im, ax)
def make_colorwheel():
"""
Generates a color wheel for optical flow visualization as presented in:
Baker et al. "A Database and Evaluation Methodology for Optical Flow" (ICCV, 2007)
URL: http://vision.middlebury.edu/flow/flowEval-iccv07.pdf
Code follows the original C++ source code of Daniel Scharstein.
Code follows the the Matlab source code of Deqing Sun.
Returns:
np.ndarray: Color wheel
"""
RY = 15
YG = 6
GC = 4
CB = 11
BM = 13
MR = 6
ncols = RY + YG + GC + CB + BM + MR
colorwheel = np.zeros((ncols, 3))
col = 0
# RY
colorwheel[0:RY, 0] = 255
colorwheel[0:RY, 1] = np.floor(255*np.arange(0,RY)/RY)
col = col+RY
# YG
colorwheel[col:col+YG, 0] = 255 - np.floor(255*np.arange(0,YG)/YG)
colorwheel[col:col+YG, 1] = 255
col = col+YG
# GC
colorwheel[col:col+GC, 1] = 255
colorwheel[col:col+GC, 2] = np.floor(255*np.arange(0,GC)/GC)
col = col+GC
# CB
colorwheel[col:col+CB, 1] = 255 - np.floor(255*np.arange(CB)/CB)
colorwheel[col:col+CB, 2] = 255
col = col+CB
# BM
colorwheel[col:col+BM, 2] = 255
colorwheel[col:col+BM, 0] = np.floor(255*np.arange(0,BM)/BM)
col = col+BM
# MR
colorwheel[col:col+MR, 2] = 255 - np.floor(255*np.arange(MR)/MR)
colorwheel[col:col+MR, 0] = 255
return colorwheel
def flow_uv_to_colors(u, v, convert_to_bgr=False):
"""
Applies the flow color wheel to (possibly clipped) flow components u and v.
According to the C++ source code of Daniel Scharstein
According to the Matlab source code of Deqing Sun
Args:
u (np.ndarray): Input horizontal flow of shape [H,W]
v (np.ndarray): Input vertical flow of shape [H,W]
convert_to_bgr (bool, optional): Convert output image to BGR. Defaults to False.
Returns:
np.ndarray: Flow visualization image of shape [H,W,3]
"""
flow_image = np.zeros((u.shape[0], u.shape[1], 3), np.uint8)
colorwheel = make_colorwheel() # shape [55x3]
ncols = colorwheel.shape[0]
rad = np.sqrt(np.square(u) + np.square(v))
a = np.arctan2(-v, -u)/np.pi
fk = (a+1) / 2*(ncols-1)
k0 = np.floor(fk).astype(np.int32)
k1 = k0 + 1
k1[k1 == ncols] = 0
f = fk - k0
for i in range(colorwheel.shape[1]):
tmp = colorwheel[:,i]
col0 = tmp[k0] / 255.0
col1 = tmp[k1] / 255.0
col = (1-f)*col0 + f*col1
idx = (rad <= 1)
col[idx] = 1 - rad[idx] * (1-col[idx])
col[~idx] = col[~idx] * 0.75 # out of range
# Note the 2-i => BGR instead of RGB
ch_idx = 2-i if convert_to_bgr else i
flow_image[:,:,ch_idx] = np.floor(255 * col)
return flow_image
def flow_to_image(flow_uv, clip_flow=None, convert_to_bgr=False):
"""
Expects a two dimensional flow image of shape.
Args:
flow_uv (np.ndarray): Flow UV image of shape [H,W,2]
clip_flow (float, optional): Clip maximum of flow values. Defaults to None.
convert_to_bgr (bool, optional): Convert output image to BGR. Defaults to False.
Returns:
np.ndarray: Flow visualization image of shape [H,W,3]
"""
assert flow_uv.ndim == 3, 'input flow must have three dimensions'
assert flow_uv.shape[2] == 2, 'input flow must have shape [H,W,2]'
if clip_flow is not None:
flow_uv = np.clip(flow_uv, 0, clip_flow)
u = flow_uv[:,:,0]
v = flow_uv[:,:,1]
rad = np.sqrt(np.square(u) + np.square(v))
rad_max = np.max(rad)
epsilon = 1e-5
u = u / (rad_max + epsilon)
v = v / (rad_max + epsilon)
return flow_uv_to_colors(u, v, convert_to_bgr)
from decord import VideoReader, cpu
from PIL import Image
from torchvision import transforms
def get_video(video_name, num_frames=2, delta_time=4, frame=None):
decord_vr = VideoReader(video_name, num_threads=1, ctx=cpu(0))
max_end_ind = len(decord_vr) - num_frames*delta_time - 1
start_frame = frame if frame is not None else rng.randint(1, max_end_ind)
print("fps", decord_vr.get_avg_fps())
print("start frame = %d" % start_frame)
frame_id_list = list(range(start_frame, start_frame + num_frames*delta_time, delta_time))
video_data = decord_vr.get_batch(frame_id_list).asnumpy()
video_data = [Image.fromarray(video_data[t]).convert('RGB') for t, _ in enumerate(frame_id_list)]
return (torch.stack([transforms.ToTensor()(im) for im in video_data], 0), start_frame)
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