from __future__ import division
import numpy as np
from cvbase.decorators import requires_package
[docs]@requires_package('cv2')
def show_flow(flow, win_name='', wait_time=0):
"""Show optical flow
Args:
flow(ndarray or str): optical flow to be shown
win_name(str): the window name
wait_time(int): value of waitKey param
"""
from cvbase.image import rgb2bgr
from cvbase.visualize import show_img
from cvbase.optflow.io import read_flow
flow = read_flow(flow)
flow_img = flow2rgb(flow)
show_img(rgb2bgr(flow_img), win_name, wait_time)
[docs]def flow2rgb(flow, color_wheel=None, unknown_thr=1e6):
"""Convert flow map to RGB image
Args:
flow(ndarray): optical flow
color_wheel(ndarray or None): color wheel used to map flow field to RGB
colorspace. Default color wheel will be used if not specified
unknown_thr(str): values above this threshold will be marked as unknown
and thus ignored
Returns:
ndarray: an RGB image that can be visualized
"""
assert flow.ndim == 3 and flow.shape[-1] == 2
if color_wheel is None:
color_wheel = make_color_wheel()
assert color_wheel.ndim == 2 and color_wheel.shape[1] == 3
num_bins = color_wheel.shape[0]
dx = flow[:, :, 0].copy()
dy = flow[:, :, 1].copy()
ignore_inds = (np.isnan(dx) | np.isnan(dy) | (np.abs(dx) > unknown_thr) |
(np.abs(dy) > unknown_thr))
dx[ignore_inds] = 0
dy[ignore_inds] = 0
rad = np.sqrt(dx**2 + dy**2)
if np.any(rad > np.finfo(float).eps):
max_rad = np.max(rad)
dx /= max_rad
dy /= max_rad
[h, w] = dx.shape
rad = np.sqrt(dx**2 + dy**2)
angle = np.arctan2(-dy, -dx) / np.pi
bin_real = (angle + 1) / 2 * (num_bins - 1)
bin_left = np.floor(bin_real).astype(int)
bin_right = (bin_left + 1) % num_bins
w = (bin_real - bin_left.astype(np.float32))[..., None]
flow_img = (
1 - w) * color_wheel[bin_left, :] + w * color_wheel[bin_right, :]
small_ind = rad <= 1
flow_img[small_ind] = 1 - rad[small_ind, None] * (1 - flow_img[small_ind])
flow_img[np.logical_not(small_ind)] *= 0.75
flow_img[ignore_inds, :] = 0
return flow_img
[docs]def make_color_wheel(bins=None):
"""Build a color wheel
Args:
bins(list or tuple, optional): specify number of bins for each color
range, corresponding to six ranges: red -> yellow, yellow -> green,
green -> cyan, cyan -> blue, blue -> magenta, magenta -> red.
[15, 6, 4, 11, 13, 6] is used for default (see Middlebury).
Returns:
ndarray: color wheel of shape (total_bins, 3)
"""
if bins is None:
bins = [15, 6, 4, 11, 13, 6]
assert len(bins) == 6
RY, YG, GC, CB, BM, MR = tuple(bins)
ry = [1, np.arange(RY) / RY, 0]
yg = [1 - np.arange(YG) / YG, 1, 0]
gc = [0, 1, np.arange(GC) / GC]
cb = [0, 1 - np.arange(CB) / CB, 1]
bm = [np.arange(BM) / BM, 0, 1]
mr = [1, 0, 1 - np.arange(MR) / MR]
num_bins = RY + YG + GC + CB + BM + MR
color_wheel = np.zeros((3, num_bins), dtype=np.float32)
col = 0
for i, color in enumerate([ry, yg, gc, cb, bm, mr]):
for j in range(3):
color_wheel[j, col:col + bins[i]] = color[j]
col += bins[i]
return color_wheel.T