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| # Ref: https://github.com/liruoteng/OpticalFlowToolkit/blob/5cf87b947a0032f58c922bbc22c0afb30b90c418/lib/flowlib.py#L249 | |
| import numpy as np | |
| UNKNOWN_FLOW_THRESH = 1e7 | |
| def make_color_wheel(): | |
| """ | |
| Generate color wheel according Middlebury color code | |
| :return: 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.transpose(np.floor(255*np.arange(0, RY) / RY)) | |
| col += RY | |
| # YG | |
| colorwheel[col:col+YG, 0] = 255 - np.transpose(np.floor(255*np.arange(0, YG) / YG)) | |
| colorwheel[col:col+YG, 1] = 255 | |
| col += YG | |
| # GC | |
| colorwheel[col:col+GC, 1] = 255 | |
| colorwheel[col:col+GC, 2] = np.transpose(np.floor(255*np.arange(0, GC) / GC)) | |
| col += GC | |
| # CB | |
| colorwheel[col:col+CB, 1] = 255 - np.transpose(np.floor(255*np.arange(0, CB) / CB)) | |
| colorwheel[col:col+CB, 2] = 255 | |
| col += CB | |
| # BM | |
| colorwheel[col:col+BM, 2] = 255 | |
| colorwheel[col:col+BM, 0] = np.transpose(np.floor(255*np.arange(0, BM) / BM)) | |
| col += + BM | |
| # MR | |
| colorwheel[col:col+MR, 2] = 255 - np.transpose(np.floor(255 * np.arange(0, MR) / MR)) | |
| colorwheel[col:col+MR, 0] = 255 | |
| return colorwheel | |
| colorwheel = make_color_wheel() | |
| def compute_color(u, v): | |
| """ | |
| compute optical flow color map | |
| :param u: optical flow horizontal map | |
| :param v: optical flow vertical map | |
| :return: optical flow in color code | |
| """ | |
| [h, w] = u.shape | |
| img = np.zeros([h, w, 3]) | |
| nanIdx = np.isnan(u) | np.isnan(v) | |
| u[nanIdx] = 0 | |
| v[nanIdx] = 0 | |
| ncols = np.size(colorwheel, 0) | |
| rad = np.sqrt(u**2+v**2) | |
| a = np.arctan2(-v, -u) / np.pi | |
| fk = (a+1) / 2 * (ncols - 1) + 1 | |
| k0 = np.floor(fk).astype(int) | |
| k1 = k0 + 1 | |
| k1[k1 == ncols+1] = 1 | |
| f = fk - k0 | |
| for i in range(0, np.size(colorwheel,1)): | |
| tmp = colorwheel[:, i] | |
| col0 = tmp[k0-1] / 255 | |
| col1 = tmp[k1-1] / 255 | |
| col = (1-f) * col0 + f * col1 | |
| idx = rad <= 1 | |
| col[idx] = 1-rad[idx]*(1-col[idx]) | |
| notidx = np.logical_not(idx) | |
| col[notidx] *= 0.75 | |
| img[:, :, i] = np.uint8(np.floor(255 * col*(1-nanIdx))) | |
| return img | |
| def flow_to_image(flow): | |
| """ | |
| Convert flow into middlebury color code image | |
| :param flow: optical flow map | |
| :return: optical flow image in middlebury color | |
| """ | |
| u = flow[:, :, 0] | |
| v = flow[:, :, 1] | |
| maxu = -999. | |
| maxv = -999. | |
| minu = 999. | |
| minv = 999. | |
| idxUnknow = (abs(u) > UNKNOWN_FLOW_THRESH) | (abs(v) > UNKNOWN_FLOW_THRESH) | |
| u[idxUnknow] = 0 | |
| v[idxUnknow] = 0 | |
| maxu = max(maxu, np.max(u)) | |
| minu = min(minu, np.min(u)) | |
| maxv = max(maxv, np.max(v)) | |
| minv = min(minv, np.min(v)) | |
| rad = np.sqrt(u ** 2 + v ** 2) | |
| maxrad = max(-1, np.max(rad)) | |
| u = u/(maxrad + np.finfo(float).eps) | |
| v = v/(maxrad + np.finfo(float).eps) | |
| img = compute_color(u, v) | |
| idx = np.repeat(idxUnknow[:, :, np.newaxis], 3, axis=2) | |
| img[idx] = 0 | |
| return np.uint8(img) |