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| # Author: Bingxin Ke | |
| # Last modified: 2024-02-19 | |
| from pylab import count_nonzero, clip, np | |
| # Adapted from https://github.com/apple/ml-hypersim/blob/main/code/python/tools/scene_generate_images_tonemap.py | |
| def tone_map(rgb, entity_id_map): | |
| assert (entity_id_map != 0).all() | |
| gamma = 1.0 / 2.2 # standard gamma correction exponent | |
| inv_gamma = 1.0 / gamma | |
| percentile = ( | |
| 90 # we want this percentile brightness value in the unmodified image... | |
| ) | |
| brightness_nth_percentile_desired = 0.8 # ...to be this bright after scaling | |
| valid_mask = entity_id_map != -1 | |
| if count_nonzero(valid_mask) == 0: | |
| scale = 1.0 # if there are no valid pixels, then set scale to 1.0 | |
| else: | |
| brightness = ( | |
| 0.3 * rgb[:, :, 0] + 0.59 * rgb[:, :, 1] + 0.11 * rgb[:, :, 2] | |
| ) # "CCIR601 YIQ" method for computing brightness | |
| brightness_valid = brightness[valid_mask] | |
| eps = 0.0001 # if the kth percentile brightness value in the unmodified image is less than this, set the scale to 0.0 to avoid divide-by-zero | |
| brightness_nth_percentile_current = np.percentile(brightness_valid, percentile) | |
| if brightness_nth_percentile_current < eps: | |
| scale = 0.0 | |
| else: | |
| # Snavely uses the following expression in the code at https://github.com/snavely/pbrs_tonemapper/blob/master/tonemap_rgbe.py: | |
| # scale = np.exp(np.log(brightness_nth_percentile_desired)*inv_gamma - np.log(brightness_nth_percentile_current)) | |
| # | |
| # Our expression below is equivalent, but is more intuitive, because it follows more directly from the expression: | |
| # (scale*brightness_nth_percentile_current)^gamma = brightness_nth_percentile_desired | |
| scale = ( | |
| np.power(brightness_nth_percentile_desired, inv_gamma) | |
| / brightness_nth_percentile_current | |
| ) | |
| rgb_color_tm = np.power(np.maximum(scale * rgb, 0), gamma) | |
| rgb_color_tm = clip(rgb_color_tm, 0, 1) | |
| return rgb_color_tm | |
| # According to https://github.com/apple/ml-hypersim/issues/9 | |
| def dist_2_depth(width, height, flt_focal, distance): | |
| img_plane_x = ( | |
| np.linspace((-0.5 * width) + 0.5, (0.5 * width) - 0.5, width) | |
| .reshape(1, width) | |
| .repeat(height, 0) | |
| .astype(np.float32)[:, :, None] | |
| ) | |
| img_plane_y = ( | |
| np.linspace((-0.5 * height) + 0.5, (0.5 * height) - 0.5, height) | |
| .reshape(height, 1) | |
| .repeat(width, 1) | |
| .astype(np.float32)[:, :, None] | |
| ) | |
| img_plane_z = np.full([height, width, 1], flt_focal, np.float32) | |
| img_plane = np.concatenate([img_plane_x, img_plane_y, img_plane_z], 2) | |
| depth = distance / np.linalg.norm(img_plane, 2, 2) * flt_focal | |
| return depth | |