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February 2, 2021 17:01
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| #!/usr/bin/env python | |
| # Demo a brightened luminance-only inversion on 8-bit images | |
| from skimage import io | |
| import numpy as np | |
| from sys import argv | |
| # RGB <-> YCoCg-R almost straight from Wikipedia | |
| def rgb_to_yog(rgb: np.array) -> np.array: | |
| R, G, B = rgb[..., 0], rgb[..., 1], rgb[..., 2] | |
| Co = R - B | |
| tmp = B + Co / 2 | |
| Cg = G - tmp | |
| Y = tmp + Cg / 2 | |
| return np.dstack([Y, Co, Cg]) | |
| def yog_to_rgb(yog: np.array) -> np.array: | |
| Y, Co, Cg = yog[..., 0], yog[..., 1], yog[..., 2] | |
| tmp = Y - Cg / 2 | |
| G = Cg + tmp | |
| B = tmp - Co / 2 | |
| R = B + Co | |
| return np.dstack([R, G, B]) | |
| def invert_y(yog: np.array) -> np.array: | |
| yog[..., 0] *= -1 | |
| yog[..., 0] += 1 | |
| return yog | |
| def apply_gamma(yog: np.array, gamma: float) -> np.array: | |
| yog[..., 0] **= gamma | |
| return yog | |
| def read(path: str) -> np.array: | |
| return io.imread(path).astype(np.float32) / 255 | |
| def write(path: str, img: np.array): | |
| img = np.clip(img * 255, 0, 255).astype(np.uint8) | |
| io.imsave(path, img) | |
| src_path, gamma, dst_path = argv[1:] | |
| src = read(src_path) | |
| gamma = float(gamma) | |
| yog = rgb_to_yog(src) | |
| yog = invert_y(yog) | |
| yog = apply_gamma(yog, gamma) | |
| rgb = yog_to_rgb(yog) | |
| write(dst_path, rgb) |
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