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colorspace.py
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import numpy as np
def rgb_to_hcy(rgb_arr):
"""
Convert image from the red (R), green (G), blue (B) color space to the hue (H), chroma (C), luma (Y) color space.
:param rgb_arr: a uint8 numpy array with shape (N, M, 3), where N is the image height and M is the width.
:return: a (N, M, 3) numpy array in the HCY color space
"""
# Convert 8-bit values to floating point
rgb_arr = rgb_arr / 255
red = rgb_arr[:, :, 0]
green = rgb_arr[:, :, 1]
blue = rgb_arr[:, :, 2]
chroma = np.max(rgb_arr, axis=2) - np.min(rgb_arr, axis=2)
luma = 0.30 * red + 0.59 * green + 0.11 * blue
hue = np.zeros(red.shape)
red_is_max = (red == np.max(rgb_arr, axis=2)) & (chroma > 0)
green_is_max = (green == np.max(rgb_arr, axis=2)) & (chroma > 0)
blue_is_max = (blue == np.max(rgb_arr, axis=2)) & (chroma > 0)
hue[red_is_max] = 60 * (green[red_is_max] - blue[red_is_max]) / chroma[red_is_max]
hue[green_is_max] = 60 * (2 + (blue[green_is_max] - red[green_is_max]) / chroma[green_is_max])
hue[blue_is_max] = 60 * (4 + (red[blue_is_max] - green[blue_is_max]) / chroma[blue_is_max])
hue[hue < 0] += 360
return np.stack((hue, chroma, luma), axis=2)
def hcy_to_rgb(hcy_arr):
"""
Convert image from the hue (H), chroma (C), luma (Y) color space to the red (R), green (G), blue (B) color space.
:param hcy_arr: a numpy array with shape (N, M, 3), where N is the image height and M is the width.
:return: a (N, M, 3) uint8 numpy array in the RGB color space
"""
hue = hcy_arr[:, :, 0]
chroma = hcy_arr[:, :, 1]
luma = hcy_arr[:, :, 2]
hue_prime = hue / 60
X = chroma * (1 - np.abs(np.mod(hue_prime, 2) - 1))
red_1 = np.zeros(hcy_arr.shape[:2])
green_1 = np.zeros(hcy_arr.shape[:2])
blue_1 = np.zeros(hcy_arr.shape[:2])
red_1[(hue_prime >= 0) & (hue_prime <= 1)] = chroma[(hue_prime >= 0) & (hue_prime <= 1)]
green_1[(hue_prime >= 0) & (hue_prime <= 1)] = X[(hue_prime >= 0) & (hue_prime <= 1)]
red_1[(hue_prime > 1) & (hue_prime <= 2)] = X[(hue_prime > 1) & (hue_prime <= 2)]
green_1[(hue_prime > 1) & (hue_prime <= 2)] = chroma[(hue_prime > 1) & (hue_prime <= 2)]
blue_1[(hue_prime > 2) & (hue_prime <= 3)] = X[(hue_prime > 2) & (hue_prime <= 3)]
green_1[(hue_prime > 2) & (hue_prime <= 3)] = chroma[(hue_prime > 2) & (hue_prime <= 3)]
blue_1[(hue_prime > 3) & (hue_prime <= 4)] = chroma[(hue_prime > 3) & (hue_prime <= 4)]
green_1[(hue_prime > 3) & (hue_prime <= 4)] = X[(hue_prime > 3) & (hue_prime <= 4)]
blue_1[(hue_prime > 4) & (hue_prime <= 5)] = chroma[(hue_prime > 4) & (hue_prime <= 5)]
red_1[(hue_prime > 4) & (hue_prime <= 5)] = X[(hue_prime > 4) & (hue_prime <= 5)]
blue_1[(hue_prime > 5) & (hue_prime <= 6)] = X[(hue_prime > 5) & (hue_prime <= 6)]
red_1[(hue_prime > 5) & (hue_prime <= 6)] = chroma[(hue_prime > 5) & (hue_prime <= 6)]
m = luma - (0.3 * red_1 + 0.59 * green_1 + 0.11 * blue_1)
rgb_arr = (np.stack((red_1 + m, green_1 + m, blue_1 + m), axis=2) * 255).round()
rgb_arr = rgb_arr.round()
rgb_arr[rgb_arr > 255] = 255
rgb_arr[rgb_arr < 0] = 0
return rgb_arr.astype('uint8')