rgb.py

import matplotlib.pyplot as plt

def rgb(wavelength):
    if 645 <= wavelength <= 780:
        R, G, B = 1.0, 0.0, 0.0
    elif 580 <= wavelength <= 645:
        R, G, B = 1.0, -(wavelength - 645) / (645 - 580), 0.0
    elif 510 <= wavelength <= 580:
        R, G, B = (wavelength - 510) / (580 - 510), 1.0, 0.0
    elif 490 <= wavelength <= 510:
        R, G, B = 0.0, 1.0, -(wavelength - 510) / (510 - 490)
    elif 440 <= wavelength <= 490:
        R, G, B = 0.0, (wavelength - 440) / (490 - 440), 1.0
    elif 380 <= wavelength <= 440:
        R, G, B = -(wavelength - 440) / (440 - 380), 0.0, 1.0
    else:
        R = G = B = 0.0
    return (R, G, B)

def factor(wavelength):
    if 700 <= wavelength <= 780:
        factor = 0.3 + 0.7 * (780 - wavelength) / (780 - 700)
    elif 420 <= wavelength <= 700:
        factor = 1.0
    elif 380 <= wavelength <= 420:
        factor = 0.3 + 0.7 * (wavelength - 380) / (420 - 380)
    else:
        factor = 0.0
    return factor
    
wavelengths = range(380, 780)
colors = [tuple(map(lambda x: x * factor(w), rgb(w))) for w in wavelengths]

fig, ax = plt.subplots(figsize=(10, 2))
for i, color in enumerate(colors):
    ax.add_patch(plt.Rectangle((i, 0), 1, 1, color=color))
ax.set_xlim(0, len(colors))
ax.set_ylim(0, 1)
# ax.axis('off')
ax.set_xticks(range(0, len(colors) + 1, 50))
ax.set_xticklabels(range(wavelengths[0], wavelengths[-1] + 1, 50))
ax.set_yticks([])
ax.tick_params(axis='x', which='both', bottom=False, top=False)
plt.show()