python - calculate RGB equivalent of base colors with alpha of 0.5 over white background in matplotlib -

i able replicate of primary color ('r','g' or 'b') in matplotlib alpha of 0.5 on white background, while keeping alpha @ 1.

here example below, through manual experimentation i've found rgb values alpha of 1, similar matplotlib default colors alpha 0.5.

i wondering if had automated way of achieving this.

import matplotlib.pyplot plt  s=1000  plt.xlim([4,8]) plt.ylim([0,10])  red=(1,0.55,0.55) blue=(0.55,0.55,1) green=(0.54,0.77,0.56)  plt.scatter([5],[5],c='r',edgecolors='none',s=s,alpha=0.5,marker='s') plt.scatter([6],[5],c='b',edgecolors='none',s=s,alpha=0.5,marker='s') plt.scatter([7],[5],c='g',edgecolors='none',s=s,alpha=0.5,marker='s')  plt.scatter([5],[5.915],c=red,edgecolors='none',s=s,marker='s') plt.scatter([6],[5.915],c=blue,edgecolors='none',s=s,marker='s') plt.scatter([7],[5.915],c=green,edgecolors='none',s=s,marker='s') 

edit: can use formula this answer

converted python, looks this:

def make_rgb_transparent(rgb, bg_rgb, alpha):     return [alpha * c1 + (1 - alpha) * c2             (c1, c2) in zip(rgb, bg_rgb)] 

so can do:

red = [1, 0, 0] white = [1, 1, 1] alpha = 0.5  make_rgb_transparent(red, white, alpha) # [1.0, 0.5, 0.5] 

using function now, can create plot confirms works:

from matplotlib import colors import matplotlib.pyplot plt  alpha = 0.5  kwargs = dict(edgecolors='none', s=3900, marker='s') i, color in enumerate(['red', 'blue', 'green']):     rgb = colors.colorconverter.to_rgb(color)     rgb_new = make_rgb_transparent(rgb, (1, 1, 1), alpha)     print(color, rgb, rgb_new)     plt.scatter([i], [0], color=color, **kwargs)     plt.scatter([i], [1], color=color, alpha=alpha, **kwargs)     plt.scatter([i], [2], color=rgb_new, **kwargs)