Question: Percentage of each color in the palette

Hi, first of all. I would like to thank you for making this library. But how can I determine the corresponding percentages or how much each color makes up the image? For instance, if black was detected and was dominant in the image, it comprises 0.80 or 80% of the image. Perhaps the ranking of the colors in the palette if there is a method for it.

I hope for your response regarding my question. Thank you again.