color_stuff.py

#!/usr/bin/env python

# color_stuff.py
# Jim Bagrow
# Last Modified: 2016-12-01

import colorsys

def distinguishable_colors(num, sat=1.0, val=1.0):
    """Generate a list of `num' rgb hexadecimal color strings. The strings are
    linearly spaced along hue values from 0 to 1, leading to `num' colors with
    maximally different hues.
    
    Example:
    >>> print(distinguishable_colors(5))
    ['#ff0000', '#ccff00', '#00ff66', '#0066ff', '#cc00ff']
    """
    list_colors = [];
    hue = 0.0
    while abs(hue - 1.0) > 1e-4:
        rgb = [i for i in list(colorsys.hsv_to_rgb(hue, sat, val))]
        list_colors.append( rgb_to_hex(rgb) )
        hue += 1.0/num;
    return list_colors


def rgb_to_hex(rgb):
    """Convert an rgb 3-tuple to a hexadecimal color string.
    
    Example:
    >>> print(rgb_to_hex((0.50,0.2,0.8)))
    #8033cc
    """
    return '#%02x%02x%02x' % tuple([round(x*255) for x in rgb])


def hex_to_rgb(hexrgb):
    """ Convert a hexadecimal color string to an rgb 3-tuple.
    
    Example:
    >>> print(hex_to_rgb("#8033CC"))
    (0.502, 0.2, 0.8)
    """
    hexrgb = hexrgb.lstrip('#')
    lv = len(hexrgb)
    return tuple(round(int(hexrgb[i:i+lv/3], 16)/255.0,4) for i in range(0, lv, lv/3))


def darken_hex(hexrgb, factor=0.5):
    """Take an rgb color of the form #RRGGBB and darken it by `factor' without
    changing the color. Specifically the RGB is converted to HSV and V ->
    V*factor.
    
    Example:
    >>> print(darken_hex("#8033CC"))
    '#401966'
    """
    rgb = hex_to_rgb(hexrgb)
    hsv = list(colorsys.rgb_to_hsv(*rgb))
    hsv[2] = hsv[2]*factor
    rgb = colorsys.hsv_to_rgb(*hsv)
    return rgb_to_hex(rgb)


def darken_rgb(rgb, factor=0.5):
    """Take an rgb 3-tuple and darken it by `factor', approximately
    preserving the hue.
    
    Example:
    >>> print(darken_rgb((0.5,0.2,0.7)))
    (0.251, 0.098, 0.3529)
    """
    hexrgb = darken_hex(rgb_to_hex(rgb), factor=factor)
    return hex_to_rgb(hexrgb)


if __name__ == '__main__':
    print(darken_rgb((0.5,0.2,0.7)) )
    print(darken_hex("#8033CC"))
    print(hex_to_rgb("#8033CC") )
    print(rgb_to_hex((0.50,0.2,0.8)))
    print(distinguishable_colors(5))