Take fullcolor image and constrain it to dictionary of colors

Question

I'm using Python, and've got a dictionary like this.

COLORTABLE = {
0: (0, 0, 0),
1: (109, 111, 113),
2: (7, 145, 205),
3: (105, 156, 65),
4: (244, 126, 32),
5: (214, 22, 59),
6: (110, 26, 17),
7: (248, 222, 215),
8: (255, 255, 255),
9: (209, 211, 212),
10: (115, 207, 242),
11: (155, 204, 102),
12: (255, 236, 0),
13: (214, 128, 170),
14: (129, 36, 104),
15: (142, 104, 76),
}

How do I take an RGB tuple and match it to the closest tuple in the dictionary?

Should I loop through for each element in the source and find the closest match? This seems rather inefficient.

Answer 1

I did this:

HEXATABLE = {}
for key, value in COLORTABLE.items():
    HEXATABLE[key] = rgb2hex(value)

def rgb2hex(rgb):
    return (rgb[0] << 16) + (rgb[1] << 8) + rgb[2];

def hex2rgb(hexcolor):
    r = ( hexcolor >> 16 ) & 0xFF;

    g = ( hexcolor >> 8 ) & 0xFF;

    b = hexcolor & 0xFF;

    return r, g, b

def takeClosest(num,collection):
   return min(collection,key=lambda x:abs(x-num))


for x in range(img.get_width()):
    for y in range(img.get_height()):
        color = rgb2hex(tuple(img.get_at((x, y))))
        newcolor = hex2rgb(takeClosest(color, HEXATABLE.values()))

Cobbled together out of chunks of code from StackOverflow.