Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
Convert values between RGB hex codes and xterm-256 color codes.
#! /usr/bin/env python
""" Convert values between RGB hex codes and xterm-256 color codes.
Nice long listing of all 256 colors and their codes. Useful for
developing console color themes, or even script output schemes.
Resources:
* http://en.wikipedia.org/wiki/8-bit_color
* http://en.wikipedia.org/wiki/ANSI_escape_code
* /usr/share/X11/rgb.txt
I'm not sure where this script was inspired from. I think I must have
written it from scratch, though it's been several years now.
"""
__author__ = 'Micah Elliott http://MicahElliott.com'
__version__ = '0.1'
__copyright__ = 'Copyright (C) 2011 Micah Elliott. All rights reserved.'
__license__ = 'WTFPL http://sam.zoy.org/wtfpl/'
#---------------------------------------------------------------------
import sys, re
CLUT = [ # color look-up table
# 8-bit, RGB hex
# Primary 3-bit (8 colors). Unique representation!
('00', '000000'),
('01', '800000'),
('02', '008000'),
('03', '808000'),
('04', '000080'),
('05', '800080'),
('06', '008080'),
('07', 'c0c0c0'),
# Equivalent "bright" versions of original 8 colors.
('08', '808080'),
('09', 'ff0000'),
('10', '00ff00'),
('11', 'ffff00'),
('12', '0000ff'),
('13', 'ff00ff'),
('14', '00ffff'),
('15', 'ffffff'),
# Strictly ascending.
('16', '000000'),
('17', '00005f'),
('18', '000087'),
('19', '0000af'),
('20', '0000d7'),
('21', '0000ff'),
('22', '005f00'),
('23', '005f5f'),
('24', '005f87'),
('25', '005faf'),
('26', '005fd7'),
('27', '005fff'),
('28', '008700'),
('29', '00875f'),
('30', '008787'),
('31', '0087af'),
('32', '0087d7'),
('33', '0087ff'),
('34', '00af00'),
('35', '00af5f'),
('36', '00af87'),
('37', '00afaf'),
('38', '00afd7'),
('39', '00afff'),
('40', '00d700'),
('41', '00d75f'),
('42', '00d787'),
('43', '00d7af'),
('44', '00d7d7'),
('45', '00d7ff'),
('46', '00ff00'),
('47', '00ff5f'),
('48', '00ff87'),
('49', '00ffaf'),
('50', '00ffd7'),
('51', '00ffff'),
('52', '5f0000'),
('53', '5f005f'),
('54', '5f0087'),
('55', '5f00af'),
('56', '5f00d7'),
('57', '5f00ff'),
('58', '5f5f00'),
('59', '5f5f5f'),
('60', '5f5f87'),
('61', '5f5faf'),
('62', '5f5fd7'),
('63', '5f5fff'),
('64', '5f8700'),
('65', '5f875f'),
('66', '5f8787'),
('67', '5f87af'),
('68', '5f87d7'),
('69', '5f87ff'),
('70', '5faf00'),
('71', '5faf5f'),
('72', '5faf87'),
('73', '5fafaf'),
('74', '5fafd7'),
('75', '5fafff'),
('76', '5fd700'),
('77', '5fd75f'),
('78', '5fd787'),
('79', '5fd7af'),
('80', '5fd7d7'),
('81', '5fd7ff'),
('82', '5fff00'),
('83', '5fff5f'),
('84', '5fff87'),
('85', '5fffaf'),
('86', '5fffd7'),
('87', '5fffff'),
('88', '870000'),
('89', '87005f'),
('90', '870087'),
('91', '8700af'),
('92', '8700d7'),
('93', '8700ff'),
('94', '875f00'),
('95', '875f5f'),
('96', '875f87'),
('97', '875faf'),
('98', '875fd7'),
('99', '875fff'),
('100', '878700'),
('101', '87875f'),
('102', '878787'),
('103', '8787af'),
('104', '8787d7'),
('105', '8787ff'),
('106', '87af00'),
('107', '87af5f'),
('108', '87af87'),
('109', '87afaf'),
('110', '87afd7'),
('111', '87afff'),
('112', '87d700'),
('113', '87d75f'),
('114', '87d787'),
('115', '87d7af'),
('116', '87d7d7'),
('117', '87d7ff'),
('118', '87ff00'),
('119', '87ff5f'),
('120', '87ff87'),
('121', '87ffaf'),
('122', '87ffd7'),
('123', '87ffff'),
('124', 'af0000'),
('125', 'af005f'),
('126', 'af0087'),
('127', 'af00af'),
('128', 'af00d7'),
('129', 'af00ff'),
('130', 'af5f00'),
('131', 'af5f5f'),
('132', 'af5f87'),
('133', 'af5faf'),
('134', 'af5fd7'),
('135', 'af5fff'),
('136', 'af8700'),
('137', 'af875f'),
('138', 'af8787'),
('139', 'af87af'),
('140', 'af87d7'),
('141', 'af87ff'),
('142', 'afaf00'),
('143', 'afaf5f'),
('144', 'afaf87'),
('145', 'afafaf'),
('146', 'afafd7'),
('147', 'afafff'),
('148', 'afd700'),
('149', 'afd75f'),
('150', 'afd787'),
('151', 'afd7af'),
('152', 'afd7d7'),
('153', 'afd7ff'),
('154', 'afff00'),
('155', 'afff5f'),
('156', 'afff87'),
('157', 'afffaf'),
('158', 'afffd7'),
('159', 'afffff'),
('160', 'd70000'),
('161', 'd7005f'),
('162', 'd70087'),
('163', 'd700af'),
('164', 'd700d7'),
('165', 'd700ff'),
('166', 'd75f00'),
('167', 'd75f5f'),
('168', 'd75f87'),
('169', 'd75faf'),
('170', 'd75fd7'),
('171', 'd75fff'),
('172', 'd78700'),
('173', 'd7875f'),
('174', 'd78787'),
('175', 'd787af'),
('176', 'd787d7'),
('177', 'd787ff'),
('178', 'd7af00'),
('179', 'd7af5f'),
('180', 'd7af87'),
('181', 'd7afaf'),
('182', 'd7afd7'),
('183', 'd7afff'),
('184', 'd7d700'),
('185', 'd7d75f'),
('186', 'd7d787'),
('187', 'd7d7af'),
('188', 'd7d7d7'),
('189', 'd7d7ff'),
('190', 'd7ff00'),
('191', 'd7ff5f'),
('192', 'd7ff87'),
('193', 'd7ffaf'),
('194', 'd7ffd7'),
('195', 'd7ffff'),
('196', 'ff0000'),
('197', 'ff005f'),
('198', 'ff0087'),
('199', 'ff00af'),
('200', 'ff00d7'),
('201', 'ff00ff'),
('202', 'ff5f00'),
('203', 'ff5f5f'),
('204', 'ff5f87'),
('205', 'ff5faf'),
('206', 'ff5fd7'),
('207', 'ff5fff'),
('208', 'ff8700'),
('209', 'ff875f'),
('210', 'ff8787'),
('211', 'ff87af'),
('212', 'ff87d7'),
('213', 'ff87ff'),
('214', 'ffaf00'),
('215', 'ffaf5f'),
('216', 'ffaf87'),
('217', 'ffafaf'),
('218', 'ffafd7'),
('219', 'ffafff'),
('220', 'ffd700'),
('221', 'ffd75f'),
('222', 'ffd787'),
('223', 'ffd7af'),
('224', 'ffd7d7'),
('225', 'ffd7ff'),
('226', 'ffff00'),
('227', 'ffff5f'),
('228', 'ffff87'),
('229', 'ffffaf'),
('230', 'ffffd7'),
('231', 'ffffff'),
# Gray-scale range.
('232', '080808'),
('233', '121212'),
('234', '1c1c1c'),
('235', '262626'),
('236', '303030'),
('237', '3a3a3a'),
('238', '444444'),
('239', '4e4e4e'),
('240', '585858'),
('241', '626262'),
('242', '6c6c6c'),
('243', '767676'),
('244', '808080'),
('245', '8a8a8a'),
('246', '949494'),
('247', '9e9e9e'),
('248', 'a8a8a8'),
('249', 'b2b2b2'),
('250', 'bcbcbc'),
('251', 'c6c6c6'),
('252', 'd0d0d0'),
('253', 'dadada'),
('254', 'e4e4e4'),
('255', 'eeeeee'),
]
def _str2hex(hexstr):
return int(hexstr, 16)
def _strip_hash(rgb):
# Strip leading `#` if exists.
if rgb.startswith('#'):
rgb = rgb.lstrip('#')
return rgb
def _create_dicts():
short2rgb_dict = dict(CLUT)
rgb2short_dict = {}
for k, v in short2rgb_dict.items():
rgb2short_dict[v] = k
return rgb2short_dict, short2rgb_dict
def short2rgb(short):
return SHORT2RGB_DICT[short]
def print_all():
""" Print all 256 xterm color codes.
"""
for short, rgb in CLUT:
sys.stdout.write('\033[48;5;%sm%s:%s' % (short, short, rgb))
sys.stdout.write("\033[0m ")
sys.stdout.write('\033[38;5;%sm%s:%s' % (short, short, rgb))
sys.stdout.write("\033[0m\n")
print "Printed all codes."
print "You can translate a hex or 0-255 code by providing an argument."
def rgb2short(rgb):
""" Find the closest xterm-256 approximation to the given RGB value.
@param rgb: Hex code representing an RGB value, eg, 'abcdef'
@returns: String between 0 and 255, compatible with xterm.
>>> rgb2short('123456')
('23', '005f5f')
>>> rgb2short('ffffff')
('231', 'ffffff')
>>> rgb2short('0DADD6') # vimeo logo
('38', '00afd7')
"""
rgb = _strip_hash(rgb)
incs = (0x00, 0x5f, 0x87, 0xaf, 0xd7, 0xff)
# Break 6-char RGB code into 3 integer vals.
parts = [ int(h, 16) for h in re.split(r'(..)(..)(..)', rgb)[1:4] ]
res = []
for part in parts:
i = 0
while i < len(incs)-1:
s, b = incs[i], incs[i+1] # smaller, bigger
if s <= part <= b:
s1 = abs(s - part)
b1 = abs(b - part)
if s1 < b1: closest = s
else: closest = b
res.append(closest)
break
i += 1
#print '***', res
res = ''.join([ ('%02.x' % i) for i in res ])
equiv = RGB2SHORT_DICT[ res ]
#print '***', res, equiv
return equiv, res
RGB2SHORT_DICT, SHORT2RGB_DICT = _create_dicts()
#---------------------------------------------------------------------
if __name__ == '__main__':
import doctest
doctest.testmod()
if len(sys.argv) == 1:
print_all()
raise SystemExit
arg = sys.argv[1]
if len(arg) < 4 and int(arg) < 256:
rgb = short2rgb(arg)
sys.stdout.write('xterm color \033[38;5;%sm%s\033[0m -> RGB exact \033[38;5;%sm%s\033[0m' % (arg, arg, arg, rgb))
sys.stdout.write("\033[0m\n")
else:
short, rgb = rgb2short(arg)
sys.stdout.write('RGB %s -> xterm color approx \033[38;5;%sm%s (%s)' % (arg, short, short, rgb))
sys.stdout.write("\033[0m\n")
@paultag

This comment has been minimized.

Copy link

paultag commented Dec 1, 2011

Used this on a little side hack, thanks!

@MicahElliott

This comment has been minimized.

Copy link
Owner Author

MicahElliott commented Dec 1, 2011

Hey Paul. NP! This is a fun little conversion. The "color look-up table" should probably be generated instead of enumerated. Anyway, it's a nice little CLI util I've used often for translating.

@alissonsales

This comment has been minimized.

Copy link

alissonsales commented Jan 26, 2012

Thanks for this, I'm using this color table in a javascript script to colorize bash output. Did you type all these colors or is there a source or way to generate the xterm 256 color table?

@noprompt

This comment has been minimized.

Copy link

noprompt commented Feb 23, 2012

I'd like to say thanks as well! If I had not stumbled across your gist I probably wouldn't have been able to take my project to the next level. Really appreciated it!

I was able to generate most of the table using Ruby 1.9.2 array method repeated_permutations and a few other tricks.

@amcgregor

This comment has been minimized.

Copy link

amcgregor commented Dec 4, 2012

For a single direction conversion that ignores the grayscale strip and base 16 colours (obviously not optimal, but you can do those two in fast initial passes), you can use a simple colorcube transform given RGB in the range [0, 1]:

round(36 * (r * 5) + 6 * (g * 5) + (b * 5) + 16)

:)

@amcgregor

This comment has been minimized.

Copy link

amcgregor commented Dec 4, 2012

A variant that accepts a hex triplet named rgb:

round(36 * (int(rgb[:2], 16) * 5) + 6 * (int(rgb[2:4], 16) * 5) + (int(rgb[4:], 16) * 5) + 16)
@eri451

This comment has been minimized.

Copy link

eri451 commented Jun 4, 2013

very nice thanks a lot

@guolas

This comment has been minimized.

Copy link

guolas commented Jul 2, 2013

Thank you for this super handy tool!

@athaeryn

This comment has been minimized.

Copy link

athaeryn commented Jul 19, 2013

This is awesome! I ported it to Ruby to use on a little side project, although I only kept the functionality of hex -> xterm.

@ifonefox

This comment has been minimized.

Copy link

ifonefox commented Jul 20, 2013

I made some very slight modifications to make it work with python3.3. All you have to do is change it to the new print() function.

https://gist.github.com/ifonefox/6046257

@baverman

This comment has been minimized.

Copy link

baverman commented Jan 23, 2014

Bug: #242424 -> 16, should be 235

@ghost

This comment has been minimized.

Copy link

ghost commented Mar 17, 2014

262626 returns 0 instead of 235

@TerrorBite

This comment has been minimized.

Copy link

TerrorBite commented Apr 29, 2015

I admit to being a bit bewildered by the nested loops and complexity in your rgb2short function.

My own attempt (which I wrote before seeing yours) is somewhat briefer:

# Default color levels for the color cube
cubelevels = [0x00, 0x5f, 0x87, 0xaf, 0xd7, 0xff]
# Generate a list of midpoints of the above list
snaps = [(x+y)/2 for x, y in zip(cubelevels, [0]+cubelevels)[1:]]

def rgb2short(r, g, b):
    """ Converts RGB values to the nearest equivalent xterm-256 color.
    """
    # Using list of snap points, convert RGB value to cube indexes
    r, g, b = map(lambda x: len(tuple(s for s in snaps if s<x)), (r, g, b))
    # Simple colorcube transform
    return r*36 + g*6 + b + 16
@joeytwiddle

This comment has been minimized.

Copy link

joeytwiddle commented Sep 2, 2016

A recommendation for anyone wanting to do this "perfectly": It is preferable to calculate distances in YUV or CIE94 than in RGB.

Distances in the YUV and CIE94 colorspaces more closely match distances in human perception. So using one of those should output colors which appear (to our eyes) to be more similar to the input colors.

YUV is often used for image and video encoding. CIE94 is the more accurate, but YUV is faster/easier to calculate and still a good approximation.

Having said that, when quantizing as coarsely as we are here, doing this will only occasionally produce different results.

@sherifkandeel

This comment has been minimized.

Copy link

sherifkandeel commented Sep 9, 2016

I love it, specially the approx. part. cheers mate, you're awesome

@dkarter

This comment has been minimized.

Copy link

dkarter commented Sep 21, 2016

Great script thanks for sharing!

@chadj2

This comment has been minimized.

Copy link

chadj2 commented Apr 3, 2017

See this doc for an explanation of how to convert to/from SGR codes to RGB and how to manipulate RGB and HSV in Bash.
https://github.com/chadj2/bash-ui/blob/master/COLORS.md#xterm-colorspaces

@kylie-a

This comment has been minimized.

Copy link

kylie-a commented Mar 8, 2019

Thanks for writing this, I've included it in a project of mine as a utility script. I've credited you in the README and added an annotation to the script itself. If you'd like me to add credit in a different way or to not include it in my package please let me know.

Thanks for writing this :-)

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.