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@MicahElliott
Created November 29, 2010 07:57
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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")
@Bedfford
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Thanks for the info! I wonder if exist a pure mathematical formula to get the conversion RGB to the nearest ANSI 256 color code. I would to like implement under C.

@adamerose
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Here's a web UI I made to do this conversion
https://hm66hd.csb.app/

image

@ttntm
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ttntm commented Mar 21, 2024

Here's a web UI I made to do this conversion https://hm66hd.csb.app/

Thanks for that, quite helpful!

@epheien
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epheien commented Jun 9, 2024

buggy script, the 256-color conversion is all wrong

@epheien
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epheien commented Jun 9, 2024

Here's a web UI I made to do this conversion https://hm66hd.csb.app/

image

this is correct converter, but cannot found source code

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