Convert HEX to the nearest X11 color number

Question

I am looking for an algorithm / method to convert this HEX (for example, # 111111 R: 0x11, G: 0x11, B: 0x11) to the nearest X11 color number (the terminal has either 88 or 256 colors) using either Python, PHP or VIM script, and I was wondering if anyone knew a way about this or would point in that direction.

Thanks at Advance.

Answer 1

I had the same problem (taking an existing vim color scheme with gvim hex colors and filling in terminal color values). Here is the scenario I used (although the ColorDist function is likely to benefit from a better color distance metric, as some other posters suggest)

import re import math colors = { '000000': '16', '00005f': '17', '000087': '18', '0000af': '19', '0000d7': '20', '0000ff': '21', '005f00': '22', '005f5f': '23', '005f87': '24', '005faf': '25', '005fd7': '26', '005fff': '27', '008700': '28', '00875f': '29', '008787': '30', '0087af': '31', '0087d7': '32', '0087ff': '33', '00af00': '34', '00af5f': '35', '00af87': '36', '00afaf': '37', '00afd7': '38', '00afff': '39', '00d700': '40', '00d75f': '41', '00d787': '42', '00d7af': '43', '00d7d7': '44', '00d7ff': '45', '00ff00': '46', '00ff5f': '47', '00ff87': '48', '00ffaf': '49', '00ffd7': '50', '00ffff': '51', '5f0000': '52', '5f005f': '53', '5f0087': '54', '5f00af': '55', '5f00d7': '56', '5f00ff': '57', '5f5f00': '58', '5f5f5f': '59', '5f5f87': '60', '5f5faf': '61', '5f5fd7': '62', '5f5fff': '63', '5f8700': '64', '5f875f': '65', '5f8787': '66', '5f87af': '67', '5f87d7': '68', '5f87ff': '69', '5faf00': '70', '5faf5f': '71', '5faf87': '72', '5fafaf': '73', '5fafd7': '74', '5fafff': '75', '5fd700': '76', '5fd75f': '77', '5fd787': '78', '5fd7af': '79', '5fd7d7': '80', '5fd7ff': '81', '5fff00': '82', '5fff5f': '83', '5fff87': '84', '5fffaf': '85', '5fffd7': '86', '5fffff': '87', '870000': '88', '87005f': '89', '870087': '90', '8700af': '91', '8700d7': '92', '8700ff': '93', '875f00': '94', '875f5f': '95', '875f87': '96', '875faf': '97', '875fd7': '98', '875fff': '99', '878700': '100', '87875f': '101', '878787': '102', '8787af': '103', '8787d7': '104', '8787ff': '105', '87af00': '106', '87af5f': '107', '87af87': '108', '87afaf': '109', '87afd7': '110', '87afff': '111', '87d700': '112', '87d75f': '113', '87d787': '114', '87d7af': '115', '87d7d7': '116', '87d7ff': '117', '87ff00': '118', '87ff5f': '119', '87ff87': '120', '87ffaf': '121', '87ffd7': '122', '87ffff': '123', 'af0000': '124', 'af005f': '125', 'af0087': '126', 'af00af': '127', 'af00d7': '128', 'af00ff': '129', 'af5f00': '130', 'af5f5f': '131', 'af5f87': '132', 'af5faf': '133', 'af5fd7': '134', 'af5fff': '135', 'af8700': '136', 'af875f': '137', 'af8787': '138', 'af87af': '139', 'af87d7': '140', 'af87ff': '141', 'afaf00': '142', 'afaf5f': '143', 'afaf87': '144', 'afafaf': '145', 'afafd7': '146', 'afafff': '147', 'afd700': '148', 'afd75f': '149', 'afd787': '150', 'afd7af': '151', 'afd7d7': '152', 'afd7ff': '153', 'afff00': '154', 'afff5f': '155', 'afff87': '156', 'afffaf': '157', 'afffd7': '158', 'afffff': '159', 'd70000': '160', 'd7005f': '161', 'd70087': '162', 'd700af': '163', 'd700d7': '164', 'd700ff': '165', 'd75f00': '166', 'd75f5f': '167', 'd75f87': '168', 'd75faf': '169', 'd75fd7': '170', 'd75fff': '171', 'd78700': '172', 'd7875f': '173', 'd78787': '174', 'd787af': '175', 'd787d7': '176', 'd787ff': '177', 'd7af00': '178', 'd7af5f': '179', 'd7af87': '180', 'd7afaf': '181', 'd7afd7': '182', 'd7afff': '183', 'd7d700': '184', 'd7d75f': '185', 'd7d787': '186', 'd7d7af': '187', 'd7d7d7': '188', 'd7d7ff': '189', 'd7ff00': '190', 'd7ff5f': '191', 'd7ff87': '192', 'd7ffaf': '193', 'd7ffd7': '194', 'd7ffff': '195', 'ff0000': '196', 'ff005f': '197', 'ff0087': '198', 'ff00af': '199', 'ff00d7': '200', 'ff00ff': '201', 'ff5f00': '202', 'ff5f5f': '203', 'ff5f87': '204', 'ff5faf': '205', 'ff5fd7': '206', 'ff5fff': '207', 'ff8700': '208', 'ff875f': '209', 'ff8787': '210', 'ff87af': '211', 'ff87d7': '212', 'ff87ff': '213', 'ffaf00': '214', 'ffaf5f': '215', 'ffaf87': '216', 'ffafaf': '217', 'ffafd7': '218', 'ffafff': '219', 'ffd700': '220', 'ffd75f': '221', 'ffd787': '222', 'ffd7af': '223', 'ffd7d7': '224', 'ffd7ff': '225', 'ffff00': '226', 'ffff5f': '227', 'ffff87': '228', 'ffffaf': '229', 'ffffd7': '230', 'ffffff': '231', '080808': '232', '121212': '233', '1c1c1c': '234', '262626': '235', '303030': '236', '3a3a3a': '237', '444444': '238', '4e4e4e': '239', '585858': '240', '626262': '241', '6c6c6c': '242', '767676': '243', '808080': '244', '8a8a8a': '245', '949494': '246', '9e9e9e': '247', 'a8a8a8': '248', 'b2b2b2': '249', 'bcbcbc': '250', 'c6c6c6': '251', 'd0d0d0': '252', 'dadada': '253', 'e4e4e4': '254', 'eeeeee': '255', } ## Example line from a vim colorscheme file ##hi Normal ctermfg=NONE ctermbg=NONE gui=NONE guifg=#b7af9f guibg=#202020 def Decompose(hexval): return float(int(hexval[0:2], 16)), float(int(hexval[2:4], 16)), float(int(hexval[4:6], 16)) def Normalize(r, g, b): magsqr = r*r + g*g + b*b if magsqr < 0.0001: return 0.0, 0.0, 0.0 n = 1.0 / math.sqrt(magsqr) return r*n, g*n, b*n def ColorDist(c1, c2): c1r, c1g, c1b = Decompose(c1) c2r, c2g, c2b = Decompose(c2) dr = c1r - c2r dg = c1g - c2g db = c1b - c2b return dr*dr + dg*dg + db*db def BestMatch(hexval): best = None bestdist = 0.0 for key in colors.keys(): dist = ColorDist(hexval, key) if best is None or dist < bestdist: best = colors[key] bestdist = dist return best ## 1 2 3 4 5 6 fg = re.compile(r'^(.*)(ctermfg=)NONE(.*)(guifg=#)([^ ]*)(.*)\n$') bg = re.compile(r'^(.*)(ctermbg=)NONE(.*)(guibg=#)([^ ]*)(.*)\n$') with open(r'input_color_scheme.vim', 'r') as f: with open(r'output_color_scheme.vim', 'w') as fout: for line in f.readlines(): fgmatch = fg.match(line) if fgmatch is not None: line = (fgmatch.group(1) + fgmatch.group(2) + BestMatch(fgmatch.group(5)) + fgmatch.group(3) + fgmatch.group(4) + fgmatch.group(5) + fgmatch.group(6)) + '\n' bgmatch = bg.match(line) if bgmatch is not None: line = (bgmatch.group(1) + bgmatch.group(2) + BestMatch(bgmatch.group(5)) + bgmatch.group(3) + bgmatch.group(4) + bgmatch.group(5) + bgmatch.group(6) + '\n') ## -- print the line fout.write(line) 

Answer 2

Go to Wolfram Alpha , enter your hex value, i.e. "#acdffa". Go to the "HTML Colors with Nearby Names" section

I know this is not code, but you said “algorithm / path”.

Hurrah

Answer 3

This is an implementation of C, although it is easy to convert to other languages, but note that it uses integer arithmetic:

 // Convert RGB24 to xterm-256 8-bit value // For simplicity, assume RGB space is perceptually uniform. // There are 5 places where one of two outputs needs to be chosen when the // input is the exact middle: // - The r/g/b channels and the gray value: the higher value output is chosen. // - If the gray and color have same distance from the input - color is chosen. static int rgb_to_x256(uint8_t r, uint8_t g, uint8_t b) { // Calculate the nearest 0-based color index at 16 .. 231 # define v2ci(v) (v < 48 ? 0 : v < 115 ? 1 : (v - 35) / 40) int ir = v2ci(r), ig = v2ci(g), ib = v2ci(b); // 0..5 each # define color_index() (36 * ir + 6 * ig + ib) /* 0..215, lazy evaluation */ // Calculate the nearest 0-based gray index at 232 .. 255 int average = (r + g + b) / 3; int gray_index = average > 238 ? 23 : (average - 3) / 10; // 0..23 // Calculate the represented colors back from the index static const int i2cv[6] = {0, 0x5f, 0x87, 0xaf, 0xd7, 0xff}; int cr = i2cv[ir], cg = i2cv[ig], cb = i2cv[ib]; // r/g/b, 0..255 each int gv = 8 + 10 * gray_index; // same value for r/g/b, 0..255 // Return the one which is nearer to the original input rgb value # define dist_square(A,B,C, a,b,c) ((Aa)*(Aa) + (Bb)*(Bb) + (Cc)*(Cc)) int color_err = dist_square(cr, cg, cb, r, g, b); int gray_err = dist_square(gv, gv, gv, r, g, b); return color_err <= gray_err ? 16 + color_index() : 232 + gray_index; } 

This is the same implementation that is currently used by tmux and mpv . You can find some explanation of the algorithm in tmux port request on github .

Answer 4

Once you know the RGB values ​​of the X11 colors , you can determine which of these colors the given input color is “closest to.”

There is a good, quick measurement of the distance between colors.

fooobar.com/questions/38353 / ...