"""Color Database. This file contains one class, called ColorDB, and several utility functions. The class must be instantiated by the get_colordb() function in this file, passing it a filename to read a database out of. The get_colordb() function will try to examine the file to figure out what the format of the file is. If it can't figure out the file format, or it has trouble reading the file, None is returned. You can pass get_colordb() an optional filetype argument. Supporte file types are: X_RGB_TXT -- X Consortium rgb.txt format files. Three columns of numbers from 0 .. 255 separated by whitespace. Arbitrary trailing columns used as the color name. The utility functions are useful for converting between the various expected color formats, and for calculating other color values. """ import sys import re from types import * import operator class BadColor(Exception): pass DEFAULT_DB = None SPACE = ' ' COMMASPACE = ', '  # generic class class ColorDB: def __init__(self, fp): lineno = 2 self.__name = fp.name # Maintain several dictionaries for indexing into the color database. # Note that while Tk supports RGB intensities of 4, 8, 12, or 16 bits, # for now we only support 8 bit intensities. At least on OpenWindows, # all intensities in the /usr/openwin/lib/rgb.txt file are 8-bit # # key is (red, green, blue) tuple, value is (name, [aliases]) self.__byrgb = {} # key is name, value is (red, green, blue) self.__byname = {} # all unique names (non-aliases). built-on demand self.__allnames = None for line in fp: # get this compiled regular expression from derived class mo = self._re.match(line) if not mo: print >> sys.stderr, 'Error in', fp.name, ' line', lineno lineno += 1 continue # extract the red, green, blue, and name red, green, blue = self._extractrgb(mo) name = self._extractname(mo) keyname = name.lower() # BAW: for now the `name' is just the first named color with the # rgb values we find. Later, we might want to make the two word # version the `name', or the CapitalizedVersion, etc. key = (red, green, blue) foundname, aliases = self.__byrgb.get(key, (name, [])) if foundname <> name and foundname not in aliases: aliases.append(name) self.__byrgb[key] = (foundname, aliases) # add to byname lookup self.__byname[keyname] = key lineno = lineno + 1 # override in derived classes def _extractrgb(self, mo): return [int(x) for x in mo.group('red', 'green', 'blue')] def _extractname(self, mo): return mo.group('name') def filename(self): return self.__name def find_byrgb(self, rgbtuple): """Return name for rgbtuple""" try: return self.__byrgb[rgbtuple] except KeyError: raise BadColor(rgbtuple) def find_byname(self, name): """Return (red, green, blue) for name""" name = name.lower() try: return self.__byname[name] except KeyError: raise BadColor(name) def nearest(self, red, green, blue): """Return the name of color nearest (red, green, blue)""" # BAW: should we use Voronoi diagrams, Delaunay triangulation, or # octree for speeding up the locating of nearest point? Exhaustive # search is inefficient, but seems fast enough. nearest = -1 nearest_name = '' for name, aliases in self.__byrgb.values(): r, g, b = self.__byname[name.lower()] rdelta = red - r gdelta = green - g bdelta = blue - b distance = rdelta * rdelta + gdelta * gdelta + bdelta * bdelta if nearest == -1 or distance < nearest: nearest = distance nearest_name = name return nearest_name def unique_names(self): # sorted if not self.__allnames: self.__allnames = [] for name, aliases in self.__byrgb.values(): self.__allnames.append(name) # sort irregardless of case def nocase_cmp(n1, n2): return cmp(n1.lower(), n2.lower()) self.__allnames.sort(nocase_cmp) return self.__allnames def aliases_of(self, red, green, blue): try: name, aliases = self.__byrgb[(red, green, blue)] except KeyError: raise BadColor((red, green, blue)) return [name] + aliases  class RGBColorDB(ColorDB): _re = re.compile( '\s*(?P\d+)\s+(?P\d+)\s+(?P\d+)\s+(?P.*)') class HTML40DB(ColorDB): _re = re.compile('(?P\S+)\s+(?P#[0-9a-fA-F]{6})') def _extractrgb(self, mo): return rrggbb_to_triplet(mo.group('hexrgb')) class LightlinkDB(HTML40DB): _re = re.compile('(?P(.+))\s+(?P#[0-9a-fA-F]{6})') def _extractname(self, mo): return mo.group('name').strip() class WebsafeDB(ColorDB): _re = re.compile('(?P#[0-9a-fA-F]{6})') def _extractrgb(self, mo): return rrggbb_to_triplet(mo.group('hexrgb')) def _extractname(self, mo): return mo.group('hexrgb').upper()  # format is a tuple (RE, SCANLINES, CLASS) where RE is a compiled regular # expression, SCANLINES is the number of header lines to scan, and CLASS is # the class to instantiate if a match is found FILETYPES = [ (re.compile('Xorg'), RGBColorDB), (re.compile('XConsortium'), RGBColorDB), (re.compile('HTML'), HTML40DB), (re.compile('lightlink'), LightlinkDB), (re.compile('Websafe'), WebsafeDB), ] def get_colordb(file, filetype=None): colordb = None fp = open(file) try: line = fp.readline() if not line: return None # try to determine the type of RGB file it is if filetype is None: filetypes = FILETYPES else: filetypes = [filetype] for typere, class_ in filetypes: mo = typere.search(line) if mo: break else: # no matching type return None # we know the type and the class to grok the type, so suck it in colordb = class_(fp) finally: fp.close() # save a global copy global DEFAULT_DB DEFAULT_DB = colordb return colordb  _namedict = {} def rrggbb_to_triplet(color): """Converts a #rrggbb color to the tuple (red, green, blue).""" rgbtuple = _namedict.get(color) if rgbtuple is None: if color[0] <> '#': raise BadColor(color) red = color[1:3] green = color[3:5] blue = color[5:7] rgbtuple = int(red, 16), int(green, 16), int(blue, 16) _namedict[color] = rgbtuple return rgbtuple _tripdict = {} def triplet_to_rrggbb(rgbtuple): """Converts a (red, green, blue) tuple to #rrggbb.""" global _tripdict hexname = _tripdict.get(rgbtuple) if hexname is None: hexname = '#%02x%02x%02x' % rgbtuple _tripdict[rgbtuple] = hexname return hexname _maxtuple = (256.0,) * 3 def triplet_to_fractional_rgb(rgbtuple): return map(operator.__div__, rgbtuple, _maxtuple) def triplet_to_brightness(rgbtuple): # return the brightness (grey level) along the scale 0.0==black to # 1.0==white r = 0.299 g = 0.587 b = 0.114 return r*rgbtuple[0] + g*rgbtuple[1] + b*rgbtuple[2]  if __name__ == '__main__': colordb = get_colordb('/usr/openwin/lib/rgb.txt') if not colordb: print 'No parseable color database found' sys.exit(1) # on my system, this color matches exactly target = 'navy' red, green, blue = rgbtuple = colordb.find_byname(target) print target, ':', red, green, blue, triplet_to_rrggbb(rgbtuple) name, aliases = colordb.find_byrgb(rgbtuple) print 'name:', name, 'aliases:', COMMASPACE.join(aliases) r, g, b = (1, 1, 128) # nearest to navy r, g, b = (145, 238, 144) # nearest to lightgreen r, g, b = (255, 251, 250) # snow print 'finding nearest to', target, '...' import time t0 = time.time() nearest = colordb.nearest(r, g, b) t1 = time.time() print 'found nearest color', nearest, 'in', t1-t0, 'seconds' # dump the database for n in colordb.unique_names(): r, g, b = colordb.find_byname(n) aliases = colordb.aliases_of(r, g, b) print '%20s: (%3d/%3d/%3d) == %s' % (n, r, g, b, SPACE.join(aliases[1:]))