"""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 string import re from types import * import operator class BadColor(Exception): pass DEFAULT_DB = None # generic class class ColorDB: def __init__(self, fp, lineno): # 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 while 1: line = fp.readline() if not line: break # get this compiled regular expression from derived class mo = self._re.match(line) if not mo: sys.stderr.write('Error in %s, line %d\n' % (fp.name, lineno)) lineno = lineno + 1 continue # # extract the red, green, blue, and name # red, green, blue = map(int, mo.group('red', 'green', 'blue')) name = mo.group('name') keyname = string.lower(name) # # TBD: 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 def find_byrgb(self, rgbtuple): try: return self.__byrgb[rgbtuple] except KeyError: raise BadColor(rgbtuple) def find_byname(self, name): name = string.lower(name) try: return self.__byname[name] except KeyError: raise BadColor(name) def nearest(self, red, green, blue): # TBD: use Voronoi diagrams, Delaunay triangulation, or octree for # speeding up the locating of nearest point. Exhaustive search is # inefficient, but may be fast enough. nearest = -1 nearest_name = '' for name, aliases in self.__byrgb.values(): r, g, b = self.__byname[string.lower(name)] 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(string.lower(n1), string.lower(n2)) 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.*)') # 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 X_RGB_TXT = re.compile('XConsortium'), 1, RGBColorDB def get_colordb(file, filetype=X_RGB_TXT): colordb = None fp = None typere, scanlines, class_ = filetype try: try: lineno = 0 fp = open(file) while lineno < scanlines: line = fp.readline() if not line: break mo = typere.search(line) if mo: colordb = class_(fp, lineno) break lineno = lineno + 1 except IOError: pass finally: if fp: fp.close() # save a global copy global DEFAULT_DB DEFAULT_DB = colordb return colordb _namedict = {} def rrggbb_to_triplet(color, atoi=string.atoi): """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 = (atoi(red, 16), atoi(green, 16), atoi(blue, 16)) _namedict[color] = rgbtuple return rgbtuple _tripdict = {} def triplet_to_rrggbb(rgbtuple): """Converts a (red, green, blue) tuple to #rrggbb.""" 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__': import string 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:', string.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, string.join(aliases[1:]))