"""Color Database. To create a class that contains color lookup methods, use the module global function `get_colordb(file)'. This 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. """ import sys import string import re from types import * 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 = {} # 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, rgbtuple): # 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. red, green, blue = rgbtuple 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 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 def rrggbb_to_triplet(color): """Converts a #rrggbb color to the tuple (red, green, blue).""" if color[0] <> '#': raise BadColor(color) red = color[1:3] green = color[3:5] blue = color[5:7] return tuple(map(lambda v: string.atoi(v, 16), (red, green, blue))) def triplet_to_rrggbb(rgbtuple): """Converts a (red, green, blue) tuple to #rrggbb.""" def hexify(v): hexstr = hex(v)[2:4] if len(hexstr) < 2: hexstr = '0' + hexstr return hexstr return '#%s%s%s' % tuple(map(hexify, rgbtuple)) 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' target = 'snow' red, green, blue = colordb.find_byname(target) print target, ':', red, green, blue, hex(rrggbb) name, aliases = colordb.find_byrgb((red, green, blue)) print 'name:', name, 'aliases:', string.join(aliases, ", ") target = (1, 1, 128) # nearest to navy target = (145, 238, 144) # nearest to lightgreen target = (255, 251, 250) # snow print 'finding nearest to', target, '...' import time t0 = time.time() nearest = apply(colordb.nearest, target) t1 = time.time() print 'found nearest color', nearest, 'in', t1-t0, 'seconds'