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"""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 *
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 = {}
#
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<red>\d+)\s+(?P<green>\d+)\s+(?P<blue>\d+)\s+(?P<name>.*)')
# 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:
assert color[0] == '#'
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_pmwrgb(rgbtuple):
return map(operator.__div__, rgbtuple, _maxtuple)
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'
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