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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 re
class BadColor(Exception):
pass
# 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 rrggbb, value is (name, [aliases])
self.__byrrggbb = {}
#
# key is name, value is (red, green, blue, rrggbb)
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')
#
# calculate the 24 bit representation of the color
rrggbb = (red << 16) + (blue << 8) + green
#
# 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.
foundname, aliases = self.__byrrggbb.get(rrggbb, (name, []))
if foundname <> name and foundname not in aliases:
aliases.append(name)
#
# add to by 24bit value
self.__byrrggbb[rrggbb] = (foundname, aliases)
#
# add to byname lookup
point = (red, green, blue, rrggbb)
self.__byname[name] = point
lineno = lineno + 1
def find(self, red, green, blue):
rrggbb = (red << 16) + (blue << 8) + green
try:
return self.__byrrggbb[rrggbb]
except KeyError:
raise BadColor(red, green, blue)
def find_byname(self, 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. This is really
# inefficient!
nearest = -1
nearest_name = ''
for name, aliases in self.__byrrggbb.values():
r, g, b, rrggbb = self.__byname[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()
return colordb
def rrggbb_to_triplet(color):
"""Converts a #rrggbb color to the tuple (red, green, blue)."""
if color[0] <> '#':
raise BadColor(color)
zero = ord('0')
a = ord('a')
A = ord('A')
def _hexchar(c, zero=zero, a=a, A=A):
v = ord(c)
if v >= zero and v <= zero+9:
return v - zero
elif v >= a and v <= a+26:
return v - a + 10
elif v >= A and v <= A+26:
return v - A + 10
else:
raise BadColor
try:
digits = map(_hexchar, color[1:])
except BadColor:
raise BadColor(color)
red = digits[0] * 16 + digits[1]
green = digits[2] * 16 + digits[3]
blue = digits[4] * 16 + digits[5]
return (red, green, blue)
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, rrggbb = colordb.find_byname(target)
print target, ':', red, green, blue, hex(rrggbb)
name, aliases = colordb.find(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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