diff --git a/python-stdlib/colorsys/colorsys.py b/python-stdlib/colorsys/colorsys.py new file mode 100644 index 000000000..9bdc83e37 --- /dev/null +++ b/python-stdlib/colorsys/colorsys.py @@ -0,0 +1,166 @@ +"""Conversion functions between RGB and other color systems. + +This modules provides two functions for each color system ABC: + + rgb_to_abc(r, g, b) --> a, b, c + abc_to_rgb(a, b, c) --> r, g, b + +All inputs and outputs are triples of floats in the range [0.0...1.0] +(with the exception of I and Q, which covers a slightly larger range). +Inputs outside the valid range may cause exceptions or invalid outputs. + +Supported color systems: +RGB: Red, Green, Blue components +YIQ: Luminance, Chrominance (used by composite video signals) +HLS: Hue, Luminance, Saturation +HSV: Hue, Saturation, Value +""" + +# References: +# http://en.wikipedia.org/wiki/YIQ +# http://en.wikipedia.org/wiki/HLS_color_space +# http://en.wikipedia.org/wiki/HSV_color_space + +__all__ = ["rgb_to_yiq","yiq_to_rgb","rgb_to_hls","hls_to_rgb", + "rgb_to_hsv","hsv_to_rgb"] + +# Some floating point constants + +ONE_THIRD = 1.0/3.0 +ONE_SIXTH = 1.0/6.0 +TWO_THIRD = 2.0/3.0 + +# YIQ: used by composite video signals (linear combinations of RGB) +# Y: perceived grey level (0.0 == black, 1.0 == white) +# I, Q: color components +# +# There are a great many versions of the constants used in these formulae. +# The ones in this library uses constants from the FCC version of NTSC. + +def rgb_to_yiq(r, g, b): + y = 0.30*r + 0.59*g + 0.11*b + i = 0.74*(r-y) - 0.27*(b-y) + q = 0.48*(r-y) + 0.41*(b-y) + return (y, i, q) + +def yiq_to_rgb(y, i, q): + # r = y + (0.27*q + 0.41*i) / (0.74*0.41 + 0.27*0.48) + # b = y + (0.74*q - 0.48*i) / (0.74*0.41 + 0.27*0.48) + # g = y - (0.30*(r-y) + 0.11*(b-y)) / 0.59 + + r = y + 0.9468822170900693*i + 0.6235565819861433*q + g = y - 0.27478764629897834*i - 0.6356910791873801*q + b = y - 1.1085450346420322*i + 1.7090069284064666*q + + if r < 0.0: + r = 0.0 + if g < 0.0: + g = 0.0 + if b < 0.0: + b = 0.0 + if r > 1.0: + r = 1.0 + if g > 1.0: + g = 1.0 + if b > 1.0: + b = 1.0 + return (r, g, b) + + +# HLS: Hue, Luminance, Saturation +# H: position in the spectrum +# L: color lightness +# S: color saturation + +def rgb_to_hls(r, g, b): + maxc = max(r, g, b) + minc = min(r, g, b) + sumc = (maxc+minc) + rangec = (maxc-minc) + l = sumc/2.0 + if minc == maxc: + return 0.0, l, 0.0 + if l <= 0.5: + s = rangec / sumc + else: + s = rangec / (2.0-sumc) + rc = (maxc-r) / rangec + gc = (maxc-g) / rangec + bc = (maxc-b) / rangec + if r == maxc: + h = bc-gc + elif g == maxc: + h = 2.0+rc-bc + else: + h = 4.0+gc-rc + h = (h/6.0) % 1.0 + return h, l, s + +def hls_to_rgb(h, l, s): + if s == 0.0: + return l, l, l + if l <= 0.5: + m2 = l * (1.0+s) + else: + m2 = l+s-(l*s) + m1 = 2.0*l - m2 + return (_v(m1, m2, h+ONE_THIRD), _v(m1, m2, h), _v(m1, m2, h-ONE_THIRD)) + +def _v(m1, m2, hue): + hue = hue % 1.0 + if hue < ONE_SIXTH: + return m1 + (m2-m1)*hue*6.0 + if hue < 0.5: + return m2 + if hue < TWO_THIRD: + return m1 + (m2-m1)*(TWO_THIRD-hue)*6.0 + return m1 + + +# HSV: Hue, Saturation, Value +# H: position in the spectrum +# S: color saturation ("purity") +# V: color brightness + +def rgb_to_hsv(r, g, b): + maxc = max(r, g, b) + minc = min(r, g, b) + rangec = (maxc-minc) + v = maxc + if minc == maxc: + return 0.0, 0.0, v + s = rangec / maxc + rc = (maxc-r) / rangec + gc = (maxc-g) / rangec + bc = (maxc-b) / rangec + if r == maxc: + h = bc-gc + elif g == maxc: + h = 2.0+rc-bc + else: + h = 4.0+gc-rc + h = (h/6.0) % 1.0 + return h, s, v + +def hsv_to_rgb(h, s, v): + if s == 0.0: + return v, v, v + i = int(h*6.0) # XXX assume int() truncates! + f = (h*6.0) - i + p = v*(1.0 - s) + q = v*(1.0 - s*f) + t = v*(1.0 - s*(1.0-f)) + i = i%6 + if i == 0: + return v, t, p + if i == 1: + return q, v, p + if i == 2: + return p, v, t + if i == 3: + return p, q, v + if i == 4: + return t, p, v + if i == 5: + return v, p, q + # Cannot get here diff --git a/python-stdlib/colorsys/test_colorsys.py b/python-stdlib/colorsys/test_colorsys.py new file mode 100644 index 000000000..a41eec349 --- /dev/null +++ b/python-stdlib/colorsys/test_colorsys.py @@ -0,0 +1,100 @@ +import unittest +import colorsys + +def frange(start, stop, step): + while start <= stop: + yield start + start += step + +class ColorsysTest(unittest.TestCase): + + def assertTripleEqual(self, tr1, tr2): + self.assertEqual(len(tr1), 3) + self.assertEqual(len(tr2), 3) + self.assertAlmostEqual(tr1[0], tr2[0]) + self.assertAlmostEqual(tr1[1], tr2[1]) + self.assertAlmostEqual(tr1[2], tr2[2]) + + def test_hsv_roundtrip(self): + for r in frange(0.0, 1.0, 0.2): + for g in frange(0.0, 1.0, 0.2): + for b in frange(0.0, 1.0, 0.2): + rgb = (r, g, b) + self.assertTripleEqual( + rgb, + colorsys.hsv_to_rgb(*colorsys.rgb_to_hsv(*rgb)) + ) + + def test_hsv_values(self): + values = [ + # rgb, hsv + ((0.0, 0.0, 0.0), ( 0 , 0.0, 0.0)), # black + ((0.0, 0.0, 1.0), (4./6., 1.0, 1.0)), # blue + ((0.0, 1.0, 0.0), (2./6., 1.0, 1.0)), # green + ((0.0, 1.0, 1.0), (3./6., 1.0, 1.0)), # cyan + ((1.0, 0.0, 0.0), ( 0 , 1.0, 1.0)), # red + ((1.0, 0.0, 1.0), (5./6., 1.0, 1.0)), # purple + ((1.0, 1.0, 0.0), (1./6., 1.0, 1.0)), # yellow + ((1.0, 1.0, 1.0), ( 0 , 0.0, 1.0)), # white + ((0.5, 0.5, 0.5), ( 0 , 0.0, 0.5)), # grey + ] + for (rgb, hsv) in values: + self.assertTripleEqual(hsv, colorsys.rgb_to_hsv(*rgb)) + self.assertTripleEqual(rgb, colorsys.hsv_to_rgb(*hsv)) + + def test_hls_roundtrip(self): + for r in frange(0.0, 1.0, 0.2): + for g in frange(0.0, 1.0, 0.2): + for b in frange(0.0, 1.0, 0.2): + rgb = (r, g, b) + self.assertTripleEqual( + rgb, + colorsys.hls_to_rgb(*colorsys.rgb_to_hls(*rgb)) + ) + + def test_hls_values(self): + values = [ + # rgb, hls + ((0.0, 0.0, 0.0), ( 0 , 0.0, 0.0)), # black + ((0.0, 0.0, 1.0), (4./6., 0.5, 1.0)), # blue + ((0.0, 1.0, 0.0), (2./6., 0.5, 1.0)), # green + ((0.0, 1.0, 1.0), (3./6., 0.5, 1.0)), # cyan + ((1.0, 0.0, 0.0), ( 0 , 0.5, 1.0)), # red + ((1.0, 0.0, 1.0), (5./6., 0.5, 1.0)), # purple + ((1.0, 1.0, 0.0), (1./6., 0.5, 1.0)), # yellow + ((1.0, 1.0, 1.0), ( 0 , 1.0, 0.0)), # white + ((0.5, 0.5, 0.5), ( 0 , 0.5, 0.0)), # grey + ] + for (rgb, hls) in values: + self.assertTripleEqual(hls, colorsys.rgb_to_hls(*rgb)) + self.assertTripleEqual(rgb, colorsys.hls_to_rgb(*hls)) + + def test_yiq_roundtrip(self): + for r in frange(0.0, 1.0, 0.2): + for g in frange(0.0, 1.0, 0.2): + for b in frange(0.0, 1.0, 0.2): + rgb = (r, g, b) + self.assertTripleEqual( + rgb, + colorsys.yiq_to_rgb(*colorsys.rgb_to_yiq(*rgb)) + ) + + def test_yiq_values(self): + values = [ + # rgb, yiq + ((0.0, 0.0, 0.0), (0.0, 0.0, 0.0)), # black + ((0.0, 0.0, 1.0), (0.11, -0.3217, 0.3121)), # blue + ((0.0, 1.0, 0.0), (0.59, -0.2773, -0.5251)), # green + ((0.0, 1.0, 1.0), (0.7, -0.599, -0.213)), # cyan + ((1.0, 0.0, 0.0), (0.3, 0.599, 0.213)), # red + ((1.0, 0.0, 1.0), (0.41, 0.2773, 0.5251)), # purple + ((1.0, 1.0, 0.0), (0.89, 0.3217, -0.3121)), # yellow + ((1.0, 1.0, 1.0), (1.0, 0.0, 0.0)), # white + ((0.5, 0.5, 0.5), (0.5, 0.0, 0.0)), # grey + ] + for (rgb, yiq) in values: + self.assertTripleEqual(yiq, colorsys.rgb_to_yiq(*rgb)) + self.assertTripleEqual(rgb, colorsys.yiq_to_rgb(*yiq)) + +if __name__ == "__main__": + unittest.main() \ No newline at end of file