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| -rw-r--r-- | Lib/colorsys.py | 119 |
1 files changed, 119 insertions, 0 deletions
diff --git a/Lib/colorsys.py b/Lib/colorsys.py new file mode 100644 index 0000000..c48b2cb --- /dev/null +++ b/Lib/colorsys.py @@ -0,0 +1,119 @@ +# Conversion functions between RGB and other color systems. +# +# Define two functions for each color system XYZ: +# rgb_to_xyz(r, g, b) --> x, y, z +# xyz_to_rgb(x, y, z) --> r, g, b +# All inputs and outputs are triples of floats in the range [0.0...1.0]. +# Inputs outside this range may cause exceptions or invalid outputs. +# +# Supported color systems: +# RGB: Red, Green, Blue components +# YIQ: used by composite video signals +# HLS: Hue, Luminance, S??? +# HSV: Hue, Saturation, Value(?) +# +# References: +# XXX Where's the literature? + + +# 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 + +def rgb_to_yiq(r, g, b): + y = 0.30*r + 0.59*g + 0.11*b + i = 0.60*r - 0.28*g - 0.32*b + q = 0.21*r - 0.52*g + 0.31*b + return (y, i, q) + +def yiq_to_rgb(y, i, q): + r = y + 0.948262*i + 0.624013*q + g = y - 0.276066*i - 0.639810*q + b = y - 1.105450*i + 1.729860*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, S??? +# H: position in the spectrum +# L: ??? +# S: ??? + +def rgb_to_hls(r, g, b): + maxc = max(r, g, b) + minc = min(r, g, b) + # XXX Can optimize (maxc+minc) and (maxc-minc) + l = (minc+maxc)/2.0 + if minc == maxc: return 0.0, l, 0.0 + if l <= 0.5: s = (maxc-minc) / (maxc+minc) + else: s = (maxc-minc) / (2.0-maxc-minc) + rc = (maxc-r) / (maxc-minc) + gc = (maxc-g) / (maxc-minc) + bc = (maxc-b) / (maxc-minc) + 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: ??? +# V: ??? + +def rgb_to_hsv(r, g, b): + maxc = max(r, g, b) + minc = min(r, g, b) + v = maxc + if minc == maxc: return 0.0, 0.0, v + s = (maxc-minc) / maxc + rc = (maxc-r) / (maxc-minc) + gc = (maxc-g) / (maxc-minc) + bc = (maxc-b) / (maxc-minc) + 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)) + if i%6 == 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 |