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oasis-root

Compiled tree of Oasis Linux based on own branch at <https://hacktivis.me/git/oasis/> git clone https://anongit.hacktivis.me/git/oasis-root.git

colorsys.py (4017B)

    

  1. """Conversion functions between RGB and other color systems.
  3. This modules provides two functions for each color system ABC:
  5.   rgb_to_abc(r, g, b) --> a, b, c
  6.   abc_to_rgb(a, b, c) --> r, g, b
  8. All inputs and outputs are triples of floats in the range [0.0...1.0]
  9. (with the exception of I and Q, which covers a slightly larger range).
  10. Inputs outside the valid range may cause exceptions or invalid outputs.
  12. Supported color systems:
  13. RGB: Red, Green, Blue components
  14. YIQ: Luminance, Chrominance (used by composite video signals)
  15. HLS: Hue, Luminance, Saturation
  16. HSV: Hue, Saturation, Value
  17. """
  19. # References:
  20. # http://en.wikipedia.org/wiki/YIQ
  21. # http://en.wikipedia.org/wiki/HLS_color_space
  22. # http://en.wikipedia.org/wiki/HSV_color_space
  24. __all__ = ["rgb_to_yiq","yiq_to_rgb","rgb_to_hls","hls_to_rgb",
  25.            "rgb_to_hsv","hsv_to_rgb"]
  27. # Some floating point constants
  29. ONE_THIRD = 1.0/3.0
  30. ONE_SIXTH = 1.0/6.0
  31. TWO_THIRD = 2.0/3.0
  33. # YIQ: used by composite video signals (linear combinations of RGB)
  34. # Y: perceived grey level (0.0 == black, 1.0 == white)
  35. # I, Q: color components
  36. #
  37. # There are a great many versions of the constants used in these formulae.
  38. # The ones in this library uses constants from the FCC version of NTSC.
  40. def rgb_to_yiq(r, g, b):
  41.     y = 0.30*r + 0.59*g + 0.11*b
  42.     i = 0.74*(r-y) - 0.27*(b-y)
  43.     q = 0.48*(r-y) + 0.41*(b-y)
  44.     return (y, i, q)
  46. def yiq_to_rgb(y, i, q):
  47.     # r = y + (0.27*q + 0.41*i) / (0.74*0.41 + 0.27*0.48)
  48.     # b = y + (0.74*q - 0.48*i) / (0.74*0.41 + 0.27*0.48)
  49.     # g = y - (0.30*(r-y) + 0.11*(b-y)) / 0.59
  51.     r = y + 0.9468822170900693*i + 0.6235565819861433*q
  52.     g = y - 0.27478764629897834*i - 0.6356910791873801*q
  53.     b = y - 1.1085450346420322*i + 1.7090069284064666*q
  55.     if r < 0.0:
  56.         r = 0.0
  57.     if g < 0.0:
  58.         g = 0.0
  59.     if b < 0.0:
  60.         b = 0.0
  61.     if r > 1.0:
  62.         r = 1.0
  63.     if g > 1.0:
  64.         g = 1.0
  65.     if b > 1.0:
  66.         b = 1.0
  67.     return (r, g, b)
  70. # HLS: Hue, Luminance, Saturation
  71. # H: position in the spectrum
  72. # L: color lightness
  73. # S: color saturation
  75. def rgb_to_hls(r, g, b):
  76.     maxc = max(r, g, b)
  77.     minc = min(r, g, b)
  78.     sumc = (maxc+minc)
  79.     rangec = (maxc-minc)
  80.     l = sumc/2.0
  81.     if minc == maxc:
  82.         return 0.0, l, 0.0
  83.     if l <= 0.5:
  84.         s = rangec / sumc
  85.     else:
  86.         s = rangec / (2.0-sumc)
  87.     rc = (maxc-r) / rangec
  88.     gc = (maxc-g) / rangec
  89.     bc = (maxc-b) / rangec
  90.     if r == maxc:
  91.         h = bc-gc
  92.     elif g == maxc:
  93.         h = 2.0+rc-bc
  94.     else:
  95.         h = 4.0+gc-rc
  96.     h = (h/6.0) % 1.0
  97.     return h, l, s
  99. def hls_to_rgb(h, l, s):
  100.     if s == 0.0:
  101.         return l, l, l
  102.     if l <= 0.5:
  103.         m2 = l * (1.0+s)
  104.     else:
  105.         m2 = l+s-(l*s)
  106.     m1 = 2.0*l - m2
  107.     return (_v(m1, m2, h+ONE_THIRD), _v(m1, m2, h), _v(m1, m2, h-ONE_THIRD))
  109. def _v(m1, m2, hue):
  110.     hue = hue % 1.0
  111.     if hue < ONE_SIXTH:
  112.         return m1 + (m2-m1)*hue*6.0
  113.     if hue < 0.5:
  114.         return m2
  115.     if hue < TWO_THIRD:
  116.         return m1 + (m2-m1)*(TWO_THIRD-hue)*6.0
  117.     return m1
  120. # HSV: Hue, Saturation, Value
  121. # H: position in the spectrum
  122. # S: color saturation ("purity")
  123. # V: color brightness
  125. def rgb_to_hsv(r, g, b):
  126.     maxc = max(r, g, b)
  127.     minc = min(r, g, b)
  128.     v = maxc
  129.     if minc == maxc:
  130.         return 0.0, 0.0, v
  131.     s = (maxc-minc) / maxc
  132.     rc = (maxc-r) / (maxc-minc)
  133.     gc = (maxc-g) / (maxc-minc)
  134.     bc = (maxc-b) / (maxc-minc)
  135.     if r == maxc:
  136.         h = bc-gc
  137.     elif g == maxc:
  138.         h = 2.0+rc-bc
  139.     else:
  140.         h = 4.0+gc-rc
  141.     h = (h/6.0) % 1.0
  142.     return h, s, v
  144. def hsv_to_rgb(h, s, v):
  145.     if s == 0.0:
  146.         return v, v, v
  147.     i = int(h*6.0) # XXX assume int() truncates!
  148.     f = (h*6.0) - i
  149.     p = v*(1.0 - s)
  150.     q = v*(1.0 - s*f)
  151.     t = v*(1.0 - s*(1.0-f))
  152.     i = i%6
  153.     if i == 0:
  154.         return v, t, p
  155.     if i == 1:
  156.         return q, v, p
  157.     if i == 2:
  158.         return p, v, t
  159.     if i == 3:
  160.         return p, q, v
  161.     if i == 4:
  162.         return t, p, v
  163.     if i == 5:
  164.         return v, p, q
  165.     # Cannot get here