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615842fba6
any hue value and do the modulo itself, except it doesn't quite do it in all cases. At least, the "cannot get here" comment was wrong.
127 lines
3.4 KiB
Python
127 lines
3.4 KiB
Python
"""Conversion functions between RGB and other color systems.
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This modules provides two functions for each color system ABC:
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rgb_to_abc(r, g, b) --> a, b, c
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abc_to_rgb(a, b, c) --> r, g, b
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All inputs and outputs are triples of floats in the range [0.0...1.0]
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(with the exception of I and Q, which covers a slightly larger range).
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Inputs outside the valid range may cause exceptions or invalid outputs.
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Supported color systems:
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RGB: Red, Green, Blue components
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YIQ: Luminance, Chrominance (used by composite video signals)
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HLS: Hue, Luminance, Saturation
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HSV: Hue, Saturation, Value
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"""
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# References:
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# http://en.wikipedia.org/wiki/YIQ
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# http://en.wikipedia.org/wiki/HLS_color_space
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# http://en.wikipedia.org/wiki/HSV_color_space
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__all__ = ["rgb_to_yiq","yiq_to_rgb","rgb_to_hls","hls_to_rgb",
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"rgb_to_hsv","hsv_to_rgb"]
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# Some floating point constants
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ONE_THIRD = 1.0/3.0
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ONE_SIXTH = 1.0/6.0
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TWO_THIRD = 2.0/3.0
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# YIQ: used by composite video signals (linear combinations of RGB)
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# Y: perceived grey level (0.0 == black, 1.0 == white)
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# I, Q: color components
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def rgb_to_yiq(r, g, b):
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y = 0.30*r + 0.59*g + 0.11*b
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i = 0.60*r - 0.28*g - 0.32*b
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q = 0.21*r - 0.52*g + 0.31*b
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return (y, i, q)
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def yiq_to_rgb(y, i, q):
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r = y + 0.948262*i + 0.624013*q
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g = y - 0.276066*i - 0.639810*q
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b = y - 1.105450*i + 1.729860*q
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if r < 0.0: r = 0.0
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if g < 0.0: g = 0.0
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if b < 0.0: b = 0.0
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if r > 1.0: r = 1.0
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if g > 1.0: g = 1.0
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if b > 1.0: b = 1.0
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return (r, g, b)
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# HLS: Hue, Luminance, Saturation
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# H: position in the spectrum
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# L: color lightness
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# S: color saturation
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def rgb_to_hls(r, g, b):
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maxc = max(r, g, b)
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minc = min(r, g, b)
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# XXX Can optimize (maxc+minc) and (maxc-minc)
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l = (minc+maxc)/2.0
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if minc == maxc: return 0.0, l, 0.0
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if l <= 0.5: s = (maxc-minc) / (maxc+minc)
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else: s = (maxc-minc) / (2.0-maxc-minc)
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rc = (maxc-r) / (maxc-minc)
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gc = (maxc-g) / (maxc-minc)
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bc = (maxc-b) / (maxc-minc)
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if r == maxc: h = bc-gc
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elif g == maxc: h = 2.0+rc-bc
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else: h = 4.0+gc-rc
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h = (h/6.0) % 1.0
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return h, l, s
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def hls_to_rgb(h, l, s):
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if s == 0.0: return l, l, l
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if l <= 0.5: m2 = l * (1.0+s)
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else: m2 = l+s-(l*s)
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m1 = 2.0*l - m2
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return (_v(m1, m2, h+ONE_THIRD), _v(m1, m2, h), _v(m1, m2, h-ONE_THIRD))
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def _v(m1, m2, hue):
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hue = hue % 1.0
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if hue < ONE_SIXTH: return m1 + (m2-m1)*hue*6.0
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if hue < 0.5: return m2
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if hue < TWO_THIRD: return m1 + (m2-m1)*(TWO_THIRD-hue)*6.0
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return m1
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# HSV: Hue, Saturation, Value
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# H: position in the spectrum
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# S: color saturation ("purity")
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# V: color brightness
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def rgb_to_hsv(r, g, b):
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maxc = max(r, g, b)
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minc = min(r, g, b)
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v = maxc
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if minc == maxc: return 0.0, 0.0, v
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s = (maxc-minc) / maxc
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rc = (maxc-r) / (maxc-minc)
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gc = (maxc-g) / (maxc-minc)
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bc = (maxc-b) / (maxc-minc)
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if r == maxc: h = bc-gc
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elif g == maxc: h = 2.0+rc-bc
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else: h = 4.0+gc-rc
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h = (h/6.0) % 1.0
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return h, s, v
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def hsv_to_rgb(h, s, v):
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if s == 0.0: return v, v, v
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i = int(h*6.0) # XXX assume int() truncates!
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f = (h*6.0) - i
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p = v*(1.0 - s)
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q = v*(1.0 - s*f)
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t = v*(1.0 - s*(1.0-f))
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i = i%6
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if i == 0: return v, t, p
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if i == 1: return q, v, p
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if i == 2: return p, v, t
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if i == 3: return p, q, v
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if i == 4: return t, p, v
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if i == 5: return v, p, q
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# Cannot get here
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