Jack added new color systems (unfortunately using old lay-out).

Demo/sgi/video/colorsys.py

-# Conversions between RGB and YIQ color spaces.
 #
-# R, G, B are amounts of Red, Green and Blue;
-# Y, I, Q are intensity (Y) and two difference signals (I, Q).
-
+# Module color - do color conversions
+#
 
-# Convert a (R, G, B) triple to (Y, I, Q).
-# Scale is arbitrary (output uses the same scale as input).
+ONE_THIRD=1.0/3.0
+ONE_SIXTH=1.0/6.0
+TWO_THIRD=2.0/3.0
 
-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 rgb_to_yiq(r,g,b):
+    y = 0.3*r + 0.59*g + 0.11*b
+    i = 0.6*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)
 
+def _v(m1,m2,hue):
+    if hue >= 1.0: hue = hue - 1.0
+    if hue <  0.0: 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
 
-# Convert a (Y, I, Q) triple to (R, G, B).
-# Input and output values are in the interval [0.0 ... 1.0].
+def rgb_to_hls(r,g,b):
+    maxc = max(r,g,b)
+    minc = min(r,g,b)
+    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-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
+    if h < 0.0:
+	h = h + 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 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
+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
+    if h < 0.0:
+	h = h + 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)
+    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 in (0,6): 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
+    print i, h, f
+    print h, s, v
+    raise 'Bad color'