Source Code for Module Vision.colours

 1  """ 
 2  Some simple functions to generate colours. 
 3  """ 
 4  from matplotlib.numerix import asarray, asum 
 5  from matplotlib.mlab import linspace 
 6  from matplotlib.colors import colorConverter 
 7  from matplotlib.numerix import sum 
 8   
 9 -def pastel(colour, weight=2.4): 
10      """ Convert colour into a nice pastel shade""" 
11      rgb = asarray(colorConverter.to_rgb(colour)) 
12      # scale colour  
13      maxc = max(rgb) 
14      if maxc < 1.0 and maxc > 0: 
15          # scale colour 
16          scale = 1.0 / maxc 
17          rgb = rgb * scale 
18      # now decrease saturation 
19      total = asum(rgb) 
20      slack = 0 
21      for x in rgb: 
22          slack += 1.0 - x 
23   
24      # want to increase weight from total to weight 
25      # pick x s.t.  slack * x == weight - total 
26      # x = (weight - total) / slack 
27      x = (weight - total) / slack 
28   
29      rgb = [c + (x * (1.0-c)) for c in rgb] 
30   
31      return rgb 
32   
33 -def get_colours(n): 
34      """ Return n pastel colours. """ 
35      base = asarray([[1,0,0], [0,1,0], [0,0,1]]) 
36   
37      if n <= 3: 
38          return base[0:n] 
39   
40      # how many new colours to we need to insert between 
41      # red and green and between green and blue? 
42      needed = (((n - 3) + 1) / 2, (n - 3) / 2) 
43   
44      colours = [] 
45      for start in (0, 1): 
46          for x in linspace(0, 1, needed[start]+2): 
47              colours.append((base[start] * (1.0 - x)) + 
48                             (base[start+1] * x)) 
49   
50      return [pastel(c) for c in colours[0:n]] 
51