| [iarec] [Up] [iafloyd] | Halftoning Approximation |
Ordered dither (Bayer 1973).
>>> f1 = iaramp([20,150], 256, [0,255])
>>> f2 = iaresize(iaread('woodlog.pgm'), [150,150])
>>> f = Numeric.concatenate((f1, f2))
>>> g_4 = iadither(f, 4)
>>> g_32 = iadither(f, 32)
>>> iashow(f)
(170, 150) Min= 0 Max= 255 Mean=95.406 Std=57.48
>>> iashow(g_4)
(170, 150) Min= 0 Max= 1 Mean=0.385 Std=0.49
>>> iashow(g_32)
(170, 150) Min= 0 Max= 1 Mean=0.379 Std=0.49
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| f | g_4 | g_32 |
def iadither(f, n):
from Numeric import array, log, ones, concatenate, ravel
D = 1.*array([[0,2],[3,1]])
d = 1*D
k = log(n/2.)/log(2.)
for i in range(k):
u = ones(D.shape)
d1 = 4*D + d[0,0]*u
d2 = 4*D + d[0,1]*u
d3 = 4*D + d[1,0]*u
d4 = 4*D + d[1,1]*u
D = concatenate((concatenate((d1,d2),1), concatenate((d3,d4),1)))
D = 255*abs(D/max(ravel(D)))
g = iatile(D.astype('b'), f.shape)
g = ianormalize(f,[0,255]) >= g
return g
| [iarec] [Up] [iafloyd] |  |