ii-pix/dither_pattern.py

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"""Error diffusion dither patterns."""
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import numpy as np
class DitherPattern:
PATTERN = None
ORIGIN = None
class NoDither(DitherPattern):
"""No dithering."""
PATTERN = np.array(((0, 0), (0, 0)),
dtype=np.float32).reshape(2, 2) / np.float(16)
ORIGIN = (0, 1)
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class FloydSteinbergDither(DitherPattern):
"""Floyd-Steinberg dither."""
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# 0 * 7
# 3 5 1
PATTERN = np.array(((0, 0, 7), (3, 5, 1)),
dtype=np.float32).reshape(2, 3) / np.float(16)
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ORIGIN = (0, 1)
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class FloydSteinbergDither2(DitherPattern):
"""Floyd-Steinberg dither."""
# 0 * 7
# 3 5 1
PATTERN = np.array(
((0, 0, 0, 0, 0, 7),
(3, 5, 1, 0, 0, 0)),
dtype=np.float32).reshape(2, 6) / np.float(16)
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ORIGIN = (0, 2)
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class BuckelsDither(DitherPattern):
"""Default dither from bmp2dhr."""
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# 0 * 2 1
# 1 2 1 0
# 0 1 0 0
PATTERN = np.array(((0, 0, 2, 1), (1, 2, 1, 0), (0, 1, 0, 0)),
dtype=np.float32).reshape(3, 4) / np.float32(8)
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ORIGIN = (0, 1)
class JarvisDither(DitherPattern):
"""Jarvis-Judice-Ninke dithering."""
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# 0 0 X 7 5
# 3 5 7 5 3
# 1 3 5 3 1
PATTERN = np.array(((0, 0, 0, 7, 5), (3, 5, 7, 5, 3), (1, 3, 5, 3, 1)),
dtype=np.float32).reshape(3, 5) / np.float32(48)
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ORIGIN = (0, 2)
class JarvisModifiedDither(DitherPattern):
"""Jarvis dithering, modified to diffuse errors to 4 forward x positions.
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This works well for double hi-res dithering, since the "best" colour
match to a given pixel may only be accessible up to 4 x-positions further
on. Standard Jarvis dithering only propagates errors for 2 x-positions
in the forward direction, which means that errors may have diffused away
before we get to the pixel that can best take advantage of it.
"""
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# 0 0 X 7 5
# 3 5 7 5 3
# 1 3 5 3 1
PATTERN = np.array((
(0, 0, 0, 15, 11, 7, 3),
(3, 5, 7, 5, 3, 1, 0),
(1, 3, 5, 3, 1, 0, 0)), dtype=np.float32).reshape(3, 7)
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PATTERN /= np.sum(PATTERN)
ORIGIN = (0, 2)
PATTERNS = {
'floyd': FloydSteinbergDither,
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'floyd2': FloydSteinbergDither2,
'floyd-steinberg': FloydSteinbergDither,
'buckels': BuckelsDither,
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'jarvis': JarvisDither,
'jarvis-mod': JarvisModifiedDither,
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'none': NoDither
}
DEFAULT_PATTERN = 'jarvis-mod'