1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/optimiserlib.py Sat Oct 10 15:36:48 2015 +0200
1.3 @@ -0,0 +1,186 @@
1.4 +#!/usr/bin/env python
1.5 +
1.6 +"""
1.7 +Convert and optimise images for display in an Acorn Electron MODE 1 variant
1.8 +with four colours per line but eight colours available for selection on each
1.9 +line.
1.10 +
1.11 +Copyright (C) 2015 Paul Boddie <paul@boddie.org.uk>
1.12 +
1.13 +This program is free software; you can redistribute it and/or modify it under
1.14 +the terms of the GNU General Public License as published by the Free Software
1.15 +Foundation; either version 3 of the License, or (at your option) any later
1.16 +version.
1.17 +
1.18 +This program is distributed in the hope that it will be useful, but WITHOUT ANY
1.19 +WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
1.20 +PARTICULAR PURPOSE. See the GNU General Public License for more details.
1.21 +
1.22 +You should have received a copy of the GNU General Public License along
1.23 +with this program. If not, see <http://www.gnu.org/licenses/>.
1.24 +"""
1.25 +
1.26 +from random import random, randrange
1.27 +
1.28 +corners = [
1.29 + (0, 0, 0), (255, 0, 0), (0, 255, 0), (255, 255, 0),
1.30 + (0, 0, 255), (255, 0, 255), (0, 255, 255), (255, 255, 255)
1.31 + ]
1.32 +
1.33 +# Basic colour operations.
1.34 +
1.35 +def within(v, lower, upper):
1.36 + return min(max(v, lower), upper)
1.37 +
1.38 +def clip(v):
1.39 + return int(within(v, 0, 255))
1.40 +
1.41 +def restore(srgb):
1.42 + r, g, b = srgb
1.43 + return int(r * 255.0), int(g * 255.0), int(b * 255.0)
1.44 +
1.45 +def scale(rgb):
1.46 + r, g, b = rgb
1.47 + return r / 255.0, g / 255.0, b / 255.0
1.48 +
1.49 +def invert(srgb):
1.50 + r, g, b = srgb
1.51 + return 1.0 - r, 1.0 - g, 1.0 - b
1.52 +
1.53 +scaled_corners = map(scale, corners)
1.54 +zipped_corners = zip(corners, scaled_corners)
1.55 +
1.56 +# Colour distribution functions.
1.57 +
1.58 +def combination(rgb):
1.59 +
1.60 + "Return the colour distribution for 'rgb'."
1.61 +
1.62 + # Get the colour with components scaled from 0 to 1, plus the inverted
1.63 + # component values.
1.64 +
1.65 + srgb = scale(rgb)
1.66 + rgbi = invert(srgb)
1.67 + pairs = zip(rgbi, srgb)
1.68 +
1.69 + # For each corner of the colour cube (primary and secondary colours plus
1.70 + # black and white), calculate the corner value's contribution to the
1.71 + # input colour.
1.72 +
1.73 + d = []
1.74 + for corner, scaled in zipped_corners:
1.75 + rs, gs, bs = scaled
1.76 +
1.77 + # Obtain inverted channel values where corner channels are low;
1.78 + # obtain original channel values where corner channels are high.
1.79 +
1.80 + d.append((pairs[0][int(rs)] * pairs[1][int(gs)] * pairs[2][int(bs)], corner))
1.81 +
1.82 + # Balance the corner contributions.
1.83 +
1.84 + return balance(d)
1.85 +
1.86 +def complements(rgb):
1.87 +
1.88 + "Return 'rgb' and its complement."
1.89 +
1.90 + r, g, b = rgb
1.91 + return rgb, restore(invert(scale(rgb)))
1.92 +
1.93 +bases = [(0, 0, 0), (255, 0, 0), (0, 255, 0), (0, 0, 255)]
1.94 +base_complements = map(complements, bases)
1.95 +
1.96 +def balance(d):
1.97 +
1.98 + """
1.99 + Balance distribution 'd', cancelling opposing values and their complements
1.100 + and replacing their common contributions with black and white contributions.
1.101 + """
1.102 +
1.103 + dd = dict([(value, f) for f, value in d])
1.104 + for primary, secondary in base_complements:
1.105 + common = min(dd[primary], dd[secondary])
1.106 + dd[primary] -= common
1.107 + dd[secondary] -= common
1.108 + return [(f, value) for value, f in dd.items()]
1.109 +
1.110 +def combine(d):
1.111 +
1.112 + "Combine distribution 'd' to get a colour value."
1.113 +
1.114 + out = [0, 0, 0]
1.115 + for v, rgb in d:
1.116 + out[0] += v * rgb[0]
1.117 + out[1] += v * rgb[1]
1.118 + out[2] += v * rgb[2]
1.119 + return tuple(map(int, out))
1.120 +
1.121 +def pattern(rgb, chosen=None):
1.122 +
1.123 + """
1.124 + Obtain a sorted colour distribution for 'rgb', optionally limited to any
1.125 + specified 'chosen' colours.
1.126 + """
1.127 +
1.128 + l = [(f, value) for f, value in combination(rgb) if not chosen or value in chosen]
1.129 + l.sort(reverse=True)
1.130 + return l
1.131 +
1.132 +def get_value(rgb, chosen=None, fail=False):
1.133 +
1.134 + """
1.135 + Get an output colour for 'rgb', optionally limited to any specified 'chosen'
1.136 + colours. If 'fail' is set to a true value, return None if the colour cannot
1.137 + be expressed using any of the chosen colours.
1.138 + """
1.139 +
1.140 + l = pattern(rgb, chosen)
1.141 + limit = sum([f for f, c in l])
1.142 + if not limit:
1.143 + if fail:
1.144 + return None
1.145 + else:
1.146 + return l[randrange(0, len(l))][1]
1.147 +
1.148 + choose = random() * limit
1.149 + threshold = 0
1.150 + for f, c in l:
1.151 + threshold += f
1.152 + if choose < threshold:
1.153 + return c
1.154 + return c
1.155 +
1.156 +# Colour processing operations.
1.157 +
1.158 +def sign(x):
1.159 + if x >= 0:
1.160 + return 1
1.161 + else:
1.162 + return -1
1.163 +
1.164 +def saturate_rgb(rgb, exp):
1.165 + r, g, b = rgb
1.166 + return saturate_value(r, exp), saturate_value(g, exp), saturate_value(b, exp)
1.167 +
1.168 +def saturate_value(x, exp):
1.169 + return int(127.5 + sign(x - 127.5) * 127.5 * pow(abs(x - 127.5) / 127.5, exp))
1.170 +
1.171 +def amplify_rgb(rgb, exp):
1.172 + r, g, b = rgb
1.173 + return amplify_value(r, exp), amplify_value(g, exp), amplify_value(b, exp)
1.174 +
1.175 +def amplify_value(x, exp):
1.176 + return int(pow(x / 255.0, exp) * 255.0)
1.177 +
1.178 +# Exercise functions for Shedskin.
1.179 +
1.180 +if __name__ == "__main__":
1.181 + rgb = (200, 100, 50)
1.182 + saturate_rgb(rgb, 1.0)
1.183 + amplify_rgb(rgb, 1.0)
1.184 + get_value(rgb)
1.185 + get_value(rgb, [(255, 255, 255), (255, 0, 0), (255, 255, 0), (0, 0, 0)])
1.186 + combine([(1.0, (255, 0, 0)), (0.0, (0, 0, 0))])
1.187 + clip(200.0)
1.188 +
1.189 +# vim: tabstop=4 expandtab shiftwidth=4
