| paul@83 | 1 | #!/usr/bin/env python |
| paul@83 | 2 | |
| paul@83 | 3 | """ |
| paul@83 | 4 | Convert and optimise images for display in an Acorn Electron MODE 1 variant |
| paul@83 | 5 | with four colours per line but eight colours available for selection on each |
| paul@83 | 6 | line. |
| paul@83 | 7 | |
| paul@83 | 8 | Copyright (C) 2015 Paul Boddie <paul@boddie.org.uk> |
| paul@83 | 9 | |
| paul@83 | 10 | This program is free software; you can redistribute it and/or modify it under |
| paul@83 | 11 | the terms of the GNU General Public License as published by the Free Software |
| paul@83 | 12 | Foundation; either version 3 of the License, or (at your option) any later |
| paul@83 | 13 | version. |
| paul@83 | 14 | |
| paul@83 | 15 | This program is distributed in the hope that it will be useful, but WITHOUT ANY |
| paul@83 | 16 | WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A |
| paul@83 | 17 | PARTICULAR PURPOSE. See the GNU General Public License for more details. |
| paul@83 | 18 | |
| paul@83 | 19 | You should have received a copy of the GNU General Public License along |
| paul@83 | 20 | with this program. If not, see <http://www.gnu.org/licenses/>. |
| paul@83 | 21 | """ |
| paul@83 | 22 | |
| paul@83 | 23 | from random import random, randrange |
| paul@83 | 24 | |
| paul@83 | 25 | corners = [ |
| paul@83 | 26 | (0, 0, 0), (255, 0, 0), (0, 255, 0), (255, 255, 0), |
| paul@83 | 27 | (0, 0, 255), (255, 0, 255), (0, 255, 255), (255, 255, 255) |
| paul@83 | 28 | ] |
| paul@83 | 29 | |
| paul@83 | 30 | # Basic colour operations. |
| paul@83 | 31 | |
| paul@83 | 32 | def within(v, lower, upper): |
| paul@83 | 33 | return min(max(v, lower), upper) |
| paul@83 | 34 | |
| paul@83 | 35 | def clip(v): |
| paul@83 | 36 | return int(within(v, 0, 255)) |
| paul@83 | 37 | |
| paul@83 | 38 | def restore(srgb): |
| paul@83 | 39 | r, g, b = srgb |
| paul@83 | 40 | return int(r * 255.0), int(g * 255.0), int(b * 255.0) |
| paul@83 | 41 | |
| paul@83 | 42 | def scale(rgb): |
| paul@83 | 43 | r, g, b = rgb |
| paul@83 | 44 | return r / 255.0, g / 255.0, b / 255.0 |
| paul@83 | 45 | |
| paul@83 | 46 | def invert(srgb): |
| paul@83 | 47 | r, g, b = srgb |
| paul@83 | 48 | return 1.0 - r, 1.0 - g, 1.0 - b |
| paul@83 | 49 | |
| paul@83 | 50 | scaled_corners = map(scale, corners) |
| paul@83 | 51 | zipped_corners = zip(corners, scaled_corners) |
| paul@83 | 52 | |
| paul@83 | 53 | # Colour distribution functions. |
| paul@83 | 54 | |
| paul@83 | 55 | def combination(rgb): |
| paul@83 | 56 | |
| paul@83 | 57 | "Return the colour distribution for 'rgb'." |
| paul@83 | 58 | |
| paul@83 | 59 | # Get the colour with components scaled from 0 to 1, plus the inverted |
| paul@83 | 60 | # component values. |
| paul@83 | 61 | |
| paul@83 | 62 | srgb = scale(rgb) |
| paul@83 | 63 | rgbi = invert(srgb) |
| paul@83 | 64 | pairs = zip(rgbi, srgb) |
| paul@83 | 65 | |
| paul@83 | 66 | # For each corner of the colour cube (primary and secondary colours plus |
| paul@83 | 67 | # black and white), calculate the corner value's contribution to the |
| paul@83 | 68 | # input colour. |
| paul@83 | 69 | |
| paul@83 | 70 | d = [] |
| paul@83 | 71 | for corner, scaled in zipped_corners: |
| paul@83 | 72 | rs, gs, bs = scaled |
| paul@83 | 73 | |
| paul@83 | 74 | # Obtain inverted channel values where corner channels are low; |
| paul@83 | 75 | # obtain original channel values where corner channels are high. |
| paul@83 | 76 | |
| paul@83 | 77 | d.append((pairs[0][int(rs)] * pairs[1][int(gs)] * pairs[2][int(bs)], corner)) |
| paul@83 | 78 | |
| paul@83 | 79 | # Balance the corner contributions. |
| paul@83 | 80 | |
| paul@83 | 81 | return balance(d) |
| paul@83 | 82 | |
| paul@83 | 83 | def complements(rgb): |
| paul@83 | 84 | |
| paul@83 | 85 | "Return 'rgb' and its complement." |
| paul@83 | 86 | |
| paul@83 | 87 | r, g, b = rgb |
| paul@83 | 88 | return rgb, restore(invert(scale(rgb))) |
| paul@83 | 89 | |
| paul@83 | 90 | bases = [(0, 0, 0), (255, 0, 0), (0, 255, 0), (0, 0, 255)] |
| paul@83 | 91 | base_complements = map(complements, bases) |
| paul@83 | 92 | |
| paul@83 | 93 | def balance(d): |
| paul@83 | 94 | |
| paul@83 | 95 | """ |
| paul@83 | 96 | Balance distribution 'd', cancelling opposing values and their complements |
| paul@83 | 97 | and replacing their common contributions with black and white contributions. |
| paul@83 | 98 | """ |
| paul@83 | 99 | |
| paul@83 | 100 | dd = dict([(value, f) for f, value in d]) |
| paul@83 | 101 | for primary, secondary in base_complements: |
| paul@83 | 102 | common = min(dd[primary], dd[secondary]) |
| paul@83 | 103 | dd[primary] -= common |
| paul@83 | 104 | dd[secondary] -= common |
| paul@83 | 105 | return [(f, value) for value, f in dd.items()] |
| paul@83 | 106 | |
| paul@83 | 107 | def combine(d): |
| paul@83 | 108 | |
| paul@83 | 109 | "Combine distribution 'd' to get a colour value." |
| paul@83 | 110 | |
| paul@83 | 111 | out = [0, 0, 0] |
| paul@83 | 112 | for v, rgb in d: |
| paul@83 | 113 | out[0] += v * rgb[0] |
| paul@83 | 114 | out[1] += v * rgb[1] |
| paul@83 | 115 | out[2] += v * rgb[2] |
| paul@83 | 116 | return tuple(map(int, out)) |
| paul@83 | 117 | |
| paul@83 | 118 | def pattern(rgb, chosen=None): |
| paul@83 | 119 | |
| paul@83 | 120 | """ |
| paul@83 | 121 | Obtain a sorted colour distribution for 'rgb', optionally limited to any |
| paul@83 | 122 | specified 'chosen' colours. |
| paul@83 | 123 | """ |
| paul@83 | 124 | |
| paul@83 | 125 | l = [(f, value) for f, value in combination(rgb) if not chosen or value in chosen] |
| paul@83 | 126 | l.sort(reverse=True) |
| paul@83 | 127 | return l |
| paul@83 | 128 | |
| paul@83 | 129 | def get_value(rgb, chosen=None, fail=False): |
| paul@83 | 130 | |
| paul@83 | 131 | """ |
| paul@83 | 132 | Get an output colour for 'rgb', optionally limited to any specified 'chosen' |
| paul@83 | 133 | colours. If 'fail' is set to a true value, return None if the colour cannot |
| paul@83 | 134 | be expressed using any of the chosen colours. |
| paul@83 | 135 | """ |
| paul@83 | 136 | |
| paul@83 | 137 | l = pattern(rgb, chosen) |
| paul@83 | 138 | limit = sum([f for f, c in l]) |
| paul@83 | 139 | if not limit: |
| paul@83 | 140 | if fail: |
| paul@83 | 141 | return None |
| paul@83 | 142 | else: |
| paul@83 | 143 | return l[randrange(0, len(l))][1] |
| paul@83 | 144 | |
| paul@83 | 145 | choose = random() * limit |
| paul@83 | 146 | threshold = 0 |
| paul@83 | 147 | for f, c in l: |
| paul@83 | 148 | threshold += f |
| paul@83 | 149 | if choose < threshold: |
| paul@83 | 150 | return c |
| paul@83 | 151 | return c |
| paul@83 | 152 | |
| paul@83 | 153 | # Colour processing operations. |
| paul@83 | 154 | |
| paul@83 | 155 | def sign(x): |
| paul@83 | 156 | if x >= 0: |
| paul@83 | 157 | return 1 |
| paul@83 | 158 | else: |
| paul@83 | 159 | return -1 |
| paul@83 | 160 | |
| paul@83 | 161 | def saturate_rgb(rgb, exp): |
| paul@83 | 162 | r, g, b = rgb |
| paul@83 | 163 | return saturate_value(r, exp), saturate_value(g, exp), saturate_value(b, exp) |
| paul@83 | 164 | |
| paul@83 | 165 | def saturate_value(x, exp): |
| paul@83 | 166 | return int(127.5 + sign(x - 127.5) * 127.5 * pow(abs(x - 127.5) / 127.5, exp)) |
| paul@83 | 167 | |
| paul@83 | 168 | def amplify_rgb(rgb, exp): |
| paul@83 | 169 | r, g, b = rgb |
| paul@83 | 170 | return amplify_value(r, exp), amplify_value(g, exp), amplify_value(b, exp) |
| paul@83 | 171 | |
| paul@83 | 172 | def amplify_value(x, exp): |
| paul@83 | 173 | return int(pow(x / 255.0, exp) * 255.0) |
| paul@83 | 174 | |
| paul@83 | 175 | # Exercise functions for Shedskin. |
| paul@83 | 176 | |
| paul@83 | 177 | if __name__ == "__main__": |
| paul@83 | 178 | rgb = (200, 100, 50) |
| paul@83 | 179 | saturate_rgb(rgb, 1.0) |
| paul@83 | 180 | amplify_rgb(rgb, 1.0) |
| paul@83 | 181 | get_value(rgb) |
| paul@83 | 182 | get_value(rgb, [(255, 255, 255), (255, 0, 0), (255, 255, 0), (0, 0, 0)]) |
| paul@83 | 183 | combine([(1.0, (255, 0, 0)), (0.0, (0, 0, 0))]) |
| paul@83 | 184 | clip(200.0) |
| paul@83 | 185 | |
| paul@83 | 186 | # vim: tabstop=4 expandtab shiftwidth=4 |
