1 #!/usr/bin/env python 2 3 """ 4 Convert and optimise images for display in an Acorn Electron MODE 1 variant 5 with four colours per line but eight colours available for selection on each 6 line. 7 8 Copyright (C) 2015 Paul Boddie <paul@boddie.org.uk> 9 10 This program is free software; you can redistribute it and/or modify it under 11 the terms of the GNU General Public License as published by the Free Software 12 Foundation; either version 3 of the License, or (at your option) any later 13 version. 14 15 This program is distributed in the hope that it will be useful, but WITHOUT ANY 16 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A 17 PARTICULAR PURPOSE. See the GNU General Public License for more details. 18 19 You should have received a copy of the GNU General Public License along 20 with this program. If not, see <http://www.gnu.org/licenses/>. 21 """ 22 23 from random import random, randrange 24 from os.path import split, splitext 25 import EXIF 26 import PIL.Image 27 import itertools 28 import sys 29 30 corners = [ 31 (0, 0, 0), (255, 0, 0), (0, 255, 0), (255, 255, 0), 32 (0, 0, 255), (255, 0, 255), (0, 255, 255), (255, 255, 255) 33 ] 34 35 # Basic colour operations. 36 37 def within(v, lower, upper): 38 return min(max(v, lower), upper) 39 40 def clip(v): 41 return int(within(v, 0, 255)) 42 43 def restore(srgb): 44 r, g, b = srgb 45 return int(r * 255.0), int(g * 255.0), int(b * 255.0) 46 47 def scale(rgb): 48 r, g, b = rgb 49 return r / 255.0, g / 255.0, b / 255.0 50 51 def invert(srgb): 52 r, g, b = srgb 53 return 1.0 - r, 1.0 - g, 1.0 - b 54 55 scaled_corners = map(scale, corners) 56 zipped_corners = zip(corners, scaled_corners) 57 58 # Colour distribution functions. 59 60 def combination(rgb): 61 62 "Return the colour distribution for 'rgb'." 63 64 # Get the colour with components scaled from 0 to 1, plus the inverted 65 # component values. 66 67 srgb = scale(rgb) 68 rgbi = invert(srgb) 69 pairs = zip(rgbi, srgb) 70 71 # For each corner of the colour cube (primary and secondary colours plus 72 # black and white), calculate the corner value's contribution to the 73 # input colour. 74 75 d = [] 76 for corner, scaled in zipped_corners: 77 rs, gs, bs = scaled 78 79 # Obtain inverted channel values where corner channels are low; 80 # obtain original channel values where corner channels are high. 81 82 d.append((pairs[0][int(rs)] * pairs[1][int(gs)] * pairs[2][int(bs)], corner)) 83 84 # Balance the corner contributions. 85 86 return balance(d) 87 88 def complements(rgb): 89 90 "Return 'rgb' and its complement." 91 92 r, g, b = rgb 93 return rgb, restore(invert(scale(rgb))) 94 95 bases = [(0, 0, 0), (255, 0, 0), (0, 255, 0), (0, 0, 255)] 96 base_complements = map(complements, bases) 97 98 def balance(d): 99 100 """ 101 Balance distribution 'd', cancelling opposing values and their complements 102 and replacing their common contributions with black and white contributions. 103 """ 104 105 d = dict([(value, f) for f, value in d]) 106 for primary, secondary in base_complements: 107 common = min(d[primary], d[secondary]) 108 d[primary] -= common 109 d[secondary] -= common 110 return [(f, value) for value, f in d.items()] 111 112 def combine(d): 113 114 "Combine distribution 'd' to get a colour value." 115 116 out = [0, 0, 0] 117 for v, rgb in d: 118 out[0] += v * rgb[0] 119 out[1] += v * rgb[1] 120 out[2] += v * rgb[2] 121 return tuple(map(int, out)) 122 123 def pattern(rgb, chosen=None): 124 125 """ 126 Obtain a sorted colour distribution for 'rgb', optionally limited to any 127 specified 'chosen' colours. 128 """ 129 130 l = [(f, value) for f, value in combination(rgb) if not chosen or value in chosen] 131 l.sort(reverse=True) 132 return l 133 134 def get_value(rgb, chosen=None, fail=False): 135 136 """ 137 Get an output colour for 'rgb', optionally limited to any specified 'chosen' 138 colours. If 'fail' is set to a true value, return None if the colour cannot 139 be expressed using any of the chosen colours. 140 """ 141 142 l = pattern(rgb, chosen) 143 limit = sum([f for f, c in l]) 144 if not limit: 145 if fail: 146 return None 147 else: 148 return l[randrange(0, len(l))][1] 149 150 choose = random() * limit 151 threshold = 0 152 for f, c in l: 153 threshold += f 154 if choose < threshold: 155 return c 156 return c 157 158 # Colour processing operations. 159 160 def sign(x): 161 return x >= 0 and 1 or -1 162 163 def saturate_rgb(rgb, exp): 164 r, g, b = rgb 165 return saturate_value(r, exp), saturate_value(g, exp), saturate_value(b, exp) 166 167 def saturate_value(x, exp): 168 return int(127.5 + sign(x - 127.5) * 127.5 * pow(abs(x - 127.5) / 127.5, exp)) 169 170 def amplify_rgb(rgb, exp): 171 r, g, b = rgb 172 return amplify_value(r, exp), amplify_value(g, exp), amplify_value(b, exp) 173 174 def amplify_value(x, exp): 175 return int(pow(x / 255.0, exp) * 255.0) 176 177 # Image operations. 178 179 def get_colours(im, y): 180 181 "Get a colour distribution from image 'im' for the row 'y'." 182 183 width, height = im.size 184 c = {} 185 for x in range(0, width): 186 rgb = im.getpixel((x, y)) 187 188 # Sum the colour probabilities. 189 190 for f, value in combination(rgb): 191 if not c.has_key(value): 192 c[value] = f 193 else: 194 c[value] += f 195 196 d = [(n/width, value) for value, n in c.items()] 197 d.sort(reverse=True) 198 return d 199 200 def get_combinations(c, n): 201 202 """ 203 Get combinations of colours from 'c' of size 'n' in decreasing order of 204 probability. 205 """ 206 207 all = [] 208 for l in itertools.combinations(c, n): 209 total = 0 210 for f, value in l: 211 total += f 212 all.append((total, l)) 213 all.sort(reverse=True) 214 return [l for total, l in all] 215 216 def test(): 217 218 "Generate slices of the colour cube." 219 220 size = 512 221 for r in (0, 63, 127, 191, 255): 222 im = PIL.Image.new("RGB", (size, size)) 223 for g in range(0, size): 224 for b in range(0, size): 225 value = get_value((r, (g * 256) / size, (b * 256 / size))) 226 im.putpixel((g, b), value) 227 im.save("rgb%d.png" % r) 228 229 def test_flat(rgb): 230 231 "Generate a flat image for the colour 'rgb'." 232 233 size = 64 234 im = PIL.Image.new("RGB", (size, size)) 235 for y in range(0, size): 236 for x in range(0, size): 237 im.putpixel((x, y), get_value(rgb)) 238 im.save("rgb%02d%02d%02d.png" % rgb) 239 240 def rotate_and_scale(exif, im, width, height, rotate): 241 242 """ 243 Using the given 'exif' information, rotate and scale image 'im' given the 244 indicated 'width' and 'height' constraints and any explicit 'rotate' 245 indication. The returned image will be within the given 'width' and 246 'height', filling either or both, and preserve its original aspect ratio. 247 """ 248 249 if rotate or exif and exif["Image Orientation"].values == [6L]: 250 im = im.rotate(270) 251 252 w, h = im.size 253 if w > h: 254 height = (width * h) / w 255 else: 256 width = (height * w) / h 257 258 return im.resize((width, height)) 259 260 def count_colours(im, colours): 261 262 """ 263 Count colours on each row of image 'im', returning a tuple indicating the 264 first row with more than the given number of 'colours' together with the 265 found colours; otherwise returning None. 266 """ 267 268 width, height = im.size 269 270 for y in range(0, height): 271 l = set() 272 for x in range(0, width): 273 l.add(im.getpixel((x, y))) 274 if len(l) > colours: 275 return (y, l) 276 return None 277 278 def process_image(im, saturate, desaturate, darken, brighten): 279 280 """ 281 Process image 'im' using the given options: 'saturate', 'desaturate', 282 'darken', 'brighten'. 283 """ 284 285 width, height = im.size 286 287 if saturate or desaturate or darken or brighten: 288 for y in range(0, height): 289 for x in range(0, width): 290 rgb = im.getpixel((x, y)) 291 if saturate or desaturate: 292 rgb = saturate_rgb(rgb, saturate and 0.5 / saturate or 2 * desaturate) 293 if darken or brighten: 294 rgb = amplify_rgb(rgb, brighten and 0.5 / brighten or 2 * darken) 295 im.putpixel((x, y), rgb) 296 297 def convert_image(im, colours): 298 299 "Convert image 'im' to an appropriate output representation." 300 301 width, height = im.size 302 303 for y in range(0, height): 304 c = get_colours(im, y) 305 306 for l in get_combinations(c, colours): 307 most = [value for f, value in l] 308 for x in range(0, width): 309 rgb = im.getpixel((x, y)) 310 value = get_value(rgb, most, True) 311 if value is None: 312 break # try next combination 313 else: 314 break # use this combination 315 else: 316 most = [value for f, value in c[:colours]] # use the first colours 317 318 for x in range(0, width): 319 rgb = im.getpixel((x, y)) 320 value = get_value(rgb, most) 321 im.putpixel((x, y), value) 322 323 if x < width - 1: 324 rgbn = im.getpixel((x+1, y)) 325 rgbn = ( 326 clip(rgbn[0] + (rgb[0] - value[0]) / 4.0), 327 clip(rgbn[1] + (rgb[1] - value[1]) / 4.0), 328 clip(rgbn[2] + (rgb[2] - value[2]) / 4.0) 329 ) 330 im.putpixel((x+1, y), rgbn) 331 332 if y < height - 1: 333 rgbn = im.getpixel((x, y+1)) 334 rgbn = ( 335 clip(rgbn[0] + (rgb[0] - value[0]) / 2.0), 336 clip(rgbn[1] + (rgb[1] - value[1]) / 2.0), 337 clip(rgbn[2] + (rgb[2] - value[2]) / 2.0) 338 ) 339 im.putpixel((x, y+1), rgbn) 340 341 def get_parameter(options, flag, conversion, default, missing): 342 343 """ 344 From 'options', return any parameter following the given 'flag', applying 345 the 'conversion' which has the given 'default' if no valid parameter is 346 found, or returning the given 'missing' value if the flag does not appear at 347 all. 348 """ 349 350 try: 351 i = options.index(flag) 352 try: 353 return conversion(options[i+1]) 354 except (IndexError, ValueError): 355 return default 356 except ValueError: 357 return missing 358 359 # Main program. 360 361 if __name__ == "__main__": 362 363 # Test options. 364 365 if "--test" in sys.argv: 366 test() 367 sys.exit(0) 368 elif "--test-flat" in sys.argv: 369 test_flat((120, 40, 60)) 370 sys.exit(0) 371 elif "--help" in sys.argv: 372 print >>sys.stderr, """\ 373 Usage: %s <input filename> <output filename> [ <options> ] 374 375 Options are... 376 377 -W - Indicate the output width (default is 320) 378 -C - Number of colours per scanline (default is 4) 379 380 -s - Saturate the input image (optional float, 1.0 if unspecified) 381 -d - Desaturate the input image (optional float, 1.0 if unspecified) 382 -D - Darken the input image (optional float, 1.0 if unspecified) 383 -B - Brighten the input image (optional float, 1.0 if unspecified) 384 385 -r - Rotate the input image clockwise 386 -p - Generate a separate preview image 387 -h - Make the preview image with half horizontal resolution (MODE 2) 388 -v - Verify the output image (loaded if -n is given) 389 -n - Generate no output image 390 """ % split(sys.argv[0])[1] 391 sys.exit(1) 392 393 base_width = 320 394 height = 256 395 396 input_filename, output_filename = sys.argv[1:3] 397 basename, ext = splitext(output_filename) 398 preview_filename = "".join([basename + "_preview", ext]) 399 400 options = sys.argv[3:] 401 402 # Basic image properties. 403 404 width = get_parameter(options, "-W", int, base_width, base_width) 405 number_of_colours = get_parameter(options, "-C", int, 4, 4) 406 407 # Preprocessing options that employ parameters. 408 409 saturate = get_parameter(options, "-s", float, 1.0, 0.0) 410 desaturate = get_parameter(options, "-d", float, 1.0, 0.0) 411 darken = get_parameter(options, "-D", float, 1.0, 0.0) 412 brighten = get_parameter(options, "-B", float, 1.0, 0.0) 413 414 # General output options. 415 416 rotate = "-r" in options 417 preview = "-p" in options 418 half_resolution_preview = "-h" in options 419 verify = "-v" in options 420 no_normal_output = "-n" in options 421 make_image = not no_normal_output 422 423 # Load the input image if requested. 424 425 if make_image or preview: 426 exif = EXIF.process_file(open(input_filename)) 427 im = PIL.Image.open(input_filename).convert("RGB") 428 im = rotate_and_scale(exif, im, base_width, height, rotate) 429 430 # Scale images to the appropriate width. 431 432 if width != base_width: 433 im = im.resize((width, height)) 434 435 process_image(im, saturate, desaturate, darken, brighten) 436 437 # Generate a preview if requested. 438 439 if preview: 440 imp = im.copy() 441 if half_resolution_preview: 442 imp = imp.resize((width / 2, height)) 443 convert_image(imp, 8) 444 if half_resolution_preview: 445 imp = imp.resize((width, height)) 446 imp.save(preview_filename) 447 448 # Generate an output image if requested. 449 450 if make_image: 451 convert_image(im, number_of_colours) 452 im.save(output_filename) 453 454 # Verify the output image (which may be loaded) if requested. 455 456 if verify: 457 if no_normal_output: 458 im = PIL.Image.open(output_filename).convert("RGB") 459 460 result = count_colours(im, number_of_colours) 461 if result is not None: 462 y, colours = result 463 print "Image %s: row %d has the following colours: %s" % (output_filename, y, "; ".join([repr(c) for c in colours])) 464 465 # vim: tabstop=4 expandtab shiftwidth=4