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 suggestions = [] 307 308 for l in get_combinations(c, colours): 309 most = [value for f, value in l] 310 missing = 0 311 312 for x in range(0, width): 313 rgb = im.getpixel((x, y)) 314 value = get_value(rgb, most, True) 315 if value is None: 316 missing += 1 317 318 if not missing: 319 break # use this combination 320 suggestions.append((missing, l)) 321 322 # Find the most accurate suggestion. 323 324 else: 325 suggestions.sort() 326 most = [value for f, value in suggestions[0][1]] # get the combination 327 328 for x in range(0, width): 329 rgb = im.getpixel((x, y)) 330 value = get_value(rgb, most) 331 im.putpixel((x, y), value) 332 333 if x < width - 1: 334 rgbn = im.getpixel((x+1, y)) 335 rgbn = ( 336 clip(rgbn[0] + (rgb[0] - value[0]) / 4.0), 337 clip(rgbn[1] + (rgb[1] - value[1]) / 4.0), 338 clip(rgbn[2] + (rgb[2] - value[2]) / 4.0) 339 ) 340 im.putpixel((x+1, y), rgbn) 341 342 if y < height - 1: 343 rgbn = im.getpixel((x, y+1)) 344 rgbn = ( 345 clip(rgbn[0] + (rgb[0] - value[0]) / 2.0), 346 clip(rgbn[1] + (rgb[1] - value[1]) / 2.0), 347 clip(rgbn[2] + (rgb[2] - value[2]) / 2.0) 348 ) 349 im.putpixel((x, y+1), rgbn) 350 351 def get_parameter(options, flag, conversion, default, missing): 352 353 """ 354 From 'options', return any parameter following the given 'flag', applying 355 the 'conversion' which has the given 'default' if no valid parameter is 356 found, or returning the given 'missing' value if the flag does not appear at 357 all. 358 """ 359 360 try: 361 i = options.index(flag) 362 try: 363 return conversion(options[i+1]) 364 except (IndexError, ValueError): 365 return default 366 except ValueError: 367 return missing 368 369 # Main program. 370 371 if __name__ == "__main__": 372 373 # Test options. 374 375 if "--test" in sys.argv: 376 test() 377 sys.exit(0) 378 elif "--test-flat" in sys.argv: 379 test_flat((120, 40, 60)) 380 sys.exit(0) 381 elif "--help" in sys.argv: 382 print >>sys.stderr, """\ 383 Usage: %s <input filename> <output filename> [ <options> ] 384 385 Options are... 386 387 -W - Indicate the output width (default is 320) 388 -C - Number of colours per scanline (default is 4) 389 390 -s - Saturate the input image (optional float, 1.0 if unspecified) 391 -d - Desaturate the input image (optional float, 1.0 if unspecified) 392 -D - Darken the input image (optional float, 1.0 if unspecified) 393 -B - Brighten the input image (optional float, 1.0 if unspecified) 394 395 -r - Rotate the input image clockwise 396 -p - Generate a separate preview image 397 -h - Make the preview image with half horizontal resolution (MODE 2) 398 -v - Verify the output image (loaded if -n is given) 399 -n - Generate no output image 400 """ % split(sys.argv[0])[1] 401 sys.exit(1) 402 403 base_width = 320 404 height = 256 405 406 input_filename, output_filename = sys.argv[1:3] 407 basename, ext = splitext(output_filename) 408 preview_filename = "".join([basename + "_preview", ext]) 409 410 options = sys.argv[3:] 411 412 # Basic image properties. 413 414 width = get_parameter(options, "-W", int, base_width, base_width) 415 number_of_colours = get_parameter(options, "-C", int, 4, 4) 416 417 # Preprocessing options that employ parameters. 418 419 saturate = get_parameter(options, "-s", float, 1.0, 0.0) 420 desaturate = get_parameter(options, "-d", float, 1.0, 0.0) 421 darken = get_parameter(options, "-D", float, 1.0, 0.0) 422 brighten = get_parameter(options, "-B", float, 1.0, 0.0) 423 424 # General output options. 425 426 rotate = "-r" in options 427 preview = "-p" in options 428 half_resolution_preview = "-h" in options 429 verify = "-v" in options 430 no_normal_output = "-n" in options 431 make_image = not no_normal_output 432 433 # Load the input image if requested. 434 435 if make_image or preview: 436 exif = EXIF.process_file(open(input_filename)) 437 im = PIL.Image.open(input_filename).convert("RGB") 438 im = rotate_and_scale(exif, im, base_width, height, rotate) 439 440 # Scale images to the appropriate width. 441 442 if width != base_width: 443 im = im.resize((width, height)) 444 445 process_image(im, saturate, desaturate, darken, brighten) 446 447 # Generate a preview if requested. 448 449 if preview: 450 imp = im.copy() 451 if half_resolution_preview: 452 imp = imp.resize((width / 2, height)) 453 convert_image(imp, 8) 454 if half_resolution_preview: 455 imp = imp.resize((width, height)) 456 imp.save(preview_filename) 457 458 # Generate an output image if requested. 459 460 if make_image: 461 convert_image(im, number_of_colours) 462 im.save(output_filename) 463 464 # Verify the output image (which may be loaded) if requested. 465 466 if verify: 467 if no_normal_output: 468 im = PIL.Image.open(output_filename).convert("RGB") 469 470 result = count_colours(im, number_of_colours) 471 if result is not None: 472 y, colours = result 473 print "Image %s: row %d has the following colours: %s" % (output_filename, y, "; ".join([repr(c) for c in colours])) 474 475 # vim: tabstop=4 expandtab shiftwidth=4