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(pim, saturate, desaturate, darken, brighten): 279 280 """ 281 Process image 'pim' using the given options: 'saturate', 'desaturate', 282 'darken', 'brighten'. 283 """ 284 285 width, height = pim.size 286 im = SimpleImage(list(pim.getdata()), pim.size) 287 288 if saturate or desaturate or darken or brighten: 289 for y in range(0, height): 290 for x in range(0, width): 291 rgb = im.getpixel((x, y)) 292 if saturate or desaturate: 293 rgb = saturate_rgb(rgb, saturate and 0.5 / saturate or 2 * desaturate) 294 if darken or brighten: 295 rgb = amplify_rgb(rgb, brighten and 0.5 / brighten or 2 * darken) 296 im.putpixel((x, y), rgb) 297 298 pim.putdata(im.getdata()) 299 300 def convert_image(pim, colours): 301 302 "Convert image 'pim' to an appropriate output representation." 303 304 width, height = pim.size 305 im = SimpleImage(list(pim.getdata()), pim.size) 306 307 for y in range(0, height): 308 c = get_colours(im, y) 309 310 for l in get_combinations(c, colours): 311 most = [value for f, value in l] 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 break # try next combination 317 else: 318 break # use this combination 319 else: 320 most = [value for f, value in c[:colours]] # use the first colours 321 322 for x in range(0, width): 323 rgb = im.getpixel((x, y)) 324 value = get_value(rgb, most) 325 im.putpixel((x, y), value) 326 327 if x < width - 1: 328 rgbn = im.getpixel((x+1, y)) 329 rgbn = ( 330 clip(rgbn[0] + (rgb[0] - value[0]) / 4.0), 331 clip(rgbn[1] + (rgb[1] - value[1]) / 4.0), 332 clip(rgbn[2] + (rgb[2] - value[2]) / 4.0) 333 ) 334 im.putpixel((x+1, y), rgbn) 335 336 if y < height - 1: 337 rgbn = im.getpixel((x, y+1)) 338 rgbn = ( 339 clip(rgbn[0] + (rgb[0] - value[0]) / 2.0), 340 clip(rgbn[1] + (rgb[1] - value[1]) / 2.0), 341 clip(rgbn[2] + (rgb[2] - value[2]) / 2.0) 342 ) 343 im.putpixel((x, y+1), rgbn) 344 345 pim.putdata(im.getdata()) 346 347 def get_parameter(options, flag, conversion, default, missing): 348 349 """ 350 From 'options', return any parameter following the given 'flag', applying 351 the 'conversion' which has the given 'default' if no valid parameter is 352 found, or returning the given 'missing' value if the flag does not appear at 353 all. 354 """ 355 356 try: 357 i = options.index(flag) 358 try: 359 return conversion(options[i+1]) 360 except (IndexError, ValueError): 361 return default 362 except ValueError: 363 return missing 364 365 class SimpleImage: 366 367 "An image behaving like PIL.Image." 368 369 def __init__(self, data, size): 370 self.data = data 371 self.width, self.height = self.size = size 372 373 def copy(self): 374 return SimpleImage(self.data[:], self.size) 375 376 def getpixel(self, xy): 377 x, y = xy 378 return self.data[y * self.width + x] 379 380 def putpixel(self, xy, value): 381 x, y = xy 382 self.data[y * self.width + x] = value 383 384 def getdata(self): 385 return self.data 386 387 # Main program. 388 389 if __name__ == "__main__": 390 391 # Test options. 392 393 if "--test" in sys.argv: 394 test() 395 sys.exit(0) 396 elif "--test-flat" in sys.argv: 397 test_flat((120, 40, 60)) 398 sys.exit(0) 399 elif "--help" in sys.argv: 400 print >>sys.stderr, """\ 401 Usage: %s <input filename> <output filename> [ <options> ] 402 403 Options are... 404 405 -W - Indicate the output width (default is 320) 406 -C - Number of colours per scanline (default is 4) 407 408 -s - Saturate the input image (optional float, 1.0 if unspecified) 409 -d - Desaturate the input image (optional float, 1.0 if unspecified) 410 -D - Darken the input image (optional float, 1.0 if unspecified) 411 -B - Brighten the input image (optional float, 1.0 if unspecified) 412 413 -r - Rotate the input image clockwise 414 -p - Generate a separate preview image 415 -h - Make the preview image with half horizontal resolution (MODE 2) 416 -v - Verify the output image (loaded if -n is given) 417 -n - Generate no output image 418 """ % split(sys.argv[0])[1] 419 sys.exit(1) 420 421 base_width = 320 422 height = 256 423 424 input_filename, output_filename = sys.argv[1:3] 425 basename, ext = splitext(output_filename) 426 preview_filename = "".join([basename + "_preview", ext]) 427 428 options = sys.argv[3:] 429 430 # Basic image properties. 431 432 width = get_parameter(options, "-W", int, base_width, base_width) 433 number_of_colours = get_parameter(options, "-C", int, 4, 4) 434 435 # Preprocessing options that employ parameters. 436 437 saturate = get_parameter(options, "-s", float, 1.0, 0.0) 438 desaturate = get_parameter(options, "-d", float, 1.0, 0.0) 439 darken = get_parameter(options, "-D", float, 1.0, 0.0) 440 brighten = get_parameter(options, "-B", float, 1.0, 0.0) 441 442 # General output options. 443 444 rotate = "-r" in options 445 preview = "-p" in options 446 half_resolution_preview = "-h" in options 447 verify = "-v" in options 448 no_normal_output = "-n" in options 449 make_image = not no_normal_output 450 451 # Load the input image if requested. 452 453 if make_image or preview: 454 exif = EXIF.process_file(open(input_filename)) 455 im = PIL.Image.open(input_filename).convert("RGB") 456 im = rotate_and_scale(exif, im, base_width, height, rotate) 457 458 # Scale images to the appropriate width. 459 460 if width != base_width: 461 im = im.resize((width, height)) 462 463 process_image(im, saturate, desaturate, darken, brighten) 464 465 # Generate a preview if requested. 466 467 if preview: 468 imp = im.copy() 469 if half_resolution_preview: 470 imp = imp.resize((width / 2, height)) 471 convert_image(imp, 8) 472 if half_resolution_preview: 473 imp = imp.resize((width, height)) 474 imp.save(preview_filename) 475 476 # Generate an output image if requested. 477 478 if make_image: 479 convert_image(im, number_of_colours) 480 im.save(output_filename) 481 482 # Verify the output image (which may be loaded) if requested. 483 484 if verify: 485 if no_normal_output: 486 im = PIL.Image.open(output_filename).convert("RGB") 487 488 result = count_colours(im, number_of_colours) 489 if result is not None: 490 y, colours = result 491 print "Image %s: row %d has the following colours: %s" % (output_filename, y, "; ".join([repr(c) for c in colours])) 492 493 # vim: tabstop=4 expandtab shiftwidth=4