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 preview_image(pim, half_resolution_preview=False): 301 302 "Return a preview copy of image 'pim'." 303 304 width, height = pim.size 305 imp = pim.copy() 306 im = SimpleImage(list(pim.getdata()), pim.size) 307 step = half_resolution_preview and 2 or 1 308 309 for y in range(0, height): 310 for x in range(0, width, step): 311 rgb = im.getpixel((x, y)) 312 value = get_value(rgb) 313 im.putpixel((x, y), value) 314 if half_resolution_preview: 315 im.putpixel((x+1, y), value) 316 317 imp.putdata(im.getdata()) 318 return imp 319 320 def convert_image(pim): 321 322 "Convert image 'pim' to an appropriate output representation." 323 324 width, height = pim.size 325 im = SimpleImage(list(pim.getdata()), pim.size) 326 327 for y in range(0, height): 328 c = get_colours(im, y) 329 330 for l in get_combinations(c, 4): 331 most = [value for f, value in l] 332 for x in range(0, width): 333 rgb = im.getpixel((x, y)) 334 value = get_value(rgb, most, True) 335 if value is None: 336 break # try next combination 337 else: 338 break # use this combination 339 else: 340 most = [value for f, value in c[:4]] # use the first four 341 342 for x in range(0, width): 343 rgb = im.getpixel((x, y)) 344 value = get_value(rgb, most) 345 im.putpixel((x, y), value) 346 347 if x < width - 1: 348 rgbn = im.getpixel((x+1, y)) 349 rgbn = ( 350 clip(rgbn[0] + (rgb[0] - value[0]) / 4.0), 351 clip(rgbn[1] + (rgb[1] - value[1]) / 4.0), 352 clip(rgbn[2] + (rgb[2] - value[2]) / 4.0) 353 ) 354 im.putpixel((x+1, y), rgbn) 355 356 if y < height - 1: 357 rgbn = im.getpixel((x, y+1)) 358 rgbn = ( 359 clip(rgbn[0] + (rgb[0] - value[0]) / 2.0), 360 clip(rgbn[1] + (rgb[1] - value[1]) / 2.0), 361 clip(rgbn[2] + (rgb[2] - value[2]) / 2.0) 362 ) 363 im.putpixel((x, y+1), rgbn) 364 365 pim.putdata(im.getdata()) 366 367 def get_float(options, flag): 368 try: 369 i = options.index(flag) 370 try: 371 return float(options[i+1]) 372 except (IndexError, ValueError): 373 return 1.0 374 except ValueError: 375 return 0.0 376 377 class SimpleImage: 378 379 "An image behaving like PIL.Image." 380 381 def __init__(self, data, size): 382 self.data = data 383 self.width, self.height = self.size = size 384 385 def copy(self): 386 return SimpleImage(self.data[:], self.size) 387 388 def getpixel(self, xy): 389 x, y = xy 390 return self.data[y * self.width + x] 391 392 def putpixel(self, xy, value): 393 x, y = xy 394 self.data[y * self.width + x] = value 395 396 def getdata(self): 397 return self.data 398 399 # Main program. 400 401 if __name__ == "__main__": 402 403 # Test options. 404 405 if "--test" in sys.argv: 406 test() 407 sys.exit(0) 408 elif "--test-flat" in sys.argv: 409 test_flat((120, 40, 60)) 410 sys.exit(0) 411 elif "--help" in sys.argv: 412 print >>sys.stderr, """\ 413 Usage: %s <input filename> <output filename> [ <options> ] 414 415 Options are... 416 417 -s - Saturate the input image (can be followed by a float, default 1.0) 418 -d - Desaturate the input image (can be followed by a float, default 1.0) 419 -D - Darken the input image (can be followed by a float, default 1.0) 420 -B - Brighten the input image (can be followed by a float, default 1.0) 421 422 -r - Rotate the input image clockwise 423 -p - Generate a separate preview image 424 -h - Make the preview image with half horizontal resolution (MODE 2) 425 -v - Verify the output image (loaded if -n is given) 426 -n - Generate no output image 427 """ % split(sys.argv[0])[1] 428 sys.exit(1) 429 430 width = 320 431 height = 256 432 433 input_filename, output_filename = sys.argv[1:3] 434 basename, ext = splitext(output_filename) 435 preview_filename = "".join([basename + "_preview", ext]) 436 437 options = sys.argv[3:] 438 439 # Preprocessing options that can be repeated for extra effect. 440 441 saturate = get_float(options, "-s") 442 desaturate = get_float(options, "-d") 443 darken = get_float(options, "-D") 444 brighten = get_float(options, "-B") 445 446 # General output options. 447 448 rotate = "-r" in options 449 preview = "-p" in options 450 half_resolution_preview = "-h" in options 451 verify = "-v" in options 452 no_normal_output = "-n" in options 453 make_image = not no_normal_output 454 455 # Load the input image if requested. 456 457 if make_image or preview: 458 exif = EXIF.process_file(open(input_filename)) 459 im = PIL.Image.open(input_filename).convert("RGB") 460 im = rotate_and_scale(exif, im, width, height, rotate) 461 462 process_image(im, saturate, desaturate, darken, brighten) 463 464 # Generate a preview if requested. 465 466 if preview: 467 preview_image(im, half_resolution_preview).save(preview_filename) 468 469 # Generate an output image if requested. 470 471 if make_image: 472 convert_image(im) 473 im.save(output_filename) 474 475 # Verify the output image (which may be loaded) if requested. 476 477 if verify: 478 if no_normal_output: 479 im = PIL.Image.open(output_filename).convert("RGB") 480 481 result = count_colours(im, 4) 482 if result is not None: 483 y, colours = result 484 print "Image %s: row %d has the following colours: %s" % (output_filename, y, "; ".join([repr(c) for c in colours])) 485 486 # vim: tabstop=4 expandtab shiftwidth=4