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1 | /* |

2 | * jquant1.c |

3 | * |

4 | * Copyright (C) 1991-1996, Thomas G. Lane. |

5 | * This file is part of the Independent JPEG Group's software. |

6 | * For conditions of distribution and use, see the accompanying README file. |

7 | * |

8 | * This file contains 1-pass color quantization (color mapping) routines. |

9 | * These routines provide mapping to a fixed color map using equally spaced |

10 | * color values. Optional Floyd-Steinberg or ordered dithering is available. |

11 | */ |

12 | |

13 | #define JPEG_INTERNALS |

14 | #include "jinclude.h" |

15 | #include "jpeglib.h" |

16 | |

17 | #ifdef QUANT_1PASS_SUPPORTED |

18 | |

19 | |

20 | /* |

21 | * The main purpose of 1-pass quantization is to provide a fast, if not very |

22 | * high quality, colormapped output capability. A 2-pass quantizer usually |

23 | * gives better visual quality; however, for quantized grayscale output this |

24 | * quantizer is perfectly adequate. Dithering is highly recommended with this |

25 | * quantizer, though you can turn it off if you really want to. |

26 | * |

27 | * In 1-pass quantization the colormap must be chosen in advance of seeing the |

28 | * image. We use a map consisting of all combinations of Ncolors[i] color |

29 | * values for the i'th component. The Ncolors[] values are chosen so that |

30 | * their product, the total number of colors, is no more than that requested. |

31 | * (In most cases, the product will be somewhat less.) |

32 | * |

33 | * Since the colormap is orthogonal, the representative value for each color |

34 | * component can be determined without considering the other components; |

35 | * then these indexes can be combined into a colormap index by a standard |

36 | * N-dimensional-array-subscript calculation. Most of the arithmetic involved |

37 | * can be precalculated and stored in the lookup table colorindex[]. |

38 | * colorindex[i][j] maps pixel value j in component i to the nearest |

39 | * representative value (grid plane) for that component; this index is |

40 | * multiplied by the array stride for component i, so that the |

41 | * index of the colormap entry closest to a given pixel value is just |

42 | * sum( colorindex[component-number][pixel-component-value] ) |

43 | * Aside from being fast, this scheme allows for variable spacing between |

44 | * representative values with no additional lookup cost. |

45 | * |

46 | * If gamma correction has been applied in color conversion, it might be wise |

47 | * to adjust the color grid spacing so that the representative colors are |

48 | * equidistant in linear space. At this writing, gamma correction is not |

49 | * implemented by jdcolor, so nothing is done here. |

50 | */ |

51 | |

52 | |

53 | /* Declarations for ordered dithering. |

54 | * |

55 | * We use a standard 16x16 ordered dither array. The basic concept of ordered |

56 | * dithering is described in many references, for instance Dale Schumacher's |

57 | * chapter II.2 of Graphics Gems II (James Arvo, ed. Academic Press, 1991). |

58 | * In place of Schumacher's comparisons against a "threshold" value, we add a |

59 | * "dither" value to the input pixel and then round the result to the nearest |

60 | * output value. The dither value is equivalent to (0.5 - threshold) times |

61 | * the distance between output values. For ordered dithering, we assume that |

62 | * the output colors are equally spaced; if not, results will probably be |

63 | * worse, since the dither may be too much or too little at a given point. |

64 | * |

65 | * The normal calculation would be to form pixel value + dither, range-limit |

66 | * this to 0..MAXJSAMPLE, and then index into the colorindex table as usual. |

67 | * We can skip the separate range-limiting step by extending the colorindex |

68 | * table in both directions. |

69 | */ |

70 | |

71 | #define ODITHER_SIZE 16 /* dimension of dither matrix */ |

72 | /* NB: if ODITHER_SIZE is not a power of 2, ODITHER_MASK uses will break */ |

73 | #define ODITHER_CELLS (ODITHER_SIZE*ODITHER_SIZE) /* # cells in matrix */ |

74 | #define ODITHER_MASK (ODITHER_SIZE-1) /* mask for wrapping around counters */ |

75 | |

76 | typedef int ODITHER_MATRIX[ODITHER_SIZE][ODITHER_SIZE]; |

77 | typedef int (*ODITHER_MATRIX_PTR)[ODITHER_SIZE]; |

78 | |

79 | static const UINT8 base_dither_matrix[ODITHER_SIZE][ODITHER_SIZE] = { |

80 | /* Bayer's order-4 dither array. Generated by the code given in |

81 | * Stephen Hawley's article "Ordered Dithering" in Graphics Gems I. |

82 | * The values in this array must range from 0 to ODITHER_CELLS-1. |

83 | */ |

84 | { 0,192, 48,240, 12,204, 60,252, 3,195, 51,243, 15,207, 63,255 }, |

85 | { 128, 64,176,112,140, 76,188,124,131, 67,179,115,143, 79,191,127 }, |

86 | { 32,224, 16,208, 44,236, 28,220, 35,227, 19,211, 47,239, 31,223 }, |

87 | { 160, 96,144, 80,172,108,156, 92,163, 99,147, 83,175,111,159, 95 }, |

88 | { 8,200, 56,248, 4,196, 52,244, 11,203, 59,251, 7,199, 55,247 }, |

89 | { 136, 72,184,120,132, 68,180,116,139, 75,187,123,135, 71,183,119 }, |

90 | { 40,232, 24,216, 36,228, 20,212, 43,235, 27,219, 39,231, 23,215 }, |

91 | { 168,104,152, 88,164,100,148, 84,171,107,155, 91,167,103,151, 87 }, |

92 | { 2,194, 50,242, 14,206, 62,254, 1,193, 49,241, 13,205, 61,253 }, |

93 | { 130, 66,178,114,142, 78,190,126,129, 65,177,113,141, 77,189,125 }, |

94 | { 34,226, 18,210, 46,238, 30,222, 33,225, 17,209, 45,237, 29,221 }, |

95 | { 162, 98,146, 82,174,110,158, 94,161, 97,145, 81,173,109,157, 93 }, |

96 | { 10,202, 58,250, 6,198, 54,246, 9,201, 57,249, 5,197, 53,245 }, |

97 | { 138, 74,186,122,134, 70,182,118,137, 73,185,121,133, 69,181,117 }, |

98 | { 42,234, 26,218, 38,230, 22,214, 41,233, 25,217, 37,229, 21,213 }, |

99 | { 170,106,154, 90,166,102,150, 86,169,105,153, 89,165,101,149, 85 } |

100 | }; |

101 | |

102 | |

103 | /* Declarations for Floyd-Steinberg dithering. |

104 | * |

105 | * Errors are accumulated into the array fserrors[], at a resolution of |

106 | * 1/16th of a pixel count. The error at a given pixel is propagated |

107 | * to its not-yet-processed neighbors using the standard F-S fractions, |

108 | * ... (here) 7/16 |

109 | * 3/16 5/16 1/16 |

110 | * We work left-to-right on even rows, right-to-left on odd rows. |

111 | * |

112 | * We can get away with a single array (holding one row's worth of errors) |

113 | * by using it to store the current row's errors at pixel columns not yet |

114 | * processed, but the next row's errors at columns already processed. We |

115 | * need only a few extra variables to hold the errors immediately around the |

116 | * current column. (If we are lucky, those variables are in registers, but |

117 | * even if not, they're probably cheaper to access than array elements are.) |

118 | * |

119 | * The fserrors[] array is indexed [component#][position]. |

120 | * We provide (#columns + 2) entries per component; the extra entry at each |

121 | * end saves us from special-casing the first and last pixels. |

122 | * |

123 | * Note: on a wide image, we might not have enough room in a PC's near data |

124 | * segment to hold the error array; so it is allocated with alloc_large. |

125 | */ |

126 | |

127 | #if BITS_IN_JSAMPLE == 8 |

128 | typedef INT16 FSERROR; /* 16 bits should be enough */ |

129 | typedef int LOCFSERROR; /* use 'int' for calculation temps */ |

130 | #else |

131 | typedef INT32 FSERROR; /* may need more than 16 bits */ |

132 | typedef INT32 LOCFSERROR; /* be sure calculation temps are big enough */ |

133 | #endif |

134 | |

135 | typedef FSERROR FAR *FSERRPTR; /* pointer to error array (in FAR storage!) */ |

136 | |

137 | |

138 | /* Private subobject */ |

139 | |

140 | #define MAX_Q_COMPS 4 /* max components I can handle */ |

141 | |

142 | typedef struct { |

143 | struct jpeg_color_quantizer pub; /* public fields */ |

144 | |

145 | /* Initially allocated colormap is saved here */ |

146 | JSAMPARRAY sv_colormap; /* The color map as a 2-D pixel array */ |

147 | int sv_actual; /* number of entries in use */ |

148 | |

149 | JSAMPARRAY colorindex; /* Precomputed mapping for speed */ |

150 | /* colorindex[i][j] = index of color closest to pixel value j in component i, |

151 | * premultiplied as described above. Since colormap indexes must fit into |

152 | * JSAMPLEs, the entries of this array will too. |

153 | */ |

154 | boolean is_padded; /* is the colorindex padded for odither? */ |

155 | |

156 | int Ncolors[MAX_Q_COMPS]; /* # of values alloced to each component */ |

157 | |

158 | /* Variables for ordered dithering */ |

159 | int row_index; /* cur row's vertical index in dither matrix */ |

160 | ODITHER_MATRIX_PTR odither[MAX_Q_COMPS]; /* one dither array per component */ |

161 | |

162 | /* Variables for Floyd-Steinberg dithering */ |

163 | FSERRPTR fserrors[MAX_Q_COMPS]; /* accumulated errors */ |

164 | boolean on_odd_row; /* flag to remember which row we are on */ |

165 | } my_cquantizer; |

166 | |

167 | typedef my_cquantizer * my_cquantize_ptr; |

168 | |

169 | |

170 | /* |

171 | * Policy-making subroutines for create_colormap and create_colorindex. |

172 | * These routines determine the colormap to be used. The rest of the module |

173 | * only assumes that the colormap is orthogonal. |

174 | * |

175 | * * select_ncolors decides how to divvy up the available colors |

176 | * among the components. |

177 | * * output_value defines the set of representative values for a component. |

178 | * * largest_input_value defines the mapping from input values to |

179 | * representative values for a component. |

180 | * Note that the latter two routines may impose different policies for |

181 | * different components, though this is not currently done. |

182 | */ |

183 | |

184 | |

185 | LOCAL(int) |

186 | select_ncolors (j_decompress_ptr cinfo, int Ncolors[]) |

187 | /* Determine allocation of desired colors to components, */ |

188 | /* and fill in Ncolors[] array to indicate choice. */ |

189 | /* Return value is total number of colors (product of Ncolors[] values). */ |

190 | { |

191 | int nc = cinfo->out_color_components; /* number of color components */ |

192 | int max_colors = cinfo->desired_number_of_colors; |

193 | int total_colors, iroot, i, j; |

194 | boolean changed; |

195 | long temp; |

196 | static const int RGB_order[3] = { RGB_GREEN, RGB_RED, RGB_BLUE }; |

197 | |

198 | /* We can allocate at least the nc'th root of max_colors per component. */ |

199 | /* Compute floor(nc'th root of max_colors). */ |

200 | iroot = 1; |

201 | do { |

202 | iroot++; |

203 | temp = iroot; /* set temp = iroot ** nc */ |

204 | for (i = 1; i < nc; i++) |

205 | temp *= iroot; |

206 | } while (temp <= (long) max_colors); /* repeat till iroot exceeds root */ |

207 | iroot--; /* now iroot = floor(root) */ |

208 | |

209 | /* Must have at least 2 color values per component */ |

210 | if (iroot < 2) |

211 | ERREXIT1(cinfo, JERR_QUANT_FEW_COLORS, (int) temp); |

212 | |

213 | /* Initialize to iroot color values for each component */ |

214 | total_colors = 1; |

215 | for (i = 0; i < nc; i++) { |

216 | Ncolors[i] = iroot; |

217 | total_colors *= iroot; |

218 | } |

219 | /* We may be able to increment the count for one or more components without |

220 | * exceeding max_colors, though we know not all can be incremented. |

221 | * Sometimes, the first component can be incremented more than once! |

222 | * (Example: for 16 colors, we start at 2*2*2, go to 3*2*2, then 4*2*2.) |

223 | * In RGB colorspace, try to increment G first, then R, then B. |

224 | */ |

225 | do { |

226 | changed = FALSE; |

227 | for (i = 0; i < nc; i++) { |

228 | j = (cinfo->out_color_space == JCS_RGB ? RGB_order[i] : i); |

229 | /* calculate new total_colors if Ncolors[j] is incremented */ |

230 | temp = total_colors / Ncolors[j]; |

231 | temp *= Ncolors[j]+1; /* done in long arith to avoid oflo */ |

232 | if (temp > (long) max_colors) |

233 | break; /* won't fit, done with this pass */ |

234 | Ncolors[j]++; /* OK, apply the increment */ |

235 | total_colors = (int) temp; |

236 | changed = TRUE; |

237 | } |

238 | } while (changed); |

239 | |

240 | return total_colors; |

241 | } |

242 | |

243 | |

244 | LOCAL(int) |

245 | output_value (j_decompress_ptr cinfo, int ci, int j, int maxj) |

246 | /* Return j'th output value, where j will range from 0 to maxj */ |

247 | /* The output values must fall in 0..MAXJSAMPLE in increasing order */ |

248 | { |

249 | /* We always provide values 0 and MAXJSAMPLE for each component; |

250 | * any additional values are equally spaced between these limits. |

251 | * (Forcing the upper and lower values to the limits ensures that |

252 | * dithering can't produce a color outside the selected gamut.) |

253 | */ |

254 | return (int) (((INT32) j * MAXJSAMPLE + maxj/2) / maxj); |

255 | } |

256 | |

257 | |

258 | LOCAL(int) |

259 | largest_input_value (j_decompress_ptr cinfo, int ci, int j, int maxj) |

260 | /* Return largest input value that should map to j'th output value */ |

261 | /* Must have largest(j=0) >= 0, and largest(j=maxj) >= MAXJSAMPLE */ |

262 | { |

263 | /* Breakpoints are halfway between values returned by output_value */ |

264 | return (int) (((INT32) (2*j + 1) * MAXJSAMPLE + maxj) / (2*maxj)); |

265 | } |

266 | |

267 | |

268 | /* |

269 | * Create the colormap. |

270 | */ |

271 | |

272 | LOCAL(void) |

273 | create_colormap (j_decompress_ptr cinfo) |

274 | { |

275 | my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |

276 | JSAMPARRAY colormap; /* Created colormap */ |

277 | int total_colors; /* Number of distinct output colors */ |

278 | int i,j,k, nci, blksize, blkdist, ptr, val; |

279 | |

280 | /* Select number of colors for each component */ |

281 | total_colors = select_ncolors(cinfo, cquantize->Ncolors); |

282 | |

283 | /* Report selected color counts */ |

284 | if (cinfo->out_color_components == 3) |

285 | TRACEMS4(cinfo, 1, JTRC_QUANT_3_NCOLORS, |

286 | total_colors, cquantize->Ncolors[0], |

287 | cquantize->Ncolors[1], cquantize->Ncolors[2]); |

288 | else |

289 | TRACEMS1(cinfo, 1, JTRC_QUANT_NCOLORS, total_colors); |

290 | |

291 | /* Allocate and fill in the colormap. */ |

292 | /* The colors are ordered in the map in standard row-major order, */ |

293 | /* i.e. rightmost (highest-indexed) color changes most rapidly. */ |

294 | |

295 | colormap = (*cinfo->mem->alloc_sarray) |

296 | ((j_common_ptr) cinfo, JPOOL_IMAGE, |

297 | (JDIMENSION) total_colors, (JDIMENSION) cinfo->out_color_components); |

298 | |

299 | /* blksize is number of adjacent repeated entries for a component */ |

300 | /* blkdist is distance between groups of identical entries for a component */ |

301 | blkdist = total_colors; |

302 | |

303 | for (i = 0; i < cinfo->out_color_components; i++) { |

304 | /* fill in colormap entries for i'th color component */ |

305 | nci = cquantize->Ncolors[i]; /* # of distinct values for this color */ |

306 | blksize = blkdist / nci; |

307 | for (j = 0; j < nci; j++) { |

308 | /* Compute j'th output value (out of nci) for component */ |

309 | val = output_value(cinfo, i, j, nci-1); |

310 | /* Fill in all colormap entries that have this value of this component */ |

311 | for (ptr = j * blksize; ptr < total_colors; ptr += blkdist) { |

312 | /* fill in blksize entries beginning at ptr */ |

313 | for (k = 0; k < blksize; k++) |

314 | colormap[i][ptr+k] = (JSAMPLE) val; |

315 | } |

316 | } |

317 | blkdist = blksize; /* blksize of this color is blkdist of next */ |

318 | } |

319 | |

320 | /* Save the colormap in private storage, |

321 | * where it will survive color quantization mode changes. |

322 | */ |

323 | cquantize->sv_colormap = colormap; |

324 | cquantize->sv_actual = total_colors; |

325 | } |

326 | |

327 | |

328 | /* |

329 | * Create the color index table. |

330 | */ |

331 | |

332 | LOCAL(void) |

333 | create_colorindex (j_decompress_ptr cinfo) |

334 | { |

335 | my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |

336 | JSAMPROW indexptr; |

337 | int i,j,k, nci, blksize, val, pad; |

338 | |

339 | /* For ordered dither, we pad the color index tables by MAXJSAMPLE in |

340 | * each direction (input index values can be -MAXJSAMPLE .. 2*MAXJSAMPLE). |

341 | * This is not necessary in the other dithering modes. However, we |

342 | * flag whether it was done in case user changes dithering mode. |

343 | */ |

344 | if (cinfo->dither_mode == JDITHER_ORDERED) { |

345 | pad = MAXJSAMPLE*2; |

346 | cquantize->is_padded = TRUE; |

347 | } else { |

348 | pad = 0; |

349 | cquantize->is_padded = FALSE; |

350 | } |

351 | |

352 | cquantize->colorindex = (*cinfo->mem->alloc_sarray) |

353 | ((j_common_ptr) cinfo, JPOOL_IMAGE, |

354 | (JDIMENSION) (MAXJSAMPLE+1 + pad), |

355 | (JDIMENSION) cinfo->out_color_components); |

356 | |

357 | /* blksize is number of adjacent repeated entries for a component */ |

358 | blksize = cquantize->sv_actual; |

359 | |

360 | for (i = 0; i < cinfo->out_color_components; i++) { |

361 | /* fill in colorindex entries for i'th color component */ |

362 | nci = cquantize->Ncolors[i]; /* # of distinct values for this color */ |

363 | blksize = blksize / nci; |

364 | |

365 | /* adjust colorindex pointers to provide padding at negative indexes. */ |

366 | if (pad) |

367 | cquantize->colorindex[i] += MAXJSAMPLE; |

368 | |

369 | /* in loop, val = index of current output value, */ |

370 | /* and k = largest j that maps to current val */ |

371 | indexptr = cquantize->colorindex[i]; |

372 | val = 0; |

373 | k = largest_input_value(cinfo, i, 0, nci-1); |

374 | for (j = 0; j <= MAXJSAMPLE; j++) { |

375 | while (j > k) /* advance val if past boundary */ |

376 | k = largest_input_value(cinfo, i, ++val, nci-1); |

377 | /* premultiply so that no multiplication needed in main processing */ |

378 | indexptr[j] = (JSAMPLE) (val * blksize); |

379 | } |

380 | /* Pad at both ends if necessary */ |

381 | if (pad) |

382 | for (j = 1; j <= MAXJSAMPLE; j++) { |

383 | indexptr[-j] = indexptr[0]; |

384 | indexptr[MAXJSAMPLE+j] = indexptr[MAXJSAMPLE]; |

385 | } |

386 | } |

387 | } |

388 | |

389 | |

390 | /* |

391 | * Create an ordered-dither array for a component having ncolors |

392 | * distinct output values. |

393 | */ |

394 | |

395 | LOCAL(ODITHER_MATRIX_PTR) |

396 | make_odither_array (j_decompress_ptr cinfo, int ncolors) |

397 | { |

398 | ODITHER_MATRIX_PTR odither; |

399 | int j,k; |

400 | INT32 num,den; |

401 | |

402 | odither = (ODITHER_MATRIX_PTR) |

403 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |

404 | SIZEOF(ODITHER_MATRIX)); |

405 | /* The inter-value distance for this color is MAXJSAMPLE/(ncolors-1). |

406 | * Hence the dither value for the matrix cell with fill order f |

407 | * (f=0..N-1) should be (N-1-2*f)/(2*N) * MAXJSAMPLE/(ncolors-1). |

408 | * On 16-bit-int machine, be careful to avoid overflow. |

409 | */ |

410 | den = 2 * ODITHER_CELLS * ((INT32) (ncolors - 1)); |

411 | for (j = 0; j < ODITHER_SIZE; j++) { |

412 | for (k = 0; k < ODITHER_SIZE; k++) { |

413 | num = ((INT32) (ODITHER_CELLS-1 - 2*((int)base_dither_matrix[j][k]))) |

414 | * MAXJSAMPLE; |

415 | /* Ensure round towards zero despite C's lack of consistency |

416 | * about rounding negative values in integer division... |

417 | */ |

418 | odither[j][k] = (int) (num<0 ? -((-num)/den) : num/den); |

419 | } |

420 | } |

421 | return odither; |

422 | } |

423 | |

424 | |

425 | /* |

426 | * Create the ordered-dither tables. |

427 | * Components having the same number of representative colors may |

428 | * share a dither table. |

429 | */ |

430 | |

431 | LOCAL(void) |

432 | create_odither_tables (j_decompress_ptr cinfo) |

433 | { |

434 | my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |

435 | ODITHER_MATRIX_PTR odither; |

436 | int i, j, nci; |

437 | |

438 | for (i = 0; i < cinfo->out_color_components; i++) { |

439 | nci = cquantize->Ncolors[i]; /* # of distinct values for this color */ |

440 | odither = NULL; /* search for matching prior component */ |

441 | for (j = 0; j < i; j++) { |

442 | if (nci == cquantize->Ncolors[j]) { |

443 | odither = cquantize->odither[j]; |

444 | break; |

445 | } |

446 | } |

447 | if (odither == NULL) /* need a new table? */ |

448 | odither = make_odither_array(cinfo, nci); |

449 | cquantize->odither[i] = odither; |

450 | } |

451 | } |

452 | |

453 | |

454 | /* |

455 | * Map some rows of pixels to the output colormapped representation. |

456 | */ |

457 | |

458 | METHODDEF(void) |

459 | color_quantize (j_decompress_ptr cinfo, JSAMPARRAY input_buf, |

460 | JSAMPARRAY output_buf, int num_rows) |

461 | /* General case, no dithering */ |

462 | { |

463 | my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |

464 | JSAMPARRAY colorindex = cquantize->colorindex; |

465 | register int pixcode, ci; |

466 | register JSAMPROW ptrin, ptrout; |

467 | int row; |

468 | JDIMENSION col; |

469 | JDIMENSION width = cinfo->output_width; |

470 | register int nc = cinfo->out_color_components; |

471 | |

472 | for (row = 0; row < num_rows; row++) { |

473 | ptrin = input_buf[row]; |

474 | ptrout = output_buf[row]; |

475 | for (col = width; col > 0; col--) { |

476 | pixcode = 0; |

477 | for (ci = 0; ci < nc; ci++) { |

478 | pixcode += GETJSAMPLE(colorindex[ci][GETJSAMPLE(*ptrin++)]); |

479 | } |

480 | *ptrout++ = (JSAMPLE) pixcode; |

481 | } |

482 | } |

483 | } |

484 | |

485 | |

486 | METHODDEF(void) |

487 | color_quantize3 (j_decompress_ptr cinfo, JSAMPARRAY input_buf, |

488 | JSAMPARRAY output_buf, int num_rows) |

489 | /* Fast path for out_color_components==3, no dithering */ |

490 | { |

491 | my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |

492 | register int pixcode; |

493 | register JSAMPROW ptrin, ptrout; |

494 | JSAMPROW colorindex0 = cquantize->colorindex[0]; |

495 | JSAMPROW colorindex1 = cquantize->colorindex[1]; |

496 | JSAMPROW colorindex2 = cquantize->colorindex[2]; |

497 | int row; |

498 | JDIMENSION col; |

499 | JDIMENSION width = cinfo->output_width; |

500 | |

501 | for (row = 0; row < num_rows; row++) { |

502 | ptrin = input_buf[row]; |

503 | ptrout = output_buf[row]; |

504 | for (col = width; col > 0; col--) { |

505 | pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*ptrin++)]); |

506 | pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*ptrin++)]); |

507 | pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*ptrin++)]); |

508 | *ptrout++ = (JSAMPLE) pixcode; |

509 | } |

510 | } |

511 | } |

512 | |

513 | |

514 | METHODDEF(void) |

515 | quantize_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, |

516 | JSAMPARRAY output_buf, int num_rows) |

517 | /* General case, with ordered dithering */ |

518 | { |

519 | my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |

520 | register JSAMPROW input_ptr; |

521 | register JSAMPROW output_ptr; |

522 | JSAMPROW colorindex_ci; |

523 | int * dither; /* points to active row of dither matrix */ |

524 | int row_index, col_index; /* current indexes into dither matrix */ |

525 | int nc = cinfo->out_color_components; |

526 | int ci; |

527 | int row; |

528 | JDIMENSION col; |

529 | JDIMENSION width = cinfo->output_width; |

530 | |

531 | for (row = 0; row < num_rows; row++) { |

532 | /* Initialize output values to 0 so can process components separately */ |

533 | jzero_far((void FAR *) output_buf[row], |

534 | (size_t) (width * SIZEOF(JSAMPLE))); |

535 | row_index = cquantize->row_index; |

536 | for (ci = 0; ci < nc; ci++) { |

537 | input_ptr = input_buf[row] + ci; |

538 | output_ptr = output_buf[row]; |

539 | colorindex_ci = cquantize->colorindex[ci]; |

540 | dither = cquantize->odither[ci][row_index]; |

541 | col_index = 0; |

542 | |

543 | for (col = width; col > 0; col--) { |

544 | /* Form pixel value + dither, range-limit to 0..MAXJSAMPLE, |

545 | * select output value, accumulate into output code for this pixel. |

546 | * Range-limiting need not be done explicitly, as we have extended |

547 | * the colorindex table to produce the right answers for out-of-range |

548 | * inputs. The maximum dither is +- MAXJSAMPLE; this sets the |

549 | * required amount of padding. |

550 | */ |

551 | *output_ptr += colorindex_ci[GETJSAMPLE(*input_ptr)+dither[col_index]]; |

552 | input_ptr += nc; |

553 | output_ptr++; |

554 | col_index = (col_index + 1) & ODITHER_MASK; |

555 | } |

556 | } |

557 | /* Advance row index for next row */ |

558 | row_index = (row_index + 1) & ODITHER_MASK; |

559 | cquantize->row_index = row_index; |

560 | } |

561 | } |

562 | |

563 | |

564 | METHODDEF(void) |

565 | quantize3_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, |

566 | JSAMPARRAY output_buf, int num_rows) |

567 | /* Fast path for out_color_components==3, with ordered dithering */ |

568 | { |

569 | my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |

570 | register int pixcode; |

571 | register JSAMPROW input_ptr; |

572 | register JSAMPROW output_ptr; |

573 | JSAMPROW colorindex0 = cquantize->colorindex[0]; |

574 | JSAMPROW colorindex1 = cquantize->colorindex[1]; |

575 | JSAMPROW colorindex2 = cquantize->colorindex[2]; |

576 | int * dither0; /* points to active row of dither matrix */ |

577 | int * dither1; |

578 | int * dither2; |

579 | int row_index, col_index; /* current indexes into dither matrix */ |

580 | int row; |

581 | JDIMENSION col; |

582 | JDIMENSION width = cinfo->output_width; |

583 | |

584 | for (row = 0; row < num_rows; row++) { |

585 | row_index = cquantize->row_index; |

586 | input_ptr = input_buf[row]; |

587 | output_ptr = output_buf[row]; |

588 | dither0 = cquantize->odither[0][row_index]; |

589 | dither1 = cquantize->odither[1][row_index]; |

590 | dither2 = cquantize->odither[2][row_index]; |

591 | col_index = 0; |

592 | |

593 | for (col = width; col > 0; col--) { |

594 | pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*input_ptr++) + |

595 | dither0[col_index]]); |

596 | pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*input_ptr++) + |

597 | dither1[col_index]]); |

598 | pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*input_ptr++) + |

599 | dither2[col_index]]); |

600 | *output_ptr++ = (JSAMPLE) pixcode; |

601 | col_index = (col_index + 1) & ODITHER_MASK; |

602 | } |

603 | row_index = (row_index + 1) & ODITHER_MASK; |

604 | cquantize->row_index = row_index; |

605 | } |

606 | } |

607 | |

608 | |

609 | METHODDEF(void) |

610 | quantize_fs_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf, |

611 | JSAMPARRAY output_buf, int num_rows) |

612 | /* General case, with Floyd-Steinberg dithering */ |

613 | { |

614 | my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |

615 | register LOCFSERROR cur; /* current error or pixel value */ |

616 | LOCFSERROR belowerr; /* error for pixel below cur */ |

617 | LOCFSERROR bpreverr; /* error for below/prev col */ |

618 | LOCFSERROR bnexterr; /* error for below/next col */ |

619 | LOCFSERROR delta; |

620 | register FSERRPTR errorptr; /* => fserrors[] at column before current */ |

621 | register JSAMPROW input_ptr; |

622 | register JSAMPROW output_ptr; |

623 | JSAMPROW colorindex_ci; |

624 | JSAMPROW colormap_ci; |

625 | int pixcode; |

626 | int nc = cinfo->out_color_components; |

627 | int dir; /* 1 for left-to-right, -1 for right-to-left */ |

628 | int dirnc; /* dir * nc */ |

629 | int ci; |

630 | int row; |

631 | JDIMENSION col; |

632 | JDIMENSION width = cinfo->output_width; |

633 | JSAMPLE *range_limit = cinfo->sample_range_limit; |

634 | SHIFT_TEMPS |

635 | |

636 | for (row = 0; row < num_rows; row++) { |

637 | /* Initialize output values to 0 so can process components separately */ |

638 | jzero_far((void FAR *) output_buf[row], |

639 | (size_t) (width * SIZEOF(JSAMPLE))); |

640 | for (ci = 0; ci < nc; ci++) { |

641 | input_ptr = input_buf[row] + ci; |

642 | output_ptr = output_buf[row]; |

643 | if (cquantize->on_odd_row) { |

644 | /* work right to left in this row */ |

645 | input_ptr += (width-1) * nc; /* so point to rightmost pixel */ |

646 | output_ptr += width-1; |

647 | dir = -1; |

648 | dirnc = -nc; |

649 | errorptr = cquantize->fserrors[ci] + (width+1); /* => entry after last column */ |

650 | } else { |

651 | /* work left to right in this row */ |

652 | dir = 1; |

653 | dirnc = nc; |

654 | errorptr = cquantize->fserrors[ci]; /* => entry before first column */ |

655 | } |

656 | colorindex_ci = cquantize->colorindex[ci]; |

657 | colormap_ci = cquantize->sv_colormap[ci]; |

658 | /* Preset error values: no error propagated to first pixel from left */ |

659 | cur = 0; |

660 | /* and no error propagated to row below yet */ |

661 | belowerr = bpreverr = 0; |

662 | |

663 | for (col = width; col > 0; col--) { |

664 | /* cur holds the error propagated from the previous pixel on the |

665 | * current line. Add the error propagated from the previous line |

666 | * to form the complete error correction term for this pixel, and |

667 | * round the error term (which is expressed * 16) to an integer. |

668 | * RIGHT_SHIFT rounds towards minus infinity, so adding 8 is correct |

669 | * for either sign of the error value. |

670 | * Note: errorptr points to *previous* column's array entry. |

671 | */ |

672 | cur = RIGHT_SHIFT(cur + errorptr[dir] + 8, 4); |

673 | /* Form pixel value + error, and range-limit to 0..MAXJSAMPLE. |

674 | * The maximum error is +- MAXJSAMPLE; this sets the required size |

675 | * of the range_limit array. |

676 | */ |

677 | cur += GETJSAMPLE(*input_ptr); |

678 | cur = GETJSAMPLE(range_limit[cur]); |

679 | /* Select output value, accumulate into output code for this pixel */ |

680 | pixcode = GETJSAMPLE(colorindex_ci[cur]); |

681 | *output_ptr += (JSAMPLE) pixcode; |

682 | /* Compute actual representation error at this pixel */ |

683 | /* Note: we can do this even though we don't have the final */ |

684 | /* pixel code, because the colormap is orthogonal. */ |

685 | cur -= GETJSAMPLE(colormap_ci[pixcode]); |

686 | /* Compute error fractions to be propagated to adjacent pixels. |

687 | * Add these into the running sums, and simultaneously shift the |

688 | * next-line error sums left by 1 column. |

689 | */ |

690 | bnexterr = cur; |

691 | delta = cur * 2; |

692 | cur += delta; /* form error * 3 */ |

693 | errorptr[0] = (FSERROR) (bpreverr + cur); |

694 | cur += delta; /* form error * 5 */ |

695 | bpreverr = belowerr + cur; |

696 | belowerr = bnexterr; |

697 | cur += delta; /* form error * 7 */ |

698 | /* At this point cur contains the 7/16 error value to be propagated |

699 | * to the next pixel on the current line, and all the errors for the |

700 | * next line have been shifted over. We are therefore ready to move on. |

701 | */ |

702 | input_ptr += dirnc; /* advance input ptr to next column */ |

703 | output_ptr += dir; /* advance output ptr to next column */ |

704 | errorptr += dir; /* advance errorptr to current column */ |

705 | } |

706 | /* Post-loop cleanup: we must unload the final error value into the |

707 | * final fserrors[] entry. Note we need not unload belowerr because |

708 | * it is for the dummy column before or after the actual array. |

709 | */ |

710 | errorptr[0] = (FSERROR) bpreverr; /* unload prev err into array */ |

711 | } |

712 | cquantize->on_odd_row = (cquantize->on_odd_row ? FALSE : TRUE); |

713 | } |

714 | } |

715 | |

716 | |

717 | /* |

718 | * Allocate workspace for Floyd-Steinberg errors. |

719 | */ |

720 | |

721 | LOCAL(void) |

722 | alloc_fs_workspace (j_decompress_ptr cinfo) |

723 | { |

724 | my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |

725 | size_t arraysize; |

726 | int i; |

727 | |

728 | arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR)); |

729 | for (i = 0; i < cinfo->out_color_components; i++) { |

730 | cquantize->fserrors[i] = (FSERRPTR) |

731 | (*cinfo->mem->alloc_large)((j_common_ptr) cinfo, JPOOL_IMAGE, arraysize); |

732 | } |

733 | } |

734 | |

735 | |

736 | /* |

737 | * Initialize for one-pass color quantization. |

738 | */ |

739 | |

740 | METHODDEF(void) |

741 | start_pass_1_quant (j_decompress_ptr cinfo, boolean is_pre_scan) |

742 | { |

743 | my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize; |

744 | size_t arraysize; |

745 | int i; |

746 | |

747 | /* Install my colormap. */ |

748 | cinfo->colormap = cquantize->sv_colormap; |

749 | cinfo->actual_number_of_colors = cquantize->sv_actual; |

750 | |

751 | /* Initialize for desired dithering mode. */ |

752 | switch (cinfo->dither_mode) { |

753 | case JDITHER_NONE: |

754 | if (cinfo->out_color_components == 3) |

755 | cquantize->pub.color_quantize = color_quantize3; |

756 | else |

757 | cquantize->pub.color_quantize = color_quantize; |

758 | break; |

759 | case JDITHER_ORDERED: |

760 | if (cinfo->out_color_components == 3) |

761 | cquantize->pub.color_quantize = quantize3_ord_dither; |

762 | else |

763 | cquantize->pub.color_quantize = quantize_ord_dither; |

764 | cquantize->row_index = 0; /* initialize state for ordered dither */ |

765 | /* If user changed to ordered dither from another mode, |

766 | * we must recreate the color index table with padding. |

767 | * This will cost extra space, but probably isn't very likely. |

768 | */ |

769 | if (! cquantize->is_padded) |

770 | create_colorindex(cinfo); |

771 | /* Create ordered-dither tables if we didn't already. */ |

772 | if (cquantize->odither[0] == NULL) |

773 | create_odither_tables(cinfo); |

774 | break; |

775 | case JDITHER_FS: |

776 | cquantize->pub.color_quantize = quantize_fs_dither; |

777 | cquantize->on_odd_row = FALSE; /* initialize state for F-S dither */ |

778 | /* Allocate Floyd-Steinberg workspace if didn't already. */ |

779 | if (cquantize->fserrors[0] == NULL) |

780 | alloc_fs_workspace(cinfo); |

781 | /* Initialize the propagated errors to zero. */ |

782 | arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR)); |

783 | for (i = 0; i < cinfo->out_color_components; i++) |

784 | jzero_far((void FAR *) cquantize->fserrors[i], arraysize); |

785 | break; |

786 | default: |

787 | ERREXIT(cinfo, JERR_NOT_COMPILED); |

788 | break; |

789 | } |

790 | } |

791 | |

792 | |

793 | /* |

794 | * Finish up at the end of the pass. |

795 | */ |

796 | |

797 | METHODDEF(void) |

798 | finish_pass_1_quant (j_decompress_ptr cinfo) |

799 | { |

800 | /* no work in 1-pass case */ |

801 | } |

802 | |

803 | |

804 | /* |

805 | * Switch to a new external colormap between output passes. |

806 | * Shouldn't get to this module! |

807 | */ |

808 | |

809 | METHODDEF(void) |

810 | new_color_map_1_quant (j_decompress_ptr cinfo) |

811 | { |

812 | ERREXIT(cinfo, JERR_MODE_CHANGE); |

813 | } |

814 | |

815 | |

816 | /* |

817 | * Module initialization routine for 1-pass color quantization. |

818 | */ |

819 | |

820 | GLOBAL(void) |

821 | jinit_1pass_quantizer (j_decompress_ptr cinfo) |

822 | { |

823 | my_cquantize_ptr cquantize; |

824 | |

825 | cquantize = (my_cquantize_ptr) |

826 | (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, |

827 | SIZEOF(my_cquantizer)); |

828 | cinfo->cquantize = (struct jpeg_color_quantizer *) cquantize; |

829 | cquantize->pub.start_pass = start_pass_1_quant; |

830 | cquantize->pub.finish_pass = finish_pass_1_quant; |

831 | cquantize->pub.new_color_map = new_color_map_1_quant; |

832 | cquantize->fserrors[0] = NULL; /* Flag FS workspace not allocated */ |

833 | cquantize->odither[0] = NULL; /* Also flag odither arrays not allocated */ |

834 | |

835 | /* Make sure my internal arrays won't overflow */ |

836 | if (cinfo->out_color_components > MAX_Q_COMPS) |

837 | ERREXIT1(cinfo, JERR_QUANT_COMPONENTS, MAX_Q_COMPS); |

838 | /* Make sure colormap indexes can be represented by JSAMPLEs */ |

839 | if (cinfo->desired_number_of_colors > (MAXJSAMPLE+1)) |

840 | ERREXIT1(cinfo, JERR_QUANT_MANY_COLORS, MAXJSAMPLE+1); |

841 | |

842 | /* Create the colormap and color index table. */ |

843 | create_colormap(cinfo); |

844 | create_colorindex(cinfo); |

845 | |

846 | /* Allocate Floyd-Steinberg workspace now if requested. |

847 | * We do this now since it is FAR storage and may affect the memory |

848 | * manager's space calculations. If the user changes to FS dither |

849 | * mode in a later pass, we will allocate the space then, and will |

850 | * possibly overrun the max_memory_to_use setting. |

851 | */ |

852 | if (cinfo->dither_mode == JDITHER_FS) |

853 | alloc_fs_workspace(cinfo); |

854 | } |

855 | |

856 | #endif /* QUANT_1PASS_SUPPORTED */ |

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