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trunk/third/jpeg/jcdctmgr.c
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1 | /* |

2 | * jcdctmgr.c |

3 | * |

4 | * Copyright (C) 1994-1996, 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 the forward-DCT management logic. |

9 | * This code selects a particular DCT implementation to be used, |

10 | * and it performs related housekeeping chores including coefficient |

11 | * quantization. |

12 | */ |

13 | |

14 | #define JPEG_INTERNALS |

15 | #include "jinclude.h" |

16 | #include "jpeglib.h" |

17 | #include "jdct.h" /* Private declarations for DCT subsystem */ |

18 | |

19 | |

20 | /* Private subobject for this module */ |

21 | |

22 | typedef struct { |

23 | struct jpeg_forward_dct pub; /* public fields */ |

24 | |

25 | /* Pointer to the DCT routine actually in use */ |

26 | forward_DCT_method_ptr do_dct; |

27 | |

28 | /* The actual post-DCT divisors --- not identical to the quant table |

29 | * entries, because of scaling (especially for an unnormalized DCT). |

30 | * Each table is given in normal array order. |

31 | */ |

32 | DCTELEM * divisors[NUM_QUANT_TBLS]; |

33 | |

34 | #ifdef DCT_FLOAT_SUPPORTED |

35 | /* Same as above for the floating-point case. */ |

36 | float_DCT_method_ptr do_float_dct; |

37 | FAST_FLOAT * float_divisors[NUM_QUANT_TBLS]; |

38 | #endif |

39 | } my_fdct_controller; |

40 | |

41 | typedef my_fdct_controller * my_fdct_ptr; |

42 | |

43 | |

44 | /* |

45 | * Initialize for a processing pass. |

46 | * Verify that all referenced Q-tables are present, and set up |

47 | * the divisor table for each one. |

48 | * In the current implementation, DCT of all components is done during |

49 | * the first pass, even if only some components will be output in the |

50 | * first scan. Hence all components should be examined here. |

51 | */ |

52 | |

53 | METHODDEF(void) |

54 | start_pass_fdctmgr (j_compress_ptr cinfo) |

55 | { |

56 | my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct; |

57 | int ci, qtblno, i; |

58 | jpeg_component_info *compptr; |

59 | JQUANT_TBL * qtbl; |

60 | DCTELEM * dtbl; |

61 | |

62 | for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; |

63 | ci++, compptr++) { |

64 | qtblno = compptr->quant_tbl_no; |

65 | /* Make sure specified quantization table is present */ |

66 | if (qtblno < 0 || qtblno >= NUM_QUANT_TBLS || |

67 | cinfo->quant_tbl_ptrs[qtblno] == NULL) |

68 | ERREXIT1(cinfo, JERR_NO_QUANT_TABLE, qtblno); |

69 | qtbl = cinfo->quant_tbl_ptrs[qtblno]; |

70 | /* Compute divisors for this quant table */ |

71 | /* We may do this more than once for same table, but it's not a big deal */ |

72 | switch (cinfo->dct_method) { |

73 | #ifdef DCT_ISLOW_SUPPORTED |

74 | case JDCT_ISLOW: |

75 | /* For LL&M IDCT method, divisors are equal to raw quantization |

76 | * coefficients multiplied by 8 (to counteract scaling). |

77 | */ |

78 | if (fdct->divisors[qtblno] == NULL) { |

79 | fdct->divisors[qtblno] = (DCTELEM *) |

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

81 | DCTSIZE2 * SIZEOF(DCTELEM)); |

82 | } |

83 | dtbl = fdct->divisors[qtblno]; |

84 | for (i = 0; i < DCTSIZE2; i++) { |

85 | dtbl[i] = ((DCTELEM) qtbl->quantval[i]) << 3; |

86 | } |

87 | break; |

88 | #endif |

89 | #ifdef DCT_IFAST_SUPPORTED |

90 | case JDCT_IFAST: |

91 | { |

92 | /* For AA&N IDCT method, divisors are equal to quantization |

93 | * coefficients scaled by scalefactor[row]*scalefactor[col], where |

94 | * scalefactor[0] = 1 |

95 | * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7 |

96 | * We apply a further scale factor of 8. |

97 | */ |

98 | #define CONST_BITS 14 |

99 | static const INT16 aanscales[DCTSIZE2] = { |

100 | /* precomputed values scaled up by 14 bits */ |

101 | 16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520, |

102 | 22725, 31521, 29692, 26722, 22725, 17855, 12299, 6270, |

103 | 21407, 29692, 27969, 25172, 21407, 16819, 11585, 5906, |

104 | 19266, 26722, 25172, 22654, 19266, 15137, 10426, 5315, |

105 | 16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520, |

106 | 12873, 17855, 16819, 15137, 12873, 10114, 6967, 3552, |

107 | 8867, 12299, 11585, 10426, 8867, 6967, 4799, 2446, |

108 | 4520, 6270, 5906, 5315, 4520, 3552, 2446, 1247 |

109 | }; |

110 | SHIFT_TEMPS |

111 | |

112 | if (fdct->divisors[qtblno] == NULL) { |

113 | fdct->divisors[qtblno] = (DCTELEM *) |

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

115 | DCTSIZE2 * SIZEOF(DCTELEM)); |

116 | } |

117 | dtbl = fdct->divisors[qtblno]; |

118 | for (i = 0; i < DCTSIZE2; i++) { |

119 | dtbl[i] = (DCTELEM) |

120 | DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i], |

121 | (INT32) aanscales[i]), |

122 | CONST_BITS-3); |

123 | } |

124 | } |

125 | break; |

126 | #endif |

127 | #ifdef DCT_FLOAT_SUPPORTED |

128 | case JDCT_FLOAT: |

129 | { |

130 | /* For float AA&N IDCT method, divisors are equal to quantization |

131 | * coefficients scaled by scalefactor[row]*scalefactor[col], where |

132 | * scalefactor[0] = 1 |

133 | * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7 |

134 | * We apply a further scale factor of 8. |

135 | * What's actually stored is 1/divisor so that the inner loop can |

136 | * use a multiplication rather than a division. |

137 | */ |

138 | FAST_FLOAT * fdtbl; |

139 | int row, col; |

140 | static const double aanscalefactor[DCTSIZE] = { |

141 | 1.0, 1.387039845, 1.306562965, 1.175875602, |

142 | 1.0, 0.785694958, 0.541196100, 0.275899379 |

143 | }; |

144 | |

145 | if (fdct->float_divisors[qtblno] == NULL) { |

146 | fdct->float_divisors[qtblno] = (FAST_FLOAT *) |

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

148 | DCTSIZE2 * SIZEOF(FAST_FLOAT)); |

149 | } |

150 | fdtbl = fdct->float_divisors[qtblno]; |

151 | i = 0; |

152 | for (row = 0; row < DCTSIZE; row++) { |

153 | for (col = 0; col < DCTSIZE; col++) { |

154 | fdtbl[i] = (FAST_FLOAT) |

155 | (1.0 / (((double) qtbl->quantval[i] * |

156 | aanscalefactor[row] * aanscalefactor[col] * 8.0))); |

157 | i++; |

158 | } |

159 | } |

160 | } |

161 | break; |

162 | #endif |

163 | default: |

164 | ERREXIT(cinfo, JERR_NOT_COMPILED); |

165 | break; |

166 | } |

167 | } |

168 | } |

169 | |

170 | |

171 | /* |

172 | * Perform forward DCT on one or more blocks of a component. |

173 | * |

174 | * The input samples are taken from the sample_data[] array starting at |

175 | * position start_row/start_col, and moving to the right for any additional |

176 | * blocks. The quantized coefficients are returned in coef_blocks[]. |

177 | */ |

178 | |

179 | METHODDEF(void) |

180 | forward_DCT (j_compress_ptr cinfo, jpeg_component_info * compptr, |

181 | JSAMPARRAY sample_data, JBLOCKROW coef_blocks, |

182 | JDIMENSION start_row, JDIMENSION start_col, |

183 | JDIMENSION num_blocks) |

184 | /* This version is used for integer DCT implementations. */ |

185 | { |

186 | /* This routine is heavily used, so it's worth coding it tightly. */ |

187 | my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct; |

188 | forward_DCT_method_ptr do_dct = fdct->do_dct; |

189 | DCTELEM * divisors = fdct->divisors[compptr->quant_tbl_no]; |

190 | DCTELEM workspace[DCTSIZE2]; /* work area for FDCT subroutine */ |

191 | JDIMENSION bi; |

192 | |

193 | sample_data += start_row; /* fold in the vertical offset once */ |

194 | |

195 | for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) { |

196 | /* Load data into workspace, applying unsigned->signed conversion */ |

197 | { register DCTELEM *workspaceptr; |

198 | register JSAMPROW elemptr; |

199 | register int elemr; |

200 | |

201 | workspaceptr = workspace; |

202 | for (elemr = 0; elemr < DCTSIZE; elemr++) { |

203 | elemptr = sample_data[elemr] + start_col; |

204 | #if DCTSIZE == 8 /* unroll the inner loop */ |

205 | *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |

206 | *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |

207 | *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |

208 | *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |

209 | *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |

210 | *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |

211 | *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |

212 | *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |

213 | #else |

214 | { register int elemc; |

215 | for (elemc = DCTSIZE; elemc > 0; elemc--) { |

216 | *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE; |

217 | } |

218 | } |

219 | #endif |

220 | } |

221 | } |

222 | |

223 | /* Perform the DCT */ |

224 | (*do_dct) (workspace); |

225 | |

226 | /* Quantize/descale the coefficients, and store into coef_blocks[] */ |

227 | { register DCTELEM temp, qval; |

228 | register int i; |

229 | register JCOEFPTR output_ptr = coef_blocks[bi]; |

230 | |

231 | for (i = 0; i < DCTSIZE2; i++) { |

232 | qval = divisors[i]; |

233 | temp = workspace[i]; |

234 | /* Divide the coefficient value by qval, ensuring proper rounding. |

235 | * Since C does not specify the direction of rounding for negative |

236 | * quotients, we have to force the dividend positive for portability. |

237 | * |

238 | * In most files, at least half of the output values will be zero |

239 | * (at default quantization settings, more like three-quarters...) |

240 | * so we should ensure that this case is fast. On many machines, |

241 | * a comparison is enough cheaper than a divide to make a special test |

242 | * a win. Since both inputs will be nonnegative, we need only test |

243 | * for a < b to discover whether a/b is 0. |

244 | * If your machine's division is fast enough, define FAST_DIVIDE. |

245 | */ |

246 | #ifdef FAST_DIVIDE |

247 | #define DIVIDE_BY(a,b) a /= b |

248 | #else |

249 | #define DIVIDE_BY(a,b) if (a >= b) a /= b; else a = 0 |

250 | #endif |

251 | if (temp < 0) { |

252 | temp = -temp; |

253 | temp += qval>>1; /* for rounding */ |

254 | DIVIDE_BY(temp, qval); |

255 | temp = -temp; |

256 | } else { |

257 | temp += qval>>1; /* for rounding */ |

258 | DIVIDE_BY(temp, qval); |

259 | } |

260 | output_ptr[i] = (JCOEF) temp; |

261 | } |

262 | } |

263 | } |

264 | } |

265 | |

266 | |

267 | #ifdef DCT_FLOAT_SUPPORTED |

268 | |

269 | METHODDEF(void) |

270 | forward_DCT_float (j_compress_ptr cinfo, jpeg_component_info * compptr, |

271 | JSAMPARRAY sample_data, JBLOCKROW coef_blocks, |

272 | JDIMENSION start_row, JDIMENSION start_col, |

273 | JDIMENSION num_blocks) |

274 | /* This version is used for floating-point DCT implementations. */ |

275 | { |

276 | /* This routine is heavily used, so it's worth coding it tightly. */ |

277 | my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct; |

278 | float_DCT_method_ptr do_dct = fdct->do_float_dct; |

279 | FAST_FLOAT * divisors = fdct->float_divisors[compptr->quant_tbl_no]; |

280 | FAST_FLOAT workspace[DCTSIZE2]; /* work area for FDCT subroutine */ |

281 | JDIMENSION bi; |

282 | |

283 | sample_data += start_row; /* fold in the vertical offset once */ |

284 | |

285 | for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) { |

286 | /* Load data into workspace, applying unsigned->signed conversion */ |

287 | { register FAST_FLOAT *workspaceptr; |

288 | register JSAMPROW elemptr; |

289 | register int elemr; |

290 | |

291 | workspaceptr = workspace; |

292 | for (elemr = 0; elemr < DCTSIZE; elemr++) { |

293 | elemptr = sample_data[elemr] + start_col; |

294 | #if DCTSIZE == 8 /* unroll the inner loop */ |

295 | *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |

296 | *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |

297 | *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |

298 | *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |

299 | *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |

300 | *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |

301 | *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |

302 | *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |

303 | #else |

304 | { register int elemc; |

305 | for (elemc = DCTSIZE; elemc > 0; elemc--) { |

306 | *workspaceptr++ = (FAST_FLOAT) |

307 | (GETJSAMPLE(*elemptr++) - CENTERJSAMPLE); |

308 | } |

309 | } |

310 | #endif |

311 | } |

312 | } |

313 | |

314 | /* Perform the DCT */ |

315 | (*do_dct) (workspace); |

316 | |

317 | /* Quantize/descale the coefficients, and store into coef_blocks[] */ |

318 | { register FAST_FLOAT temp; |

319 | register int i; |

320 | register JCOEFPTR output_ptr = coef_blocks[bi]; |

321 | |

322 | for (i = 0; i < DCTSIZE2; i++) { |

323 | /* Apply the quantization and scaling factor */ |

324 | temp = workspace[i] * divisors[i]; |

325 | /* Round to nearest integer. |

326 | * Since C does not specify the direction of rounding for negative |

327 | * quotients, we have to force the dividend positive for portability. |

328 | * The maximum coefficient size is +-16K (for 12-bit data), so this |

329 | * code should work for either 16-bit or 32-bit ints. |

330 | */ |

331 | output_ptr[i] = (JCOEF) ((int) (temp + (FAST_FLOAT) 16384.5) - 16384); |

332 | } |

333 | } |

334 | } |

335 | } |

336 | |

337 | #endif /* DCT_FLOAT_SUPPORTED */ |

338 | |

339 | |

340 | /* |

341 | * Initialize FDCT manager. |

342 | */ |

343 | |

344 | GLOBAL(void) |

345 | jinit_forward_dct (j_compress_ptr cinfo) |

346 | { |

347 | my_fdct_ptr fdct; |

348 | int i; |

349 | |

350 | fdct = (my_fdct_ptr) |

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

352 | SIZEOF(my_fdct_controller)); |

353 | cinfo->fdct = (struct jpeg_forward_dct *) fdct; |

354 | fdct->pub.start_pass = start_pass_fdctmgr; |

355 | |

356 | switch (cinfo->dct_method) { |

357 | #ifdef DCT_ISLOW_SUPPORTED |

358 | case JDCT_ISLOW: |

359 | fdct->pub.forward_DCT = forward_DCT; |

360 | fdct->do_dct = jpeg_fdct_islow; |

361 | break; |

362 | #endif |

363 | #ifdef DCT_IFAST_SUPPORTED |

364 | case JDCT_IFAST: |

365 | fdct->pub.forward_DCT = forward_DCT; |

366 | fdct->do_dct = jpeg_fdct_ifast; |

367 | break; |

368 | #endif |

369 | #ifdef DCT_FLOAT_SUPPORTED |

370 | case JDCT_FLOAT: |

371 | fdct->pub.forward_DCT = forward_DCT_float; |

372 | fdct->do_float_dct = jpeg_fdct_float; |

373 | break; |

374 | #endif |

375 | default: |

376 | ERREXIT(cinfo, JERR_NOT_COMPILED); |

377 | break; |

378 | } |

379 | |

380 | /* Mark divisor tables unallocated */ |

381 | for (i = 0; i < NUM_QUANT_TBLS; i++) { |

382 | fdct->divisors[i] = NULL; |

383 | #ifdef DCT_FLOAT_SUPPORTED |

384 | fdct->float_divisors[i] = NULL; |

385 | #endif |

386 | } |

387 | } |

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