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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 | } |