Details | Last modification | View Log | RSS feed
Rev | Author | Line No. | Line |
---|---|---|---|
6417 | ashmew2 | 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 | }>>>>>>>>>>>>><>>>> |