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jddctmgr.c
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1 /*
2  * jddctmgr.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 inverse-DCT management logic.
9  * This code selects a particular IDCT implementation to be used,
10  * and it performs related housekeeping chores. No code in this file
11  * is executed per IDCT step, only during output pass setup.
12  *
13  * Note that the IDCT routines are responsible for performing coefficient
14  * dequantization as well as the IDCT proper. This module sets up the
15  * dequantization multiplier table needed by the IDCT routine.
16  */
17 
18 #define JPEG_INTERNALS
19 #include "jinclude.h"
20 #include "jpeglib.h"
21 #include "jdct.h" /* Private declarations for DCT subsystem */
22 
23 
24 /*
25  * The decompressor input side (jdinput.c) saves away the appropriate
26  * quantization table for each component at the start of the first scan
27  * involving that component. (This is necessary in order to correctly
28  * decode files that reuse Q-table slots.)
29  * When we are ready to make an output pass, the saved Q-table is converted
30  * to a multiplier table that will actually be used by the IDCT routine.
31  * The multiplier table contents are IDCT-method-dependent. To support
32  * application changes in IDCT method between scans, we can remake the
33  * multiplier tables if necessary.
34  * In buffered-image mode, the first output pass may occur before any data
35  * has been seen for some components, and thus before their Q-tables have
36  * been saved away. To handle this case, multiplier tables are preset
37  * to zeroes; the result of the IDCT will be a neutral gray level.
38  */
39 
40 
41 /* Private subobject for this module */
42 
43 typedef struct {
44  struct jpeg_inverse_dct pub; /* public fields */
45 
46  /* This array contains the IDCT method code that each multiplier table
47  * is currently set up for, or -1 if it's not yet set up.
48  * The actual multiplier tables are pointed to by dct_table in the
49  * per-component comp_info structures.
50  */
51  int cur_method[MAX_COMPONENTS];
53 
55 
56 
57 /* Allocated multiplier tables: big enough for any supported variant */
58 
59 typedef union {
60  ISLOW_MULT_TYPE islow_array[DCTSIZE2];
61 #ifdef DCT_IFAST_SUPPORTED
62  IFAST_MULT_TYPE ifast_array[DCTSIZE2];
63 #endif
64 #ifdef DCT_FLOAT_SUPPORTED
65  FLOAT_MULT_TYPE float_array[DCTSIZE2];
66 #endif
68 
69 
70 /* The current scaled-IDCT routines require ISLOW-style multiplier tables,
71  * so be sure to compile that code if either ISLOW or SCALING is requested.
72  */
73 #ifdef DCT_ISLOW_SUPPORTED
74 #define PROVIDE_ISLOW_TABLES
75 #else
76 #ifdef IDCT_SCALING_SUPPORTED
77 #define PROVIDE_ISLOW_TABLES
78 #endif
79 #endif
80 
81 
82 /*
83  * Prepare for an output pass.
84  * Here we select the proper IDCT routine for each component and build
85  * a matching multiplier table.
86  */
87 
88 METHODDEF(void)
90 {
91  my_idct_ptr idct = (my_idct_ptr) cinfo->idct;
92  int ci, i;
94  int method = 0;
95  inverse_DCT_method_ptr method_ptr = NULL;
96  JQUANT_TBL * qtbl;
97 
98  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
99  ci++, compptr++) {
100  /* Select the proper IDCT routine for this component's scaling */
101  switch (compptr->DCT_scaled_size) {
102 #ifdef IDCT_SCALING_SUPPORTED
103  case 1:
104  method_ptr = jpeg_idct_1x1;
105  method = JDCT_ISLOW; /* jidctred uses islow-style table */
106  break;
107  case 2:
108  method_ptr = jpeg_idct_2x2;
109  method = JDCT_ISLOW; /* jidctred uses islow-style table */
110  break;
111  case 4:
112  method_ptr = jpeg_idct_4x4;
113  method = JDCT_ISLOW; /* jidctred uses islow-style table */
114  break;
115 #endif
116  case DCTSIZE:
117  switch (cinfo->dct_method) {
118 #ifdef DCT_ISLOW_SUPPORTED
119  case JDCT_ISLOW:
120  method_ptr = jpeg_idct_islow;
121  method = JDCT_ISLOW;
122  break;
123 #endif
124 #ifdef DCT_IFAST_SUPPORTED
125  case JDCT_IFAST:
126  method_ptr = jpeg_idct_ifast;
127  method = JDCT_IFAST;
128  break;
129 #endif
130 #ifdef DCT_FLOAT_SUPPORTED
131  case JDCT_FLOAT:
132  method_ptr = jpeg_idct_float;
133  method = JDCT_FLOAT;
134  break;
135 #endif
136  default:
137  ERREXIT(cinfo, JERR_NOT_COMPILED);
138  break;
139  }
140  break;
141  default:
143  break;
144  }
145  idct->pub.inverse_DCT[ci] = method_ptr;
146  /* Create multiplier table from quant table.
147  * However, we can skip this if the component is uninteresting
148  * or if we already built the table. Also, if no quant table
149  * has yet been saved for the component, we leave the
150  * multiplier table all-zero; we'll be reading zeroes from the
151  * coefficient controller's buffer anyway.
152  */
153  if (! compptr->component_needed || idct->cur_method[ci] == method)
154  continue;
155  qtbl = compptr->quant_table;
156  if (qtbl == NULL) /* happens if no data yet for component */
157  continue;
158  idct->cur_method[ci] = method;
159  switch (method) {
160 #ifdef PROVIDE_ISLOW_TABLES
161  case JDCT_ISLOW:
162  {
163  /* For LL&M IDCT method, multipliers are equal to raw quantization
164  * coefficients, but are stored as ints to ensure access efficiency.
165  */
167  for (i = 0; i < DCTSIZE2; i++) {
168  ismtbl[i] = (ISLOW_MULT_TYPE) qtbl->quantval[i];
169  }
170  }
171  break;
172 #endif
173 #ifdef DCT_IFAST_SUPPORTED
174  case JDCT_IFAST:
175  {
176  /* For AA&N IDCT method, multipliers are equal to quantization
177  * coefficients scaled by scalefactor[row]*scalefactor[col], where
178  * scalefactor[0] = 1
179  * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7
180  * For integer operation, the multiplier table is to be scaled by
181  * IFAST_SCALE_BITS.
182  */
184 #define CONST_BITS 14
185  static const INT16 aanscales[DCTSIZE2] = {
186  /* precomputed values scaled up by 14 bits */
187  16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
188  22725, 31521, 29692, 26722, 22725, 17855, 12299, 6270,
189  21407, 29692, 27969, 25172, 21407, 16819, 11585, 5906,
190  19266, 26722, 25172, 22654, 19266, 15137, 10426, 5315,
191  16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
192  12873, 17855, 16819, 15137, 12873, 10114, 6967, 3552,
193  8867, 12299, 11585, 10426, 8867, 6967, 4799, 2446,
194  4520, 6270, 5906, 5315, 4520, 3552, 2446, 1247
195  };
197 
198  for (i = 0; i < DCTSIZE2; i++) {
199  ifmtbl[i] = (IFAST_MULT_TYPE)
200  DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i],
201  (INT32) aanscales[i]),
203  }
204  }
205  break;
206 #endif
207 #ifdef DCT_FLOAT_SUPPORTED
208  case JDCT_FLOAT:
209  {
210  /* For float AA&N IDCT method, multipliers are equal to quantization
211  * coefficients scaled by scalefactor[row]*scalefactor[col], where
212  * scalefactor[0] = 1
213  * scalefactor[k] = cos(k*PI/16) * sqrt(2) for k=1..7
214  */
216  int row, col;
217  static const double aanscalefactor[DCTSIZE] = {
218  1.0, 1.387039845, 1.306562965, 1.175875602,
219  1.0, 0.785694958, 0.541196100, 0.275899379
220  };
221 
222  i = 0;
223  for (row = 0; row < DCTSIZE; row++) {
224  for (col = 0; col < DCTSIZE; col++) {
225  fmtbl[i] = (FLOAT_MULT_TYPE)
226  ((double) qtbl->quantval[i] *
227  aanscalefactor[row] * aanscalefactor[col]);
228  i++;
229  }
230  }
231  }
232  break;
233 #endif
234  default:
235  ERREXIT(cinfo, JERR_NOT_COMPILED);
236  break;
237  }
238  }
239 }
240 
241 
242 /*
243  * Initialize IDCT manager.
244  */
245 
246 GLOBAL(void)
248 {
249  my_idct_ptr idct;
250  int ci;
252 
253  idct = (my_idct_ptr)
254  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
256  cinfo->idct = (struct jpeg_inverse_dct *) idct;
257  idct->pub.start_pass = start_pass;
258 
259  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
260  ci++, compptr++) {
261  /* Allocate and pre-zero a multiplier table for each component */
262  compptr->dct_table =
263  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
266  /* Mark multiplier table not yet set up for any method */
267  idct->cur_method[ci] = -1;
268  }
269 }
#define define(p, t, e)
int col
Definition: gsftopk.c:443
MULTIPLIER ISLOW_MULT_TYPE
Definition: jdct.h:56
INT32 IFAST_MULT_TYPE
Definition: jdct.h:61
#define MULTIPLY16V16(var1, var2)
Definition: jdct.h:175
#define IFAST_SCALE_BITS
Definition: jdct.h:62
jpeg_component_info * compptr
Definition: jdct.h:102
FAST_FLOAT FLOAT_MULT_TYPE
Definition: jdct.h:64
#define DESCALE(x, n)
Definition: jdct.h:146
static void start_pass(j_decompress_ptr cinfo)
Definition: jddctmgr.c:89
#define CONST_BITS
void jinit_inverse_dct(j_decompress_ptr cinfo)
Definition: jddctmgr.c:247
my_idct_controller * my_idct_ptr
Definition: jddctmgr.c:54
#define ERREXIT(cinfo, code)
Definition: jerror.h:205
@ JERR_NOT_COMPILED
Definition: jerror.h:95
@ JERR_BAD_DCTSIZE
Definition: jerror.h:49
#define ERREXIT1(cinfo, code, p1)
Definition: jerror.h:208
void jpeg_idct_float(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)
Definition: jidctflt.c:68
void jpeg_idct_ifast(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)
Definition: jidctfst.c:168
void jpeg_idct_islow(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)
Definition: jidctint.c:148
void jpeg_idct_4x4(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)
Definition: jidctred.c:118
void jpeg_idct_2x2(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)
Definition: jidctred.c:271
void jpeg_idct_1x1(j_decompress_ptr cinfo, jpeg_component_info *compptr, JCOEFPTR coef_block, JSAMPARRAY output_buf, JDIMENSION output_col)
Definition: jidctred.c:379
#define SIZEOF(object)
Definition: jinclude.h:80
#define MEMZERO(target, size)
Definition: jinclude.h:67
long INT32
Definition: jmorecfg.h:161
short INT16
Definition: jmorecfg.h:155
#define MAX_COMPONENTS
Definition: jmorecfg.h:35
#define METHODDEF(type)
Definition: jmorecfg.h:184
#define GLOBAL(type)
Definition: jmorecfg.h:188
#define SHIFT_TEMPS
Definition: jpegint.h:289
struct jpeg_common_struct * j_common_ptr
Definition: jpeglib.h:261
#define DCTSIZE
Definition: jpeglib.h:41
#define JPOOL_IMAGE
Definition: jpeglib.h:749
@ JDCT_IFAST
Definition: jpeglib.h:219
@ JDCT_FLOAT
Definition: jpeglib.h:220
@ JDCT_ISLOW
Definition: jpeglib.h:218
#define DCTSIZE2
Definition: jpeglib.h:42
#define NULL
Definition: ftobjs.h:61
small capitals from c petite p scientific i
Definition: afcover.h:80
for(n=0;n< outline->n_points;n++)
Definition: ftbbox.c:494
#define INT32
Definition: gd_topal.c:107
static int row
Definition: ps2pk.c:587
boolean component_needed
Definition: jpeglib.h:160
JQUANT_TBL * quant_table
Definition: jpeglib.h:175
inverse_DCT_method_ptr inverse_DCT[MAX_COMPONENTS]
Definition: jpegint.h:228
struct jpeg_inverse_dct pub
Definition: jddctmgr.c:44
int cur_method[10]
Definition: jddctmgr.c:51