LCOV - code coverage report
Current view: directory - media/libjpeg - jidctred.c (source / functions) Found Hit Coverage
Test: app.info Lines: 126 0 0.0 %
Date: 2012-06-02 Functions: 3 0 0.0 %

       1                 : /*
       2                 :  * jidctred.c
       3                 :  *
       4                 :  * Copyright (C) 1994-1998, 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 inverse-DCT routines that produce reduced-size output:
       9                 :  * either 4x4, 2x2, or 1x1 pixels from an 8x8 DCT block.
      10                 :  *
      11                 :  * The implementation is based on the Loeffler, Ligtenberg and Moschytz (LL&M)
      12                 :  * algorithm used in jidctint.c.  We simply replace each 8-to-8 1-D IDCT step
      13                 :  * with an 8-to-4 step that produces the four averages of two adjacent outputs
      14                 :  * (or an 8-to-2 step producing two averages of four outputs, for 2x2 output).
      15                 :  * These steps were derived by computing the corresponding values at the end
      16                 :  * of the normal LL&M code, then simplifying as much as possible.
      17                 :  *
      18                 :  * 1x1 is trivial: just take the DC coefficient divided by 8.
      19                 :  *
      20                 :  * See jidctint.c for additional comments.
      21                 :  */
      22                 : 
      23                 : #define JPEG_INTERNALS
      24                 : #include "jinclude.h"
      25                 : #include "jpeglib.h"
      26                 : #include "jdct.h"             /* Private declarations for DCT subsystem */
      27                 : 
      28                 : #ifdef IDCT_SCALING_SUPPORTED
      29                 : 
      30                 : 
      31                 : /*
      32                 :  * This module is specialized to the case DCTSIZE = 8.
      33                 :  */
      34                 : 
      35                 : #if DCTSIZE != 8
      36                 :   Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
      37                 : #endif
      38                 : 
      39                 : 
      40                 : /* Scaling is the same as in jidctint.c. */
      41                 : 
      42                 : #if BITS_IN_JSAMPLE == 8
      43                 : #define CONST_BITS  13
      44                 : #define PASS1_BITS  2
      45                 : #else
      46                 : #define CONST_BITS  13
      47                 : #define PASS1_BITS  1           /* lose a little precision to avoid overflow */
      48                 : #endif
      49                 : 
      50                 : /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
      51                 :  * causing a lot of useless floating-point operations at run time.
      52                 :  * To get around this we use the following pre-calculated constants.
      53                 :  * If you change CONST_BITS you may want to add appropriate values.
      54                 :  * (With a reasonable C compiler, you can just rely on the FIX() macro...)
      55                 :  */
      56                 : 
      57                 : #if CONST_BITS == 13
      58                 : #define FIX_0_211164243  ((INT32)  1730)        /* FIX(0.211164243) */
      59                 : #define FIX_0_509795579  ((INT32)  4176)        /* FIX(0.509795579) */
      60                 : #define FIX_0_601344887  ((INT32)  4926)        /* FIX(0.601344887) */
      61                 : #define FIX_0_720959822  ((INT32)  5906)        /* FIX(0.720959822) */
      62                 : #define FIX_0_765366865  ((INT32)  6270)        /* FIX(0.765366865) */
      63                 : #define FIX_0_850430095  ((INT32)  6967)        /* FIX(0.850430095) */
      64                 : #define FIX_0_899976223  ((INT32)  7373)        /* FIX(0.899976223) */
      65                 : #define FIX_1_061594337  ((INT32)  8697)        /* FIX(1.061594337) */
      66                 : #define FIX_1_272758580  ((INT32)  10426)       /* FIX(1.272758580) */
      67                 : #define FIX_1_451774981  ((INT32)  11893)       /* FIX(1.451774981) */
      68                 : #define FIX_1_847759065  ((INT32)  15137)       /* FIX(1.847759065) */
      69                 : #define FIX_2_172734803  ((INT32)  17799)       /* FIX(2.172734803) */
      70                 : #define FIX_2_562915447  ((INT32)  20995)       /* FIX(2.562915447) */
      71                 : #define FIX_3_624509785  ((INT32)  29692)       /* FIX(3.624509785) */
      72                 : #else
      73                 : #define FIX_0_211164243  FIX(0.211164243)
      74                 : #define FIX_0_509795579  FIX(0.509795579)
      75                 : #define FIX_0_601344887  FIX(0.601344887)
      76                 : #define FIX_0_720959822  FIX(0.720959822)
      77                 : #define FIX_0_765366865  FIX(0.765366865)
      78                 : #define FIX_0_850430095  FIX(0.850430095)
      79                 : #define FIX_0_899976223  FIX(0.899976223)
      80                 : #define FIX_1_061594337  FIX(1.061594337)
      81                 : #define FIX_1_272758580  FIX(1.272758580)
      82                 : #define FIX_1_451774981  FIX(1.451774981)
      83                 : #define FIX_1_847759065  FIX(1.847759065)
      84                 : #define FIX_2_172734803  FIX(2.172734803)
      85                 : #define FIX_2_562915447  FIX(2.562915447)
      86                 : #define FIX_3_624509785  FIX(3.624509785)
      87                 : #endif
      88                 : 
      89                 : 
      90                 : /* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
      91                 :  * For 8-bit samples with the recommended scaling, all the variable
      92                 :  * and constant values involved are no more than 16 bits wide, so a
      93                 :  * 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
      94                 :  * For 12-bit samples, a full 32-bit multiplication will be needed.
      95                 :  */
      96                 : 
      97                 : #if BITS_IN_JSAMPLE == 8
      98                 : #define MULTIPLY(var,const)  MULTIPLY16C16(var,const)
      99                 : #else
     100                 : #define MULTIPLY(var,const)  ((var) * (const))
     101                 : #endif
     102                 : 
     103                 : 
     104                 : /* Dequantize a coefficient by multiplying it by the multiplier-table
     105                 :  * entry; produce an int result.  In this module, both inputs and result
     106                 :  * are 16 bits or less, so either int or short multiply will work.
     107                 :  */
     108                 : 
     109                 : #define DEQUANTIZE(coef,quantval)  (((ISLOW_MULT_TYPE) (coef)) * (quantval))
     110                 : 
     111                 : 
     112                 : /*
     113                 :  * Perform dequantization and inverse DCT on one block of coefficients,
     114                 :  * producing a reduced-size 4x4 output block.
     115                 :  */
     116                 : 
     117                 : GLOBAL(void)
     118               0 : jpeg_idct_4x4 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
     119                 :                JCOEFPTR coef_block,
     120                 :                JSAMPARRAY output_buf, JDIMENSION output_col)
     121                 : {
     122                 :   INT32 tmp0, tmp2, tmp10, tmp12;
     123                 :   INT32 z1, z2, z3, z4;
     124                 :   JCOEFPTR inptr;
     125                 :   ISLOW_MULT_TYPE * quantptr;
     126                 :   int * wsptr;
     127                 :   JSAMPROW outptr;
     128               0 :   JSAMPLE *range_limit = IDCT_range_limit(cinfo);
     129                 :   int ctr;
     130                 :   int workspace[DCTSIZE*4];     /* buffers data between passes */
     131                 :   SHIFT_TEMPS
     132                 : 
     133                 :   /* Pass 1: process columns from input, store into work array. */
     134                 : 
     135               0 :   inptr = coef_block;
     136               0 :   quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
     137               0 :   wsptr = workspace;
     138               0 :   for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
     139                 :     /* Don't bother to process column 4, because second pass won't use it */
     140               0 :     if (ctr == DCTSIZE-4)
     141               0 :       continue;
     142               0 :     if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 &&
     143               0 :         inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*5] == 0 &&
     144               0 :         inptr[DCTSIZE*6] == 0 && inptr[DCTSIZE*7] == 0) {
     145                 :       /* AC terms all zero; we need not examine term 4 for 4x4 output */
     146               0 :       int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS;
     147                 :       
     148               0 :       wsptr[DCTSIZE*0] = dcval;
     149               0 :       wsptr[DCTSIZE*1] = dcval;
     150               0 :       wsptr[DCTSIZE*2] = dcval;
     151               0 :       wsptr[DCTSIZE*3] = dcval;
     152                 :       
     153               0 :       continue;
     154                 :     }
     155                 :     
     156                 :     /* Even part */
     157                 :     
     158               0 :     tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
     159               0 :     tmp0 <<= (CONST_BITS+1);
     160                 :     
     161               0 :     z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
     162               0 :     z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);
     163                 : 
     164               0 :     tmp2 = MULTIPLY(z2, FIX_1_847759065) + MULTIPLY(z3, - FIX_0_765366865);
     165                 :     
     166               0 :     tmp10 = tmp0 + tmp2;
     167               0 :     tmp12 = tmp0 - tmp2;
     168                 :     
     169                 :     /* Odd part */
     170                 :     
     171               0 :     z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
     172               0 :     z2 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
     173               0 :     z3 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
     174               0 :     z4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
     175                 :     
     176               0 :     tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
     177               0 :          + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
     178               0 :          + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
     179               0 :          + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */
     180                 :     
     181               0 :     tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
     182               0 :          + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
     183               0 :          + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
     184               0 :          + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */
     185                 : 
     186                 :     /* Final output stage */
     187                 :     
     188               0 :     wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp2, CONST_BITS-PASS1_BITS+1);
     189               0 :     wsptr[DCTSIZE*3] = (int) DESCALE(tmp10 - tmp2, CONST_BITS-PASS1_BITS+1);
     190               0 :     wsptr[DCTSIZE*1] = (int) DESCALE(tmp12 + tmp0, CONST_BITS-PASS1_BITS+1);
     191               0 :     wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 - tmp0, CONST_BITS-PASS1_BITS+1);
     192                 :   }
     193                 :   
     194                 :   /* Pass 2: process 4 rows from work array, store into output array. */
     195                 : 
     196               0 :   wsptr = workspace;
     197               0 :   for (ctr = 0; ctr < 4; ctr++) {
     198               0 :     outptr = output_buf[ctr] + output_col;
     199                 :     /* It's not clear whether a zero row test is worthwhile here ... */
     200                 : 
     201                 : #ifndef NO_ZERO_ROW_TEST
     202               0 :     if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 &&
     203               0 :         wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
     204                 :       /* AC terms all zero */
     205               0 :       JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3)
     206                 :                                   & RANGE_MASK];
     207                 :       
     208               0 :       outptr[0] = dcval;
     209               0 :       outptr[1] = dcval;
     210               0 :       outptr[2] = dcval;
     211               0 :       outptr[3] = dcval;
     212                 :       
     213               0 :       wsptr += DCTSIZE;         /* advance pointer to next row */
     214               0 :       continue;
     215                 :     }
     216                 : #endif
     217                 :     
     218                 :     /* Even part */
     219                 :     
     220               0 :     tmp0 = ((INT32) wsptr[0]) << (CONST_BITS+1);
     221                 :     
     222               0 :     tmp2 = MULTIPLY((INT32) wsptr[2], FIX_1_847759065)
     223               0 :          + MULTIPLY((INT32) wsptr[6], - FIX_0_765366865);
     224                 :     
     225               0 :     tmp10 = tmp0 + tmp2;
     226               0 :     tmp12 = tmp0 - tmp2;
     227                 :     
     228                 :     /* Odd part */
     229                 :     
     230               0 :     z1 = (INT32) wsptr[7];
     231               0 :     z2 = (INT32) wsptr[5];
     232               0 :     z3 = (INT32) wsptr[3];
     233               0 :     z4 = (INT32) wsptr[1];
     234                 :     
     235               0 :     tmp0 = MULTIPLY(z1, - FIX_0_211164243) /* sqrt(2) * (c3-c1) */
     236               0 :          + MULTIPLY(z2, FIX_1_451774981) /* sqrt(2) * (c3+c7) */
     237               0 :          + MULTIPLY(z3, - FIX_2_172734803) /* sqrt(2) * (-c1-c5) */
     238               0 :          + MULTIPLY(z4, FIX_1_061594337); /* sqrt(2) * (c5+c7) */
     239                 :     
     240               0 :     tmp2 = MULTIPLY(z1, - FIX_0_509795579) /* sqrt(2) * (c7-c5) */
     241               0 :          + MULTIPLY(z2, - FIX_0_601344887) /* sqrt(2) * (c5-c1) */
     242               0 :          + MULTIPLY(z3, FIX_0_899976223) /* sqrt(2) * (c3-c7) */
     243               0 :          + MULTIPLY(z4, FIX_2_562915447); /* sqrt(2) * (c1+c3) */
     244                 : 
     245                 :     /* Final output stage */
     246                 :     
     247               0 :     outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp2,
     248                 :                                           CONST_BITS+PASS1_BITS+3+1)
     249                 :                             & RANGE_MASK];
     250               0 :     outptr[3] = range_limit[(int) DESCALE(tmp10 - tmp2,
     251                 :                                           CONST_BITS+PASS1_BITS+3+1)
     252                 :                             & RANGE_MASK];
     253               0 :     outptr[1] = range_limit[(int) DESCALE(tmp12 + tmp0,
     254                 :                                           CONST_BITS+PASS1_BITS+3+1)
     255                 :                             & RANGE_MASK];
     256               0 :     outptr[2] = range_limit[(int) DESCALE(tmp12 - tmp0,
     257                 :                                           CONST_BITS+PASS1_BITS+3+1)
     258                 :                             & RANGE_MASK];
     259                 :     
     260               0 :     wsptr += DCTSIZE;           /* advance pointer to next row */
     261                 :   }
     262               0 : }
     263                 : 
     264                 : 
     265                 : /*
     266                 :  * Perform dequantization and inverse DCT on one block of coefficients,
     267                 :  * producing a reduced-size 2x2 output block.
     268                 :  */
     269                 : 
     270                 : GLOBAL(void)
     271               0 : jpeg_idct_2x2 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
     272                 :                JCOEFPTR coef_block,
     273                 :                JSAMPARRAY output_buf, JDIMENSION output_col)
     274                 : {
     275                 :   INT32 tmp0, tmp10, z1;
     276                 :   JCOEFPTR inptr;
     277                 :   ISLOW_MULT_TYPE * quantptr;
     278                 :   int * wsptr;
     279                 :   JSAMPROW outptr;
     280               0 :   JSAMPLE *range_limit = IDCT_range_limit(cinfo);
     281                 :   int ctr;
     282                 :   int workspace[DCTSIZE*2];     /* buffers data between passes */
     283                 :   SHIFT_TEMPS
     284                 : 
     285                 :   /* Pass 1: process columns from input, store into work array. */
     286                 : 
     287               0 :   inptr = coef_block;
     288               0 :   quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
     289               0 :   wsptr = workspace;
     290               0 :   for (ctr = DCTSIZE; ctr > 0; inptr++, quantptr++, wsptr++, ctr--) {
     291                 :     /* Don't bother to process columns 2,4,6 */
     292               0 :     if (ctr == DCTSIZE-2 || ctr == DCTSIZE-4 || ctr == DCTSIZE-6)
     293               0 :       continue;
     294               0 :     if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*3] == 0 &&
     295               0 :         inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*7] == 0) {
     296                 :       /* AC terms all zero; we need not examine terms 2,4,6 for 2x2 output */
     297               0 :       int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS;
     298                 :       
     299               0 :       wsptr[DCTSIZE*0] = dcval;
     300               0 :       wsptr[DCTSIZE*1] = dcval;
     301                 :       
     302               0 :       continue;
     303                 :     }
     304                 :     
     305                 :     /* Even part */
     306                 :     
     307               0 :     z1 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
     308               0 :     tmp10 = z1 << (CONST_BITS+2);
     309                 :     
     310                 :     /* Odd part */
     311                 : 
     312               0 :     z1 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
     313               0 :     tmp0 = MULTIPLY(z1, - FIX_0_720959822); /* sqrt(2) * (c7-c5+c3-c1) */
     314               0 :     z1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
     315               0 :     tmp0 += MULTIPLY(z1, FIX_0_850430095); /* sqrt(2) * (-c1+c3+c5+c7) */
     316               0 :     z1 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
     317               0 :     tmp0 += MULTIPLY(z1, - FIX_1_272758580); /* sqrt(2) * (-c1+c3-c5-c7) */
     318               0 :     z1 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
     319               0 :     tmp0 += MULTIPLY(z1, FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */
     320                 : 
     321                 :     /* Final output stage */
     322                 :     
     323               0 :     wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp0, CONST_BITS-PASS1_BITS+2);
     324               0 :     wsptr[DCTSIZE*1] = (int) DESCALE(tmp10 - tmp0, CONST_BITS-PASS1_BITS+2);
     325                 :   }
     326                 :   
     327                 :   /* Pass 2: process 2 rows from work array, store into output array. */
     328                 : 
     329               0 :   wsptr = workspace;
     330               0 :   for (ctr = 0; ctr < 2; ctr++) {
     331               0 :     outptr = output_buf[ctr] + output_col;
     332                 :     /* It's not clear whether a zero row test is worthwhile here ... */
     333                 : 
     334                 : #ifndef NO_ZERO_ROW_TEST
     335               0 :     if (wsptr[1] == 0 && wsptr[3] == 0 && wsptr[5] == 0 && wsptr[7] == 0) {
     336                 :       /* AC terms all zero */
     337               0 :       JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3)
     338                 :                                   & RANGE_MASK];
     339                 :       
     340               0 :       outptr[0] = dcval;
     341               0 :       outptr[1] = dcval;
     342                 :       
     343               0 :       wsptr += DCTSIZE;         /* advance pointer to next row */
     344               0 :       continue;
     345                 :     }
     346                 : #endif
     347                 :     
     348                 :     /* Even part */
     349                 :     
     350               0 :     tmp10 = ((INT32) wsptr[0]) << (CONST_BITS+2);
     351                 :     
     352                 :     /* Odd part */
     353                 : 
     354               0 :     tmp0 = MULTIPLY((INT32) wsptr[7], - FIX_0_720959822) /* sqrt(2) * (c7-c5+c3-c1) */
     355               0 :          + MULTIPLY((INT32) wsptr[5], FIX_0_850430095) /* sqrt(2) * (-c1+c3+c5+c7) */
     356               0 :          + MULTIPLY((INT32) wsptr[3], - FIX_1_272758580) /* sqrt(2) * (-c1+c3-c5-c7) */
     357               0 :          + MULTIPLY((INT32) wsptr[1], FIX_3_624509785); /* sqrt(2) * (c1+c3+c5+c7) */
     358                 : 
     359                 :     /* Final output stage */
     360                 :     
     361               0 :     outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp0,
     362                 :                                           CONST_BITS+PASS1_BITS+3+2)
     363                 :                             & RANGE_MASK];
     364               0 :     outptr[1] = range_limit[(int) DESCALE(tmp10 - tmp0,
     365                 :                                           CONST_BITS+PASS1_BITS+3+2)
     366                 :                             & RANGE_MASK];
     367                 :     
     368               0 :     wsptr += DCTSIZE;           /* advance pointer to next row */
     369                 :   }
     370               0 : }
     371                 : 
     372                 : 
     373                 : /*
     374                 :  * Perform dequantization and inverse DCT on one block of coefficients,
     375                 :  * producing a reduced-size 1x1 output block.
     376                 :  */
     377                 : 
     378                 : GLOBAL(void)
     379               0 : jpeg_idct_1x1 (j_decompress_ptr cinfo, jpeg_component_info * compptr,
     380                 :                JCOEFPTR coef_block,
     381                 :                JSAMPARRAY output_buf, JDIMENSION output_col)
     382                 : {
     383                 :   int dcval;
     384                 :   ISLOW_MULT_TYPE * quantptr;
     385               0 :   JSAMPLE *range_limit = IDCT_range_limit(cinfo);
     386                 :   SHIFT_TEMPS
     387                 : 
     388                 :   /* We hardly need an inverse DCT routine for this: just take the
     389                 :    * average pixel value, which is one-eighth of the DC coefficient.
     390                 :    */
     391               0 :   quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
     392               0 :   dcval = DEQUANTIZE(coef_block[0], quantptr[0]);
     393               0 :   dcval = (int) DESCALE((INT32) dcval, 3);
     394                 : 
     395               0 :   output_buf[0][output_col] = range_limit[dcval & RANGE_MASK];
     396               0 : }
     397                 : 
     398                 : #endif /* IDCT_SCALING_SUPPORTED */

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