LCOV - code coverage report
Current view: directory - media/libjpeg - jfdctflt.c (source / functions) Found Hit Coverage
Test: app.info Lines: 68 0 0.0 %
Date: 2012-06-02 Functions: 1 0 0.0 %

       1                 : /*
       2                 :  * jfdctflt.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 a floating-point implementation of the
       9                 :  * forward DCT (Discrete Cosine Transform).
      10                 :  *
      11                 :  * This implementation should be more accurate than either of the integer
      12                 :  * DCT implementations.  However, it may not give the same results on all
      13                 :  * machines because of differences in roundoff behavior.  Speed will depend
      14                 :  * on the hardware's floating point capacity.
      15                 :  *
      16                 :  * A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT
      17                 :  * on each column.  Direct algorithms are also available, but they are
      18                 :  * much more complex and seem not to be any faster when reduced to code.
      19                 :  *
      20                 :  * This implementation is based on Arai, Agui, and Nakajima's algorithm for
      21                 :  * scaled DCT.  Their original paper (Trans. IEICE E-71(11):1095) is in
      22                 :  * Japanese, but the algorithm is described in the Pennebaker & Mitchell
      23                 :  * JPEG textbook (see REFERENCES section in file README).  The following code
      24                 :  * is based directly on figure 4-8 in P&M.
      25                 :  * While an 8-point DCT cannot be done in less than 11 multiplies, it is
      26                 :  * possible to arrange the computation so that many of the multiplies are
      27                 :  * simple scalings of the final outputs.  These multiplies can then be
      28                 :  * folded into the multiplications or divisions by the JPEG quantization
      29                 :  * table entries.  The AA&N method leaves only 5 multiplies and 29 adds
      30                 :  * to be done in the DCT itself.
      31                 :  * The primary disadvantage of this method is that with a fixed-point
      32                 :  * implementation, accuracy is lost due to imprecise representation of the
      33                 :  * scaled quantization values.  However, that problem does not arise if
      34                 :  * we use floating point arithmetic.
      35                 :  */
      36                 : 
      37                 : #define JPEG_INTERNALS
      38                 : #include "jinclude.h"
      39                 : #include "jpeglib.h"
      40                 : #include "jdct.h"             /* Private declarations for DCT subsystem */
      41                 : 
      42                 : #ifdef DCT_FLOAT_SUPPORTED
      43                 : 
      44                 : 
      45                 : /*
      46                 :  * This module is specialized to the case DCTSIZE = 8.
      47                 :  */
      48                 : 
      49                 : #if DCTSIZE != 8
      50                 :   Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
      51                 : #endif
      52                 : 
      53                 : 
      54                 : /*
      55                 :  * Perform the forward DCT on one block of samples.
      56                 :  */
      57                 : 
      58                 : GLOBAL(void)
      59               0 : jpeg_fdct_float (FAST_FLOAT * data)
      60                 : {
      61                 :   FAST_FLOAT tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
      62                 :   FAST_FLOAT tmp10, tmp11, tmp12, tmp13;
      63                 :   FAST_FLOAT z1, z2, z3, z4, z5, z11, z13;
      64                 :   FAST_FLOAT *dataptr;
      65                 :   int ctr;
      66                 : 
      67                 :   /* Pass 1: process rows. */
      68                 : 
      69               0 :   dataptr = data;
      70               0 :   for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
      71               0 :     tmp0 = dataptr[0] + dataptr[7];
      72               0 :     tmp7 = dataptr[0] - dataptr[7];
      73               0 :     tmp1 = dataptr[1] + dataptr[6];
      74               0 :     tmp6 = dataptr[1] - dataptr[6];
      75               0 :     tmp2 = dataptr[2] + dataptr[5];
      76               0 :     tmp5 = dataptr[2] - dataptr[5];
      77               0 :     tmp3 = dataptr[3] + dataptr[4];
      78               0 :     tmp4 = dataptr[3] - dataptr[4];
      79                 :     
      80                 :     /* Even part */
      81                 :     
      82               0 :     tmp10 = tmp0 + tmp3;        /* phase 2 */
      83               0 :     tmp13 = tmp0 - tmp3;
      84               0 :     tmp11 = tmp1 + tmp2;
      85               0 :     tmp12 = tmp1 - tmp2;
      86                 :     
      87               0 :     dataptr[0] = tmp10 + tmp11; /* phase 3 */
      88               0 :     dataptr[4] = tmp10 - tmp11;
      89                 :     
      90               0 :     z1 = (tmp12 + tmp13) * ((FAST_FLOAT) 0.707106781); /* c4 */
      91               0 :     dataptr[2] = tmp13 + z1;    /* phase 5 */
      92               0 :     dataptr[6] = tmp13 - z1;
      93                 :     
      94                 :     /* Odd part */
      95                 : 
      96               0 :     tmp10 = tmp4 + tmp5;        /* phase 2 */
      97               0 :     tmp11 = tmp5 + tmp6;
      98               0 :     tmp12 = tmp6 + tmp7;
      99                 : 
     100                 :     /* The rotator is modified from fig 4-8 to avoid extra negations. */
     101               0 :     z5 = (tmp10 - tmp12) * ((FAST_FLOAT) 0.382683433); /* c6 */
     102               0 :     z2 = ((FAST_FLOAT) 0.541196100) * tmp10 + z5; /* c2-c6 */
     103               0 :     z4 = ((FAST_FLOAT) 1.306562965) * tmp12 + z5; /* c2+c6 */
     104               0 :     z3 = tmp11 * ((FAST_FLOAT) 0.707106781); /* c4 */
     105                 : 
     106               0 :     z11 = tmp7 + z3;            /* phase 5 */
     107               0 :     z13 = tmp7 - z3;
     108                 : 
     109               0 :     dataptr[5] = z13 + z2;      /* phase 6 */
     110               0 :     dataptr[3] = z13 - z2;
     111               0 :     dataptr[1] = z11 + z4;
     112               0 :     dataptr[7] = z11 - z4;
     113                 : 
     114               0 :     dataptr += DCTSIZE;         /* advance pointer to next row */
     115                 :   }
     116                 : 
     117                 :   /* Pass 2: process columns. */
     118                 : 
     119               0 :   dataptr = data;
     120               0 :   for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
     121               0 :     tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*7];
     122               0 :     tmp7 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*7];
     123               0 :     tmp1 = dataptr[DCTSIZE*1] + dataptr[DCTSIZE*6];
     124               0 :     tmp6 = dataptr[DCTSIZE*1] - dataptr[DCTSIZE*6];
     125               0 :     tmp2 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*5];
     126               0 :     tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*5];
     127               0 :     tmp3 = dataptr[DCTSIZE*3] + dataptr[DCTSIZE*4];
     128               0 :     tmp4 = dataptr[DCTSIZE*3] - dataptr[DCTSIZE*4];
     129                 :     
     130                 :     /* Even part */
     131                 :     
     132               0 :     tmp10 = tmp0 + tmp3;        /* phase 2 */
     133               0 :     tmp13 = tmp0 - tmp3;
     134               0 :     tmp11 = tmp1 + tmp2;
     135               0 :     tmp12 = tmp1 - tmp2;
     136                 :     
     137               0 :     dataptr[DCTSIZE*0] = tmp10 + tmp11; /* phase 3 */
     138               0 :     dataptr[DCTSIZE*4] = tmp10 - tmp11;
     139                 :     
     140               0 :     z1 = (tmp12 + tmp13) * ((FAST_FLOAT) 0.707106781); /* c4 */
     141               0 :     dataptr[DCTSIZE*2] = tmp13 + z1; /* phase 5 */
     142               0 :     dataptr[DCTSIZE*6] = tmp13 - z1;
     143                 :     
     144                 :     /* Odd part */
     145                 : 
     146               0 :     tmp10 = tmp4 + tmp5;        /* phase 2 */
     147               0 :     tmp11 = tmp5 + tmp6;
     148               0 :     tmp12 = tmp6 + tmp7;
     149                 : 
     150                 :     /* The rotator is modified from fig 4-8 to avoid extra negations. */
     151               0 :     z5 = (tmp10 - tmp12) * ((FAST_FLOAT) 0.382683433); /* c6 */
     152               0 :     z2 = ((FAST_FLOAT) 0.541196100) * tmp10 + z5; /* c2-c6 */
     153               0 :     z4 = ((FAST_FLOAT) 1.306562965) * tmp12 + z5; /* c2+c6 */
     154               0 :     z3 = tmp11 * ((FAST_FLOAT) 0.707106781); /* c4 */
     155                 : 
     156               0 :     z11 = tmp7 + z3;            /* phase 5 */
     157               0 :     z13 = tmp7 - z3;
     158                 : 
     159               0 :     dataptr[DCTSIZE*5] = z13 + z2; /* phase 6 */
     160               0 :     dataptr[DCTSIZE*3] = z13 - z2;
     161               0 :     dataptr[DCTSIZE*1] = z11 + z4;
     162               0 :     dataptr[DCTSIZE*7] = z11 - z4;
     163                 : 
     164               0 :     dataptr++;                  /* advance pointer to next column */
     165                 :   }
     166               0 : }
     167                 : 
     168                 : #endif /* DCT_FLOAT_SUPPORTED */

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