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plt-scheme  4.2.1
Classes | Defines | Typedefs | Functions
jcdctmgr.c File Reference
#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h"

Go to the source code of this file.

Classes

struct  my_fdct_controller

Defines

#define JPEG_INTERNALS
#define CONST_BITS   14
#define DIVIDE_BY(a, b)   if (a >= b) a /= b; else a = 0

Typedefs

typedef my_fdct_controllermy_fdct_ptr

Functions

 start_pass_fdctmgr (j_compress_ptr cinfo)
 forward_DCT (j_compress_ptr cinfo, jpeg_component_info *compptr, JSAMPARRAY sample_data, JBLOCKROW coef_blocks, JDIMENSION start_row, JDIMENSION start_col, JDIMENSION num_blocks)
 forward_DCT_float (j_compress_ptr cinfo, jpeg_component_info *compptr, JSAMPARRAY sample_data, JBLOCKROW coef_blocks, JDIMENSION start_row, JDIMENSION start_col, JDIMENSION num_blocks)
 jinit_forward_dct (j_compress_ptr cinfo)

Class Documentation

struct my_fdct_controller

Definition at line 22 of file jcdctmgr.c.

Class Members
DCTELEM * divisors
forward_DCT_method_ptr do_dct
float_DCT_method_ptr do_float_dct
FAST_FLOAT * float_divisors

Define Documentation

#define CONST_BITS   14
#define DIVIDE_BY (   a,
  b 
)    if (a >= b) a /= b; else a = 0
#define JPEG_INTERNALS

Definition at line 14 of file jcdctmgr.c.


Typedef Documentation

Definition at line 41 of file jcdctmgr.c.


Function Documentation

forward_DCT ( j_compress_ptr  cinfo,
jpeg_component_info compptr,
JSAMPARRAY  sample_data,
JBLOCKROW  coef_blocks,
JDIMENSION  start_row,
JDIMENSION  start_col,
JDIMENSION  num_blocks 
)

Definition at line 180 of file jcdctmgr.c.

{
  /* This routine is heavily used, so it's worth coding it tightly. */
  my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
  forward_DCT_method_ptr do_dct = fdct->do_dct;
  DCTELEM * divisors = fdct->divisors[compptr->quant_tbl_no];
  DCTELEM workspace[DCTSIZE2];     /* work area for FDCT subroutine */
  JDIMENSION bi;

  sample_data += start_row; /* fold in the vertical offset once */

  for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) {
    /* Load data into workspace, applying unsigned->signed conversion */
    { register DCTELEM *workspaceptr;
      register JSAMPROW elemptr;
      register int elemr;

      workspaceptr = workspace;
      for (elemr = 0; elemr < DCTSIZE; elemr++) {
       elemptr = sample_data[elemr] + start_col;
#if DCTSIZE == 8            /* unroll the inner loop */
       *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
       *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
       *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
       *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
       *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
       *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
       *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
       *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
#else
       { register int elemc;
         for (elemc = DCTSIZE; elemc > 0; elemc--) {
           *workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
         }
       }
#endif
      }
    }

    /* Perform the DCT */
    (*do_dct) (workspace);

    /* Quantize/descale the coefficients, and store into coef_blocks[] */
    { register DCTELEM temp, qval;
      register int i;
      register JCOEFPTR output_ptr = coef_blocks[bi];

      for (i = 0; i < DCTSIZE2; i++) {
       qval = divisors[i];
       temp = workspace[i];
       /* Divide the coefficient value by qval, ensuring proper rounding.
        * Since C does not specify the direction of rounding for negative
        * quotients, we have to force the dividend positive for portability.
        *
        * In most files, at least half of the output values will be zero
        * (at default quantization settings, more like three-quarters...)
        * so we should ensure that this case is fast.  On many machines,
        * a comparison is enough cheaper than a divide to make a special test
        * a win.  Since both inputs will be nonnegative, we need only test
        * for a < b to discover whether a/b is 0.
        * If your machine's division is fast enough, define FAST_DIVIDE.
        */
#ifdef FAST_DIVIDE
#define DIVIDE_BY(a,b)      a /= b
#else
#define DIVIDE_BY(a,b)      if (a >= b) a /= b; else a = 0
#endif
       if (temp < 0) {
         temp = -temp;
         temp += qval>>1;   /* for rounding */
         DIVIDE_BY(temp, qval);
         temp = -temp;
       } else {
         temp += qval>>1;   /* for rounding */
         DIVIDE_BY(temp, qval);
       }
       output_ptr[i] = (JCOEF) temp;
      }
    }
  }
}

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forward_DCT_float ( j_compress_ptr  cinfo,
jpeg_component_info compptr,
JSAMPARRAY  sample_data,
JBLOCKROW  coef_blocks,
JDIMENSION  start_row,
JDIMENSION  start_col,
JDIMENSION  num_blocks 
)

Definition at line 270 of file jcdctmgr.c.

{
  /* This routine is heavily used, so it's worth coding it tightly. */
  my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
  float_DCT_method_ptr do_dct = fdct->do_float_dct;
  FAST_FLOAT * divisors = fdct->float_divisors[compptr->quant_tbl_no];
  FAST_FLOAT workspace[DCTSIZE2]; /* work area for FDCT subroutine */
  JDIMENSION bi;

  sample_data += start_row; /* fold in the vertical offset once */

  for (bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE) {
    /* Load data into workspace, applying unsigned->signed conversion */
    { register FAST_FLOAT *workspaceptr;
      register JSAMPROW elemptr;
      register int elemr;

      workspaceptr = workspace;
      for (elemr = 0; elemr < DCTSIZE; elemr++) {
       elemptr = sample_data[elemr] + start_col;
#if DCTSIZE == 8            /* unroll the inner loop */
       *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
       *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
       *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
       *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
       *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
       *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
       *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
       *workspaceptr++ = (FAST_FLOAT)(GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
#else
       { register int elemc;
         for (elemc = DCTSIZE; elemc > 0; elemc--) {
           *workspaceptr++ = (FAST_FLOAT)
             (GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
         }
       }
#endif
      }
    }

    /* Perform the DCT */
    (*do_dct) (workspace);

    /* Quantize/descale the coefficients, and store into coef_blocks[] */
    { register FAST_FLOAT temp;
      register int i;
      register JCOEFPTR output_ptr = coef_blocks[bi];

      for (i = 0; i < DCTSIZE2; i++) {
       /* Apply the quantization and scaling factor */
       temp = workspace[i] * divisors[i];
       /* Round to nearest integer.
        * Since C does not specify the direction of rounding for negative
        * quotients, we have to force the dividend positive for portability.
        * The maximum coefficient size is +-16K (for 12-bit data), so this
        * code should work for either 16-bit or 32-bit ints.
        */
       output_ptr[i] = (JCOEF) ((int) (temp + (FAST_FLOAT) 16384.5) - 16384);
      }
    }
  }
}

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Definition at line 345 of file jcdctmgr.c.

{
  my_fdct_ptr fdct;
  int i;

  fdct = (my_fdct_ptr)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                            SIZEOF(my_fdct_controller));
  cinfo->fdct = (struct jpeg_forward_dct *) fdct;
  fdct->pub.start_pass = start_pass_fdctmgr;

  switch (cinfo->dct_method) {
#ifdef DCT_ISLOW_SUPPORTED
  case JDCT_ISLOW:
    fdct->pub.forward_DCT = forward_DCT;
    fdct->do_dct = jpeg_fdct_islow;
    break;
#endif
#ifdef DCT_IFAST_SUPPORTED
  case JDCT_IFAST:
    fdct->pub.forward_DCT = forward_DCT;
    fdct->do_dct = jpeg_fdct_ifast;
    break;
#endif
#ifdef DCT_FLOAT_SUPPORTED
  case JDCT_FLOAT:
    fdct->pub.forward_DCT = forward_DCT_float;
    fdct->do_float_dct = jpeg_fdct_float;
    break;
#endif
  default:
    ERREXIT(cinfo, JERR_NOT_COMPILED);
    break;
  }

  /* Mark divisor tables unallocated */
  for (i = 0; i < NUM_QUANT_TBLS; i++) {
    fdct->divisors[i] = NULL;
#ifdef DCT_FLOAT_SUPPORTED
    fdct->float_divisors[i] = NULL;
#endif
  }
}

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Definition at line 54 of file jcdctmgr.c.

{
  my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
  int ci, qtblno, i;
  jpeg_component_info *compptr;
  JQUANT_TBL * qtbl;
  DCTELEM * dtbl;

  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    qtblno = compptr->quant_tbl_no;
    /* Make sure specified quantization table is present */
    if (qtblno < 0 || qtblno >= NUM_QUANT_TBLS ||
       cinfo->quant_tbl_ptrs[qtblno] == NULL)
      ERREXIT1(cinfo, JERR_NO_QUANT_TABLE, qtblno);
    qtbl = cinfo->quant_tbl_ptrs[qtblno];
    /* Compute divisors for this quant table */
    /* We may do this more than once for same table, but it's not a big deal */
    switch (cinfo->dct_method) {
#ifdef DCT_ISLOW_SUPPORTED
    case JDCT_ISLOW:
      /* For LL&M IDCT method, divisors are equal to raw quantization
       * coefficients multiplied by 8 (to counteract scaling).
       */
      if (fdct->divisors[qtblno] == NULL) {
       fdct->divisors[qtblno] = (DCTELEM *)
         (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                  DCTSIZE2 * SIZEOF(DCTELEM));
      }
      dtbl = fdct->divisors[qtblno];
      for (i = 0; i < DCTSIZE2; i++) {
       dtbl[i] = ((DCTELEM) qtbl->quantval[i]) << 3;
      }
      break;
#endif
#ifdef DCT_IFAST_SUPPORTED
    case JDCT_IFAST:
      {
       /* For AA&N IDCT method, divisors are equal to quantization
        * coefficients scaled by scalefactor[row]*scalefactor[col], where
        *   scalefactor[0] = 1
        *   scalefactor[k] = cos(k*PI/16) * sqrt(2)    for k=1..7
        * We apply a further scale factor of 8.
        */
#define CONST_BITS 14
       static const INT16 aanscales[DCTSIZE2] = {
         /* precomputed values scaled up by 14 bits */
         16384, 22725, 21407, 19266, 16384, 12873,  8867,  4520,
         22725, 31521, 29692, 26722, 22725, 17855, 12299,  6270,
         21407, 29692, 27969, 25172, 21407, 16819, 11585,  5906,
         19266, 26722, 25172, 22654, 19266, 15137, 10426,  5315,
         16384, 22725, 21407, 19266, 16384, 12873,  8867,  4520,
         12873, 17855, 16819, 15137, 12873, 10114,  6967,  3552,
          8867, 12299, 11585, 10426,  8867,  6967,  4799,  2446,
          4520,  6270,  5906,  5315,  4520,  3552,  2446,  1247
       };
       SHIFT_TEMPS

       if (fdct->divisors[qtblno] == NULL) {
         fdct->divisors[qtblno] = (DCTELEM *)
           (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                   DCTSIZE2 * SIZEOF(DCTELEM));
       }
       dtbl = fdct->divisors[qtblno];
       for (i = 0; i < DCTSIZE2; i++) {
         dtbl[i] = (DCTELEM)
           DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[i],
                              (INT32) aanscales[i]),
                  CONST_BITS-3);
       }
      }
      break;
#endif
#ifdef DCT_FLOAT_SUPPORTED
    case JDCT_FLOAT:
      {
       /* For float AA&N IDCT method, divisors are equal to quantization
        * coefficients scaled by scalefactor[row]*scalefactor[col], where
        *   scalefactor[0] = 1
        *   scalefactor[k] = cos(k*PI/16) * sqrt(2)    for k=1..7
        * We apply a further scale factor of 8.
        * What's actually stored is 1/divisor so that the inner loop can
        * use a multiplication rather than a division.
        */
       FAST_FLOAT * fdtbl;
       int row, col;
       static const double aanscalefactor[DCTSIZE] = {
         1.0, 1.387039845, 1.306562965, 1.175875602,
         1.0, 0.785694958, 0.541196100, 0.275899379
       };

       if (fdct->float_divisors[qtblno] == NULL) {
         fdct->float_divisors[qtblno] = (FAST_FLOAT *)
           (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                   DCTSIZE2 * SIZEOF(FAST_FLOAT));
       }
       fdtbl = fdct->float_divisors[qtblno];
       i = 0;
       for (row = 0; row < DCTSIZE; row++) {
         for (col = 0; col < DCTSIZE; col++) {
           fdtbl[i] = (FAST_FLOAT)
             (1.0 / (((double) qtbl->quantval[i] *
                     aanscalefactor[row] * aanscalefactor[col] * 8.0)));
           i++;
         }
       }
      }
      break;
#endif
    default:
      ERREXIT(cinfo, JERR_NOT_COMPILED);
      break;
    }
  }
}

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