jcarith.c

It is possible that certain products which can be built using this software modules might form inve

      emit_restart(cinfo, entropy->next_restart_num);
      entropy->restarts_to_go = cinfo->restart_interval;
      entropy->next_restart_num++;
      entropy->next_restart_num &= 7;
    }
    entropy->restarts_to_go--;
  }

  /* Encode the MCU data block */
  block = MCU_data[0];
  tbl = cinfo->cur_comp_info[0]->ac_tbl_no;

  /* Sections F.1.4.2 & F.1.4.4.2: Encoding of AC coefficients */

  /* Establish EOB (end-of-block) index */
  for (ke = cinfo->Se + 1; ke > 1; ke--)
    /* We must apply the point transform by Al.  For AC coefficients this
     * is an integer division with rounding towards 0.  To do this portably
     * in C, we shift after obtaining the absolute value.
     */
    if ((v = (*block)[jpeg_natural_order[ke - 1]]) >= 0) {
      if (v >>= cinfo->Al) break;
    } else {
      v = -v;
      if (v >>= cinfo->Al) break;
    }

  /* Figure F.5: Encode_AC_Coefficients */
  for (k = cinfo->Ss; k < ke; k++) {
    st = entropy->ac_stats[tbl] + 3 * (k - 1);
    arith_encode(cinfo, st, 0);		/* EOB decision */
    entropy->ac_stats[tbl][245] = 0;
    for (;;) {
      if ((v = (*block)[jpeg_natural_order[k]]) >= 0) {
	if (v >>= cinfo->Al) {
	  arith_encode(cinfo, st + 1, 1);
	  arith_encode(cinfo, entropy->ac_stats[tbl] + 245, 0);
	  break;
	}
      } else {
	v = -v;
	if (v >>= cinfo->Al) {
	  arith_encode(cinfo, st + 1, 1);
	  arith_encode(cinfo, entropy->ac_stats[tbl] + 245, 1);
	  break;
	}
      }
      arith_encode(cinfo, st + 1, 0); st += 3; k++;
    }
    st += 2;
    /* Figure F.8: Encoding the magnitude category of v */
    m = 0;
    if (v -= 1) {
      arith_encode(cinfo, st, 1);
      m = 1;
      v2 = v;
      if (v2 >>= 1) {
	arith_encode(cinfo, st, 1);
	m <<= 1;
	st = entropy->ac_stats[tbl] +
	     (k <= cinfo->arith_ac_K[tbl] ? 189 : 217);
	while (v2 >>= 1) {
	  arith_encode(cinfo, st, 1);
	  m <<= 1;
	  st += 1;
	}
      }
    }
    arith_encode(cinfo, st, 0);
    /* Figure F.9: Encoding the magnitude bit pattern of v */
    st += 14;
    while (m >>= 1)
      arith_encode(cinfo, st, (m & v) ? 1 : 0);
  }
  /* Encode EOB decision only if k <= cinfo->Se */
  if (k <= cinfo->Se) {
    st = entropy->ac_stats[tbl] + 3 * (k - 1);
    arith_encode(cinfo, st, 1);
  }

  return TRUE;
}


/*
 * MCU encoding for DC successive approximation refinement scan.
 */

METHODDEF(boolean)
encode_mcu_DC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
{
  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
  unsigned char st[4];
  int Al, blkn;

  /* Emit restart marker if needed */
  if (cinfo->restart_interval) {
    if (entropy->restarts_to_go == 0) {
      emit_restart(cinfo, entropy->next_restart_num);
      entropy->restarts_to_go = cinfo->restart_interval;
      entropy->next_restart_num++;
      entropy->next_restart_num &= 7;
    }
    entropy->restarts_to_go--;
  }

  Al = cinfo->Al;

  /* Encode the MCU data blocks */
  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
    st[0] = 0;	/* use fixed probability estimation */
    /* We simply emit the Al'th bit of the DC coefficient value. */
    arith_encode(cinfo, st, (MCU_data[blkn][0][0] >> Al) & 1);
  }

  return TRUE;
}


/*
 * MCU encoding for AC successive approximation refinement scan.
 */

METHODDEF(boolean)
encode_mcu_AC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
{
  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
  JBLOCKROW block;
  unsigned char *st;
  int tbl, k, ke, kex;
  int v;

  /* Emit restart marker if needed */
  if (cinfo->restart_interval) {
    if (entropy->restarts_to_go == 0) {
      emit_restart(cinfo, entropy->next_restart_num);
      entropy->restarts_to_go = cinfo->restart_interval;
      entropy->next_restart_num++;
      entropy->next_restart_num &= 7;
    }
    entropy->restarts_to_go--;
  }

  /* Encode the MCU data block */
  block = MCU_data[0];
  tbl = cinfo->cur_comp_info[0]->ac_tbl_no;

  /* Section G.1.3.3: Encoding of AC coefficients */

  /* Establish EOB (end-of-block) index */
  for (ke = cinfo->Se + 1; ke > 1; ke--)
    /* We must apply the point transform by Al.  For AC coefficients this
     * is an integer division with rounding towards 0.  To do this portably
     * in C, we shift after obtaining the absolute value.
     */
    if ((v = (*block)[jpeg_natural_order[ke - 1]]) >= 0) {
      if (v >>= cinfo->Al) break;
    } else {
      v = -v;
      if (v >>= cinfo->Al) break;
    }

  /* Establish EOBx (previous stage end-of-block) index */
  for (kex = ke; kex > 1; kex--)
    if ((v = (*block)[jpeg_natural_order[kex - 1]]) >= 0) {
      if (v >>= cinfo->Ah) break;
    } else {
      v = -v;
      if (v >>= cinfo->Ah) break;
    }

  /* Figure G.10: Encode_AC_Coefficients_SA */
  for (k = cinfo->Ss; k < ke; k++) {
    st = entropy->ac_stats[tbl] + 3 * (k - 1);
    if (k >= kex)
      arith_encode(cinfo, st, 0);	/* EOB decision */
    entropy->ac_stats[tbl][245] = 0;
    for (;;) {
      if ((v = (*block)[jpeg_natural_order[k]]) >= 0) {
	if (v >>= cinfo->Al) {
	  if (v >> 1)		/* previously nonzero coef */
	    arith_encode(cinfo, st + 2, (v & 1));
	  else {		/* newly nonzero coef */
	    arith_encode(cinfo, st + 1, 1);
	    arith_encode(cinfo, entropy->ac_stats[tbl] + 245, 0);
	  }
	  break;
	}
      } else {
	v = -v;
	if (v >>= cinfo->Al) {
	  if (v >> 1)		/* previously nonzero coef */
	    arith_encode(cinfo, st + 2, (v & 1));
	  else {		/* newly nonzero coef */
	    arith_encode(cinfo, st + 1, 1);
	    arith_encode(cinfo, entropy->ac_stats[tbl] + 245, 1);
	  }
	  break;
	}
      }
      arith_encode(cinfo, st + 1, 0); st += 3; k++;
    }
  }
  /* Encode EOB decision only if k <= cinfo->Se */
  if (k <= cinfo->Se) {
    st = entropy->ac_stats[tbl] + 3 * (k - 1);
    arith_encode(cinfo, st, 1);
  }

  return TRUE;
}


/*
 * Encode and output one MCU's worth of arithmetic-compressed coefficients.
 */

METHODDEF(boolean)
encode_mcu (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
{
  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
  jpeg_component_info * compptr;
  JBLOCKROW block;
  unsigned char *st;
  int blkn, ci, tbl, k, ke;
  int v, v2, m;

  /* Emit restart marker if needed */
  if (cinfo->restart_interval) {
    if (entropy->restarts_to_go == 0) {
      emit_restart(cinfo, entropy->next_restart_num);
      entropy->restarts_to_go = cinfo->restart_interval;
      entropy->next_restart_num++;
      entropy->next_restart_num &= 7;
    }
    entropy->restarts_to_go--;
  }

  /* Encode the MCU data blocks */
  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
    block = MCU_data[blkn];
    ci = cinfo->MCU_membership[blkn];
    compptr = cinfo->cur_comp_info[ci];

    /* Sections F.1.4.1 & F.1.4.4.1: Encoding of DC coefficients */

    tbl = compptr->dc_tbl_no;

    /* Table F.4: Point to statistics bin S0 for DC coefficient coding */
    st = entropy->dc_stats[tbl] + entropy->dc_context[ci];

    /* Figure F.4: Encode_DC_DIFF */
    if ((v = (*block)[0] - entropy->last_dc_val[ci]) == 0) {
      arith_encode(cinfo, st, 0);
      entropy->dc_context[ci] = 0;	/* zero diff category */
    } else {
      entropy->last_dc_val[ci] = (*block)[0];
      arith_encode(cinfo, st, 1);
      /* Figure F.6: Encoding nonzero value v */
      /* Figure F.7: Encoding the sign of v */
      if (v > 0) {
	arith_encode(cinfo, st + 1, 0);	/* Table F.4: SS = S0 + 1 */
	st += 2;			/* Table F.4: SP = S0 + 2 */
	entropy->dc_context[ci] = 4;	/* small positive diff category */
      } else {
	v = -v;
	arith_encode(cinfo, st + 1, 1);	/* Table F.4: SS = S0 + 1 */
	st += 3;			/* Table F.4: SN = S0 + 3 */
	entropy->dc_context[ci] = 8;	/* small negative diff category */
      }
      /* Figure F.8: Encoding the magnitude category of v */
      m = 0;
      if (v -= 1) {
	arith_encode(cinfo, st, 1);
	m = 1;
	v2 = v;
	st = entropy->dc_stats[tbl] + 20; /* Table F.4: X1 = 20 */
	while (v2 >>= 1) {
	  arith_encode(cinfo, st, 1);
	  m <<= 1;
	  st += 1;
	}
      }
      arith_encode(cinfo, st, 0);
      /* Section F.1.4.4.1.2: Establish dc_context conditioning category */
      if (m < (int) (((INT32) 1 << cinfo->arith_dc_L[tbl]) >> 1))
	entropy->dc_context[ci] = 0;	/* zero diff category */
      else if (m > (int) (((INT32) 1 << cinfo->arith_dc_U[tbl]) >> 1))
	entropy->dc_context[ci] += 8;	/* large diff category */
      /* Figure F.9: Encoding the magnitude bit pattern of v */
      st += 14;
      while (m >>= 1)
	arith_encode(cinfo, st, (m & v) ? 1 : 0);
    }

    /* Sections F.1.4.2 & F.1.4.4.2: Encoding of AC coefficients */

    tbl = compptr->ac_tbl_no;

    /* Establish EOB (end-of-block) index */
    for (ke = DCTSIZE2; ke > 1; ke--)
      if ((*block)[jpeg_natural_order[ke - 1]]) break;

    /* Figure F.5: Encode_AC_Coefficients */
    for (k = 1; k < ke; k++) {
      st = entropy->ac_stats[tbl] + 3 * (k - 1);
      arith_encode(cinfo, st, 0);	/* EOB decision */
      while ((v = (*block)[jpeg_natural_order[k]]) == 0) {
	arith_encode(cinfo, st + 1, 0); st += 3; k++;
      }
      arith_encode(cinfo, st + 1, 1);
      /* Figure F.6: Encoding nonzero value v */
      /* Figure F.7: Encoding the sign of v */
      entropy->ac_stats[tbl][245] = 0;
      if (v > 0) {
	arith_encode(cinfo, entropy->ac_stats[tbl] + 245, 0);
      } else {
	v = -v;
	arith_encode(cinfo, entropy->ac_stats[tbl] + 245, 1);
      }
      st += 2;
      /* Figure F.8: Encoding the magnitude category of v */
      m = 0;
      if (v -= 1) {
	arith_encode(cinfo, st, 1);
	m = 1;
	v2 = v;
	if (v2 >>= 1) {
	  arith_encode(cinfo, st, 1);
	  m <<= 1;
	  st = entropy->ac_stats[tbl] +
	       (k <= cinfo->arith_ac_K[tbl] ? 189 : 217);
	  while (v2 >>= 1) {
	    arith_encode(cinfo, st, 1);
	    m <<= 1;
	    st += 1;
	  }
	}
      }
      arith_encode(cinfo, st, 0);
      /* Figure F.9: Encoding the magnitude bit pattern of v */
      st += 14;
      while (m >>= 1)
	arith_encode(cinfo, st, (m & v) ? 1 : 0);
    }
    /* Encode EOB decision only if k < DCTSIZE2 */
    if (k < DCTSIZE2) {
      st = entropy->ac_stats[tbl] + 3 * (k - 1);
      arith_encode(cinfo, st, 1);
    }
  }

  return TRUE;
}


/*
 * Initialize for an arithmetic-compressed scan.
 */

METHODDEF(void)
start_pass (j_compress_ptr cinfo, boolean gather_statistics)
{
  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
  int ci, tbl;
  jpeg_component_info * compptr;

  if (gather_statistics)
    /* Make sure to avoid that in the master control logic!
     * We are fully adaptive here and need no extra
     * statistics gathering pass!
     */
    ERREXIT(cinfo, JERR_NOT_COMPILED);

  /* We assume jcmaster.c already validated the progressive scan parameters. */

  /* Select execution routines */
  if (cinfo->progressive_mode) {
    if (cinfo->Ah == 0) {
      if (cinfo->Ss == 0)
	entropy->pub.encode_mcu = encode_mcu_DC_first;
      else
	entropy->pub.encode_mcu = encode_mcu_AC_first;
    } else {
      if (cinfo->Ss == 0)
	entropy->pub.encode_mcu = encode_mcu_DC_refine;
      else
	entropy->pub.encode_mcu = encode_mcu_AC_refine;
    }
  } else
    entropy->pub.encode_mcu = encode_mcu;

  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
    compptr = cinfo->cur_comp_info[ci];
    /* Allocate & initialize requested statistics areas */
    if (cinfo->progressive_mode == 0 || (cinfo->Ss == 0 && cinfo->Ah == 0)) {
      tbl = compptr->dc_tbl_no;
      if (tbl < 0 || tbl >= NUM_ARITH_TBLS)
	ERREXIT1(cinfo, JERR_NO_ARITH_TABLE, tbl);
      if (entropy->dc_stats[tbl] == NULL)
	entropy->dc_stats[tbl] = (unsigned char *) (*cinfo->mem->alloc_small)
	  ((j_common_ptr) cinfo, JPOOL_IMAGE, DC_STAT_BINS);
      MEMZERO(entropy->dc_stats[tbl], DC_STAT_BINS);
      /* Initialize DC predictions to 0 */
      entropy->last_dc_val[ci] = 0;
      entropy->dc_context[ci] = 0;
    }
    if (cinfo->progressive_mode == 0 || cinfo->Ss) {
      tbl = compptr->ac_tbl_no;
      if (tbl < 0 || tbl >= NUM_ARITH_TBLS)
	ERREXIT1(cinfo, JERR_NO_ARITH_TABLE, tbl);
      if (entropy->ac_stats[tbl] == NULL)
	entropy->ac_stats[tbl] = (unsigned char *) (*cinfo->mem->alloc_small)
	  ((j_common_ptr) cinfo, JPOOL_IMAGE, AC_STAT_BINS);
      MEMZERO(entropy->ac_stats[tbl], AC_STAT_BINS);
#ifdef CALCULATE_SPECTRAL_CONDITIONING
      if (cinfo->progressive_mode)
	/* Section G.1.3.2: Set appropriate arithmetic conditioning value Kx */
	cinfo->arith_ac_K[tbl] = cinfo->Ss + ((8 + cinfo->Se - cinfo->Ss) >> 4);
#endif
    }
  }

  /* Initialize arithmetic encoding variables */
  entropy->c = 0;
  entropy->a = 0x10000L;
  entropy->sc = 0;
  entropy->zc = 0;
  entropy->ct = 11;
  entropy->buffer = -1;  /* empty */

  /* Initialize restart stuff */
  entropy->restarts_to_go = cinfo->restart_interval;
  entropy->next_restart_num = 0;
}


/*
 * Module initialization routine for arithmetic entropy encoding.
 */

GLOBAL(void)
jinit_arith_encoder (j_compress_ptr cinfo)
{
  arith_entropy_ptr entropy;
  int i;

  entropy = (arith_entropy_ptr)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				SIZEOF(arith_entropy_encoder));
  cinfo->entropy = (struct jpeg_entropy_encoder *) entropy;
  entropy->pub.start_pass = start_pass;
  entropy->pub.finish_pass = finish_pass;

  /* Mark tables unallocated */
  for (i = 0; i < NUM_ARITH_TBLS; i++) {
    entropy->dc_stats[i] = NULL;
    entropy->ac_stats[i] = NULL;
  }
}