jdphuff.c

这是在PCA下的基于IPP库示例代码例子,在网上下了IPP的库之后,设置相关参数就可以编译该代码.

      (*block)[0] = (JCOEF) (s << Al);
    }

    /* Completed MCU, so update state */
    BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
    ASSIGN_STATE(entropy->saved, state);
  }

  /* Account for restart interval (no-op if not using restarts) */
  entropy->restarts_to_go--;

  return TRUE;
}


/*
 * MCU decoding for AC initial scan (either spectral selection,
 * or first pass of successive approximation).
 */

METHODDEF(boolean)
decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
{
  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
  int Se = cinfo->Se;
  int Al = cinfo->Al;
  register int s, k, r;
  unsigned int EOBRUN;
  JBLOCKROW block;
  BITREAD_STATE_VARS;
  d_derived_tbl * tbl;

  /* Process restart marker if needed; may have to suspend */
  if (cinfo->restart_interval) {
    if (entropy->restarts_to_go == 0)
      if (! process_restart(cinfo))
        return FALSE;
  }

  /* If we've run out of data, just leave the MCU set to zeroes.
   * This way, we return uniform gray for the remainder of the segment.
   */
  if (! entropy->pub.insufficient_data) {

    /* Load up working state.
     * We can avoid loading/saving bitread state if in an EOB run.
     */
    EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */

    /* There is always only one block per MCU */

    if (EOBRUN > 0)   /* if it's a band of zeroes... */
      EOBRUN--;     /* ...process it now (we do nothing) */
    else {
      BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
      block = MCU_data[0];
      tbl = entropy->ac_derived_tbl;

      for (k = cinfo->Ss; k <= Se; k++) {
        HUFF_DECODE(s, br_state, tbl, return FALSE, label2);
        r = s >> 4;
        s &= 15;
        if (s) {
          k += r;
          CHECK_BIT_BUFFER(br_state, s, return FALSE);
          r = GET_BITS(s);
          s = HUFF_EXTEND(r, s);
          /* Scale and output coefficient in natural (dezigzagged) order */
          (*block)[jpeg_natural_order[k]] = (JCOEF) (s << Al);
        } else {
          if (r == 15) {  /* ZRL */
            k += 15;    /* skip 15 zeroes in band */
          } else {    /* EOBr, run length is 2^r + appended bits */
            EOBRUN = 1 << r;
            if (r) {    /* EOBr, r > 0 */
              CHECK_BIT_BUFFER(br_state, r, return FALSE);
              r = GET_BITS(r);
              EOBRUN += r;
            }
            EOBRUN--;   /* this band is processed at this moment */
            break;    /* force end-of-band */
          }
        }
      }

      BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
    }

    /* Completed MCU, so update state */
    entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
  }

  /* Account for restart interval (no-op if not using restarts) */
  entropy->restarts_to_go--;

  return TRUE;
}


/*
 * MCU decoding for DC successive approximation refinement scan.
 * Note: we assume such scans can be multi-component, although the spec
 * is not very clear on the point.
 */

METHODDEF(boolean)
decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
{
  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
  int p1 = 1 << cinfo->Al;  /* 1 in the bit position being coded */
  int blkn;
  JBLOCKROW block;
  BITREAD_STATE_VARS;

  /* Process restart marker if needed; may have to suspend */
  if (cinfo->restart_interval) {
    if (entropy->restarts_to_go == 0)
      if (! process_restart(cinfo))
        return FALSE;
  }

  /* Not worth the cycles to check insufficient_data here,
   * since we will not change the data anyway if we read zeroes.
   */

  /* Load up working state */
  BITREAD_LOAD_STATE(cinfo,entropy->bitstate);

  /* Outer loop handles each block in the MCU */

  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
    block = MCU_data[blkn];

    /* Encoded data is simply the next bit of the two's-complement DC value */
    CHECK_BIT_BUFFER(br_state, 1, return FALSE);
    if (GET_BITS(1))
      (*block)[0] |= p1;
    /* Note: since we use |=, repeating the assignment later is safe */
  }

  /* Completed MCU, so update state */
  BITREAD_SAVE_STATE(cinfo,entropy->bitstate);

  /* Account for restart interval (no-op if not using restarts) */
  entropy->restarts_to_go--;

  return TRUE;
}


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

METHODDEF(boolean)
decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
{
  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
  int Se = cinfo->Se;
  int p1 = 1 << cinfo->Al;  /* 1 in the bit position being coded */
  int m1 = (-1) << cinfo->Al; /* -1 in the bit position being coded */
  register int s, k, r;
  unsigned int EOBRUN;
  JBLOCKROW block;
  JCOEFPTR thiscoef;
  BITREAD_STATE_VARS;
  d_derived_tbl * tbl;
  int num_newnz;
  int newnz_pos[DCTSIZE2];

  /* Process restart marker if needed; may have to suspend */
  if (cinfo->restart_interval) {
    if (entropy->restarts_to_go == 0)
      if (! process_restart(cinfo))
        return FALSE;
  }

  /* If we've run out of data, don't modify the MCU.
   */
  if (! entropy->pub.insufficient_data) {

    /* Load up working state */
    BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
    EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */

    /* There is always only one block per MCU */
    block = MCU_data[0];
    tbl = entropy->ac_derived_tbl;

    /* If we are forced to suspend, we must undo the assignments to any newly
     * nonzero coefficients in the block, because otherwise we'd get confused
     * next time about which coefficients were already nonzero.
     * But we need not undo addition of bits to already-nonzero coefficients;
     * instead, we can test the current bit to see if we already did it.
     */
    num_newnz = 0;

    /* initialize coefficient loop counter to start of band */
    k = cinfo->Ss;

    if (EOBRUN == 0) {
      for (; k <= Se; k++) {
        HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
        r = s >> 4;
        s &= 15;
        if (s) {
          if (s != 1)   /* size of new coef should always be 1 */
            WARNMS(cinfo, JWRN_HUFF_BAD_CODE);
          CHECK_BIT_BUFFER(br_state, 1, goto undoit);
          if (GET_BITS(1))
            s = p1;   /* newly nonzero coef is positive */
          else
            s = m1;   /* newly nonzero coef is negative */
        } else {
          if (r != 15) {
            EOBRUN = 1 << r;  /* EOBr, run length is 2^r + appended bits */
          if (r) {
            CHECK_BIT_BUFFER(br_state, r, goto undoit);
            r = GET_BITS(r);
            EOBRUN += r;
          }
          break;    /* rest of block is handled by EOB logic */
          }
          /* note s = 0 for processing ZRL */
        }
        /* Advance over already-nonzero coefs and r still-zero coefs,
         * appending correction bits to the nonzeroes.  A correction bit is 1
         * if the absolute value of the coefficient must be increased.
         */
        do {
          thiscoef = *block + jpeg_natural_order[k];
          if (*thiscoef != 0) {
            CHECK_BIT_BUFFER(br_state, 1, goto undoit);
            if (GET_BITS(1)) {
              if ((*thiscoef & p1) == 0) { /* do nothing if already set it */
                if (*thiscoef >= 0)
                  *thiscoef += p1;
                else
                  *thiscoef += m1;
              }
            }
          } else {
            if (--r < 0)
              break;    /* reached target zero coefficient */
          }
          k++;
        } while (k <= Se);
        if (s) {
          int pos = jpeg_natural_order[k];
          /* Output newly nonzero coefficient */
          (*block)[pos] = (JCOEF) s;
          /* Remember its position in case we have to suspend */
          newnz_pos[num_newnz++] = pos;
        }
      }
    }

    if (EOBRUN > 0) {
      /* Scan any remaining coefficient positions after the end-of-band
       * (the last newly nonzero coefficient, if any).  Append a correction
       * bit to each already-nonzero coefficient.  A correction bit is 1
       * if the absolute value of the coefficient must be increased.
       */
      for (; k <= Se; k++) {
        thiscoef = *block + jpeg_natural_order[k];
        if (*thiscoef != 0) {
          CHECK_BIT_BUFFER(br_state, 1, goto undoit);
          if (GET_BITS(1)) {
            if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */
              if (*thiscoef >= 0)
                *thiscoef += p1;
              else
                *thiscoef += m1;
            }
          }
        }
      }
      /* Count one block completed in EOB run */
      EOBRUN--;
    }

    /* Completed MCU, so update state */
    BITREAD_SAVE_STATE(cinfo,entropy->bitstate);
    entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
  }

  /* Account for restart interval (no-op if not using restarts) */
  entropy->restarts_to_go--;

  return TRUE;

undoit:
  /* Re-zero any output coefficients that we made newly nonzero */
  while (num_newnz > 0)
    (*block)[newnz_pos[--num_newnz]] = 0;

  return FALSE;
}


/*
 * Module initialization routine for progressive Huffman entropy decoding.
 */

GLOBAL(void)
jinit_phuff_decoder (j_decompress_ptr cinfo)
{
  phuff_entropy_ptr entropy;
  int *coef_bit_ptr;
  int ci, i;

  entropy = (phuff_entropy_ptr)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
        SIZEOF(phuff_entropy_decoder));
  cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;
  entropy->pub.start_pass = start_pass_phuff_decoder;

  /* Mark derived tables unallocated */
  for (i = 0; i < NUM_HUFF_TBLS; i++) {
    entropy->derived_tbls[i] = NULL;
  }

  /* Create progression status table */
  cinfo->coef_bits = (int (*)[DCTSIZE2])
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
        cinfo->num_components*DCTSIZE2*SIZEOF(int));
  coef_bit_ptr = & cinfo->coef_bits[0][0];
  for (ci = 0; ci < cinfo->num_components; ci++)
    for (i = 0; i < DCTSIZE2; i++)
      *coef_bit_ptr++ = -1;
}

#endif /* D_PROGRESSIVE_SUPPORTED */