blocks.cpp

该源码是JPEG2000的c++源代码,希望对研究JPEG2000标准以及编解码的朋友们有用.

    { // Has been included at least once before
      head.put_bit((included)?1:0);
    }
  if (!included)
    return;

  // If we get here, the code-block does contribute to the current layer.

  if (pass_idx == 0)
    { // First time contribution.  Need to get MSB's.
      for (msbs_wbar=0; msbs_wbar <= msbs_w; )
        { // Run tag tree decoder.
          kd_block *scan, *prev, *next;

          // Walk up to the root note in the tree.
          scan=this; prev=NULL;
          while ((next=scan->up_down) != NULL)
            { scan->up_down=prev; prev=scan; scan=next; }
          scan->up_down = prev;

          // Walk back down the tree, performing the decoding steps.
          kdu_byte wbar_min = 0;
          kdu_byte threshold = msbs_wbar+1;
          prev = NULL;
          while (scan != NULL)
            {
              if (scan->msbs_wbar < wbar_min)
                scan->msbs_wbar = wbar_min;
              while ((scan->msbs_w >= scan->msbs_wbar) &&
                     (scan->msbs_wbar < threshold))
                {
                  scan->msbs_wbar++;
                  head.put_bit((scan->msbs_w >= scan->msbs_wbar)?0:1);
                }
              wbar_min =
                (scan->msbs_w<scan->msbs_wbar)?scan->msbs_w:scan->msbs_wbar;
              next=scan->up_down; scan->up_down=prev; prev=scan; scan=next;
            }
        }
      beta = 3;
    }

  // Encode number of passes.

  int val = pending_new_passes - 1;
  int delta = (val > 1)?1:val;
  val -= delta;
  head.put_bit(delta);
  if (delta)
    { // new_passes > 1
      delta = (val > 1)?1:val;
      val -= delta;
      head.put_bit(delta);
      if (delta)
        { // new_passes > 2
          delta = (val > 3)?3:val;
          val -= delta;
          head.put_bits(delta,2);
          if (delta == 3)
            {
              delta = (val > 31)?31:val;
              val -= delta;
              head.put_bits(delta,5);
              if (delta == 31)
                {
                  delta = (val > 127)?127:val;
                  val -= delta;
                  head.put_bits(delta,7);
                }
            }
        }
    }
  assert(val == 0);

  // Finally, encode the length information.

  int segment_passes, segment_bytes, total_bytes, length_bits, new_passes, idx;
  bool bypass_term = ((((int) modes) & Cmodes_BYPASS) != 0);
  bool all_term = ((((int) modes) & Cmodes_RESTART) != 0);
  if (all_term)
    bypass_term = false;

  // Save buffer status
  kd_code_buffer *save_current_buf = current_buf;
  kdu_byte save_buf_pos = buf_pos;

  // Walk through the coding passes a first time to determine beta.
  for (total_bytes=0, idx=pass_idx, new_passes=pending_new_passes;
       new_passes > 0; new_passes-=segment_passes,
       total_bytes+=segment_bytes, idx+=segment_passes)
    {
      if (all_term)
        segment_passes = 1;
      else if (bypass_term)
        {
          if (idx < 10)
            segment_passes = 10-idx;
          else if (((idx-10) % 3) == 0)
            segment_passes = 2;
          else
            segment_passes = 1;
          if (segment_passes > new_passes)
            segment_passes = new_passes;
        }
      else
        segment_passes = new_passes;
      for (length_bits=0; (1<<length_bits) <= segment_passes; length_bits++);
      length_bits--;
      length_bits += beta;
      for (segment_bytes=0, val=segment_passes; val > 0; val--)
        {
          get_byte(); get_byte();
          delta = get_byte(); delta = (delta<<8) + get_byte();
          segment_bytes += delta;
        }
      while (segment_bytes >= (1<<length_bits))
        {
          head.put_bit(1);
          length_bits++;
          beta++;
        }
    }
  assert(total_bytes == (int) temp_length);
  head.put_bit(0); // End of the `beta' signalling comma code.

  // Restore buffer status for second time through
  current_buf = save_current_buf;
  buf_pos = save_buf_pos;

  // Walk through the coding passes a second time to encode the segment lengths
  for (total_bytes=0, idx=pass_idx, new_passes=pending_new_passes;
       new_passes > 0; new_passes-=segment_passes,
       total_bytes+=segment_bytes, idx+=segment_passes)
    {
      if (all_term)
        segment_passes = 1;
      else if (bypass_term)
        {
          if (idx < 10)
            segment_passes = 10-idx;
          else if (((idx-10) % 3) == 0)
            segment_passes = 2;
          else
            segment_passes = 1;
          if (segment_passes > new_passes)
            segment_passes = new_passes;
        }
      else
        segment_passes = new_passes;
      for (length_bits=0; (1<<length_bits) <= segment_passes; length_bits++);
      length_bits--;
      length_bits += beta;
      for (segment_bytes=0, val=segment_passes; val > 0; val--)
        {
          get_byte(); get_byte();
          delta = get_byte(); delta = (delta<<8) + get_byte();
          segment_bytes += delta;
        }
      assert(segment_bytes < (1<<length_bits));
      head.put_bits(segment_bytes,length_bits);
    }
  assert(total_bytes == (int) temp_length);

  if (simulate)
    { // Restore buffer status so we can try different thresholds for this layer
      current_buf = save_current_buf;
      buf_pos = save_buf_pos;
    }
  else
    { // Commit state changes for this layer
      if (pass_idx == 0)
        body_bytes_offset = ((kdu_uint16) num_passes) << 2;
      pass_idx += pending_new_passes;
      pending_new_passes = 0;
    }
}

/*****************************************************************************/
/*                         kd_block::write_body_bytes                        */
/*****************************************************************************/

void
  kd_block::write_body_bytes(kdu_output *dest)
{
  if (temp_length == 0)
    return;

  int pos = body_bytes_offset;
  kd_code_buffer *scan = first_buf;
  while (pos >= KD_CODE_BUFFER_LEN)
    {
      pos -= KD_CODE_BUFFER_LEN;
      scan = scan->next;
      assert(scan != NULL);
    }
  int new_bytes = temp_length;
  assert((new_bytes+(int) body_bytes_offset) < (2<<16));
  body_bytes_offset += temp_length;
  temp_length = 0;
  while (new_bytes > 0)
    {
      int xfer_bytes = KD_CODE_BUFFER_LEN-pos;
      assert((xfer_bytes > 0) && (scan != NULL));
      if (xfer_bytes > new_bytes)
        xfer_bytes = new_bytes;
      new_bytes -= xfer_bytes;
      dest->write(scan->buf+pos,xfer_bytes);
      scan = scan->next;
      pos = 0;
    }
  pending_new_passes = 0;
}

/*****************************************************************************/
/* STATIC MEMBER              kd_block::build_tree                           */
/*****************************************************************************/

kd_block *
  kd_block::build_tree(kdu_coords size, int *return_num_nodes)
{
  int level_nodes, total_nodes, level_idx, num_levels;
  kdu_coords level_size;

  total_nodes = level_nodes = size.x*size.y;
  assert(total_nodes >= 0);
  level_size = size;
  num_levels = 1;
  while (level_nodes > 1)
    {
      level_size.x = (level_size.x+1)>>1;
      level_size.y = (level_size.y+1)>>1;
      level_nodes = level_size.x*level_size.y;
      total_nodes += level_nodes;
      num_levels++;
    }
  if (return_num_nodes != NULL)
    *return_num_nodes = total_nodes;
  if (total_nodes == 0)
    return NULL;

  kd_block *blocks = new kd_block[total_nodes];
  memset(blocks,0,(size_t)(sizeof(kd_block)*total_nodes));
  kd_block *node, *next;
  kdu_coords next_size;
  for (node=blocks, level_size=size, level_idx=0;
       level_idx < num_levels;
       level_idx++, level_size=next_size)
    {
      next_size.x = (level_size.x+1)>>1;
      next_size.y = (level_size.y+1)>>1;
      level_nodes = level_size.x*level_size.y;
      next = node+level_nodes;

      for (int y=0; y < level_size.y; y++)
        for (int x=0; x < level_size.x; x++, node++)
          {
            node->up_down = next + (y>>1)*next_size.x + (x>>1);
            if (level_idx == (num_levels-1))
              {
                assert((x==0) && (y==0));
                node->up_down = NULL;
              }
          }
    }
  assert(node == (blocks+total_nodes));
  return blocks;
}

/*****************************************************************************/
/* STATIC MEMBER          kd_block::reset_output_tree                        */
/*****************************************************************************/

void
  kd_block::reset_output_tree(kd_block *node, kdu_coords size)
{
  bool leaf_node = true;
  int x, y;

  if ((size.x == 0) || (size.y == 0))
    return;
  do {
      if (leaf_node)
        {
          x = size.x; y = size.y;
          node += x*y;
        }
      else
        {
          for (y=0; y < size.y; y++)
            for (x=0; x < size.x; x++, node++)
              {
                node->msbs_wbar = 0;
                node->layer_wbar = 0;
                node->msbs_w = 0xFF;
                node->layer_w = 0xFFFF;
              }
        }
      size.y = (size.y+1)>>1;
      size.x = (size.x+1)>>1;
      leaf_node = false;
    } while ((x > 1) || (y > 1));
}

/*****************************************************************************/
/* STATIC MEMBER           kd_block::save_output_tree                        */
/*****************************************************************************/

void
  kd_block::save_output_tree(kd_block *node, kdu_coords size)
{
  bool leaf_node = true;
  int x, y;

  if ((size.x == 0) || (size.y == 0))
    return;
  do {
      for (y=0; y < size.y; y++)
        for (x=0; x < size.x; x++, node++)
          {
            if (leaf_node)
              { // Commit the pending new coding passes.
                int buf_pos = node->buf_pos;
                buf_pos += ((int) node->pending_new_passes)<<2;
                while (buf_pos > KD_CODE_BUFFER_LEN)
                  {
                    node->current_buf = node->current_buf->next;
                    assert(node->current_buf != NULL);
                    buf_pos -= KD_CODE_BUFFER_LEN;
                  }
                node->buf_pos = (kdu_byte) buf_pos;
                node->pass_idx += node->pending_new_passes;
                node->pending_new_passes = 0;
                node->save_beta = node->beta;
              }
            else
              {
                node->save_layer_w = node->layer_w;
                node->save_layer_wbar = node->layer_wbar;
                node->save_msbs_wbar = node->msbs_wbar;
              }
          }
      size.y = (size.y+1)>>1;
      size.x = (size.x+1)>>1;
      leaf_node = false;
    } while ((x > 1) || (y > 1));
}

/*****************************************************************************/
/* STATIC MEMBER          kd_block::restore_output_tree                      */
/*****************************************************************************/

void
  kd_block::restore_output_tree(kd_block *node, kdu_coords size)
{
  bool leaf_node = true;
  int x, y;

  if ((size.x == 0) || (size.y == 0))
    return;
  do {
      if (leaf_node)
        {
          for (y=0; y < size.y; y++)
            for (x=0; x < size.x; x++, node++)
              node->beta = node->save_beta;
        }
      else
        { // Only restore non-leaf node state.
          for (y=0; y < size.y; y++)
            for (x=0; x < size.x; x++, node++)
              {
                node->layer_w = node->save_layer_w;
                node->layer_wbar = node->save_layer_wbar;
                node->msbs_wbar = node->save_msbs_wbar;
              }
        }
      size.y = (size.y+1)>>1;
      size.x = (size.x+1)>>1;
      leaf_node = false;
    } while ((x > 1) || (y > 1));
}