jdmarker.pas

用pascal寫的jpeg codec, 測試過的

    MEMCOPY(@(htblptr^)^.bits, @bits, SIZEOF((htblptr^)^.bits));
    MEMCOPY(@(htblptr^)^.huffval, @huffval, SIZEOF((htblptr^)^.huffval));
  end;

  { Unload the local copies --- do this only at a restart boundary }
  datasrc^.next_input_byte := next_input_byte;
  datasrc^.bytes_in_buffer := bytes_in_buffer;

  get_dht := TRUE;
end;  { get_dht }


{LOCAL}
function get_dqt (cinfo : j_decompress_ptr) : boolean;
{ Process a DQT marker }
var
  length : INT32;
  n, i, prec : int;
  tmp : uint;
  quant_ptr : JQUANT_TBL_PTR;
var
  datasrc : jpeg_source_mgr_ptr;
  next_input_byte : JOCTETptr;
  bytes_in_buffer : size_t;
begin
  datasrc := cinfo^.src;
  next_input_byte := datasrc^.next_input_byte;
  bytes_in_buffer := datasrc^.bytes_in_buffer;

{ Read two bytes interpreted as an unsigned 16-bit integer.
  length should be declared unsigned int or perhaps INT32. }

{ make a byte available.
  Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
  but we must reload the local copies after a successful fill. }
  if (bytes_in_buffer = 0) then
  begin
    if (not datasrc^.fill_input_buffer(cinfo)) then
    begin
      get_dqt := FALSE;
      exit;
    end;
    { Reload the local copies }
    next_input_byte := datasrc^.next_input_byte;
    bytes_in_buffer := datasrc^.bytes_in_buffer;
  end;
  Dec( bytes_in_buffer );

  length := (uint( GETJOCTET(next_input_byte^)) shl 8);
  Inc( next_input_byte );
  { make a byte available.
    Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
    but we must reload the local copies after a successful fill. }
    if (bytes_in_buffer = 0) then
    begin
      if (not datasrc^.fill_input_buffer(cinfo)) then
      begin
        get_dqt := FALSE;
        exit;
      end;
      { Reload the local copies }
      next_input_byte := datasrc^.next_input_byte;
      bytes_in_buffer := datasrc^.bytes_in_buffer;
    end;
    Dec( bytes_in_buffer );

  Inc( length, GETJOCTET( next_input_byte^));
  Inc( next_input_byte );

  Dec( length, 2 );

  while (length > 0) do
  begin
    { Read a byte into variable n. If must suspend, return FALSE. }
    { make a byte available.
      Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
      but we must reload the local copies after a successful fill. }
    if (bytes_in_buffer = 0) then
    begin
      if (not datasrc^.fill_input_buffer(cinfo)) then
      begin
        get_dqt := FALSE;
        exit;
      end;
      { Reload the local copies }
      next_input_byte := datasrc^.next_input_byte;
      bytes_in_buffer := datasrc^.bytes_in_buffer;
    end;
    Dec( bytes_in_buffer );

    n := GETJOCTET(next_input_byte^);
    Inc(next_input_byte);

    prec := n shr 4;
    n := n and $0F;

    TRACEMS2(j_common_ptr(cinfo), 1, JTRC_DQT, n, prec);

    if (n >= NUM_QUANT_TBLS) then
      ERREXIT1(j_common_ptr(cinfo) , JERR_DQT_INDEX, n);
      
    if (cinfo^.quant_tbl_ptrs[n] = NIL) then
      cinfo^.quant_tbl_ptrs[n] := jpeg_alloc_quant_table(j_common_ptr(cinfo));
    quant_ptr := cinfo^.quant_tbl_ptrs[n];

    for i := 0 to Pred(DCTSIZE2) do
    begin
      if (prec <> 0) then
      begin
      { Read two bytes interpreted as an unsigned 16-bit integer.
        tmp should be declared unsigned int or perhaps INT32. }

      { make a byte available.
        Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
        but we must reload the local copies after a successful fill. }
        if (bytes_in_buffer = 0) then
        begin
          if (not datasrc^.fill_input_buffer(cinfo)) then
          begin
            get_dqt := FALSE;
            exit;
          end;
          { Reload the local copies }
          next_input_byte := datasrc^.next_input_byte;
          bytes_in_buffer := datasrc^.bytes_in_buffer;
        end;
        Dec( bytes_in_buffer );

        tmp := (uint( GETJOCTET(next_input_byte^)) shl 8);
        Inc( next_input_byte );
        { make a byte available.
          Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
          but we must reload the local copies after a successful fill. }
          if (bytes_in_buffer = 0) then
          begin
            if (not datasrc^.fill_input_buffer(cinfo)) then
            begin
              get_dqt := FALSE;
              exit;
            end;
            { Reload the local copies }
            next_input_byte := datasrc^.next_input_byte;
            bytes_in_buffer := datasrc^.bytes_in_buffer;
          end;
          Dec( bytes_in_buffer );

        Inc( tmp, GETJOCTET( next_input_byte^));
        Inc( next_input_byte );

      end
      else
      begin
      { Read a byte into variable tmp. If must suspend, return FALSE. }
      { make a byte available.
        Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
        but we must reload the local copies after a successful fill. }
        if (bytes_in_buffer = 0) then
        begin
          if (not datasrc^.fill_input_buffer(cinfo)) then
          begin
            get_dqt := FALSE;
            exit;
          end;
          { Reload the local copies }
          next_input_byte := datasrc^.next_input_byte;
          bytes_in_buffer := datasrc^.bytes_in_buffer;
        end;
        Dec( bytes_in_buffer );

        tmp := GETJOCTET(next_input_byte^);
        Inc(next_input_byte);
      end;

      { We convert the zigzag-order table to natural array order. }
      quant_ptr^.quantval[jpeg_natural_order[i]] := UINT16(tmp);
    end;

    if (cinfo^.err^.trace_level >= 2) then
    begin
      i := 0;
      while i < Pred(DCTSIZE2) do
      begin
	TRACEMS8(j_common_ptr(cinfo), 2, JTRC_QUANTVALS,
		 quant_ptr^.quantval[i],   quant_ptr^.quantval[i+1],
		 quant_ptr^.quantval[i+2], quant_ptr^.quantval[i+3],
		 quant_ptr^.quantval[i+4], quant_ptr^.quantval[i+5],
		 quant_ptr^.quantval[i+6], quant_ptr^.quantval[i+7]);
        Inc(i, 8);
      end;
    end;

    Dec( length, DCTSIZE2+1 );
    if (prec <> 0) then
      Dec( length, DCTSIZE2 );
  end;

  { Unload the local copies --- do this only at a restart boundary }
  datasrc^.next_input_byte := next_input_byte;
  datasrc^.bytes_in_buffer := bytes_in_buffer;

  get_dqt := TRUE;
end;  { get_dqt }


{LOCAL}
function get_dri (cinfo : j_decompress_ptr) : boolean;
{ Process a DRI marker }
var
  length : INT32;
  tmp : uint;
var
  datasrc : jpeg_source_mgr_ptr;
  next_input_byte : JOCTETptr;
  bytes_in_buffer : size_t;
begin
  datasrc := cinfo^.src;
  next_input_byte := datasrc^.next_input_byte;
  bytes_in_buffer := datasrc^.bytes_in_buffer;

{ Read two bytes interpreted as an unsigned 16-bit integer.
  length should be declared unsigned int or perhaps INT32. }

{ make a byte available.
  Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
  but we must reload the local copies after a successful fill. }
  if (bytes_in_buffer = 0) then
  begin
    if (not datasrc^.fill_input_buffer(cinfo)) then
    begin
      get_dri := FALSE;
      exit;
    end;
    { Reload the local copies }
    next_input_byte := datasrc^.next_input_byte;
    bytes_in_buffer := datasrc^.bytes_in_buffer;
  end;
  Dec( bytes_in_buffer );

  length := (uint( GETJOCTET(next_input_byte^)) shl 8);
  Inc( next_input_byte );
  { make a byte available.
    Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
    but we must reload the local copies after a successful fill. }
    if (bytes_in_buffer = 0) then
    begin
      if (not datasrc^.fill_input_buffer(cinfo)) then
      begin
        get_dri := FALSE;
        exit;
      end;
      { Reload the local copies }
      next_input_byte := datasrc^.next_input_byte;
      bytes_in_buffer := datasrc^.bytes_in_buffer;
    end;
    Dec( bytes_in_buffer );

  Inc( length, GETJOCTET( next_input_byte^));
  Inc( next_input_byte );

  if (length <> 4) then
    ERREXIT(j_common_ptr(cinfo), JERR_BAD_LENGTH);

{ Read two bytes interpreted as an unsigned 16-bit integer.
  tmp should be declared unsigned int or perhaps INT32. }

{ make a byte available.
  Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
  but we must reload the local copies after a successful fill. }
  if (bytes_in_buffer = 0) then
  begin
    if (not datasrc^.fill_input_buffer(cinfo)) then
    begin
      get_dri := FALSE;
      exit;
    end;
    { Reload the local copies }
    next_input_byte := datasrc^.next_input_byte;
    bytes_in_buffer := datasrc^.bytes_in_buffer;
  end;
  Dec( bytes_in_buffer );

  tmp := (uint( GETJOCTET(next_input_byte^)) shl 8);
  Inc( next_input_byte );
  { make a byte available.
    Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
    but we must reload the local copies after a successful fill. }
    if (bytes_in_buffer = 0) then
    begin
      if (not datasrc^.fill_input_buffer(cinfo)) then
      begin
        get_dri := FALSE;
        exit;
      end;
      { Reload the local copies }
      next_input_byte := datasrc^.next_input_byte;
      bytes_in_buffer := datasrc^.bytes_in_buffer;
    end;
    Dec( bytes_in_buffer );

  Inc( tmp, GETJOCTET( next_input_byte^));
  Inc( next_input_byte );

  TRACEMS1(j_common_ptr(cinfo), 1, JTRC_DRI, tmp);

  cinfo^.restart_interval := tmp;

  { Unload the local copies --- do this only at a restart boundary }
  datasrc^.next_input_byte := next_input_byte;
  datasrc^.bytes_in_buffer := bytes_in_buffer;

  get_dri := TRUE;
end;  { get_dru }


{METHODDEF}
function skip_variable (cinfo : j_decompress_ptr) : boolean; far;
{ Skip over an unknown or uninteresting variable-length marker }
var
  length : INT32;
var
  datasrc : jpeg_source_mgr_ptr;
  next_input_byte : JOCTETptr;    { Array[] of JOCTET; }
  bytes_in_buffer : size_t;
begin
  datasrc := cinfo^.src;
  next_input_byte := datasrc^.next_input_byte;
  bytes_in_buffer := datasrc^.bytes_in_buffer;

{ Read two bytes interpreted as an unsigned 16-bit integer.
  length should be declared unsigned int or perhaps INT32. }

{ make a byte available.
  Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
  but we must reload the local copies after a successful fill. }
  if (bytes_in_buffer = 0) then
  begin
    if (not datasrc^.fill_input_buffer(cinfo)) then
    begin
      skip_variable := FALSE;
      exit;
    end;
    { Reload the local copies }
    next_input_byte := datasrc^.next_input_byte;
    bytes_in_buffer := datasrc^.bytes_in_buffer;
  end;
  Dec( bytes_in_buffer );

  length := (uint( GETJOCTET(next_input_byte^)) shl 8);
  Inc( next_input_byte );
  { make a byte available.
    Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
    but we must reload the local copies after a successful fill. }
    if (bytes_in_buffer = 0) then
    begin
      if (not datasrc^.fill_input_buffer(cinfo)) then
      begin
        skip_variable := FALSE;
        exit;
      end;
      { Reload the local copies }
      next_input_byte := datasrc^.next_input_byte;
      bytes_in_buffer := datasrc^.bytes_in_buffer;
    end;
    Dec( bytes_in_buffer );

  Inc( length, GETJOCTET( next_input_byte^));
  Inc( next_input_byte );


  TRACEMS2(j_common_ptr(cinfo), 1, JTRC_MISC_MARKER,
    cinfo^.unread_marker, int(length));

  
  { Unload the local copies --- do this only at a restart boundary }
  { do before skip_input_data }
  datasrc^.next_input_byte := next_input_byte;
  datasrc^.bytes_in_buffer := bytes_in_buffer;

  cinfo^.src^.skip_input_data(cinfo, long(length) - long(2));

  skip_variable := TRUE;
end;  { skip_variable }


{ Find the next JPEG marker, save it in cinfo^.unread_marker.
  Returns FALSE if had to suspend before reaching a marker;
  in that case cinfo^.unread_marker is unchanged.

  Note that the result might not be a valid marker code,
  but it will never be 0 or FF. }

{LOCAL}
function next_marker (cinfo : j_decompress_ptr) : boolean;
var
  c : int;
var
  datasrc : jpeg_source_mgr_ptr;
  next_input_byte : JOCTETptr;
  bytes_in_buffer : size_t;
begin
  datasrc := cinfo^.src;
  next_input_byte := datasrc^.next_input_byte;
  bytes_in_buffer := datasrc^.bytes_in_buffer;

  {while TRUE do}
  repeat
    { Read a byte into variable c. If must suspend, return FALSE. }
    { make a byte available.
      Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
      but we must reload the local copies after a successful fill. }
    if (bytes_in_buffer = 0) then
    begin
      if (not datasrc^.fill_input_buffer(cinfo)) then
      begin
        next_marker := FALSE;
        exit;
      end;
      { Reload the local copies }
      next_input_byte := datasrc^.next_input_byte;
      bytes_in_buffer := datasrc^.bytes_in_buffer;
    end;
    Dec( bytes_in_buffer );

    c := GETJOCTET(next_input_byte^);
    Inc(next_input_byte);

   { Skip any non-FF bytes.