jdmarker.pas

用pascal寫的jpeg codec, 測試過的

      if (not datasrc^.fill_input_buffer(cinfo)) then
      begin
        get_sof := 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);

    compptr^.h_samp_factor := (c shr 4) and 15;
    compptr^.v_samp_factor := (c      ) and 15;

    { Read a byte into variable compptr^.quant_tbl_no.
      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_sof := 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 );

    compptr^.quant_tbl_no := GETJOCTET(next_input_byte^);
    Inc(next_input_byte);

    TRACEMS4(j_common_ptr(cinfo), 1, JTRC_SOF_COMPONENT,
	     compptr^.component_id, compptr^.h_samp_factor,
	     compptr^.v_samp_factor, compptr^.quant_tbl_no);

    Inc(compptr);
  end;

  cinfo^.marker^.saw_SOF := TRUE;

  { 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_sof := TRUE;
end;  { get_sof }


{LOCAL}
function get_sos (cinfo : j_decompress_ptr) : boolean;
{ Process a SOS marker }
label
  id_found;
var
  length : INT32;
  i, ci, n, c, cc : int;
  compptr : jpeg_component_info_ptr;
{ Declare and initialize local copies of input pointer/count }
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;

{}

  if not cinfo^.marker^.saw_SOF then
    ERREXIT(j_common_ptr(cinfo), JERR_SOS_NO_SOF);

{ 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_sos := 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_sos := 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 );


  { Read a byte into variable n (Number of components).
    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_sos := 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);


  if ((length <> (n * 2 + 6)) or (n < 1) or (n > MAX_COMPS_IN_SCAN)) then
    ERREXIT(j_common_ptr(cinfo), JERR_BAD_LENGTH);

  TRACEMS1(j_common_ptr(cinfo), 1, JTRC_SOS, n);

  cinfo^.comps_in_scan := n;

  { Collect the component-spec parameters }

  for i := 0 to Pred(n) do
  begin
    { Read a byte into variable cc. 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_sos := 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 );

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

    { 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
        get_sos := 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);

    compptr := cinfo^.comp_info;
    for ci := 0 to Pred(cinfo^.num_components) do
    begin
      if (cc = compptr^.component_id) then
	goto id_found;
      Inc(compptr);
    end;

    ERREXIT1(j_common_ptr(cinfo), JERR_BAD_COMPONENT_ID, cc);

  id_found:

    cinfo^.cur_comp_info[i] := compptr;
    compptr^.dc_tbl_no := (c shr 4) and 15;
    compptr^.ac_tbl_no := (c      ) and 15;

    TRACEMS3(j_common_ptr(cinfo), 1, JTRC_SOS_COMPONENT, cc,
	     compptr^.dc_tbl_no, compptr^.ac_tbl_no);
  end;

  { Collect the additional scan parameters Ss, Se, Ah/Al. }
  { 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
      get_sos := 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);

  cinfo^.Ss := c;

  { 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
      get_sos := 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);

  cinfo^.Se := c;

  { 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
      get_sos := 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);

  cinfo^.Ah := (c shr 4) and 15;
  cinfo^.Al := (c     ) and 15;

  TRACEMS4(j_common_ptr(cinfo), 1, JTRC_SOS_PARAMS, cinfo^.Ss, cinfo^.Se,
	   cinfo^.Ah, cinfo^.Al);

  { Prepare to scan data & restart markers }
  cinfo^.marker^.next_restart_num := 0;

  { Count another SOS marker }
  Inc( cinfo^.input_scan_number );

  { 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_sos := TRUE;
end;  { get_sos }


{METHODDEF}
function get_app0 (cinfo : j_decompress_ptr) : boolean; far;
{ Process an APP0 marker }
const
  JFIF_LEN = 14;
var
  length : INT32;
  b : Array[0..JFIF_LEN-1] of UINT8;
  buffp : 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;


{ 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_app0 := 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_app0 := 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 );

  length := length - 2;

  { See if a JFIF APP0 marker is present }

  if (length >= JFIF_LEN) then
  begin
    for buffp := 0 to Pred(JFIF_LEN) do
    begin
    { Read a byte into variable b[buffp].
      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_app0 := 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 );

      b[buffp] := GETJOCTET(next_input_byte^);
      Inc(next_input_byte);
    end;
    length := length - JFIF_LEN;

    if (b[0]=$4A) and (b[1]=$46) and (b[2]=$49)
     and (b[3]=$46) and (b[4]=0) then
    begin
      { Found JFIF APP0 marker: check version }
      { Major version must be 1, anything else signals an incompatible change.
        We used to treat this as an error, but now it's a nonfatal warning,
        because some bozo at Hijaak couldn't read the spec.
        Minor version should be 0..2, but process anyway if newer. }

      if (b[5] <> 1) then
	WARNMS2(j_common_ptr(cinfo) , JWRN_JFIF_MAJOR, b[5], b[6])
      else
        if (b[6] > 2) then
          TRACEMS2(j_common_ptr(cinfo), 1, JTRC_JFIF_MINOR, b[5], b[6]);
      { Save info }
      cinfo^.saw_JFIF_marker := TRUE;
      cinfo^.density_unit := b[7];
      cinfo^.X_density := (b[8] shl 8) + b[9];
      cinfo^.Y_density := (b[10] shl 8) + b[11];
      TRACEMS3(j_common_ptr(cinfo), 1, JTRC_JFIF,
	       cinfo^.X_density, cinfo^.Y_density, cinfo^.density_unit);
      if (b[12] or b[13]) <> 0 then
	TRACEMS2(j_common_ptr(cinfo), 1, JTRC_JFIF_THUMBNAIL, b[12], b[13]);
      if (length <> (INT32(b[12]) * INT32(b[13]) * INT32(3))) then
	TRACEMS1(j_common_ptr(cinfo), 1, JTRC_JFIF_BADTHUMBNAILSIZE,
          int(length));
    end
    else
    begin
      { Start of APP0 does not match "JFIF" }
      TRACEMS1(j_common_ptr(cinfo), 1, JTRC_APP0, int(length) + JFIF_LEN);
    end;
  end
  else
  begin
    { Too short to be JFIF marker }
    TRACEMS1(j_common_ptr(cinfo), 1, JTRC_APP0, int(length));
  end;