jdapimin.pas

用pascal寫的jpeg codec, 測試過的

           else
             if (cid0 = 82) and (cid1 = 71) and (cid2 = 66) then
               cinfo^.jpeg_color_space := JCS_RGB { ASCII 'R', 'G', 'B' }
             else
             begin
	       TRACEMS3(j_common_ptr(cinfo), 1, JTRC_UNKNOWN_IDS, cid0, cid1, cid2);
               cinfo^.jpeg_color_space := JCS_YCbCr; { assume it's YCbCr }
             end;
         end;
       { Always guess RGB is proper output colorspace. }
       cinfo^.out_color_space := JCS_RGB;
     end;

  4: begin
       if (cinfo^.saw_Adobe_marker) then
       begin
         case (cinfo^.Adobe_transform) of
         0: cinfo^.jpeg_color_space := JCS_CMYK;
         2: cinfo^.jpeg_color_space := JCS_YCCK;
         else
           begin
             WARNMS1(j_common_ptr(cinfo), JWRN_ADOBE_XFORM, cinfo^.Adobe_transform);
             cinfo^.jpeg_color_space := JCS_YCCK; { assume it's YCCK }
           end;
         end;
       end
       else
       begin
         { No special markers, assume straight CMYK. }
         cinfo^.jpeg_color_space := JCS_CMYK;
       end;
       cinfo^.out_color_space := JCS_CMYK;
     end;

  else
    begin
      cinfo^.jpeg_color_space := JCS_UNKNOWN;
      cinfo^.out_color_space := JCS_UNKNOWN;
    end;
  end;

  { Set defaults for other decompression parameters. }
  cinfo^.scale_num := 1;		{ 1:1 scaling }
  cinfo^.scale_denom := 1;
  cinfo^.output_gamma := 1.0;
  cinfo^.buffered_image := FALSE;
  cinfo^.raw_data_out := FALSE;
  cinfo^.dct_method := JDCT_DEFAULT;
  cinfo^.do_fancy_upsampling := TRUE;
  cinfo^.do_block_smoothing := TRUE;
  cinfo^.quantize_colors := FALSE;
  { We set these in case application only sets quantize_colors. }
  cinfo^.dither_mode := JDITHER_FS;
{$ifdef QUANT_2PASS_SUPPORTED}
  cinfo^.two_pass_quantize := TRUE;
{$else}
  cinfo^.two_pass_quantize := FALSE;
{$endif}
  cinfo^.desired_number_of_colors := 256;
  cinfo^.colormap := NIL;
  { Initialize for no mode change in buffered-image mode. }
  cinfo^.enable_1pass_quant := FALSE;
  cinfo^.enable_external_quant := FALSE;
  cinfo^.enable_2pass_quant := FALSE;
end;


{ Decompression startup: read start of JPEG datastream to see what's there.
  Need only initialize JPEG object and supply a data source before calling.

  This routine will read as far as the first SOS marker (ie, actual start of
  compressed data), and will save all tables and parameters in the JPEG
  object.  It will also initialize the decompression parameters to default
  values, and finally return JPEG_HEADER_OK.  On return, the application may
  adjust the decompression parameters and then call jpeg_start_decompress.
  (Or, if the application only wanted to determine the image parameters,
  the data need not be decompressed.  In that case, call jpeg_abort or
  jpeg_destroy to release any temporary space.)
  If an abbreviated (tables only) datastream is presented, the routine will
  return JPEG_HEADER_TABLES_ONLY upon reaching EOI.  The application may then
  re-use the JPEG object to read the abbreviated image datastream(s).
  It is unnecessary (but OK) to call jpeg_abort in this case.
  The JPEG_SUSPENDED return code only occurs if the data source module
  requests suspension of the decompressor.  In this case the application
  should load more source data and then re-call jpeg_read_header to resume
  processing.
  If a non-suspending data source is used and require_image is TRUE, then the
  return code need not be inspected since only JPEG_HEADER_OK is possible.

  This routine is now just a front end to jpeg_consume_input, with some
  extra error checking. }

{GLOBAL}
function jpeg_read_header (cinfo : j_decompress_ptr;
                           require_image : boolean) : int;
var
  retcode : int;
begin
  if (cinfo^.global_state <> DSTATE_START) and
     (cinfo^.global_state <> DSTATE_INHEADER) then
    ERREXIT1(j_common_ptr(cinfo), JERR_BAD_STATE, cinfo^.global_state);

  retcode := jpeg_consume_input(cinfo);

  case (retcode) of
  JPEG_REACHED_SOS:
    retcode := JPEG_HEADER_OK;
  JPEG_REACHED_EOI:
    begin
      if (require_image) then   { Complain if application wanted an image }
        ERREXIT(j_common_ptr(cinfo), JERR_NO_IMAGE);
      { Reset to start state; it would be safer to require the application to
        call jpeg_abort, but we can't change it now for compatibility reasons.
        A side effect is to free any temporary memory (there shouldn't be any). }

      jpeg_abort(j_common_ptr(cinfo)); { sets state := DSTATE_START }
      retcode := JPEG_HEADER_TABLES_ONLY;
    end;
  JPEG_SUSPENDED: ;    { no work }
  end;

  jpeg_read_header := retcode;
end;


{ Consume data in advance of what the decompressor requires.
  This can be called at any time once the decompressor object has
  been created and a data source has been set up.

  This routine is essentially a state machine that handles a couple
  of critical state-transition actions, namely initial setup and
  transition from header scanning to ready-for-start_decompress.
  All the actual input is done via the input controller's consume_input
  method. }

{GLOBAL}
function jpeg_consume_input (cinfo : j_decompress_ptr) : int;
var
  retcode : int;
begin
  retcode := JPEG_SUSPENDED;

  { NB: every possible DSTATE value should be listed in this switch }

  if (cinfo^.global_state) = DSTATE_START then
  begin {work around the FALLTHROUGH}
    { Start-of-datastream actions: reset appropriate modules }
    cinfo^.inputctl^.reset_input_controller (cinfo);
    { Initialize application's data source module }
    cinfo^.src^.init_source (cinfo);
    cinfo^.global_state := DSTATE_INHEADER;
  end;

  case (cinfo^.global_state) of
  DSTATE_START,
  DSTATE_INHEADER:
    begin
      retcode := cinfo^.inputctl^.consume_input (cinfo);
      if (retcode = JPEG_REACHED_SOS) then
      begin { Found SOS, prepare to decompress }
        { Set up default parameters based on header data }
        default_decompress_parms(cinfo);
        { Set global state: ready for start_decompress }
        cinfo^.global_state := DSTATE_READY;
      end;
    end;
  DSTATE_READY:
    { Can't advance past first SOS until start_decompress is called }
    retcode := JPEG_REACHED_SOS;

  DSTATE_PRELOAD,
  DSTATE_PRESCAN,
  DSTATE_SCANNING,
  DSTATE_RAW_OK,
  DSTATE_BUFIMAGE,
  DSTATE_BUFPOST,
  DSTATE_STOPPING:
    retcode := cinfo^.inputctl^.consume_input (cinfo);
  else
    ERREXIT1(j_common_ptr(cinfo), JERR_BAD_STATE, cinfo^.global_state);
  end;
  jpeg_consume_input := retcode;
end;


{ Have we finished reading the input file? }

{GLOBAL}
function jpeg_input_complete (cinfo : j_decompress_ptr) : boolean;
begin
  { Check for valid jpeg object }
  if (cinfo^.global_state < DSTATE_START) or
     (cinfo^.global_state > DSTATE_STOPPING) then
    ERREXIT1(j_common_ptr(cinfo), JERR_BAD_STATE, cinfo^.global_state);
  jpeg_input_complete := cinfo^.inputctl^.eoi_reached;
end;


{ Is there more than one scan? }

{GLOBAL}
function jpeg_has_multiple_scans (cinfo : j_decompress_ptr) : boolean;
begin
  { Only valid after jpeg_read_header completes }
  if (cinfo^.global_state < DSTATE_READY) or
     (cinfo^.global_state > DSTATE_STOPPING) then
    ERREXIT1(j_common_ptr(cinfo), JERR_BAD_STATE, cinfo^.global_state);
  jpeg_has_multiple_scans := cinfo^.inputctl^.has_multiple_scans;
end;


{ Finish JPEG decompression.

  This will normally just verify the file trailer and release temp storage.

  Returns FALSE if suspended.  The return value need be inspected only if
  a suspending data source is used. }

{GLOBAL}
function jpeg_finish_decompress (cinfo : j_decompress_ptr) : boolean;
begin
  if ((cinfo^.global_state = DSTATE_SCANNING) or
      (cinfo^.global_state = DSTATE_RAW_OK) and (not cinfo^.buffered_image)) then
  begin
    { Terminate final pass of non-buffered mode }
    if (cinfo^.output_scanline < cinfo^.output_height) then
      ERREXIT(j_common_ptr(cinfo), JERR_TOO_LITTLE_DATA);
    cinfo^.master^.finish_output_pass (cinfo);
    cinfo^.global_state := DSTATE_STOPPING;
  end
  else
    if (cinfo^.global_state = DSTATE_BUFIMAGE) then
    begin
      { Finishing after a buffered-image operation }
      cinfo^.global_state := DSTATE_STOPPING;
    end
    else
      if (cinfo^.global_state <> DSTATE_STOPPING) then
      begin
        { STOPPING := repeat call after a suspension, anything else is error }
        ERREXIT1(j_common_ptr(cinfo), JERR_BAD_STATE, cinfo^.global_state);
      end;
  { Read until EOI }
  while (not cinfo^.inputctl^.eoi_reached) do
  begin
    if (cinfo^.inputctl^.consume_input (cinfo) = JPEG_SUSPENDED) then
    begin
      jpeg_finish_decompress := FALSE;	{ Suspend, come back later }
      exit;
    end;
  end;
  { Do final cleanup }
  cinfo^.src^.term_source (cinfo);
  { We can use jpeg_abort to release memory and reset global_state }
  jpeg_abort(j_common_ptr(cinfo));
  jpeg_finish_decompress := TRUE;
end;

end.