djpeg.pas

DELPHI版的JPEG文件解码源程序

                          begin
                            { Use fast one-pass quantization. }
                            cinfo^.two_pass_quantize := FALSE;
                          end
                          else
                            if (keymatch(arg, '-os2', 4)) then
                            begin
                              { BMP output format (OS/2 flavor). }
                              requested_fmt := FMT_OS2;
                            end
                            else
                              if (keymatch(arg, '-outfile', 5)) then
                              begin
                                { Set output file name. }
                                Inc(argn);
                                if (argn >= argc) then	{ advance to next argument }
	                          usage;
                                outfilename := ParamStr(argn);	{ save it away for later use }
                              end
                              else
                                if (keymatch(arg, '-pnm', 2)) or
                                   (keymatch(arg, '-ppm', 2)) then
                                begin
                                  { PPM/PGM output format. }
                                  requested_fmt := FMT_PPM;
                                end
                                else
                                  if (keymatch(arg, '-rle', 2)) then
                                  begin
                                    { RLE output format. }
                                    requested_fmt := FMT_RLE;
                                  end
                                  else
                                    if (keymatch(arg, '-scale', 2)) then
                                    begin
                                      { Scale the output image by a fraction M/N. }
                                      Inc(argn);
                                      if (argn >= argc) then	{ advance to next argument }
	                                usage;
                                      arg := ParamStr(argn);
                                      Val(copy(arg, 1, Pos('/', arg)-1),
                                          cinfo^.scale_num, code);
                                      if code = 0 then
                                        Val(copy(arg, Pos('/', arg)+1,
                                             length(arg)-Pos('/', arg)),
                                            cinfo^.scale_denom, code);
                                      if code <> 0 then
	                                usage;
                                    end
                                    else
                                      if (keymatch(arg, '-targa', 2)) then
                                      begin
                                        { Targa output format. }
                                        requested_fmt := FMT_TARGA;
                                      end
                                      else
                                        usage;		{ bogus switch }
  end;

  parse_switches := argn;	{ return index of next arg (file name) }
end;


{ Marker processor for COM and interesting APPn markers.
  This replaces the library's built-in processor, which just skips the marker.
  We want to print out the marker as text, to the extent possible.
  Note this code relies on a non-suspending data source. }

{LOCAL}
function jpeg_getc (cinfo : j_decompress_ptr) : char;
{ Read next byte }
var
  datasrc : jpeg_source_mgr_ptr;
begin
  datasrc := cinfo^.src;

  if (datasrc^.bytes_in_buffer = 0) then
  begin
    if (not datasrc^.fill_input_buffer (cinfo)) then
      ERREXIT(j_common_ptr(cinfo), JERR_CANT_SUSPEND);
  end;
  Dec(datasrc^.bytes_in_buffer);
  jpeg_getc := char(GETJOCTET(datasrc^.next_input_byte^));
  Inc(datasrc^.next_input_byte);
end;


{METHODDEF}
function print_text_marker (cinfo : j_decompress_ptr) : boolean; far;
const
  LF = #10;
  CR = #13;
var
  traceit : boolean;
  length : INT32;
  ch : char;
  lastch : char;
begin
  traceit := (cinfo^.err^.trace_level >= 1);
  lastch := #0;
  length := byte(jpeg_getc(cinfo)) shl 8;
  Inc(length, byte(jpeg_getc(cinfo)));
  Dec(length, 2);			{ discount the length word itself }

  if (traceit) then
  begin
    if (cinfo^.unread_marker = JPEG_COM) then
      WriteLn('Comment, length ', long(length), ';')
    else			{ assume it is an APPn otherwise }
      WriteLn('APP', cinfo^.unread_marker - JPEG_APP0, ' length ',
	      long(length),':');
  end;

  while (length > 0) do
  begin
    Dec(length);
    ch := jpeg_getc(cinfo);
    if (traceit) then
    begin
      { Emit the character in a readable form.
        Nonprintables are converted to \nnn form,
        while \ is converted to \\.
        Newlines in CR, CR/LF, or LF form will be printed as one newline. }
      if (ch = LF) then
	WriteLn(output)
      else
        if (ch = CR) then
        begin
          if (lastch <> LF) then
	    WriteLn(output);
        end
        else
          if (ch >= ' ') and (ch <= #127) then
	    Write(output, ch)
          else
	    WriteLn(output, '\', byte(ch));
      lastch := ch;
    end;
  end;

  if (traceit) then
    WriteLn(output);

  print_text_marker := TRUE;
end;


{ The main program. }

var
  cinfo : jpeg_decompress_struct;
  jerr : jpeg_error_mgr;
{$ifdef PROGRESS_REPORT}
  progress : cdjpeg_progress_mgr;
{$endif}
  file_index : int;
  dest_mgr : djpeg_dest_ptr;
  input_file : FILE;
  output_file : FILE;
  num_scanlines : JDIMENSION;
var
  argc : int;
begin
  dest_mgr := NIL;
  argc := ParamCount;

  progname := ParamStr(0);

  { Initialize the JPEG decompression object with default error handling. }
  cinfo.err := jpeg_std_error(jerr);
  jpeg_create_decompress(@cinfo);
  { Add some application-specific error messages (from cderror.h) }
  {jerr.addon_message_table := cdjpeg_message_table;}
  jerr.first_addon_message := JMSG_FIRSTADDONCODE;
  jerr.last_addon_message := JMSG_LASTADDONCODE;

  { Insert custom marker processor for COM and APP12.
    APP12 is used by some digital camera makers for textual info,
    so we provide the ability to display it as text.
    If you like, additional APPn marker types can be selected for display,
    but don't try to override APP0 or APP14 this way (see libjpeg.doc). }

  jpeg_set_marker_processor(@cinfo, JPEG_COM, print_text_marker);
  jpeg_set_marker_processor(@cinfo, JPEG_APP0+12, print_text_marker);

  { Now safe to enable signal catcher. }
{$ifdef NEED_SIGNAL_CATCHER}
  enable_signal_catcher(j_common_ptr (@cinfo));
{$endif}

  { Scan command line to find file names. }
  { It is convenient to use just one switch-parsing routine, but the switch
    values read here are ignored; we will rescan the switches after opening
    the input file.
    (Exception: tracing level set here controls verbosity for COM markers
    found during jpeg_read_header...) }

  file_index := parse_switches(@cinfo, 0, FALSE);

{$ifdef TWO_FILE_COMMANDLINE}
  { Must have either -outfile switch or explicit output file name }
  if (outfilename = '') then
  begin
    if (file_index <> argc-1) then
    begin
      WriteLn(output, progname, ': must name one input and one output file');
      usage;
    end;
    outfilename := ParamStr(file_index+1);
  end
  else
  begin
    if (file_index <> argc) then
    begin
      WriteLn(output, progname, ': must name one input and one output file');
      usage;
    end;
  end;
{$else}
  { Unix style: expect zero or one file name }
  if (file_index < argc-1) then
  begin
    WriteLn(output, progname, ': only one input file');
    usage;
  end;
{$endif} { TWO_FILE_COMMANDLINE }

  { Open the input file. }
  if (file_index < argc) then
  begin
    assign(input_file, ParamStr(file_index));
    {$I-}
    Reset(input_file, 1);
    {$I+}
    if (IOresult <> 0) then
    begin
      WriteLn(output, progname, ': can''t open ', ParamStr(file_index));
      Halt(EXIT_FAILURE);
    end;
  end
  else
  begin
    { default input file is stdin }
    Assign(input_file, '');
    Reset(input_file, 1);
  end;

  { Open the output file. }
  if (outfilename <> '') then
  begin
    assign(output_file, outfilename);
    {$I-}
    rewrite(output_file, 1);
    {$I+}
    if (IOresult <> 0) then
    begin
      WriteLn(output, progname, ': can''t open ', outfilename);
      Halt(EXIT_FAILURE);
    end;
  end
  else
  begin
    { default output file is stdout }
    assign(output_file, '');
    rewrite(output_file, 1);
  end;

{$ifdef PROGRESS_REPORT}
  start_progress_monitor(j_common_ptr (@cinfo), @progress);
{$endif}

  { Specify data source for decompression }
  jpeg_stdio_src(@cinfo, @input_file);

  { Read file header, set default decompression parameters }
  {void} jpeg_read_header(@cinfo, TRUE);

  { Adjust default decompression parameters by re-parsing the options }
  file_index := parse_switches(@cinfo, 0, TRUE);

  { Initialize the output module now to let it override any crucial
    option settings (for instance, GIF wants to force color quantization). }

  case (requested_fmt) of
{$ifdef BMP_SUPPORTED}
  FMT_BMP:
    dest_mgr := jinit_write_bmp(@cinfo, FALSE);
  FMT_OS2:
    dest_mgr := jinit_write_bmp(@cinfo, TRUE);
{$endif}
{$ifdef GIF_SUPPORTED}
  FMT_GIF:
    dest_mgr := jinit_write_gif(@cinfo);
{$endif}
{$ifdef PPM_SUPPORTED}
  FMT_PPM:
    dest_mgr := jinit_write_ppm(@cinfo);
{$endif}
{$ifdef RLE_SUPPORTED}
  FMT_RLE:
    dest_mgr := jinit_write_rle(@cinfo);
{$endif}
{$ifdef TARGA_SUPPORTED}
  FMT_TARGA:
    dest_mgr := jinit_write_targa(@cinfo);
{$endif}
  else
    ERREXIT(j_common_ptr(@cinfo), JERR_UNSUPPORTED_FORMAT);
  end;
  dest_mgr^.output_file := @output_file;

  { Start decompressor }
  {void} jpeg_start_decompress(@cinfo);

  { Write output file header }
  dest_mgr^.start_output (@cinfo, dest_mgr);

  { Process data }
  while (cinfo.output_scanline < cinfo.output_height) do
  begin
    num_scanlines := jpeg_read_scanlines(@cinfo, dest_mgr^.buffer,
					dest_mgr^.buffer_height);
    dest_mgr^.put_pixel_rows (@cinfo, dest_mgr, num_scanlines);
  end;

{$ifdef PROGRESS_REPORT}
  { Hack: count final pass as done in case finish_output does an extra pass.
    The library won't have updated completed_passes. }

  progress.pub.completed_passes := progress.pub.total_passes;
{$endif}

  { Finish decompression and release memory.
    I must do it in this order because output module has allocated memory
    of lifespan JPOOL_IMAGE; it needs to finish before releasing memory. }

  dest_mgr^.finish_output (@cinfo, dest_mgr);
  {void} jpeg_finish_decompress(@cinfo);
  jpeg_destroy_decompress(@cinfo);

  { Close files, if we opened them }
  system.close(input_file);
  system.close(output_file);

{$ifdef PROGRESS_REPORT}
  end_progress_monitor(j_common_ptr (@cinfo));
{$endif}

  { All done. }
  if jerr.num_warnings <> 0 then
    Halt(EXIT_WARNING)
  else
    Halt(EXIT_SUCCESS);
end.