jcmaster.pas

DELPHI版的JPEG文件解码源程序

  end
  else
{$endif}
  begin
    { Prepare for single sequential-JPEG scan containing all components }
    if (cinfo^.num_components > MAX_COMPS_IN_SCAN) then
      ERREXIT2(j_common_ptr(cinfo), JERR_COMPONENT_COUNT, cinfo^.num_components,
	       MAX_COMPS_IN_SCAN);
    cinfo^.comps_in_scan := cinfo^.num_components;
    comp_infos := cinfo^.comp_info;
    for ci := 0 to pred(cinfo^.num_components) do
    begin
      cinfo^.cur_comp_info[ci] := @(comp_infos^[ci]);
    end;
    cinfo^.Ss := 0;
    cinfo^.Se := DCTSIZE2-1;
    cinfo^.Ah := 0;
    cinfo^.Al := 0;
  end;
end;


{LOCAL}
procedure per_scan_setup (cinfo : j_compress_ptr);
{ Do computations that are needed before processing a JPEG scan }
{ cinfo^.comps_in_scan and cinfo^.cur_comp_info[] are already set }
var
  ci, mcublks, tmp : int;
  compptr : jpeg_component_info_ptr;
  nominal : long;
begin
  if (cinfo^.comps_in_scan = 1) then
  begin

    { Noninterleaved (single-component) scan }
    compptr := cinfo^.cur_comp_info[0];

    { Overall image size in MCUs }
    cinfo^.MCUs_per_row := compptr^.width_in_blocks;
    cinfo^.MCU_rows_in_scan := compptr^.height_in_blocks;

    { For noninterleaved scan, always one block per MCU }
    compptr^.MCU_width := 1;
    compptr^.MCU_height := 1;
    compptr^.MCU_blocks := 1;
    compptr^.MCU_sample_width := DCTSIZE;
    compptr^.last_col_width := 1;
    { For noninterleaved scans, it is convenient to define last_row_height
      as the number of block rows present in the last iMCU row. }

    tmp := int (compptr^.height_in_blocks mod compptr^.v_samp_factor);
    if (tmp = 0) then
      tmp := compptr^.v_samp_factor;
    compptr^.last_row_height := tmp;
    
    { Prepare array describing MCU composition }
    cinfo^.blocks_in_MCU := 1;
    cinfo^.MCU_membership[0] := 0;
    
  end
  else
  begin
    
    { Interleaved (multi-component) scan }
    if (cinfo^.comps_in_scan <= 0) or
       (cinfo^.comps_in_scan > MAX_COMPS_IN_SCAN) then
      ERREXIT2(j_common_ptr(cinfo), JERR_COMPONENT_COUNT,
        cinfo^.comps_in_scan,  MAX_COMPS_IN_SCAN);

    { Overall image size in MCUs }
    cinfo^.MCUs_per_row := JDIMENSION (
      jdiv_round_up( long (cinfo^.image_width),
		     long (cinfo^.max_h_samp_factor*DCTSIZE)) );
    cinfo^.MCU_rows_in_scan := JDIMENSION (
      jdiv_round_up( long (cinfo^.image_height),
		     long (cinfo^.max_v_samp_factor*DCTSIZE)) );

    cinfo^.blocks_in_MCU := 0;

    for ci := 0 to pred(cinfo^.comps_in_scan) do
    begin
      compptr := cinfo^.cur_comp_info[ci];
      { Sampling factors give # of blocks of component in each MCU }
      compptr^.MCU_width := compptr^.h_samp_factor;
      compptr^.MCU_height := compptr^.v_samp_factor;
      compptr^.MCU_blocks := compptr^.MCU_width * compptr^.MCU_height;
      compptr^.MCU_sample_width := compptr^.MCU_width * DCTSIZE;
      { Figure number of non-dummy blocks in last MCU column & row }
      tmp := int (compptr^.width_in_blocks mod compptr^.MCU_width);
      if (tmp = 0) then
        tmp := compptr^.MCU_width;
      compptr^.last_col_width := tmp;
      tmp := int (compptr^.height_in_blocks mod compptr^.MCU_height);
      if (tmp = 0) then
        tmp := compptr^.MCU_height;
      compptr^.last_row_height := tmp;
      { Prepare array describing MCU composition }
      mcublks := compptr^.MCU_blocks;
      if (cinfo^.blocks_in_MCU + mcublks > C_MAX_BLOCKS_IN_MCU) then
	ERREXIT(j_common_ptr(cinfo), JERR_BAD_MCU_SIZE);
      while (mcublks > 0) do
      begin
        Dec(mcublks);
	cinfo^.MCU_membership[cinfo^.blocks_in_MCU] := ci;
        Inc(cinfo^.blocks_in_MCU);
      end;
    end;

  end;

  { Convert restart specified in rows to actual MCU count. }
  { Note that count must fit in 16 bits, so we provide limiting. }
  if (cinfo^.restart_in_rows > 0) then
  begin
    nominal := long(cinfo^.restart_in_rows) * long(cinfo^.MCUs_per_row);
    if nominal < long(65535) then
      cinfo^.restart_interval := uInt (nominal)
    else
      cinfo^.restart_interval := long(65535);
  end;
end;


{ Per-pass setup.
  This is called at the beginning of each pass.  We determine which modules
  will be active during this pass and give them appropriate start_pass calls.
  We also set is_last_pass to indicate whether any more passes will be
  required. }

{METHODDEF}
procedure prepare_for_pass (cinfo : j_compress_ptr); far;
var
  master : my_master_ptr;
var
  fallthrough : boolean;
begin
  master := my_master_ptr (cinfo^.master);
  fallthrough := true;

  case (master^.pass_type) of
  main_pass:
    begin
      { Initial pass: will collect input data, and do either Huffman
        optimization or data output for the first scan. }
      select_scan_parameters(cinfo);
      per_scan_setup(cinfo);
      if (not cinfo^.raw_data_in) then
      begin
        cinfo^.cconvert^.start_pass (cinfo);
        cinfo^.downsample^.start_pass (cinfo);
        cinfo^.prep^.start_pass (cinfo, JBUF_PASS_THRU);
      end;
      cinfo^.fdct^.start_pass (cinfo);
      cinfo^.entropy^.start_pass (cinfo, cinfo^.optimize_coding);
      if master^.total_passes > 1 then
        cinfo^.coef^.start_pass (cinfo, JBUF_SAVE_AND_PASS)
      else
        cinfo^.coef^.start_pass (cinfo, JBUF_PASS_THRU);
      cinfo^.main^.start_pass (cinfo, JBUF_PASS_THRU);
      if (cinfo^.optimize_coding) then
      begin
        { No immediate data output; postpone writing frame/scan headers }
        master^.pub.call_pass_startup := FALSE;
      end
      else
      begin
        { Will write frame/scan headers at first jpeg_write_scanlines call }
        master^.pub.call_pass_startup := TRUE;
      end;
    end;
{$ifdef ENTROPY_OPT_SUPPORTED}
  huff_opt_pass,
  output_pass:
    begin
      if (master^.pass_type = huff_opt_pass) then
      begin
        { Do Huffman optimization for a scan after the first one. }
        select_scan_parameters(cinfo);
        per_scan_setup(cinfo);
        if (cinfo^.Ss <> 0) or (cinfo^.Ah = 0) or (cinfo^.arith_code) then
        begin
          cinfo^.entropy^.start_pass (cinfo, TRUE);
          cinfo^.coef^.start_pass (cinfo, JBUF_CRANK_DEST);
          master^.pub.call_pass_startup := FALSE;
          fallthrough := false;
        end;
        { Special case: Huffman DC refinement scans need no Huffman table
          and therefore we can skip the optimization pass for them. }
        if fallthrough then
        begin
          master^.pass_type := output_pass;
          Inc(master^.pass_number);
          {FALLTHROUGH}
        end;
      end;
{$else}
  output_pass:
    begin
{$endif}
      if fallthrough then
      begin
        { Do a data-output pass. }
        { We need not repeat per-scan setup if prior optimization pass did it. }
        if (not cinfo^.optimize_coding) then
        begin
          select_scan_parameters(cinfo);
          per_scan_setup(cinfo);
        end;
        cinfo^.entropy^.start_pass (cinfo, FALSE);
        cinfo^.coef^.start_pass (cinfo, JBUF_CRANK_DEST);
        { We emit frame/scan headers now }
        if (master^.scan_number = 0) then
          cinfo^.marker^.write_frame_header (cinfo);
        cinfo^.marker^.write_scan_header (cinfo);
        master^.pub.call_pass_startup := FALSE;
      end;
    end;
  else
    ERREXIT(j_common_ptr(cinfo), JERR_NOT_COMPILED);
  end;

  master^.pub.is_last_pass := (master^.pass_number = master^.total_passes-1);

  { Set up progress monitor's pass info if present }
  if (cinfo^.progress <> NIL) then
  begin
    cinfo^.progress^.completed_passes := master^.pass_number;
    cinfo^.progress^.total_passes := master^.total_passes;
  end;
end;


{ Special start-of-pass hook.
  This is called by jpeg_write_scanlines if call_pass_startup is TRUE.
  In single-pass processing, we need this hook because we don't want to
  write frame/scan headers during jpeg_start_compress; we want to let the
  application write COM markers etc. between jpeg_start_compress and the
  jpeg_write_scanlines loop.
  In multi-pass processing, this routine is not used. }

{METHODDEF}
procedure pass_startup (cinfo : j_compress_ptr); far;
begin
  cinfo^.master^.call_pass_startup := FALSE; { reset flag so call only once }

  cinfo^.marker^.write_frame_header (cinfo);
  cinfo^.marker^.write_scan_header (cinfo);
end;


{ Finish up at end of pass. }

{METHODDEF}
procedure finish_pass_master (cinfo : j_compress_ptr); far;
var
  master : my_master_ptr;
begin
  master := my_master_ptr (cinfo^.master);

  { The entropy coder always needs an end-of-pass call,
    either to analyze statistics or to flush its output buffer. }
  cinfo^.entropy^.finish_pass (cinfo);

  { Update state for next pass }
  case (master^.pass_type) of
  main_pass:
    begin
      { next pass is either output of scan 0 (after optimization)
        or output of scan 1 (if no optimization). }

      master^.pass_type := output_pass;
      if (not cinfo^.optimize_coding) then
        Inc(master^.scan_number);
    end;
  huff_opt_pass:
    { next pass is always output of current scan }
    master^.pass_type := output_pass;
  output_pass:
    begin
      { next pass is either optimization or output of next scan }
      if (cinfo^.optimize_coding) then
        master^.pass_type := huff_opt_pass;
      Inc(master^.scan_number);
    end;
  end;

  Inc(master^.pass_number);
end;


{ Initialize master compression control. }

{GLOBAL}
procedure jinit_c_master_control (cinfo : j_compress_ptr;
                                  transcode_only : boolean);
var
  master : my_master_ptr;
begin
  master := my_master_ptr(
      cinfo^.mem^.alloc_small (j_common_ptr(cinfo), JPOOL_IMAGE,
				  SIZEOF(my_comp_master)) );
  cinfo^.master := jpeg_comp_master_ptr(master);
  master^.pub.prepare_for_pass := prepare_for_pass;
  master^.pub.pass_startup := pass_startup;
  master^.pub.finish_pass := finish_pass_master;
  master^.pub.is_last_pass := FALSE;

  { Validate parameters, determine derived values }
  initial_setup(cinfo);

  if (cinfo^.scan_info <> NIL) then
  begin
{$ifdef C_MULTISCAN_FILES_SUPPORTED}
    validate_script(cinfo);
{$else}
    ERREXIT(j_common_ptr(cinfo), JERR_NOT_COMPILED);
{$endif}
  end
  else
  begin
    cinfo^.progressive_mode := FALSE;
    cinfo^.num_scans := 1;
  end;

  if (cinfo^.progressive_mode) then  {  TEMPORARY HACK ??? }
    cinfo^.optimize_coding := TRUE;  { assume default tables no good for progressive mode }

  { Initialize my private state }
  if (transcode_only) then
  begin
    { no main pass in transcoding }
    if (cinfo^.optimize_coding) then
      master^.pass_type := huff_opt_pass
    else
      master^.pass_type := output_pass;
  end
  else
  begin
    { for normal compression, first pass is always this type: }
    master^.pass_type := main_pass;
  end;
  master^.scan_number := 0;
  master^.pass_number := 0;
  if (cinfo^.optimize_coding) then
    master^.total_passes := cinfo^.num_scans * 2
  else
    master^.total_passes := cinfo^.num_scans;
end;

end.