jcmaster.pas

DELPHI版的JPEG文件解码源程序

Unit JcMaster;

{ This file contains master control logic for the JPEG compressor.
  These routines are concerned with parameter validation, initial setup,
  and inter-pass control (determining the number of passes and the work
  to be done in each pass). }

{ Original: jcmaster.c ; Copyright (C) 1991-1997, Thomas G. Lane. }

interface

uses
  jmorecfg,
  jinclude,
  jdeferr,
  jerror,
  jutils,
  jpeglib;

{$I jconfig.inc}

{ Initialize master compression control. }

{GLOBAL}
procedure jinit_c_master_control (cinfo : j_compress_ptr;
                                  transcode_only : boolean);

implementation

{ Private state }

type
  c_pass_type = (
	main_pass,		{ input data, also do first output step }
	huff_opt_pass,		{ Huffman code optimization pass }
	output_pass		{ data output pass }
                );

type
  my_master_ptr = ^my_comp_master;
  my_comp_master = record
    pub : jpeg_comp_master;	{ public fields }

    pass_type : c_pass_type; 	{ the type of the current pass }

    pass_number : int;		{ # of passes completed }
    total_passes : int;		{ total # of passes needed }

    scan_number : int;		{ current index in scan_info[] }
  end;


{ Support routines that do various essential calculations. }

{LOCAL}
procedure initial_setup (cinfo : j_compress_ptr);
{ Do computations that are needed before master selection phase }
var
  ci : int;
  compptr : jpeg_component_info_ptr;
  samplesperrow : long;
  jd_samplesperrow : JDIMENSION;
begin

  { Sanity check on image dimensions }
  if (cinfo^.image_height <= 0) or (cinfo^.image_width <= 0) or
     (cinfo^.num_components <= 0) or (cinfo^.input_components <= 0) then
    ERREXIT(j_common_ptr(cinfo), JERR_EMPTY_IMAGE);

  { Make sure image isn't bigger than I can handle }
  if ( long(cinfo^.image_height) > long(JPEG_MAX_DIMENSION)) or
      ( long(cinfo^.image_width) > long(JPEG_MAX_DIMENSION)) then
    ERREXIT1(j_common_ptr(cinfo), JERR_IMAGE_TOO_BIG,
                                  uInt(JPEG_MAX_DIMENSION));

  { Width of an input scanline must be representable as JDIMENSION. }
  samplesperrow := long (cinfo^.image_width) * long (cinfo^.input_components);
  jd_samplesperrow := JDIMENSION (samplesperrow);
  if ( long(jd_samplesperrow) <> samplesperrow) then
    ERREXIT(j_common_ptr(cinfo), JERR_WIDTH_OVERFLOW);

  { For now, precision must match compiled-in value... }
  if (cinfo^.data_precision <> BITS_IN_JSAMPLE) then
    ERREXIT1(j_common_ptr(cinfo), JERR_BAD_PRECISION, cinfo^.data_precision);

  { Check that number of components won't exceed internal array sizes }
  if (cinfo^.num_components > MAX_COMPONENTS) then
    ERREXIT2(j_common_ptr(cinfo), JERR_COMPONENT_COUNT, cinfo^.num_components,
	     MAX_COMPONENTS);

  { Compute maximum sampling factors; check factor validity }
  cinfo^.max_h_samp_factor := 1;
  cinfo^.max_v_samp_factor := 1;
  compptr := jpeg_component_info_ptr(cinfo^.comp_info);
  for ci := 0 to pred(cinfo^.num_components) do
  begin
    if (compptr^.h_samp_factor<=0) or (compptr^.h_samp_factor>MAX_SAMP_FACTOR)
    or (compptr^.v_samp_factor<=0) or (compptr^.v_samp_factor>MAX_SAMP_FACTOR) then
      ERREXIT(j_common_ptr(cinfo), JERR_BAD_SAMPLING);
    { MAX }
    if cinfo^.max_h_samp_factor > compptr^.h_samp_factor then
      cinfo^.max_h_samp_factor := cinfo^.max_h_samp_factor
    else
      cinfo^.max_h_samp_factor := compptr^.h_samp_factor;
    { MAX }
    if cinfo^.max_v_samp_factor > compptr^.v_samp_factor then
      cinfo^.max_v_samp_factor := cinfo^.max_v_samp_factor
    else
      cinfo^.max_v_samp_factor := compptr^.v_samp_factor;
    Inc(compptr);
  end;

  { Compute dimensions of components }
  compptr := jpeg_component_info_ptr(cinfo^.comp_info);
  for ci := 0 to pred(cinfo^.num_components) do
  begin
    { Fill in the correct component_index value; don't rely on application }
    compptr^.component_index := ci;
    { For compression, we never do DCT scaling. }
    compptr^.DCT_scaled_size := DCTSIZE;
    { Size in DCT blocks }
    compptr^.width_in_blocks := JDIMENSION (
      jdiv_round_up(long (cinfo^.image_width) * long (compptr^.h_samp_factor),
		    long (cinfo^.max_h_samp_factor * DCTSIZE)) );
    compptr^.height_in_blocks := JDIMENSION (
      jdiv_round_up(long (cinfo^.image_height) * long (compptr^.v_samp_factor),
		    long (cinfo^.max_v_samp_factor * DCTSIZE)) );
    { Size in samples }
    compptr^.downsampled_width := JDIMENSION (
      jdiv_round_up(long(cinfo^.image_width) * long(compptr^.h_samp_factor),
		    long(cinfo^.max_h_samp_factor)) );
    compptr^.downsampled_height := JDIMENSION (
      jdiv_round_up(long (cinfo^.image_height) * long(compptr^.v_samp_factor),
		    long (cinfo^.max_v_samp_factor)) );
    { Mark component needed (this flag isn't actually used for compression) }
    compptr^.component_needed := TRUE;
    Inc(compptr);
  end;

  { Compute number of fully interleaved MCU rows (number of times that
    main controller will call coefficient controller). }

  cinfo^.total_iMCU_rows := JDIMENSION (
    jdiv_round_up(long (cinfo^.image_height),
		  long (cinfo^.max_v_samp_factor*DCTSIZE)) );
end;


{$ifdef C_MULTISCAN_FILES_SUPPORTED}

{LOCAL}
procedure validate_script (cinfo : j_compress_ptr);
{ Verify that the scan script in cinfo^.scan_info[] is valid; also
  determine whether it uses progressive JPEG, and set cinfo^.progressive_mode. }
type
  IntRow = array[0..DCTSIZE2-1] of int;
  introw_ptr = ^IntRow;
var
  {const}scanptr : jpeg_scan_info_ptr;
  scanno, ncomps, ci, coefi, thisi : int;
  Ss, Se, Ah, Al : int;
  component_sent : array[0..MAX_COMPONENTS-1] of boolean;
{$ifdef C_PROGRESSIVE_SUPPORTED}
  last_bitpos_int_ptr : int_ptr;
  last_bitpos_ptr : introw_ptr;
  last_bitpos : array[0..MAX_COMPONENTS-1] of IntRow;
  { -1 until that coefficient has been seen; then last Al for it }
  { The JPEG spec simply gives the ranges 0..13 for Ah and Al, but that
    seems wrong: the upper bound ought to depend on data precision.
    Perhaps they really meant 0..N+1 for N-bit precision.
    Here we allow 0..10 for 8-bit data; Al larger than 10 results in
    out-of-range reconstructed DC values during the first DC scan,
    which might cause problems for some decoders. }
{$ifdef BITS_IN_JSAMPLE_IS_8}
const
  MAX_AH_AL = 10;
{$else}
const
  MAX_AH_AL = 13;
{$endif}
{$endif}
begin

  if (cinfo^.num_scans <= 0) then
    ERREXIT1(j_common_ptr(cinfo), JERR_BAD_SCAN_SCRIPT, 0);

  { For sequential JPEG, all scans must have Ss=0, Se=DCTSIZE2-1;
    for progressive JPEG, no scan can have this. }

  scanptr := cinfo^.scan_info;
  if (scanptr^.Ss <> 0) or (scanptr^.Se <> DCTSIZE2-1) then
  begin
{$ifdef C_PROGRESSIVE_SUPPORTED}
    cinfo^.progressive_mode := TRUE;
    last_bitpos_int_ptr := @(last_bitpos[0][0]);
    for ci := 0 to pred(cinfo^.num_components) do
      for coefi := 0 to pred(DCTSIZE2) do
      begin
	last_bitpos_int_ptr^ := -1;
        Inc(last_bitpos_int_ptr);
      end;
{$else}
    ERREXIT(j_common_ptr(cinfo), JERR_NOT_COMPILED);
{$endif}
  end
  else
  begin
    cinfo^.progressive_mode := FALSE;
    for ci := 0 to pred(cinfo^.num_components) do
      component_sent[ci] := FALSE;
  end;

  for scanno := 1 to cinfo^.num_scans do
  begin
    { Validate component indexes }
    ncomps := scanptr^.comps_in_scan;
    if (ncomps <= 0) or (ncomps > MAX_COMPS_IN_SCAN) then
      ERREXIT2(j_common_ptr(cinfo), JERR_COMPONENT_COUNT, ncomps, MAX_COMPS_IN_SCAN);
    for ci := 0 to pred(ncomps) do
    begin
      thisi := scanptr^.component_index[ci];
      if (thisi < 0) or (thisi >= cinfo^.num_components) then
	ERREXIT1(j_common_ptr(cinfo), JERR_BAD_SCAN_SCRIPT, scanno);
      { Components must appear in SOF order within each scan }
      if (ci > 0) and (thisi <= scanptr^.component_index[ci-1]) then
	ERREXIT1(j_common_ptr(cinfo), JERR_BAD_SCAN_SCRIPT, scanno);
    end;
    { Validate progression parameters }
    Ss := scanptr^.Ss;
    Se := scanptr^.Se;
    Ah := scanptr^.Ah;
    Al := scanptr^.Al;
    if (cinfo^.progressive_mode) then
    begin
{$ifdef C_PROGRESSIVE_SUPPORTED}
      if (Ss < 0) or (Ss >= DCTSIZE2) or (Se < Ss) or (Se >= DCTSIZE2) or
	 (Ah < 0) or (Ah > MAX_AH_AL) or (Al < 0) or (Al > MAX_AH_AL) then
	ERREXIT1(j_common_ptr(cinfo), JERR_BAD_PROG_SCRIPT, scanno);

      if (Ss < 0) or (Ss >= DCTSIZE2) or (Se < Ss) or (Se >= DCTSIZE2)
       or (Ah < 0) or (Ah > MAX_AH_AL) or (Al < 0) or (Al > MAX_AH_AL) then
	ERREXIT1(j_common_ptr(cinfo), JERR_BAD_PROG_SCRIPT, scanno);
      if (Ss = 0) then
      begin
	if (Se <> 0) then	{ DC and AC together not OK }
	  ERREXIT1(j_common_ptr(cinfo), JERR_BAD_PROG_SCRIPT, scanno);
      end
      else
      begin
	if (ncomps <> 1) then  { AC scans must be for only one component }
	  ERREXIT1(j_common_ptr(cinfo), JERR_BAD_PROG_SCRIPT, scanno);
      end;
      for ci := 0 to pred(ncomps) do
      begin
	last_bitpos_ptr := @( last_bitpos[scanptr^.component_index[ci]]);
	if (Ss <> 0) and (last_bitpos_ptr^[0] < 0) then { AC without prior DC scan }
	  ERREXIT1(j_common_ptr(cinfo), JERR_BAD_PROG_SCRIPT, scanno);
	for coefi := Ss to Se do
        begin
	  if (last_bitpos_ptr^[coefi] < 0) then
          begin
	    { first scan of this coefficient }
	    if (Ah <> 0) then
	      ERREXIT1(j_common_ptr(cinfo), JERR_BAD_PROG_SCRIPT, scanno);
	  end
          else
          begin
	    { not first scan }
	    if (Ah <> last_bitpos_ptr^[coefi]) or (Al <> Ah-1) then
	      ERREXIT1(j_common_ptr(cinfo), JERR_BAD_PROG_SCRIPT, scanno);
	  end;
	  last_bitpos_ptr^[coefi] := Al;
	end;
      end;
{$endif}
    end
    else
    begin
      { For sequential JPEG, all progression parameters must be these: }
      if (Ss <> 0) or (Se <> DCTSIZE2-1) or (Ah <> 0) or (Al <> 0) then
	ERREXIT1(j_common_ptr(cinfo), JERR_BAD_PROG_SCRIPT, scanno);
      { Make sure components are not sent twice }
      for ci := 0 to pred(ncomps) do
      begin
	thisi := scanptr^.component_index[ci];
	if (component_sent[thisi]) then
	  ERREXIT1(j_common_ptr(cinfo), JERR_BAD_SCAN_SCRIPT, scanno);
	component_sent[thisi] := TRUE;
      end;
    end;
    Inc(scanptr);
  end;

  { Now verify that everything got sent. }
  if (cinfo^.progressive_mode) then
  begin
{$ifdef C_PROGRESSIVE_SUPPORTED
    { For progressive mode, we only check that at least some DC data
      got sent for each component; the spec does not require that all bits
      of all coefficients be transmitted.  Would it be wiser to enforce
      transmission of all coefficient bits?? }

    for ci := 0 to pred(cinfo^.num_components) do
    begin
      if (last_bitpos[ci][0] < 0) then
	ERREXIT(j_common_ptr(cinfo), JERR_MISSING_DATA);
    end;
{$endif}
  end
  else
  begin
    for ci := 0 to pred(cinfo^.num_components) do
    begin
      if (not component_sent[ci]) then
	ERREXIT(j_common_ptr(cinfo), JERR_MISSING_DATA);
    end;
  end;
end;

{$endif} { C_MULTISCAN_FILES_SUPPORTED }


{LOCAL}
procedure select_scan_parameters (cinfo : j_compress_ptr);
{ Set up the scan parameters for the current scan }
var
  master : my_master_ptr;
  {const} scanptr : jpeg_scan_info_ptr;
  ci : int;
var
  comp_infos : jpeg_component_info_list_ptr;
begin
{$ifdef C_MULTISCAN_FILES_SUPPORTED}
  if (cinfo^.scan_info <> NIL) then
  begin
    { Prepare for current scan --- the script is already validated }
    master := my_master_ptr (cinfo^.master);
    scanptr := cinfo^.scan_info;
    Inc(scanptr, master^.scan_number);

    cinfo^.comps_in_scan := scanptr^.comps_in_scan;
    comp_infos := cinfo^.comp_info;
    for ci := 0 to pred(scanptr^.comps_in_scan) do
    begin
      cinfo^.cur_comp_info[ci] :=
        @(comp_infos^[scanptr^.component_index[ci]]);
    end;
    cinfo^.Ss := scanptr^.Ss;
    cinfo^.Se := scanptr^.Se;
    cinfo^.Ah := scanptr^.Ah;
    cinfo^.Al := scanptr^.Al;