原创 Delphi JPEG 解码

implementation

uses  JpegDecode;
{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
var
   fileName:string;
   Bf:BITMAPFILEHEADER;
   MS:TMemoryStream;
   pImg:Pointer;
begin
  if OpenDialog1.Execute then
  begin
     fileName:=OpenDialog1.FileName;
     if LoadJpegFile(FileName,pImg) then
     begin
        MS:=TMemoryStream.Create;
        CopyMemory(@bf,pImg,sizeof(BITMAPFILEHEADER));
        MS.Write(pImg^,bf.BfSize);
        MS.Position:=0;
        Image1.Picture.Bitmap.LoadFromStream(MS);
        MS.Free;
        FreeMem(pImg);
     end else
        ShowMessage('调用失败');
  end;
end;

unit JpegDecode;

interface

uses   Windows, SysUtils, Classes, WinTypes;

const
  FUNC_OK = 0;
  FUNC_MEMORY_ERROR = 1;
  FUNC_FILE_ERROR = 2;
  FUNC_FORMAT_ERROR = 3;
  M_SOF0 = $c0;
  M_DHT  = $c4;
  M_EOI  = $d9;
  M_SOS  = $da;
  M_DQT  = $db;
  M_DRI  = $dd;
  M_APP0 = $e0;
  W1     = 2841; // 2048*sqrt(2)*cos(1*pi/16)
  W2     = 2676; // 2048*sqrt(2)*cos(2*pi/16)
  W3     = 2408; // 2048*sqrt(2)*cos(3*pi/16)
  W5     = 1609; // 2048*sqrt(2)*cos(5*pi/16)
  W6     = 1108; // 2048*sqrt(2)*cos(6*pi/16)
  W7     = 565;  // 2048*sqrt(2)*cos(7*pi/16)

  Zig_Zag: array[0..7, 0..7] of Integer =
    ((0, 1, 5, 6, 14, 15, 27, 28),
    (2, 4, 7, 13, 16, 26, 29, 42),
    (3, 8, 12, 17, 25, 30, 41, 43),
    (9, 11, 18, 24, 31, 40, 44, 53),
    (10, 19, 23, 32, 39, 45, 52, 54),
    (20, 22, 33, 38, 46, 51, 55, 60),
    (21, 34, 37, 47, 50, 56, 59, 61),
    (35, 36, 48, 49, 57, 58, 62, 63));

type
  PShortInt = ^Shortint;
  PSmallInt = ^Smallint;
  PLongInt  = ^Longint;
  PByte     = ^Byte;
  PInt      = ^Integer;
  MyInt     = array[0..7, 0..7] of Integer;

function LoadJpegFile(JpegFileName: string; var pImg: Pointer): Boolean;
function InitTag: Integer;
procedure InitTable;
function Decode: Integer;
function DecodeMCUBlock: Integer;
function HufBlock(dchufindex: Byte; achufindex: Byte): Integer;
function DecodeElement: Integer;
procedure IQtIZzMCUComponent(flag: Smallint);
procedure IQtIZzBlock(s: PSmallInt; d: PInt; flag: Smallint);
procedure GetYUV(flag: Smallint);
procedure StoreBuffer;
function ReadByte: Byte;
procedure Initialize_Fast_IDCT;
procedure Fast_IDCT(var block: MyInt);
procedure idctrow(var blk: MyInt);
procedure idctcol(var blk: MyInt);

implementation

var
  //////////////////////////////////////////////////
  ImgWidth: DWORD = 0;
  ImgHeight: DWORD = 0;
  lpImgData: PChar;
  bf: BITMAPFILEHEADER;
  bi: BITMAPINFOHEADER;
  //////////////////////////////////////////////////////////
  SampRate_Y_H, SampRate_Y_V: Smallint;
  SampRate_U_H, SampRate_U_V: Smallint;
  SampRate_V_H, SampRate_V_V: Smallint;
  H_YtoU, V_YtoU, H_YtoV, V_YtoV: Smallint;
  Y_in_MCU, U_in_MCU, V_in_MCU: Smallint;
  lpJpegBuf: PChar;
  lp, lpPtr: PChar;
  qt_table: array[0..2, 0..63] of Smallint;
  comp_num: Smallint;
  comp_index: array[0..3] of Byte;
  YDcIndex, YAcIndex, UVDcIndex, UVAcIndex: Byte;
  HufTabIndex: Byte;
  YQtTable, UQtTable, VQtTable: PSmallInt;
  MyAnd: array[0..8] of Byte = (0, 1, 3, 7, $0f, $1f, $3f, $7f, $ff);
  code_pos_table, code_len_table: array[0..3, 0..15] of Smallint;
  code_value_table: array[0..3, 0..255] of Word;
  huf_max_value, huf_min_value: array [0..3, 0..15] of Word;
  BitPos, CurByte: Smallint;
  rrun, vvalue: Smallint;
  MCUBuffer: array[0..10 * 64 - 1] of Smallint;
  QtZzMCUBuffer: array[0..10 * 64 - 1] of Integer;
  BlockBuffer: array[0..63] of Smallint;
  ycoef, ucoef, vcoef: Smallint;
  IntervalFlag: Boolean;
  Interval: Smallint = 0;
  Y, U, V: array[0..4 * 64 - 1] of Integer;
  sizei, sizej: DWORD;
  restart: Smallint;
  iclip: array[0..1023] of Longint;
  LineBytes, NumColors: DWORD;

  ////////////////////////////////////////////////////////////////
function LoadJpegFile(JpegFileName: string; var pImg: Pointer): Boolean;
var
  fjpg: TFileStream;
  ImgSize: DWORD;
  JpegBufSize: DWORD;
  funcret: Integer;
  lpImgDataTemp: PChar;
begin
  fjpg := TFileStream.Create(JpegFileName, fmOpenRead);
  //将Jpeg文件读入内存
  JpegBufSize := fjpg.Size;
  GetMem(lpJpegBuf, JpegBufSize);
  fjpg.Read(lpJpegBuf^, JpegBufSize);
  fjpg.Free;

  InitTable;
  funcret := InitTag;
  if (funcret <> FUNC_OK) then        //初始化表头不成功
  begin
    FreeMem(lpJpegBuf, JpegBufSize);
    Result := false;
    Exit;
  end;
  bi.biSize := SizeOf(BITMAPINFOHEADER);  //定义BMP头
  bi.biWidth := ImgWidth;
  bi.biHeight := ImgHeight;
  bi.biPlanes := 1;
  bi.biBitCount := 24;
  bi.biClrUsed := 0;
  bi.biClrImportant := 0;
  bi.biCompression := BI_RGB;
  NumColors := 0;
  LineBytes := DWORD((bi.biWidth * bi.biBitCount + 31) div 32 * 4);
  ImgSize := LineBytes * DWORD(bi.biHeight); //变化后的图象空间
  bf.bfType := $4d42;                        //'BM'
  bf.bfSize := SizeOf(BITMAPFILEHEADER) + SizeOf(BITMAPINFOHEADER)
    + NumColors * SizeOf(RGBQUAD) + ImgSize;
  bf.bfOffBits := DWORD(NumColors * SizeOf(RGBQUAD) +
    SizeOf(BITMAPFILEHEADER) + SizeOf(BITMAPINFOHEADER));

  GetMem(lpImgData, bf.bfSize);  //分配变换后的存储空间
  lpImgDataTemp := lpImgData;
  CopyMemory(lpImgDataTemp, @bf, SizeOf(BITMAPFILEHEADER));
  lpImgDataTemp := lpImgDataTemp + SizeOf(BITMAPFILEHEADER);
  CopyMemory(lpImgDataTemp, @bi, SizeOf(BITMAPINFOHEADER));
  lpPtr := lpImgData + bf.bfOffBits;              //实际图象数据位置

  if ((SampRate_Y_H = 0) or (SampRate_Y_V = 0)) then
  begin
    FreeMem(lpJpegBuf);
    FreeMem(lpImgData);
    Result := false;
    Exit;
  end;

  funcret := Decode;
  if (funcret = FUNC_OK) then        //解码成功
  begin
    Result := true;
    pImg   := lpImgData;
    FreeMem(lpJpegBuf);
    Exit;
  end
  else
  begin
    FreeMem(lpImgData);
    FreeMem(lpJpegBuf);
    Result := false;
    Exit;
  end;
end;
////////////////////////////////////////////////////////////////////////////////

function InitTag: Integer;
var
  finish: Boolean;
  id: Byte;
  llength: Smallint;
  i, j, k: Smallint;
  huftab1, huftab2: Smallint;
  huftabindex: Smallint;
  hf_table_index: Byte;
  qt_table_index: Byte;
  comnum: Byte;
  lptemp: PChar;
  ccount: Smallint;
begin
  finish := false;
  lp := lpJpegBuf + 2;//跳过两个字节SOI(0xFF，0xD8 Start of Image)

  while (not finish) do
  begin
    id := Byte((lp + 1)^);  //取出低位字节(高位在前，低位在后)
    lp := lp + 2;           //跳过取出的字节
    case id of
      M_APP0:   //JFIF APP0 segment marker (0xE0)
      begin
        llength := MAKEWORD(Byte((lp + 1)^), Byte(lp^));
        //MAKEWORD 转换Motorlora 与 intel 数据格式
        lp := lp + llength;//Skip JFIF segment marker
      end;
      M_DQT:   //定义量化表(0xFF,0xDB)
      begin
        llength := MAKEWORD(Byte((lp + 1)^), Byte(lp^));//(量化表长度)
        qt_table_index := (Byte((lp + 2)^) and $0f);
        //量化表信息bit 0..3: QT 号(0..3, 否则错误)
        //bit 4..7: QT 精度, 0 = 8 bit, 否则 16 bit
        lptemp := lp + 3;
        //n 字节的 QT, n = 64*(精度+1)
        if (llength < 80) then               //精度为 8 bit
        begin
          for i := 0 to 63 do
          begin
            qt_table[qt_table_index, i] := Smallint(lptemp^);
            Inc(lptemp);
          end;
        end
        else                         //精度为 16 bit
        begin
          for i := 0 to 63 do
          begin
            qt_table[qt_table_index, i] :=
              Smallint(lptemp^);
            Inc(lptemp);
          end;
          qt_table_index := Byte(lptemp^) and $0f;
          Inc(lptemp);
          for i := 0 to 63 do
          begin
            qt_table[qt_table_index, i] := Smallint(lptemp^);
            Inc(lptemp);
          end;
        end;
        lp := lp + llength; //跳过量化表
      end;
      M_SOF0:   //帧开始 (baseline JPEG 0xFF,0xC0)
      begin
        llength := MAKEWORD(Byte((lp + 1)^), Byte(lp^));
        //长度 (高字节, 低字节), 8+components*3
        ImgHeight := MAKEWORD(Byte((lp + 4)^), Byte((lp + 3)^));
        //图片高度 (高字节, 低字节), 如果不支持 DNL 就必须 >0
        ImgWidth := MAKEWORD(Byte((lp + 6)^), Byte((lp + 5)^));
        //图片宽度 (高字节, 低字节), 如果不支持 DNL 就必须 >0
        comp_num := Byte((lp + 7)^);
        //components 数量(1 byte), 灰度图是 1, YCbCr/YIQ 彩色图是 3, CMYK 彩色图是 4
        if ((comp_num <> 1) and (comp_num <> 3)) then
        begin
          Result := FUNC_FORMAT_ERROR;
          Exit;
        end;
        if (comp_num = 3) then                  //YCbCr/YIQ 彩色图
        begin
          comp_index[0] := Byte((lp + 8)^);
          //component id (1 = Y, 2 = Cb, 3 = Cr, 4 = I, 5 = Q)
          SampRate_Y_H := Byte((lp + 9)^) shr 4;      //水平采样系数
          SampRate_Y_V := Byte((lp + 9)^) and $0f;    //水平采样系数
          YQtTable := PSmallInt(@qt_table[Byte((lp + 10)^)]);
          //通过量化表号取得量化表地址
          ///  ShowMessage(IntToStr(YQtTable^));
          comp_index[1] := Byte((lp + 11)^);         //component id
          SampRate_U_H := Byte((lp + 12)^) shr 4;     //水平采样系数
          SampRate_U_V := Byte((lp + 12)^) and $0f;   //水平采样系数
          UQtTable := PSmallInt(@qt_table[Byte((lp + 13)^)]);
          //通过量化表号取得量化表地址
          comp_index[2] := Byte((lp + 14)^);         //component id
          SampRate_V_H := Byte((lp + 15)^) shr 4;     //水平采样系数
          SampRate_V_V := Byte((lp + 15)^) and $0f;   //水平采样系数
          VQtTable := PSmallInt(@qt_table[Byte((lp + 16)^)]);
          //通过量化表号取得量化表地址
        end
        else                                       //灰度图
        begin
          comp_index[0] := Byte((lp + 8)^);
          SampRate_Y_H := Byte((lp + 9)^) shr 4;
          SampRate_Y_V := Byte((lp + 9)^) and $0f;
          YQtTable := PSmallInt(@qt_table[Byte((lp + 10)^)]);
          //灰度图的量化表都一样

          comp_index[1] := Byte((lp + 8)^);
          SampRate_U_H := 1;
          SampRate_U_V := 1;
          UQtTable := PSmallInt(@qt_table[Byte((lp + 10)^)]);

          comp_index[2] := Byte((lp + 8)^);
          SampRate_V_H := 1;
          SampRate_V_V := 1;
          VQtTable := PSmallInt(@qt_table[Byte((lp + 10)^)]);
        end;
        lp := lp + llength;
      end;
      M_DHT:   //定义 Huffman Table(0xFF,0xC4)
      begin
        llength := MAKEWORD(Byte((lp + 1)^), Byte(lp^));
        //长度 (高字节, 低字节)
        if (llength < $d0) then               // Huffman Table信息 (1 byte)
        begin
          huftab1 := Smallint(Byte((lp + 2)^) shr 4);
          //huftab1=0,1(HT 类型,0 = DC 1 = AC)
          huftab2 := Smallint(Byte((lp + 2)^) and $0f);
          //huftab2=0,1(HT 号  ,0 = Y  1 = UV)
          huftabindex := huftab1 * 2 + huftab2;
          //0 = YDC 1 = UVDC 2 = YAC 3 = UVAC
          lptemp := lp + 3;
          for i := 0 to 15 do                     //16 bytes: 长度是 1..16 代码的符号数
          begin
            code_len_table[huftabindex, i] := Smallint(lptemp^);//码长为
            Inc(lptemp);
            //i的码字个数
          end;
          j := 0;
          for i := 0 to 15 do             //得出HT的所有码字的对应值
          begin
            if (code_len_table[huftabindex, i] <> 0) then
            begin
              k := 0;
              while (k < code_len_table[huftabindex, i]) do
              begin
                code_value_table[huftabindex, k + j] := Smallint(lptemp^);
                lptemp := lptemp + 1;
                k := k + 1;
              end;
              j := j + k;
            end;
          end;
          i := 0;
          while (code_len_table[huftabindex, i] = 0) do //去掉代码的符号数为零
            i := i + 1;
          for j := 0 to i - 1 do
          begin
            huf_min_value[huftabindex, j] := 0;            //码长为j的最小码字
            huf_max_value[huftabindex, j] := 0;            //码长为j的最大码字
          end;
          huf_min_value[huftabindex, i] := 0;
          huf_max_value[huftabindex, i] := code_len_table[huftabindex, i] - 1;
          for j := i + 1 to 15 do
          begin
            //码长为j的最小码字与最大码字
            huf_min_value[huftabindex, j] :=
              (huf_max_value[huftabindex, j - 1] + 1) shl 1;
            huf_max_value[huftabindex, j] :=
              huf_min_value[huftabindex, j] + code_len_table[huftabindex, j] - 1;
          end;
          code_pos_table[huftabindex, 0] := 0; //码起始位置
          for j := 1 to 15 do
            code_pos_table[huftabindex, j] :=
              code_len_table[huftabindex, j - 1] + code_pos_table[huftabindex, j - 1];
          lp := lp + llength;
        end  //if
        else
        begin
          hf_table_index := Byte((lp + 2)^);
          lp := lp + 2;
          while (hf_table_index <> $ff) do
          begin
            huftab1 := Smallint(hf_table_index shr 4);     //huftab1=0,1
            huftab2 := Smallint(hf_table_index and $0f);   //huftab2=0,1
            huftabindex := huftab1 * 2 + huftab2;
            lptemp := lp;
            Inc(lptemp);
            ccount := 0;
            for i := 0 to 15 do
            begin
              code_len_table[huftabindex, i] :=
                Smallint(lptemp^);
              Inc(lptemp);
              ccount := ccount + code_len_table[huftabindex, i];
            end;
            ccount := ccount + 17;
            j := 0;
            for i := 0 to 15 do
              if (code_len_table[huftabindex, i] <> 0) then
              begin
                k := 0;
                while (k < code_len_table[huftabindex, i]) do
                begin
                  code_value_table[huftabindex, k + j] := Smallint(lptemp^);
                  Inc(lptemp);
                  Inc(k);
                end;
                j := j + k;
              end;
            i := 0;
            while (code_len_table[huftabindex, i] = 0) do
              Inc(i);
            for j := 0 to i - 1 do
            begin
              huf_min_value[huftabindex, j] := 0;
              huf_max_value[huftabindex, j] := 0;
            end;
            huf_min_value[huftabindex, i] := 0;
            huf_max_value[huftabindex, i] := code_len_table[huftabindex, i] - 1;
            for j := i + 1 to 15 do
            begin
              huf_min_value[huftabindex, j] :=
                (huf_max_value[huftabindex, j - 1] + 1) shl 1;
              huf_max_value[huftabindex, j] :=
                huf_min_value[huftabindex, j] + code_len_table[huftabindex, j] - 1;
            end;
            code_pos_table[huftabindex, 0] := 0;
            for j := 1 to 15 do
              code_pos_table[huftabindex, j] :=
                code_len_table[huftabindex, j - 1] + code_pos_table[huftabindex, j - 1];
            lp := lp + ccount;
            hf_table_index := Byte(lp^);
          end;  //while
        end;    //else
      end;
      M_DRI: //定义重新开始间隔, 细节附后
      begin
        llength := MAKEWORD(Byte((lp + 1)^), Byte(lp^));
        restart := MAKEWORD(Byte((lp + 3)^), Byte((lp + 2)^));
        lp := lp + llength;
      end;
      M_SOS: //扫描行开始0xff, 0xda (SOS)
      begin
        llength := MAKEWORD(Byte((lp + 1)^), Byte(lp^));//长度 (高字节, 低字节),
        comnum := Byte((lp + 2)^);
        //扫描行内组件的数量 (1 byte), 必须 >:= 1 , <:=4 (否则是错的) 通常是 3
        if (comnum <> comp_num) then
        //必须是 6+2*(扫描行内组件的数量)
        begin
          Result := FUNC_FORMAT_ERROR;
          Exit;
        end;
        lptemp := lp + 3;
        for i := 0 to comp_num - 1 do
        begin                   //每组件的信息
          if (Byte(lptemp^) = comp_index[0]) then
          begin  //1 byte :Component id
            YDcIndex := Byte((lptemp + 1)^) shr 4;   //Y 使用的 Huffman 表
            YAcIndex := (Byte((lptemp + 1)^) and $0f) + 2;
          end
          else
          begin
            UVDcIndex := Byte((lptemp + 1)^) shr 4;   //U,V
            UVAcIndex := (Byte((lptemp + 1)^) and $0f) + 2;
          end;
          lptemp := lptemp + 2;
        end;  // for
        lp := lp + llength;
        finish := true;
      end;
      M_EOI:    //图片结束
      begin
        Result := FUNC_FORMAT_ERROR;
        Exit;
      end;
      else
      begin
        if ((id and $f0) <> $d0) then
        begin
          llength := MAKEWORD(Byte((lp + 1)^), Byte(lp^));
          lp := lp + llength;
        end
        else
          lp := lp + 2;
      end;
    end;
  end; //while
  Result := FUNC_OK;
end;
/////////////////////////////////////////////////////////////////

procedure InitTable;
var
  i, j: Smallint;
begin
  sizei := 0;
  sizej := 0;
  ImgWidth := 0;
  ImgHeight := 0;
  rrun := 0;
  vvalue := 0;
  BitPos := 0;
  CurByte := 0;
  IntervalFlag := false;
  restart := 0;
  for i := 0 to 2 do
    for j := 0 to 63 do
      qt_table[i, j] := 0;           //量化表
  comp_num := 0;
  HufTabIndex := 0;
  for i := 0 to 2 do
    comp_index := 0;
  for i := 0 to 3 do
    for j := 0 to 15 do
    begin
      code_len_table[i, j] := 0;
      code_pos_table[i, j] := 0;
      huf_max_value[i, j] := 0;
      huf_min_value[i, j] := 0;
    end;
  for i := 0 to 3 do
    for j := 0 to 255 do
      code_value_table[i, j] := 0;