DELPHI存取JPEG文件到SQL Server数据库（摘）

 unit Unit1;

interface

uses

  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,

  ExtCtrls, DBCtrls, Grids, DBGrids, Db, ADODB,jpeg, StdCtrls,dbtables;

   {一定要USES JPEG单元,使能存储JPG文件格式}

type

  TForm1 = class(TForm)

    DataSource1: TDataSource;

    ADOQuery1: TADOQuery;

    DBGrid1: TDBGrid;

    DBNavigator1: TDBNavigator;

    Image1: TImage;

    savebutton: TButton;

    showbutton: TButton;

    OpenDialog1: TOpenDialog;

    ADOQuery1id: TIntegerField;

    ADOQuery1pic: TBlobField;

    procedure savebuttonClick(Sender: TObject);

    procedure showbuttonClick(Sender: TObject);

    procedure DBNavigator1Click(Sender: TObject; Button: TNavigateBtn);

  private

    { Private declarations }

  public

    { Public declarations }

  end;

var

  Form1: TForm1;

implementation

{$R *.DFM}

function JpegStartsInBlob(PicField:TBlobField):integer;

   var

    ghy: TADOBlobstream;

  buffer:Word;

    hx: string;

   begin

    Result := -1;

    ghy := TADOBlobstream.Create(PicField, bmRead);

    try

     while (Result = -1) and (ghy.Position + 1 < ghy.Size) do

     begin

      ghy.ReadBuffer(buffer, 1);

      hx:=IntToHex(buffer, 2);

      if hx = 'FF' then begin

       ghy.ReadBuffer(buffer, 1);

       hx:=IntToHex(buffer, 2);

      if hx = 'D8' then Result := ghy.Position - 2

       else if hx = 'FF' then

             ghy.Position := ghy.Position-1;

      end; //if

     end; //while

     finally

      ghy.Free

     end;  //try

   end;

procedure TForm1.savebuttonClick(Sender: TObject);

var

picstream:tadoblobstream;

begin

adoquery1.edit;

picstream:=tadoblobstream.Create(tblobfield(adoquery1.fields[1]),bmWrite);

if form1.opendialog1.execute then

begin

picstream.LoadFromFile(opendialog1.filename);

picstream.Position:=0;

adoquery1.edit;

tblobfield(adoquery1.Fields[1]).loadfromstream(picstream);

adoquery1.post;

end;

end;

procedure TForm1.showbuttonClick(Sender: TObject);

var

ghy:TADOBlobstream;

pic:tjpegimage;

begin

ghy := TADOBlobstream.Create(Adoquery1pic, bmRead);

try

  ghy.Seek(JpegStartsInBlob(Adoquery1pic),soFromBeginning);

  Pic:=TJpegImage.Create;

  try

   Pic.LoadFromStream(ghy);

   Image1.Picture.Graphic:=Pic;

  finally

   Pic.Free;

  end;

finally

ghy.Free

end;

end;

procedure TForm1.DBNavigator1Click(Sender: TObject; Button: TNavigateBtn);

begin

if button in [nbFirst, nbPrior, nbNext, nbLast] then showbutton.Click;

end;

end.

如果数据库中要存储的是BMP文件，则在procedure TForm1.showbuttonClick(Sender: TObject);过程中代码更改如下即可存储显示BMP文件格式的操作。

procedure TForm1.showbuttonClick(Sender: TObject);

var

ghy:TADOBlobstream;

pic:tbitmap;

begin

ghy := TADOBlobstream.Create(Adoquery1pic, bmRead);

try

 { ghy.Seek(JpegStartsInBlob(Adoquery1pic),soFromBeginning);}

  Pic:=Tbitmap.Create;

  try

   Pic.LoadFromStream(ghy);

   Image1.Picture.Graphic:=Pic;

  finally

   Pic.Free;

  end;

finally

ghy.Free

end;

end;

　　在"DELPHI存取JPEG文件到SQL Server数据库"发表之后，有许多网友来电表示支持和相关的技术咨询，在此首先对那些关心本文的朋友们表示衷心的感谢。

　　由于网友的需要做一个档案管理系统，存取jpeg文件到sql 2000数据库中，但在dbimage中及qrdbimage中均不能正常显示jpeg的文件，此为borland的限制，虽然使用第三方控件能达到要求，但我们还是来原始的实现一下这方面的技术，其实原理十分简单，既然我们在"DELPHI存取JPEG文件到SQL Server数据库"能存储jpeg文件，也能在image中显示，但一接触db类的图象显示控件就行不通了，我们可以在jpeg文件存入数据库之前转换成bmp文件再存入数据库即可，程序运行环境delphi5+ado+sql 2000桌面版+win98se2最终版，数据库中存放图片字段的类型为image，程序源代码如下：

unit Unit1;

interface

uses

Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,

Db, DBCtrls, Grids, DBGrids, ADODB, ExtDlgs,jpeg, ExtCtrls, StdCtrls;

type

TForm1 = class(TForm)

ADOConnection1: TADOConnection;

ADOQuery1: TADOQuery;

DataSource1: TDataSource;

DBGrid1: TDBGrid;

DBImage1: TDBImage;

ADOQuery1ID: TStringField;

ADOQuery1FIELD: TStringField;

ADOQuery1STYLE: TStringField;

ADOQuery1SYSTEM: TStringField;

ADOQuery1DATE: TDateTimeField;

ADOQuery1PERSON1: TStringField;

ADOQuery1PERSON2: TStringField;

ADOQuery1PERSON3: TStringField;

ADOQuery1PHOTO: TBlobField;

ADOQuery1DESCRIPTION: TStringField;

OpenPictureDialog1: TOpenPictureDialog;

Image1: TImage;

Button1: TButton;

Memo1: TMemo;

procedure DBImage1Click(Sender: TObject);

procedure Button1Click(Sender: TObject);

procedure FormShow(Sender: TObject);

private

{ Private declarations }

public

{ Public declarations }

end;

var

Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.DBImage1Click(Sender: TObject);

var

picstream:tadoblobstream;

bmppic:tbitmap;

jpgpic:tjpegimage;

bmpstream:TMemoryStream;

begin

if form1.OpenPictureDialog1.Execute then

begin

if extractfileext(form1.openpicturedialog1.filename)='.bmp' then

begin

adoquery1.edit;

picstream:=tadoblobstream.Create(tblobfield(ADOQuery1PHOTO),bmWrite);

//注：上句代码中的ADOQuery1PHOTO是adoquery1中的固定字段photo的固定字段的name

//用户需要手工添加固定字段，也可用fields[i]来进行选择，这点在

//"DELPHI存取JPEG文件到SQL Server数据库"这篇文章中没有注释，至使许多朋友没有

//编译成功。

picstream.LoadFromFile(openpicturedialog1.filename);

picstream.Position:=0;

adoquery1.edit;

tblobfield(ADOQuery1PHOTO).loadfromstream(picstream);

adoquery1.post;

adoquery1.edit;

picstream.free;

end

else

begin

jpgpic:=tjpegimage.Create;

bmppic:=tbitmap.Create;

bmpstream:=tmemorystream.Create;

jpgpic.LoadFromFile(openpicturedialog1.filename);

bmppic.Assign(jpgpic);

bmppic.SaveToStream(bmpstream);

adoquery1.edit;

picstream:=tadoblobstream.Create(tblobfield(ADOQuery1PHOTO),bmWrite);

//注：上句代码中的ADOQuery1PHOTO是adoquery1中的固定字段photo的固定字段的name

//用户需要手工添加固定字段，也可用fields[i]来进行选择，这点在

//"DELPHI存取JPEG文件到SQL Server数据库"这篇文章中没有注释，至使许多朋友没有

//编译成功。

picstream.LoadFromStream(bmpstream);

picstream.Position:=0;

adoquery1.edit;

tblobfield(ADOQuery1PHOTO).loadfromstream(picstream);

adoquery1.post;

jpgpic.free;

bmppic.free;

bmpstream.free;

adoquery1.edit;

picstream.free;

end;

end;

end;

procedure TForm1.Button1Click(Sender: TObject);

begin

memo1.Lines.Add(form1.openpicturedialog1.filter);

end;

procedure TForm1.FormShow(Sender: TObject);

begin

form1.openpicturedialog1.filter:='All *.jpg;*.jpeg;*.bmp;|*.jpg;*.jpeg;*.bmp;)';

end;

end.