用ADO控件存取SQLServer数据库图片

用ADO控件 存取 SQL Server 数据库 图片 ，查看资料发现基本都是针对BMP文件进行操作(巨增 数据库 大小)，但发现了★eagletian★高手翻译的ADO英文技术文档，里面涉及到了 数据库 存取 JPEG文件的关键技术，在win98+sql server桌面版中测试通过，运行良好，

用ADO控件存取SQL Server数据库图片，查看资料发现基本都是针对BMP文件进行操作(巨增数据库大小)，但发现了★eagletian★高手翻译的ADO英文技术文档，里面涉及到了数据库存取JPEG文件的关键技术，在win98+sql server桌面版中测试通过，运行良好，现于源码公开如下：
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;