知识大全 DELPHI存取JPEG文件到SQL Server数据库

Posted 2022-07-21 数据库

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　近日笔者书写一个小型的学生管理系统时需要用到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win +sql server桌面版中测试通过运行良好现于源码公开如下 unit Unit ;

interface

usesWindows 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typeTForm = class(TForm)DataSource : TDataSource;ADOQuery : TADOQuery;DBGrid : TDBGrid;DBNavigator : TDBNavigator;Image : TImage;savebutton: TButton;showbutton: TButton;OpenDialog : TOpenDialog;ADOQuery id: TIntegerField;ADOQuery pic: TBlobField;procedure savebuttonClick(Sender: TObject);procedure showbuttonClick(Sender: TObject);procedure DBNavigator Click(Sender: TObject; Button: TNavigateBtn);private Private declarations public Public declarations end;

varForm : TForm ;

implementation

$R * DFM

function JpegStartsInBlob(PicField:TBlobField):integer;varghy: TADOBlobstream;buffer:Word;hx: string;beginResult := ;ghy := TADOBlobstream Create(PicField bmRead);trywhile (Result = ) and (ghy Position + < ghy Size) dobeginghy ReadBuffer(buffer );hx:=IntToHex(buffer );if hx = FF then beginghy ReadBuffer(buffer );hx:=IntToHex(buffer );if hx = D then Result := ghy Position else if hx = FF thenghy Position := ghy Position ;end; //ifend; //whilefinallyghy Freeend; //tryend;

procedure TForm savebuttonClick(Sender: TObject);varpicstream:tadoblobstream;beginadoquery edit;picstream:=tadoblobstream Create(tblobfield(adoquery fields[ ]) bmWrite);if form opendialog execute thenbeginpicstream LoadFromFile(opendialog filename);picstream Position:= ;adoquery edit;tblobfield(adoquery Fields[ ]) loadfromstream(picstream);adoquery post;end;

end;

procedure TForm showbuttonClick(Sender: TObject);varghy:TADOBlobstream;pic:tjpegimage;beginghy := TADOBlobstream Create(Adoquery pic bmRead);tryghy Seek(JpegStartsInBlob(Adoquery pic) soFromBeginning);Pic:=TJpegImage Create;tryPic LoadFromStream(ghy);Image Picture Graphic:=Pic;finallyPic Free;end;finallyghy Freeend;end;

procedure TForm DBNavigator Click(Sender: TObject; Button: TNavigateBtn);beginif button in [nbFirst nbPrior nbNext nbLast] then showbutton Click;end;

end

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