|
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; 到此用DELPHI存取JPEG文件到SQL Server数据库中的具体操作已经叙述完毕。 我的网站： http://delphijl.99898.com QQ:123168091 | 