欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页  >  数据库

用ADO控件存取SQL Server数据库图片

程序员文章站 2022-04-13 21:53:05
...

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   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;