DELPHI存取JPEG、BMP图像到数据库完整解决方案

程序代码如下所示:

unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, DB, ExtDlgs, StdCtrls, ADODB, Grids, DBGrids, ExtCtrls,jpeg,
DBCtrls;

type
TForm1 = class(TForm)
DBGrid1: TDBGrid;
ADOConnection1: TADOConnection;
ADOTable1: TADOTable;
selectimage: TButton;
savetodb: TButton;
OpenPictureDialog1: TOpenPictureDialog;
DataSource1: TDataSource;
DBNavigator1: TDBNavigator;
savetofile: TButton;
Label1: TLabel;
Label2: TLabel;
Button1: TButton;
Bevel1: TBevel;
Bevel2: TBevel;
GroupBox1: TGroupBox;
Image1: TImage;
Label3: TLabel;
Label4: TLabel;
DBImage1: TDBImage;
procedure selectimageClick(Sender: TObject);
procedure savetodbClick(Sender: TObject);
procedure ADOTable1AfterScroll(DataSet: TDataSet);
procedure savetofileClick(Sender: TObject);
procedure Button1Click(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure ADOTable1BeforeScroll(DataSet: TDataSet);
private
{ Private declarations }
    public
     { Public declarations }
end;

var
Form1: TForm1;

implementation
uses unit2;
{$R *.dfm}

procedure TForm1.selectimageClick(Sender: TObject); //选择图像
begin
   if openpicturedialog1.Execute then
     image1.Picture.LoadFromFile(openpicturedialog1.FileName );
end;

////如下保存方法only to sql and access'data
procedure TForm1.savetodbClick(Sender: TObject);//保存图像
var
strm:tmemorystream;
ext:string;
begin
   if image1.picture.Graphic <> nil then //避免image1中无图像保存出错
      begin
        ext:=extractfileext(openpicturedialog1.FileName );
        strm := tmemorystream.Create ;
      try
        image1.Picture.Graphic.SaveToStream(strm);
        adotable1.Edit ;
        strm.Position :=0;
        DBImage1.dataField :='';//dbimage只能显示BMP，否则myimage由BMP变为jpeg时会出错
        tblobfield(adotable1.FieldByName('myimage')).LoadFromStream(strm);
        //如需直接由文件保存 TBlobField(adotable1.FieldByName('myimage')).LoadFromFile          (OpenPictureDialog1.FileName);
//以下记录保存到数据库的图像格式
     if uppercase(ext) = '.BMP' then
        begin
          adotable1.FieldByName('isbmp').Value := 1;
          dbimage1.dataField := 'myimage';
        end
    else if (uppercase(ext) = '.JPG') OR ( uppercase(ext) = '.JPEG') THEN
        adotable1.FieldByName('isbmp').Value := 0;
        adotable1.Post ;
        finally
         strm.Free ;//如果你选用TBLOBSTREAM类,程序运行到此语句会出错，可该语句前添入adotable1.edit
      end;
   end;
end;
///如下显示方法不适用于paradox中的graphic字段的显示。
procedure TForm1.adoTable1AfterScroll(DataSet: TDataSet); //显示图像
var
strm:tadoblobstream;
jpegimage:tjpegimage;
bitmap:tbitmap;
begin
    strm := tadoblobstream.Create(tblobfield(adotable1.fieldbyname('MYIMAGE')),bmread);
    try//try1
    strm.position :=0;
    image1.Picture.Graphic := nil;
    DBIMAGE1.DataField := '';
   //显示时，BMP、JPEG两种图像数据必需分别处理
    if adotable1.fieldbyname('isbmp').asstring ='1' then
        begin//begin11
        bitmap := tbitmap.Create ;
        try//try11
        bitmap.LoadFromStream(strm);
        image1.Picture.Graphic := bitmap;
        DBIMAGE1.DataField := 'myimage';
        finally
        bitmap.Free;
    end;//end try11
end//end begin11
else if adotable1.fieldbyname('isbmp').asstring ='0' then
begin//begin12
    jpegimage := tjpegimage.Create ;
    try //try12
    jpegimage.LoadFromStream(strm);
    image1.Picture.Graphic := jpegimage;
    finally
    jpegimage.Free ;
  end;//end try12
end;//end begin12
finally
strm.Free ;
end;//end try1
end;

////显示时必须分bmp and jpeg 两种情况处理，而保存可统一。

procedure TForm1.savetofileClick(Sender: TObject);
var
tmpstr:string;
begin
if image1.Picture.Graphic <> nil then
   begin
      tmpstr := openpicturedialog1.Filter;
         if adotable1.fieldbyname('isbmp').asstring ='1' then
           begin
              openpicturedialog1.Filter := 'Bitmaps (*.bmp)|*.bmp';
                if openpicturedialog1.Execute then
                   image1.Picture.SaveToFile(openpicturedialog1.FileName+'.bmp');
                end
         else
    begin
        openpicturedialog1.Filter := 'JPEG Image File (*.jpg)|*.jpg';
          if openpicturedialog1.Execute then
             image1.Picture.SaveToFile(openpicturedialog1.FileName+'.jpg');
          end;
      openpicturedialog1.Filter := tmpstr;
   end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
    form2.Show;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
    adoconnection1.Connected := true;
    adoconnection1.LoginPrompt := false;
    adotable1.Active := true;

end;

procedure TForm1.ADOTable1BeforeScroll(DataSet: TDataSet);
begin
    dbimage1.dataField :=''; //这条语句不能遗漏，不信你试试
end;

end.