用Delphi编写CGI程序返回图象

珠海西门子表计公司 
汪永荣 
---- Delphi 4.0对Internet编程提供了强大的支持，Delphi 4.0编写CGI非常容易， Delphi 4.0本身提供了例程。但是笔者在实践中遇到需要CGI程序根据数据库动态 返回图象的情况，很多文章推进使用Cgi-Expert或有关的OCX控件，使用控件不仅 带来额外的开销，且缺乏灵活性，那么能否不使用这些控件自己编写代码实现，现 推荐一种方法，代码如下： 

unit ChartMod; interface uses  Windows, Messages, SysUtils, Classes, HTTPApp, Db, DBTables,  DbChart, Series, Jpeg, ExtCtrls; type  TWebModule1 = class(TWebModule)    Table1: TTable;procedure WebModule1ActionAreaAction(Sender: TObject;      Request: TWebRequest; Response: TWebResponse; var Handled:Boolean);procedure WebModule1ActionPopulationAction(Sender: TObject;      Request: TWebRequest; Response: TWebResponse; var Handled:Boolean);    procedure WebModule1Create(Sender: TObject);    procedure WebModule1Destroy(Sender: TObject);    procedure WebModule1AfterDispatch(Sender: TObject;      Request: TWebRequest; Response: TWebResponse; var Handled: Boolean);  private    Chart: TDBChart;    Series: TPieSeries;    Image: TImage;  public    { Public declarations }  end; var  WebModule1: TWebModule1; implementation {$R *.DFM} procedure TWebModule1.WebModule1ActionAreaAction(Sender: TObject;  Request: TWebRequest; Response: TWebResponse; var Handled: Boolean);begin  // set specific values  Chart.Title.Text.Clear;  Chart.Title.Text.Add ('Area of Countries');  Chart.LeftAxis.Title.Caption := 'Area';  Series.Title := 'Area';  Series.PieValues.ValueSource := 'Area';end; procedure TWebModule1.WebModule1ActionPopulationAction(Sender: TObject;  Request: TWebRequest; Response: TWebResponse; var Handled: Boolean);begin  // set specific values  Chart.Title.Text.Clear;  Chart.Title.Text.Add ('Population of Countries');  Chart.LeftAxis.Title.Caption := 'Population';  Series.Title := 'Population';  Series.PieValues.ValueSource := 'Population';end; procedure TWebModule1.WebModule1Create(Sender: TObject);begin  // open the database table  Table1.Open;  // create the chart  Chart := TDBChart.Create (nil);  Chart.Width := 600;  Chart.Height := 400;  Chart.AxisVisible := False;  Chart.Legend.Visible := False;  Chart.BottomAxis.Title.Caption := 'Name';  // create the pie series  Series := TPieSeries.Create (Chart);  Series.ParentChart := Chart;  Series.DataSource := Table1;  Series.XLabelsSource := 'Name';  Series.OtherSlice.Style := poBelowPercent;  Series.OtherSlice.Text := 'Others';  Series.OtherSlice.Value := 2;  Chart.AddSeries (Series);  // create the memory bitmap  Image := TImage.Create (nil);  Image.Width := Chart.Width;  Image.Height := Chart.Height;end; procedure TWebModule1.WebModule1Destroy(Sender: TObject);begin  Chart.Free;  Series.Free;  Image.Free;end; procedure TWebModule1.WebModule1AfterDispatch(Sender: TObject;  Request: TWebRequest; Response: TWebResponse; var Handled: Boolean);var  Jpeg: TJpegImage;  MemStr: TMemoryStream;begin  // paint the chart on the memory bitmap  Chart.Draw (Image.Canvas, Image.BoundsRect);  // create the jpeg and copy the iamge to it  Jpeg := TJpegImage.Create;  try    Jpeg.Assign (Image.Picture.Bitmap);    MemStr := TMemoryStream.Create;    try      // save to a stream and return it      Jpeg.SaveToStream (MemStr);      MemStr.Position := 0;      Response.ContentType := 'image/jpeg';      Response.ContentStream := MemStr;      Response.SendResponse;    finally      MemStr.Free;    end;  finally    Jpeg.Free;  end;end; end.