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.