其实汉字的显示是非常简单的。只要了解汉字的定位以及字模的含义，我们就可以非常方便的定位到汉字，并读取出字库数据，将其显示出来。在中英文混合显示的 时候，因为GB2312编码的区码与位码都是大于A0的。而基本的ASCII码都是小于A0的。我们可以根据这个信息来区分ASCII码和汉字。

你是否碰到过用启动盘启动系统后用DIR命令得到一串串莫名其妙的字符？有经验的朋友会告诉你：那是汉字。汉字？你不禁会问：怎么一个我一个也不认识。但那确确实实是汉字，如果你启动UCDOS或其他的汉字系统后，就会看到那是一个个熟悉的汉字。同样是汉字，为什么前后会看到不同的结果？呵呵，其实在电脑硬件中，根本没有汉字这个概念，也没有英文的概念，这铁玩意认识的概念只有——内码。

unit UnitSendMail;

interface

uses
  Windows, SysUtils, Classes,StdCtrls, ExtCtrls, ComCtrls, Dialogs,
  IdMessage, IdBaseComponent, IdComponent, IdTCPConnection, IdTCPClient,
  IdExplicitTLSClientServerBase,IdMessageClient, IdSMTPBase, IdSMTP, IdText,
  IDAttachmentFile;

function SendEMail(SenderName, SenderAddress: PChar;
    Receivename, ReceiveAddress: PChar; MailSubject, MailContent: PChar;
    JpgFileName: PChar; SendType: Integer; PicID: PChar; IsCustom: Boolean;Attachment:PChar): Boolean; stdcall;
function ConnectMailServer(Host, UserName, Password: PChar;
    Port: Integer): Boolean; stdcall;
procedure DisconnectMail; stdcall;

type
  TSendMailObj = class
  private
    FHost: String;
    FPort: Integer;
    FUserName: String;
    FPassword: String;
    ASmtp: TIdSMTP;
  public
    property Host: string read FHost write FHost;
    property Port: Integer read FPort write FPort;
    property UserName: String read FUserName write FUserName;
    property Password: String read FPassword write FPassword;
    constructor Create;
    function ConnectServer: Boolean;
    function SendEMail(SenderName, SenderAddress: PChar;
      Receivename, ReceiveAddress: PChar; MailSubject, MailContent: PChar;
      JpgFileName: PChar; SendType: Integer; PicID: PChar;
      IsCustom: Boolean;Attachment:PChar): Boolean;
  end;

var
  SendObj: TSendMailObj;

implementation

function SendEMail(SenderName, SenderAddress: PChar;
    Receivename, ReceiveAddress: PChar; MailSubject, MailContent: PChar;
    JpgFileName: PChar; SendType: Integer; PicID: PChar; IsCustom: Boolean;Attachment:PChar): Boolean; stdcall;
begin
  Result :=  SendObj.SendEMail(SenderName, SenderAddress, Receivename,
          ReceiveAddress, MailSubject, MailContent,
            JpgFileName, SendType, PicID, IsCustom,Attachment);
end;

function ConnectMailServer(Host, UserName, Password: PChar;
    Port: Integer): Boolean; stdcall;
begin
  try
    //if SendObj = nil then
    SendObj := TSendMailObj.Create;
{    if SendObj.ASmtp.Connected then
      SendObj.ASmtp.Disconnect;  }
    SendObj.Host := StrPas(Host);
    SendObj.Port := Port;
    SendObj.Username := StrPas(UserName);
    SendObj.Password := StrPas(Password);
    Result := SendObj.ConnectServer;
  except
    Result := False;
  end;
end;

procedure DisconnectMail; stdcall;
begin
  if SendObj <> nil then
  begin
    if SendObj.ASmtp <> nil then
      SendObj.ASmtp.Disconnect;
    SendObj := nil;
    SendObj.Free;
  end;
end;
{ TSendMailObj }

function TSendMailObj.ConnectServer: Boolean;
begin
  ASmtp.Host := FHost;
  ASmtp.Port := FPort;
  ASmtp.Username := FUserName;
  ASmtp.Password := FPassword;
  try
    ASmtp.Connect;
    Result := ASmtp.Connected;
  except
    Result := False;
  end;
end;

constructor TSendMailObj.Create;
begin
  ASmtp := TIdSMTP.Create(nil);

end;

function TSendMailObj.SendEMail(SenderName, SenderAddress, Receivename,
  ReceiveAddress, MailSubject, MailContent, JpgFileName: PChar;
  SendType: Integer; PicID: PChar; IsCustom: Boolean;Attachment:PChar): Boolean;
var
  IdBody, IdHtml: TIdText;
  Att: TIdAttachmentFile;
  AMessage: TIdMessage;
  ASmtp_1: TIdSMTP;
begin
  ASmtp_1 := TIdSMTP.Create(nil);
  ASmtp_1.Host := FHost;
  ASmtp_1.Port := FPort;
  ASmtp_1.Username := FUserName;
  ASmtp_1.Password := FPassword;
  //ASmtp_1.AuthType := atDefault;
  ASmtp_1.Connect; // }
  if not ASmtp.Connected then
    ASmtp.Connect;
  AMessage := TIdMessage.Create(nil);
  with AMessage do
  begin
    NoDecode := False;
    NoEncode := False;
    ContentType := 'multipart/mixed';
    Encoding := meMIME;
    MsgId := 'PrettyPic';
    if FileExists(StrPas(JpgFileName)) then
      References := ChangeFileExt(ExtractFileName(StrPas(JpgFileName)), '')
    else
      References := '';
    Recipients.Clear;
    with Recipients.Add do
    begin
      Name := StrPas(Receivename);
      Address := StrPas(ReceiveAddress);
    end;
    Subject := StrPas(MailSubject);
    Sender.Name := StrPas(SenderName);
    Sender.Address := StrPas(SenderAddress);
    From.Name := Sender.Name;
    From.Address := Sender.Address;
    if SendType = 0 then
    begin
      IdBody := TIdText.Create(MessageParts);
      IdBody.ContentType := 'text/plain';
      IdBody.Body.Add(StrPas(MailContent));
      IdBody.Body.Add('');
    end
    else
    begin
      IdHtml := TIdText.Create(MessageParts);
      IdHtml.ContentType := 'text/html;charset=gb2312';
      IdHtml.ContentTransfer := '7bit';
      IdHtml.Body.Add(' <html>');
      IdHtml.Body.Add('  <head>');
      IdHtml.Body.Add('      <title>' + StrPas(MailSubject) + ' </title>');
      IdHtml.Body.Add('  </head>');
      IdHtml.Body.Add('  <body title="' + References + '">');
      IdHtml.Body.Add('    ' + StrPas(MailContent) + ' <br>');
      if (not IsCustom) and FileExists(StrPas(JpgFileName)) then
        IdHtml.Body.Add('      <img src="cid:' + StrPas(PicID) + '" alt="' + ExtractFileName(StrPas(JpgFileName)) +
                            '" name="' + ExtractFileName(StrPas(JpgFileName)) + '" title="">');
      IdHtml.Body.Add('  </body>');
      IdHtml.Body.Add(' </html>');
    end;
    if FileExists(StrPas(JpgFileName)) then
    begin
      Att := TIdAttachmentFile.Create(MessageParts, StrPas(JpgFileName));
      Att.ExtraHeaders.Values['Content-ID'] := StrPas(PicID);
      Att.ContentType := 'image/jpg';
    end;  
    if FileExists(StrPas(Attachment)) then
    begin
      Att := TIdAttachmentFile.Create(MessageParts, StrPas(Attachment));
    end;
  end;
  try
    ASmtp_1.Send(AMessage);
    if Att <> nil then
      Att.Free;
    if IdBody <> nil then
      IdBody.Free;
    if IdHtml <> nil then
      IdHtml.Free;
    if AMessage <> nil then
      AMessage.Free;
    ASmtp_1.Disconnect;

    ASmtp_1.Free; //}
    ASmtp.Disconnect;
    Result := True;
  except on e: Exception do
  begin
    Result := False;
  end;
  end;

end;

end.