//---------------------------------------------------------------------------
#include 
#pragma hdrstop
#include "Unit1.h"
//--------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
int mouseDown;
int mouseMove;
int x1,x2,y1,y2,x3,y3,xc,yc;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
        : TForm(Owner)
{
}
//--------------------------------------------------------------------
void __fastcall TForm1::Image1MouseDown(TObject *Sender,
      TMouseButton Button, TShiftState Shift, int X, int Y)
{
 x1=X;   //這裡你可修改成抓取你原本存在的直線端點(X軸)做起點
 y1=Y;   //同上抓y座標
         //或詳細判別該劃線時的條件~,成立後mouseDown給1作畫線的準備
 mouseDown=1;
}
//--------------------------------------------------------------------
void __fastcall TForm1::Image1MouseMove(TObject *Sender, TShiftState Shift,
      int X, int Y)
{
 if(mouseDown==1&&mouseMove==0)
 {
 Image1->Canvas->Pen->Color=clRed;
 Image1->Canvas->MoveTo(x1,y1);
 Image1->Canvas->LineTo(X,Y);
 xc=X;
 yc=Y;
 }
 mouseMove=1;
 if(mouseDown==1&&mouseMove==1)   //先進行畫面清除乾淨的動作,再繼續做畫
 {
 Image1->Canvas->Pen->Color=clWhite;
 Image1->Canvas->MoveTo(x1,y1);
 Image1->Canvas->LineTo(xc,yc);
 Image1->Canvas->Pen->Color=clRed;
 Image1->Canvas->MoveTo(x1,y1);
 Image1->Canvas->LineTo(X,Y);
 xc=X;
 yc=Y;
 }
}
//--------------------------------------------------------------------
void __fastcall TForm1::FormPaint(TObject *Sender)
{
 Image1->Canvas->Pen->Color=clRed;       
}
//--------------------------------------------------------------------
void __fastcall TForm1::Image1MouseUp(TObject *Sender, TMouseButton Button,
      TShiftState Shift, int X, int Y)
{
 mouseDown=0;
 mouseMove=0;
 x1=X;
 y1=Y;
}
//--------------------------------------------------------------------
void __fastcall TForm1::FormActivate(TObject *Sender)
{
  mouseDown=0;
}
//--------------------------------------------------------------------