求救：如何用鼠标曲线？

Question

请问各位高手！如何用鼠标在画布上画曲线，
    并且鼠标的痕迹就是曲线的形状。
   拜托了！

Answer 1

var
  Down: Boolean;
  prePt: TPoint;procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  Down := True;
  Canvas.MoveTo(X, Y);
end;procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  Down := False;
end;procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  if Down then
  begin
    Canvas.LineTo(X, Y);
    prePt := Point(X, Y);
  end;
end;

Answer 2

//--------------------------------------------------------------------------//
//  Brush.cpp                                                               //
//  Project: BrushForm                                                      //
//  Copyright (c) 1997 by Jeff Cottingham                                   //
//--------------------------------------------------------------------------////---------------------------------------------------------------------------
#include <vcl\vcl.h>
#pragma hdrstop#include "Brush.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
: TForm(Owner)
{
}
//---------------------------------------------------------------------------void __fastcall TForm1::RadioGroup1Click(TObject *Sender)
{    switch(RadioGroup1->ItemIndex){
    case 8 : Check = true;
             break;
    case 7 : myBrushStyle = bsVertical;
              break;
    case 6 : myBrushStyle = bsFDiagonal;
              break;
    case 5 : myBrushStyle = bsBDiagonal;
              break;
    case 4 : myBrushStyle = bsHorizontal;
              break;
    case 3 : myBrushStyle = bsDiagCross;
              break;
    case 2 : myBrushStyle = bsClear;
              break;
    case 1 : myBrushStyle = bsCross;
              break;
    case 0 : myBrushStyle = bsSolid;
              break;
    };
}
//---------------------------------------------------------------------------
void __fastcall TForm1::RadioGroup2Click(TObject *Sender)
{
   switch(RadioGroup2->ItemIndex){
      case 15 : myMode = pmNotXor;
                break;
      case 14 : myMode = pmXor;
                break;
      case 13 : myMode = pmNotMask;
                break;
      case 12 : myMode = pmMask;
                break;
      case 11 : myMode = pmNotMerge;
                break;
      case 10 : myMode = pmMerge;
                break;
      case 9 :  myMode = pmMaskNotPen;
                break;
      case 8 :  myMode = pmMergeNotPen;
                break;
      case 7 :  myMode = pmMaskPenNot;
                break;
      case 6 :  myMode = pmMergePenNot;
                break;
      case 5 :  myMode = pmNotCopy;
                break;
      case 4 :  myMode = pmCopy;
                break;
      case 3 :  myMode = pmNot;
                break;
      case 2 :  myMode = pmNop;
                break;
      case 1 :  myMode = pmWhite;
                break;
      case 0 :  myMode = pmBlack;
                break;
   };
}
//---------------------------------------------------------------------------void __fastcall TForm1::Button1Click(TObject *Sender)
{
   int y = 20;
   int x = 20;   Image2->Canvas->Pen->Mode = myMode;
   Image2->Canvas->Pen->Width = Edit1->Text.ToInt();   for(int i = 0;i < 10 ;i++){
      Image2->Canvas->MoveTo(0,y);
      Image2->Canvas->LineTo(Image2->Width,y);
      y += 20;
   };   for(int i = 0;i < 13;i++){
      Image2->Canvas->MoveTo(x,0);
      Image2->Canvas->LineTo(x,Image2->Height);
      x += 20;
   };
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button2Click(TObject *Sender)
{
   if(Check){
      Graphics::TBitmap *CustomBrush = new Graphics::TBitmap;;
      try {
        CustomBrush->LoadFromFile("Custom.bmp");
        Image1->Canvas->Brush->Bitmap = CustomBrush;
        Image1->Canvas->FillRect(Rect(3,3,Image1->Width - 3,
                                 Image1->Height - 3));
      }
      catch (...){
        Image1->Canvas->Brush->Bitmap = NULL;
        delete CustomBrush;
      };
      Image1->Canvas->Brush->Bitmap = NULL;
      delete CustomBrush;
      Check = false;
   }
   else {
      Image1->Canvas->Brush->Style = myBrushStyle;
      Image1->Canvas->FillRect(Rect(3,3,Image1->Width - 3,Image1->Height - 3));
   };
}
//---------------------------------------------------------------------------
void __fastcall TForm1::FormShow(TObject *Sender)
{
   Image1->Canvas->Rectangle(0,0,Image1->Width,Image1->Height);
   Image2->Canvas->FillRect(Image2->Canvas->ClipRect);
   Image3->Canvas->FillRect(Image3->Canvas->ClipRect);
   Image4->Canvas->FillRect(Image4->Canvas->ClipRect);
   Image5->Canvas->FillRect(Image5->Canvas->ClipRect);
   Image6->Canvas->FillRect(Image6->Canvas->ClipRect);
   Image7->Canvas->FillRect(Image7->Canvas->ClipRect);
   Image8->Canvas->FillRect(Image8->Canvas->ClipRect);
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Edit2Change(TObject *Sender)
{
   myStyle = oldStyle;   Image3->Canvas->Font->Style = myStyle;   if(CheckBox1->Checked){
      myStyle << fsBold;
      Image3->Canvas->Font->Style = myStyle;
   };
   if(CheckBox2->Checked) {
      myStyle << fsItalic;
      Image3->Canvas->Font->Style = myStyle;
   };
   if(CheckBox3->Checked) {
      myStyle << fsUnderline;
      Image3->Canvas->Font->Style = myStyle;
   };
   if(CheckBox4->Checked) {
      myStyle << fsStrikeOut;
      Image3->Canvas->Font->Style = myStyle;
   };
   if(CheckBox5->Checked)
      Image3->Canvas->Font->Height = TFontHeight - 10;
   else {
      Image3->Canvas->Font->Height = TFontHeight;
      Image3->Canvas->Font->Size = 20;
   };   Image3->Canvas->FillRect(Image3->ClientRect);
   Image3->Canvas->TextOut(10,20,Edit2->Text);   Image4->Canvas->FillRect(Image4->ClientRect);
   Image4->Canvas->TextOut(10,20,Edit2->Text);
}
//---------------------------------------------------------------------------
void __fastcall TForm1::CheckBox1Click(TObject *Sender)
{
   Edit2->SetFocus();
   Edit2->SelStart = Edit2->SelLength;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Image5MouseDown(TObject *Sender, TMouseButton Button,
TShiftState Shift, int X, int Y)
{
   Point1.x = X;
   Point1.y = Y;
   Point2.x = X;
   Point2.y = Y;
   Rendering = true;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Image5MouseUp(TObject *Sender, TMouseButton Button,
TShiftState Shift, int X, int Y)
{
   Rendering = false;
   Image5->Canvas->Pen->Style = psSolid;
   Image5->Canvas->Pen->Mode = pmCopy;
   if(CanRender && !Rendering)DrawShape(Point1.x,Point1.y,X,Y);
   if(SpeedButton5->Down){
      Image5->Canvas->Brush->Color = clRed;
      Image5->Canvas->FloodFill(X,Y,clBlack,fsBorder);
      Image5->Canvas->Brush->Color = clWhite;
   };
}
//---------------------------------------------------------------------------void __fastcall TForm1::DrawShape(int w,int x,int y,int z)
{
   switch(dsCurrentShape){
      case dsEllipse : Image5->Canvas->Ellipse(w,x,y,z);
                       break;
      case dsRectangle : Image5->Canvas->Rectangle(w,x,y,z);
                       break;
      case dsLine : {
                     Image5->Canvas->MoveTo(w,x);
                     Image5->Canvas->LineTo(y,z);
                     break;
                    };
   };
}
//---------------------------------------------------------------------------void __fastcall TForm1::Render(int x,int y)
{
  if(CanRender && Rendering){
      Image5->Canvas->Brush->Style = bsClear;
      Image5->Canvas->Pen->Mode = pmNotXor;
      Image5->Canvas->Pen->Style = psDot;
      DrawShape(Point1.x,Point1.y,Point2.x,Point2.y);
      Point2.x = x;
      Point2.y = y;
      DrawShape(Point1.x,Point1.y,Point2.x,Point2.y);
   }
   else {
      Rendering = false;
   };
}
//---------------------------------------------------------------------------

Answer 3

void __fastcall TForm1::Image5MouseMove(TObject *Sender, TShiftState Shift,
int X, int Y)
{
   if(CanRender) Render(X,Y);
}
//---------------------------------------------------------------------------
void __fastcall TForm1::SpeedButton2Click(TObject *Sender)
{
   CanRender = true;
   dsCurrentShape = dsEllipse;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::SpeedButton4Click(TObject *Sender)
{
   CanRender = false;
   Rendering = false;
   Image5->Canvas->Brush->Style = bsSolid;
   Image5->Canvas->FillRect(Image5->ClientRect);
}
//---------------------------------------------------------------------------
void __fastcall TForm1::SpeedButton1Click(TObject *Sender)
{
   CanRender = true;
   dsCurrentShape = dsLine;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::SpeedButton3Click(TObject *Sender)
{
   if(dynamic_cast<TSpeedButton*>(Sender)->Down) CanRender = true;
   if(dynamic_cast<TSpeedButton*>(Sender)->Name == "SpeedButton1")
      dsCurrentShape = dsLine;
   else if(dynamic_cast<TSpeedButton*>(Sender)->Name == "SpeedButton2")
      dsCurrentShape = dsEllipse;
   else if(dynamic_cast<TSpeedButton*>(Sender)->Name == "SpeedButton3")
      dsCurrentShape = dsRectangle;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::RadioGroup3Click(TObject *Sender)
{
   switch(RadioGroup3->ItemIndex){
      case 14 : TCopyMode = cmWhiteness;
                break;
      case 13 : TCopyMode = cmSrcPaint;
                break;
      case 12 : TCopyMode = cmSrcInvert;
                break;
      case 11 : TCopyMode = cmSrcErase;
                break;
      case 10 : TCopyMode = cmSrcCopy;
                break;
      case 9 :  TCopyMode = cmSrcAnd;
                break;
      case 8 :  TCopyMode = cmPatPaint;
                break;
      case 7 :  TCopyMode = cmPatInvert;
                break;
      case 6 :  TCopyMode = cmPatCopy;
                break;
      case 5 :  TCopyMode = cmNotSrcErase;
                break;
      case 4 :  TCopyMode = cmNotSrcCopy;
                break;
      case 3 :  TCopyMode = cmMergePaint;
                break;
      case 2 :  TCopyMode = cmMergeCopy;
                break;
      case 1 :  TCopyMode = cmDstInvert;
                break;
      case 0 :  TCopyMode = cmBlackness;
                break;
   };
}
//---------------------------------------------------------------------------void __fastcall TForm1::BitBtn1Click(TObject *Sender)
{
   Image6->Canvas->Brush->Color = clWhite;
   Image6->Canvas->Brush->Style = bsSolid;
   Image6->Canvas->FillRect(Image6->Canvas->ClipRect);
   Image6->Canvas->Brush->Color = clGreen;
   Image6->Canvas->Rectangle(25,25,140,140);
}
//---------------------------------------------------------------------------
void __fastcall TForm1::BitBtn2Click(TObject *Sender)
{
   Image7->Canvas->Brush->Color = clWhite;
   Image7->Canvas->Brush->Style = bsSolid;
   Image7->Canvas->FillRect(Image7->Canvas->ClipRect);
   Image7->Canvas->Brush->Color = clBlue;
   Image7->Canvas->Rectangle(60,60,190,190);
}
//---------------------------------------------------------------------------
void __fastcall TForm1::BitBtn3Click(TObject *Sender)
{
   Image7->Canvas->CopyMode = TCopyMode;
   Image7->Canvas->CopyRect(Image7->Canvas->ClipRect,Image6->Canvas,
                            Image6->Canvas->ClipRect);
}
//---------------------------------------------------------------------------
void __fastcall TForm1::FormCreate(TObject *Sender)
{
   Image1->Canvas->Pen->Width = 3;
   Image1->Canvas->Pen->Color = clRed;   Image2->Canvas->Brush->Style = bsSolid;
   Image2->Canvas->Brush->Color = clBlue;
   Image2->Canvas->Pen->Color = clRed;   Image3->Canvas->Brush->Color = clBtnFace;
   Image3->Canvas->Font->Size = 20;
   TFontHeight = Image3->Canvas->Font->Height;
   oldStyle = Image3->Canvas->Font->Style;   Image4->Canvas->Brush->Color = clBtnFace;
   Image4->Canvas->Font->Size = 20;}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button3Click(TObject *Sender)
{
   HRGN MyRgn;   //Image8->Invalidate();
   MyRgn = ::CreateRectRgn(100,100,200,200);
   ::SelectClipRgn(Image8->Canvas->Handle,MyRgn);
   Ellipse(Image8->Canvas->Handle,90,90,210,210);
   Image8->Invalidate();
   ::SelectClipRgn(Image8->Canvas->Handle,NULL);
   ::DeleteObject(MyRgn);   MyRgn = CreateRectRgn(200,200,300,300);
   ::SelectClipRgn(Image8->Canvas->Handle,MyRgn);
   ::Ellipse(Image8->Canvas->Handle,190,190,310,310);
   Image8->Invalidate();
   ::SelectClipRgn(Image8->Canvas->Handle,NULL);
   ::DeleteObject(MyRgn);   MyRgn = ::CreateRectRgn(300,300,400,400);
   ::SelectClipRgn(Image8->Canvas->Handle,MyRgn);
   ::Ellipse(Image8->Canvas->Handle,290,290,410,410);
   Image8->Invalidate();
   ::SelectClipRgn(Image8->Canvas->Handle,0);
   ::DeleteObject(MyRgn);
}
//---------------------------------------------------------------------------void __fastcall TForm1::Button4Click(TObject *Sender)
{
   Image8->Canvas->FillRect(Image8->Canvas->ClipRect) ;
}
//---------------------------------------------------------------------------

Answer 4

BCB写的画图程序，稍加改造就可变成Delphi的啦！！！！！！！！！

Answer 5

//完整的程序，按鼠标左键开始画，按鼠标右键停止画。
unit Unit1;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;type
  TForm1 = class(TForm)
    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
  private
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form1: TForm1;
  b_Draw:boolean;
  p_Old,p_New:TPoint;
implementation{$R *.dfm}procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
    if (not b_Draw) and (Button=mbleft)then
    begin
        b_Draw:=true;
        form1.Canvas.Pen.Mode:=pmNotXor;
        p_Old.X:=X;
        p_Old.Y:=y;
        p_New.X:=X;
        p_New.Y:=y;
    end;end;procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
    if (b_Draw) and (Button=mbright) then
       b_Draw:=false;end;procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
    if not b_Draw then exit;
    form1.Canvas.MoveTo(p_Old.X,p_Old.Y);
    form1.Canvas.LineTo(p_New.X,p_New.Y);
    p_Old.X:=p_New.X;
    p_Old.Y:=p_New.Y;
    p_New.X:=X;
    p_New.Y:=Y;
end;end.