两个 CopyRect

Windows.CopyRect 是系统 API 函数, 功能是复制矩形的参数;
TCanvas.CopyRect 是 TCanvas 类的方法, 功能是复制矩形范围内的图像, 有点像 BitBlt 函数.

---

本例效果图:

---

代码文件:

---

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls;

type
  TForm1 = class(TForm)
    Panel1: TPanel;
    Panel2: TPanel;
    PaintBox1: TPaintBox;
    PaintBox2: TPaintBox;
    Button1: TButton;
    procedure PaintBox1Paint(Sender: TObject);
    procedure PaintBox2Paint(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.PaintBox1Paint(Sender: TObject);
begin
  PaintBox1.Canvas.Brush.Color := clWhite;
  PaintBox1.Canvas.FillRect(PaintBox1.BoundsRect);

  PaintBox1.Canvas.MoveTo(0, 0);
  PaintBox1.Canvas.LineTo(PaintBox1.Width, PaintBox1.Height);

  PaintBox1.Canvas.MoveTo(PaintBox1.Width, 0);
  PaintBox1.Canvas.LineTo(0, PaintBox1.Height);
end;

procedure TForm1.PaintBox2Paint(Sender: TObject);
begin
  PaintBox2.Canvas.Brush.Color := clGreen;
  PaintBox2.Canvas.Ellipse(0, 0, PaintBox2.Width, PaintBox2.Height);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  R1,R2: TRect;
begin
  R2 := PaintBox2.BoundsRect;

  {Windows.CopyRect}
  CopyRect(R1, R2); //相当于: R1 := R2;

  OffsetRect(R1, 10, 10);

  {TCanvas.CopyRect}
  PaintBox1.Canvas.CopyRect(R1, PaintBox2.Canvas, R2);
end;

end.

窗体文件:

---

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 161
  ClientWidth = 319
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  PixelsPerInch = 96
  TextHeight = 13
  object Panel1: TPanel
    Left = 8
    Top = 8
    Width = 169
    Height = 145
    Caption = 'Panel1'
    TabOrder = 0
    object PaintBox1: TPaintBox
      Left = 1
      Top = 1
      Width = 167
      Height = 143
      Align = alClient
      OnPaint = PaintBox1Paint
      ExplicitLeft = 32
      ExplicitTop = 24
      ExplicitWidth = 105
      ExplicitHeight = 105
    end
  end
  object Panel2: TPanel
    Left = 183
    Top = 8
    Width = 130
    Height = 105
    Caption = 'Panel2'
    TabOrder = 1
    object PaintBox2: TPaintBox
      Left = 1
      Top = 1
      Width = 128
      Height = 103
      Align = alClient
      OnPaint = PaintBox2Paint
      ExplicitLeft = 16
      ExplicitTop = 0
      ExplicitWidth = 105
      ExplicitHeight = 105
    end
  end
  object Button1: TButton
    Left = 212
    Top = 128
    Width = 75
    Height = 25
    Caption = 'Button1'
    TabOrder = 2
    OnClick = Button1Click
  end
end