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  • WinAPI: OffsetClipRgn、PtVisible

    OffsetClipRgn: 移动剪切区域; PtVisible: 判断点是否在剪切区域中.

    本例效果图:



    代码文件:
    unit Unit1;
    
    interface
    
    uses
      Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
      Dialogs;
    
    type
      TForm1 = class(TForm)
        procedure FormCreate(Sender: TObject);
        procedure FormDestroy(Sender: TObject);
        procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
          Shift: TShiftState; X, Y: Integer);
        procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
        procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
          Shift: TShiftState; X, Y: Integer);
        procedure FormPaint(Sender: TObject);
      end;
    
    var
      Form1: TForm1;
    
    implementation
    
    {$R *.dfm}
    
    var
      bit: TBITMAP;
      f: Boolean;
      x1,y1: Integer;
      cvs: TCanvas;
    
    procedure TForm1.FormCreate(Sender: TObject);
    var
      Rgn: HRGN;
    begin
      bit := TBitmap.Create;
      bit.LoadFromFile('c:\temp\Test.bmp');
      ClientWidth := bit.Width;
      ClientHeight := bit.Height;
    
      cvs := TCanvas.Create;
      cvs.Handle := GetDC(Handle);
    
      Rgn := CreateEllipticRgn(30,30,140,140);
      SelectClipRgn(cvs.Handle, Rgn);
    
      DeleteObject(Rgn);
    end;
    
    procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    begin
      if PtVisible(cvs.Handle, X, Y) then
      begin
        f := True;
        x1 := X;
        y1 := Y;
      end;
    end;
    
    procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    begin
      if not f then Exit;
      OffsetClipRgn(cvs.Handle, X-x1, Y-Y1);
      Repaint;
      x1 := X;
      y1 := Y;
    end;
    
    procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    begin
      f := False;
    end;
    
    procedure TForm1.FormPaint(Sender: TObject);
    begin
      cvs.Draw(0,0,bit);
    end;
    
    procedure TForm1.FormDestroy(Sender: TObject);
    begin
      bit.Free;
      cvs.Free;
    end;
    
    end.
    
    窗体文件:
    object Form1: TForm1
      Left = 402
      Top = 230
      Caption = 'Form1'
      ClientHeight = 206
      ClientWidth = 339
      Color = clBtnFace
      Font.Charset = DEFAULT_CHARSET
      Font.Color = clWindowText
      Font.Height = -11
      Font.Name = 'Tahoma'
      Font.Style = []
      OldCreateOrder = False
      Position = poDesigned
      OnCreate = FormCreate
      OnDestroy = FormDestroy
      OnMouseDown = FormMouseDown
      OnMouseMove = FormMouseMove
      OnMouseUp = FormMouseUp
      OnPaint = FormPaint
      PixelsPerInch = 96
      TextHeight = 13
    end
    
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  • 原文地址:https://www.cnblogs.com/del/p/1210390.html
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