代码文件:
unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs; type TForm1 = class(TForm) procedure FormPaint(Sender: TObject); 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); end; var Form1: TForm1; implementation {$R *.dfm} uses GDIPOBJ, GDIPAPI; var img: TGPImage; rt: TRect; x1,y1: Integer; flag: Boolean; procedure TForm1.FormCreate(Sender: TObject); begin img := TGPImage.Create('C:\temp\test.png'); DoubleBuffered := True; end; procedure TForm1.FormDestroy(Sender: TObject); begin img.Free; end; procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer); begin x1 := X; y1 := Y; flag := True; end; procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer); begin if flag then begin DrawFocusRect(Canvas.Handle, rt); rt := Rect(x1, y1, X, Y); DrawFocusRect(Canvas.Handle, rt); end; end; procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer); begin if flag then begin rt := Rect(x1, y1, X, Y); flag := False; Repaint; end; end; procedure TForm1.FormPaint(Sender: TObject); var g: TGPGraphics; begin g := TGPGraphics.Create(Self.Canvas.Handle); if rt.Right > 0 then g.DrawImage(img, MakeRect(rt)); g.Free; end; end.窗体文件:
object Form1: TForm1 Left = 0 Top = 0 Caption = 'Form1' ClientHeight = 267 ClientWidth = 355 Color = clBtnFace Font.Charset = DEFAULT_CHARSET Font.Color = clWindowText Font.Height = -11 Font.Name = 'Tahoma' Font.Style = [] OldCreateOrder = False Position = poDesktopCenter OnCreate = FormCreate OnDestroy = FormDestroy OnMouseDown = FormMouseDown OnMouseMove = FormMouseMove OnMouseUp = FormMouseUp OnPaint = FormPaint PixelsPerInch = 96 TextHeight = 13 end