本例效果圖:
代碼文件: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.
窗體文件: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
