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  • 再学 GDI+[86]: TGPImage(6) 拖动图像

    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 FormPaint(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;
      flag: Boolean;
      x1,y1: Integer;
    
    procedure TForm1.FormCreate(Sender: TObject);
    const
      ImgPath = 'c:\temp\test.png';
    var
      w,h: Integer;
    begin
      if not FileExists(ImgPath) then Exit;
    
      img := TGPImage.Create(ImgPath);
      w := img.GetWidth;
      h := img.GetHeight;
    
      rt.Left := (ClientWidth - w) div 2;
      rt.Top := (ClientHeight - h) div 2;
      rt.Right := rt.Left + w;
      rt.Bottom := rt.Top + h;
    
      DoubleBuffered := True;
    end;
    
    procedure TForm1.FormDestroy(Sender: TObject);
    begin
      img.Free;
    end;
    
    procedure TForm1.FormPaint(Sender: TObject);
    var
      g: TGPGraphics;
    begin
      g := TGPGraphics.Create(Canvas.Handle);
      g.DrawImage(img, MakeRect(rt.Left, rt.Top, img.GetWidth, img.GetHeight));
      g.Free;
    end;
    
    procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    begin
      if PtInRect(rt, Point(X,Y)) then
      begin
        x1 := X;
        y1 := Y;
        flag := True;
      end;
    end;
    
    procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    begin
      if not flag then Exit;
      OffsetRect(rt, X-x1, Y-y1);
      x1 := X;
      y1 := Y;
      Repaint;
    end;
    
    procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    begin
      flag := False;
    end;
    
    end.
    
    窗体文件:
    object Form1: TForm1
      Left = 0
      Top = 0
      Caption = 'Form1'
      ClientHeight = 190
      ClientWidth = 317
      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
    
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  • 原文地址:https://www.cnblogs.com/del/p/1234066.html
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