再学 GDI+[83]: TGPImage(3) - 平行四边形变换

本例效果图:

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代码文件:

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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;

  pts: array[0..2] of TGPPoint;

  flag: Integer = -1;



procedure TForm1.FormCreate(Sender: TObject);

var

  w,h: Integer;

begin

  img := TGPImage.Create('C:\temp\test.jpg');

  w := img.GetWidth;

  h := img.GetHeight;



  pts[0] := MakePoint((ClientWidth - w) div 2 + w, (ClientHeight - h) div 2);

  pts[1] := MakePoint((ClientWidth - w) div 2, (ClientHeight - h) div 2);

  pts[2] := MakePoint((ClientWidth - w) div 2 + w, (ClientHeight - h) div 2 + h);



  DoubleBuffered := True;

end;



procedure TForm1.FormDestroy(Sender: TObject);

begin

  img.Free;

end;



procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;

  Shift: TShiftState; X, Y: Integer);

var

  i: Integer;

begin

  for i := 0 to Length(pts) do

    if PtInRect(Bounds(pts[i].X-3, pts[i].Y-3, 6, 6), Point(X, Y)) then

    begin

      flag := i;

      Exit;

    end;

end;



procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,

  Y: Integer);

begin

  if flag = -1 then Exit;

  pts[flag] := MakePoint(X, Y);

  Repaint;

end;



procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;

  Shift: TShiftState; X, Y: Integer);

begin

  flag := -1;

end;



procedure TForm1.FormPaint(Sender: TObject);

var

  g: TGPGraphics;

  p: TGPPen;

  i: Integer;

begin

  g := TGPGraphics.Create(Self.Canvas.Handle);

  p := TGPPen.Create(aclRed);



  {第一点: 右上角; 第二点: 左上角; 第三点: 右下角; 第四点将根据平行四边形计算; 只能是三个点.}

  g.DrawImage(img, PGPPoint(@pts), Length(pts));



  for i := 0 to Length(pts)-1 do g.DrawRectangle(p, pts[i].X-3, pts[i].Y-3, 6, 6);



  p.Free;

  g.Free;

end;



end.


 
   

窗体文件:

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object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 206

  ClientWidth = 307

  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