再学 GDI+[83]: TGPImage(3) - 平行四边形变换

最新推荐文章于 2017-05-30 00:44:10 发布

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最新推荐文章于 2017-05-30 00:44:10 发布

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本文介绍了一个使用Delphi实现的图形图像处理案例，通过GDIPAPI库实现图片在窗体上的拖拽与变形功能。文章详细展示了如何创建和使用自定义的窗体及事件处理程序来完成图片的加载、显示、拖拽和变形等功能。

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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 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:

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