再学 GDI+[56]: 路径 Warp

通过路径的 Warp 方法可以让路径在一个范围内(四个点决定的范围)变换;

第一个参数可以是 3 个点或 4 个点的数组, 如果是 3 个的数组, 那么第 4 个点将自动跟随一个平行四边形;

第二个参数用来指定点数组的个数, 本例就是通过这个参数控制了点的个数;

第三个参数是一个矩形, 这个矩形应该是路径的外接矩形, 之后的参数都是可选的;

第四个参数也是一个矩阵变换, 因由专门的 例子 , 这里没有尝试;

第五个参数是 TWarpMode(WarpModePerspective, WarpModeBilinear) , 默认前者;

第六个参数可以指定 Flatten 变换, 前面有 例子 , 这里也没有尝试.

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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, ComCtrls, StdCtrls;

type
  TForm1 = class(TForm)
    CheckBox1: TCheckBox;
    procedure FormCreate(Sender: TObject);
    procedure FormPaint(Sender: TObject);
    procedure CheckBox1Click(Sender: TObject);
    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses GDIPOBJ, GDIPAPI;

var
  ptfs: array[0..3] of TGPPointF;
  ptCount: Integer = 4;
  pti: Integer;
  R: TRect;
  flag: Boolean;

procedure TForm1.FormCreate(Sender: TObject);
begin
  CheckBox1.Caption := '只用 3 个点控制';
  R := Rect(20, 20, ClientWidth-20, ClientHeight - 40);
  ptfs[0] := MakePoint(R.Left*1.0, R.Top);
  ptfs[1] := MakePoint(R.Right*1.0, R.Top);
  ptfs[2] := MakePoint(R.Left*1.0, R.Bottom);
  ptfs[3] := MakePoint(R.Right*1.0, R.Bottom);
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  g: TGPGraphics;
  p: TGPPen;
  b: TGPBrush;
  path: TGPGraphicsPath;
  fontFamily: TGPFontFamily;
  StringFormat: TGPStringFormat;
  rectf: TGPRectF;
  i: Integer;
begin
  g := TGPGraphics.Create(Canvas.Handle);
  p := TGPPen.Create(aclRed, 1);
  b := TGPHatchBrush.Create(HatchStyleShingle, aclDarkCyan);

  path := TGPGraphicsPath.Create;
  path.AddEllipse(MakeRect(R));
  fontFamily := TGPFontFamily.Create('Arial Black');

  StringFormat := TGPStringFormat.Create;
  StringFormat.SetAlignment(StringAlignmentCenter);
  StringFormat.SetLineAlignment(StringAlignmentCenter);

  path.GetBounds(rectf);
  path.AddString('Delphi', -1, fontFamily, FontStyleRegular, 48, rectf, StringFormat);

  path.Warp(PGPPointF(@ptfs), Length(ptfs), rectf);
  g.FillPath(b, path);

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

  StringFormat.Free;
  fontFamily.Free;
  path.Free;
  b.Free;
  p.Free;
  g.Free;
end;

procedure TForm1.CheckBox1Click(Sender: TObject);
begin
  ptCount := 4;
  if CheckBox1.Checked then ptCount := 3;
  Repaint;
end;

procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var
  i: Integer;
begin
  for i := 0 to 3 do
    if PtInRect(Bounds(Trunc(ptfs[i].X-3), Trunc(ptfs[i].Y-3), 6, 6), Point(X, Y)) then
    begin
      pti := i;
      flag := True;
      Exit;
    end;
end;

procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
  if flag then
  begin
    ptfs[pti].X := X;
    ptfs[pti].Y := Y;
    Repaint;
  end;
end;

procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  flag := False;
end;

end.

窗体文件:

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object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 220
  ClientWidth = 264
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  Position = poDesktopCenter
  OnCreate = FormCreate
  OnMouseDown = FormMouseDown
  OnMouseMove = FormMouseMove
  OnMouseUp = FormMouseUp
  OnPaint = FormPaint
  PixelsPerInch = 96
  TextHeight = 13
  object CheckBox1: TCheckBox
    Left = 151
    Top = 195
    Width = 129
    Height = 17
    Caption = 'CheckBox1'
    TabOrder = 0
    OnClick = CheckBox1Click
  end
end