GdiPlus[41]: IGPRegion 区域

// 区域建立:
TGPRegion.Create();   { 参数可以是矩形、路径、HRGN、区域数据, 或无参}
TGPRegion.FromHRGN(); { 从 HRGN 初始化 }

// 区域运算(矩形、路径、或另一个区域):
IGPRegion.Intersect();   { 交集 }
IGPRegion.Union();       { 并集 }
IGPRegion.Exclude();     { 减去 }
IGPRegion.ExclusiveOr(); { 减去交集 }
IGPRegion.Complement();  { 不相交 }

// 其他:
IGPRegion.IsVisible();       { 判断指定的点或矩形是否在区域内 }

IGPRegion.GetData;           { 获取区域数据(IGPBuffer), 其中包含数据指针和数据大小 }
IGPRegion.GetRegionScans();  { 从区域中获取矩形数组, 浮点型 }
IGPRegion.GetRegionScansI(); { 从区域中获取矩形数组, 整型 }

IGPRegion.Translate();       { 偏移 }
IGPRegion.Transform();       { Matrix 变换 }

IGPRegion.MakeInfinite;      { 初始化为无限大 }
IGPRegion.MakeEmpty;         { 初始化为空 }
IGPRegion.IsEmpty();         { 判断区域是否为空 }
IGPRegion.IsInfinite();      { 判断区域是否是无限大 }
IGPRegion.GetBounds();       { 获取边界矩形 }
IGPRegion.GetHRGN();         { 获取 HRGN(Windows 区域的句柄) }
IGPRegion.Clone;             { 复制 }
IGPRegion.Equals();          { 判断是否相同 }

区域的两个重要用途:

1、IGPRegion.IsVisible();

2、IGPGraphics.Clip 或 IGPGraphics.SetClip();

---

IsVisible 测试:

---

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;

type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
    procedure FormPaint(Sender: TObject);
    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses GdiPlus, GdiPlusHelpers;

var Region: IGPRegion;

procedure TForm1.FormCreate(Sender: TObject);
var
  Rect: TGPRect;
  Path: IGPGraphicsPath;
begin
  Rect.Initialize(ClientRect);
  Rect.Inflate(-20, -20);
  Region := TGPRegion.Create(Rect);

  Rect.Inflate(-2, -2);
  Path := TGPGraphicsPath.Create();
  Path.AddEllipse(Rect);

  Region.Exclude(Path);
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  Brush: IGPHatchBrush;
begin
  Brush := TGPHatchBrush.Create(HatchStyleMin, TGPColor.Silver, TGPColor.Red);
  Canvas.ToGPGraphics.FillRegion(Brush, Region);
end;

procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
begin
  Text := 'Form1';
  if Region.IsVisible(X, Y) then Text := '在区域中';
end;

end.

剪切区域测试:

---

uses GdiPlus;

procedure TForm1.FormPaint(Sender: TObject);
const
  Pts: array [0..3] of TGPPoint = (
    (X: 10; Y: 10), (X: 150; Y: 10), (X: 100; Y: 75), (X: 100; Y: 150));
var
  Graphics: IGPGraphics;
  Path: IGPGraphicsPath;
  Region: IGPRegion;
  Pen: IGPPen;
  Font: IGPFont;
  Brush: IGPBrush;
begin
  Graphics := TGPGraphics.Create(Handle);
  Path := TGPGraphicsPath.Create;
  Path.AddPolygon(Pts);
  Region := TGPRegion.Create(Path);
  Pen := TGPPen.Create($FF000000);
  Graphics.DrawPath(Pen, Path);

  Graphics.Clip := Region;
//  Graphics.SetClip(Region); //或者这样
  Font := TGPFont.Create('Arial', 36, [FontStyleBold], UnitPixel);
  Brush := TGPSolidBrush.Create($FFFF0000);
  Graphics.DrawString('A Clipping Region', Font, TGPPointF.Create(15, 25), Brush);
  Graphics.DrawString('A Clipping Region', Font, TGPPointF.Create(15, 68), Brush);
end;