GDI+ 批次繪製矩形群組：DrawRectangles 高效能繪製

DrawRectangles 以單次調用繪製多個矩形，比循環調用 DrawRectangle 具有顯著效能優勢 (減少 Managed/Unmanaged 邊界切換開銷)。適合繪製網格、條碼、像素圖、粒子系統等大量矩形場景。

參數說明

g.DrawRectangles(p, PGPRect(@RectArr), Length(RectArr));

• RectArr：TGPRect 靜態/動態陣列
• 單次調用提交所有矩形給 GDI+ 驅動程式

程式碼實作

表單縮放時自動計算 32 個同心縮放矩形，形成隧道視覺效果：

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    procedure FormPaint(Sender: TObject);
    procedure FormResize(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}
uses GDIPOBJ, GDIPAPI;

var
  RectArr: array[0..31] of TGPRect;

procedure TForm1.FormResize(Sender: TObject);
var
  wi, hi: Integer;
  i: Integer;
  Rect: TGPRect;
begin
  Rect.X := 0;
  Rect.Y := 0;
  Rect.Width := ClientWidth;
  Rect.Height := ClientHeight;
  wi := Rect.Width div Length(RectArr);
  hi := Rect.Height div Length(RectArr);
  for i := 0 to Length(RectArr) - 1 do
  begin
    Inc(Rect.X, wi);
    Inc(Rect.Y, hi);
    Dec(Rect.Width, wi * 2);
    Dec(Rect.Height, hi * 2);
    RectArr[i] := Rect;
  end;
  Repaint;
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  g: TGPGraphics;
  p: TGPPen;
begin
  g := TGPGraphics.Create(Canvas.Handle);
  p := TGPPen.Create(aclRed, 1);
  g.Clear(aclWhite);
  g.DrawRectangles(p, PGPRect(@RectArr), Length(RectArr));
  g.Free;
  p.Free;
end;

end.

表單設計 (DFM)

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 188
  ClientWidth = 264
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  Position = poDesktopCenter
  OnPaint = FormPaint
  OnResize = FormResize
  PixelsPerInch = 96
  TextHeight = 13
end

執行效果

效能對比

同理，DrawLines、DrawEllipses、FillRectangles 等批次方法皆具備類似優勢。