再学GDI+[59]: 路径

通过路径的辅助类 TGPGraphicsPathIterator , 可以获得更多路径数据和控制能力.

本例效果图:

代码文件:unit Unit1;
interface
uses
　Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
　Dialogs, StdCtrls;
type
　TForm1 = class(TForm)
　　Button1: TButton;
　　Button2: TButton;
　　procedure FormCreate(Sender: TObject);
　　procedure FormDestroy(Sender: TObject);
　　procedure FormPaint(Sender: TObject);
　　procedure Button1Click(Sender: TObject);
　　procedure Button2Click(Sender: TObject);
　end;
var
　Form1: TForm1;
implementation
{$R *.dfm}
uses GDIPOBJ, GDIPAPI;
var
　path: TGPGraphicsPath;
procedure TForm1.FormCreate(Sender: TObject);
var
　pt1, pt2: TPoint;
begin
　Button1.Caption := '查看路径基本数据';
　Button2.Caption := '重绘路径中的子路径';
　pt1 := Point(30, 20);
　pt2 := Point(150, 120);
　{建立路径, 并添加四个子图形}
　path := TGPGraphicsPath.Create;
　path.StartFigure;
　path.AddRectangle(MakeRect(Rect(pt1, pt2)));
　path.CloseFigure;
　path.StartFigure;
　path.AddEllipse(MakeRect(Rect(pt1, pt2)));
　path.CloseFigure;
　path.StartFigure;
　path.AddLine(pt1.X, pt1.Y, pt2.X, pt2.Y);
　path.CloseFigure;
　path.StartFigure;
　path.AddLine(pt1.X, pt2.Y, pt2.X, pt1.Y);
　path.CloseFigure;
end;
procedure TForm1.FormDestroy(Sender: TObject);
begin
　path.Free;
end;
procedure TForm1.FormPaint(Sender: TObject);
var
　g: TGPGraphics;
　p: TGPPen;
begin
　g := TGPGraphics.Create(Canvas.Handle);
　p := TGPPen.Create(aclSilver, 2);
　g.DrawPath(p, path);
　p.Free;
　g.Free;
end;
procedure TForm1.Button1Click(Sender: TObject);
var
　PathIterator: TGPGraphicsPathIterator;
　str: string;
begin
　PathIterator := TGPGraphicsPathIterator.Create(path);
　str := str + Format('路径中的总点数: %d', [PathIterator.GetCount]);
　str := str + Format(sLineBreak + '路径中的子路径数: %d', [PathIterator.GetSubpathCount]);
　str := str + Format(sLineBreak + '路径中是否包含曲线: %s', [BoolToStr (PathIterator.HasCurve, True)]);
　ShowMessage(str);
　PathIterator.Free;
end;
procedure TForm1.Button2Click(Sender: TObject);
const
　ColorArr: array[0..3] of TGPColor = (aclRed, aclGreen, aclBlue, aclYellow);
var
　PathIterator: TGPGraphicsPathIterator;
　PathSection: TGPGraphicsPath;
　bool: LongBool;
　g: TGPGraphics;
　p: TGPPen;
　i: Integer;
begin
　g := TGPGraphics.Create(Canvas.Handle);
　p := TGPPen.Create(aclRed, 2);
　PathIterator := TGPGraphicsPathIterator.Create(path);
　PathIterator.Rewind; {到路径起始点}
　for i := 0 to PathIterator.GetSubpathCount - 1 do
　begin
　　PathSection := TGPGraphicsPath.Create;
　　PathIterator.NextSubpath(PathSection, bool);
　　p.SetColor(ColorArr[i]);
　　g.DrawPath(p, PathSection);
　　PathSection.Free;
　end;
　PathIterator.Free;
　p.Free;
　g.Free;
end;
end.