再學 GDI+[69]: 路徑畫刷(9) - SetInterpolationColors 與 SetSurroundColors 的區別

本例效果圖:

　　代碼文件:unit Unit1;
interface
uses
　Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
　Dialogs, ComCtrls, StdCtrls, ExtCtrls;
type
　TForm1 = class(TForm)
　　procedure FormPaint(Sender: TObject);
　end;
var
　Form1: TForm1;
implementation
{$R *.dfm}
uses GDIPOBJ, GDIPAPI;
procedure TForm1.FormPaint(Sender: TObject);
const
　colors: array[0..3] of TGPColor = (aclRed, aclYellow, aclGreen, aclBlue);
　pos: array[0..3] of Single = (0.0, 0.2, 0.6, 1.0); {好像兩端數據必須要是 0 和 1}
var
　g: TGPGraphics;
　path: TGPGraphicsPath;
　pb: TGPPathGradIEntBrush;
　num: Integer;
　pts: array of TGPPoint;
begin
　g := TGPGraphics.Create(Canvas.Handle);
　path := TGPGraphicsPath.Create;
　{建立橢圓路徑, 並根據路徑建立路徑畫刷, 再用 SetInterpolationColors 設置顏色}
　path.AddEllipse(MakeRect(10,10,150,150));
　pb := TGPPathGradIEntBrush.Create(path);
　pb.SetInterpolationColors(@colors, @pos, Length(pos));
　g.FillPath(pb, path);
　{根據橢圓路徑建立路徑畫刷, 再用 SetSurroundColors 設置顏色}
　pb.Free;
　pb := TGPPathGradIEntBrush.Create(path);
　num := Length(pos);
　pb.SetSurroundColors(@colors, num);
　g.TranslateTransform(160, 0);
　g.FillPath(pb, path);
　{根據從橢圓路徑中提取出的點數組建立路徑畫刷, 再用 SetSurroundColors 設置顏色}
　SetLength(pts, path.GetPointCount);
　path.GetPathPoints(PGPPoint(pts), Length(pts));
　pb.Free;
　pb := TGPPathGradIEntBrush.Create(PGPPoint(pts), Length(pts));
　pb.SetCenterColor(aclWhite); {此時中心會默認黑色, 我想要白色的}
　num := Length(colors);
　pb.SetSurroundColors(@colors, num);
　g.TranslateTransform(160, 0);
　g.FillPath(pb, path);
　{根據從橢圓路徑中提取出的點數組建立路徑畫刷, 再用 SetInterpolationColors 設置顏色}
//　SetLength(pts, path.GetPointCount);
//　path.GetPathPoints(PGPPoint(pts), Length(pts));
　pb.Free;
　pb := TGPPathGradIEntBrush.Create(PGPPoint(pts), Length(pts));
//　pb.SetCenterColor(aclWhite); {這裡不需要中心色}
　num := Length(colors);
　pb.SetInterpolationColors(@colors, @pos, Length(pos));
　g.TranslateTransform(160, 0);
　g.FillPath(pb, path);
　pb.Free;
　path.Free;
　g.Free;
end;
end.窗體文件:object Form1: TForm1
　Left = 0
　Top = 0
　Caption = 'Form1'
　ClIEntHeight = 169
　ClIEntWidth = 649
　Color = clBtnFace
　Font.Charset = DEFAULT_CHARSET
　Font.Color = clWindowText
　Font.Height = -11
　Font.Name = 'Tahoma'
　Font.Style = []
　OldCreateOrder = False
　Position = poDesktopCenter
　OnPaint = FormPaint
　PixelsPerInch = 96
　TextHeight = 13
end