再学 GDI+[69]: 路径画刷(9) - SetInterpolationColors 与 SetSurroundColors 的区别

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, 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); {好像两端数据必须要是 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;



  {建立椭圆路径, 并根据路径建立路径画刷, 再用 SetInterpolationColors 设置颜色}

  path.AddEllipse(MakeRect(10,10,150,150));

  pb := TGPPathGradientBrush.Create(path);

  pb.SetInterpolationColors(@colors, @pos, Length(pos));

  g.FillPath(pb, path);



  {根据椭圆路径建立路径画刷, 再用 SetSurroundColors 设置颜色}

  pb.Free;

  pb := TGPPathGradientBrush.Create(path);

  num := Length(pos);

  pb.SetSurroundColors(@colors, num);

  g.TranslateTransform(160, 0);

  g.FillPath(pb, path);



  {根据从椭圆路径中提取出的点数组建立路径画刷, 再用 SetSurroundColors 设置颜色}

  SetLength(pts, path.GetPointCount);

  path.GetPathPoints(PGPPoint(pts), Length(pts));

  pb.Free;

  pb := TGPPathGradientBrush.Create(PGPPoint(pts), Length(pts));

  pb.SetCenterColor(aclWhite); {此时中心会默认黑色, 我想要白色的}

  num := Length(colors);

  pb.SetSurroundColors(@colors, num);

  g.TranslateTransform(160, 0);

  g.FillPath(pb, path);



  {根据从椭圆路径中提取出的点数组建立路径画刷, 再用 SetInterpolationColors 设置颜色}

//  SetLength(pts, path.GetPointCount);

//  path.GetPathPoints(PGPPoint(pts), Length(pts));

  pb.Free;

  pb := TGPPathGradientBrush.Create(PGPPoint(pts), Length(pts));

//  pb.SetCenterColor(aclWhite); {这里不需要中心色}

  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.


 
   

窗体文件:

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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