再学 GDI+[66]: 路径画刷(6) SetInterpolationColors、GetRectangle

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;

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

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses GDIPOBJ, GDIPAPI;

procedure TForm1.FormPaint(Sender: TObject);
var
  g : TGPGraphics;
  path: TGPGraphicsPath;
  pb: TGPPathGradientBrush;
  rt: TGPRect;
const
  pts: array[0..2] of TGPPoint = ((X:90; Y:10), (X:10; Y:160), (X:160; Y:160));
  colors: array[0..2] of TGPColor = (aclGreen, aclAqua, aclBlue);
  pos: array[0..2] of Single = (0.0, 0.25, 1.0); {颜色位置需要 >=0、<=1, 是百分比}
begin
  {三角}
  g := TGPGraphics.Create(Canvas.Handle);
  path := TGPGraphicsPath.Create;
  path.AddPolygon(PGPPoint(@pts), Length(pts));
  pb:= TGPPathGradientBrush.Create(path);
  pb.SetInterpolationColors(@colors, @pos, Length(colors)); {SetInterpolationColors}
  g.FillPath(pb, path);

  {矩形}
  pb.GetRectangle(rt); {GetRectangle}
  path.Reset;
  path.AddRectangle(rt);
  pb.Free;
  pb:= TGPPathGradientBrush.Create(path);
  pb.SetInterpolationColors(@colors, @pos, Length(colors));
  g.TranslateTransform(160, 0);
  g.FillPath(pb, path);

  {椭圆}
  path.Reset;
  path.AddEllipse(rt);
  pb.Free;
  pb:= TGPPathGradientBrush.Create(path);
  pb.SetInterpolationColors(@colors, @pos, Length(colors));
  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 = 164
  ClientWidth = 491
  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