再学 GDI+[57]: 路径 - Widen

GDI+ Widen 方法详解

最新推荐文章于 2016-07-16 13:25:22 发布

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最新推荐文章于 2016-07-16 13:25:22 发布

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原文链接：https://my.oschina.net/hermer/blog/320228

本文详细介绍了GDI+中的Widen方法，该方法能够将路径中的线条根据指定画笔的宽度和样式转换为一个区域。文章通过一个具体实例展示了如何使用此方法，并提供了完整的代码实现。

为什么80%的码农都做不了架构师？>>>

路径的 Widen 方法可以把路径中的线, 根据指定画笔的宽度与样式, 转换为一个范围(有点类似区域); 但转换后再描绘路径就只能使用 FillPath 而不是 DrawPath 了. 本例没有测试它的两个默认参数, 因为前面已多次提到了.

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)
    CheckBox1: TCheckBox;
    CheckBox2: TCheckBox;
    procedure FormCreate(Sender: TObject);
    procedure FormPaint(Sender: TObject);
    procedure CheckBox1Click(Sender: TObject);
    procedure CheckBox2Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses GDIPOBJ, GDIPAPI;

procedure TForm1.FormCreate(Sender: TObject);
begin
  CheckBox1.Caption := '执行 Widen';
  CheckBox2.Caption := '显示路径中所有的点';
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  g: TGPGraphics;
  p: TGPPen;
  b1,b2: TGPBrush;
  path: TGPGraphicsPath;
  pts: array of TGPPoint;
  i: Integer;
begin
  g := TGPGraphics.Create(Canvas.Handle);
  p := TGPPen.Create(aclSlateGray, 20);
  p.SetEndCap(LineCapArrowAnchor);
  b1 := TGPSolidBrush.Create(aclRed);
  b2 := TGPHatchBrush.Create(HatchStyleDiagonalCross, aclSilver, aclSlateGray);

  path := TGPGraphicsPath.Create;
  path.AddLine(40, 50, ClientWidth-40, 50);

  if CheckBox1.Checked then
  begin
    path.Widen(p);
    g.FillPath(b2, path);
  end else g.DrawPath(p, path);

  if CheckBox2.Checked then
  begin
    SetLength(pts, path.GetPointCount);
    path.GetPathPoints(PGPPoint(pts), Length(pts));
    TGPSolidBrush(b1).SetColor(aclRed);
    for i := 0 to Length(pts) - 1 do
      g.FillRectangle(b1, pts[i].X-3, pts[i].Y-3, 6, 6);
  end;

  path.Free;
  b1.Free;
  b2.Free;
  p.Free;
  g.Free;
end;

procedure TForm1.CheckBox1Click(Sender: TObject);
begin
  Repaint;
end;

procedure TForm1.CheckBox2Click(Sender: TObject);
begin
  Repaint;
end;

end.

窗体文件:

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 136
  ClientWidth = 287
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = False
  Position = poDesktopCenter
  OnCreate = FormCreate
  OnPaint = FormPaint
  PixelsPerInch = 96
  TextHeight = 13
  object CheckBox1: TCheckBox
    Left = 43
    Top = 104
    Width = 97
    Height = 17
    Caption = 'CheckBox1'
    TabOrder = 0
    OnClick = CheckBox1Click
  end
  object CheckBox2: TCheckBox
    Left = 138
    Top = 104
    Width = 125
    Height = 17
    Caption = 'CheckBox2'
    TabOrder = 1
    OnClick = CheckBox2Click
  end
end

转载于:https://my.oschina.net/hermer/blog/320228