GdiPlus[29]: IGPPen: 虚线样式

通过画笔的 DashStyle 属性可设置或读取虚线样式.

通过 SetDashPattern 方法或 DashPattern 属性可自定义虚线样式.

通过 DashPattern 属性还可以读出已有样式定义时的数组.

自定义虚线样式样式时, 需要元素数是双数的数组数组, 元素值依次表示实线与空白的长度.

通过 DashOffset 属性可设置虚线偏移.

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系统提供的虚线样式效果:

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自定义的两种样式效果:

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虚线偏移效果:

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测试系统提供的虚线样式:

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uses GdiPlus;

procedure TForm1.FormPaint(Sender: TObject);
var
  Graphics: IGPGraphics;
  Pen: IGPPen;
  Pt1,Pt2: TGPPoint;
  i: Integer;
begin
  Graphics := TGPGraphics.Create(Handle);
  Pt1.Initialize(20, 20);
  Pt2.Initialize(200, 20);

  Pen := TGPPen.Create(TGPColor.Red, 3);

  for i := 0 to 4 do
  begin
    Pen.DashStyle := TGPDashStyle(i);
    Graphics.DrawLine(Pen, Pt1, Pt2);
    Graphics.TranslateTransform(0, Pt1.Y);
  end;
end;

测试自定义样式:

---

uses GdiPlus;

procedure TForm1.FormPaint(Sender: TObject);
const
  DashPatternArr: array[0..1] of Single = (16, 2);
var
  Graphics: IGPGraphics;
  Pen: IGPPen;
  Pt1,Pt2: TGPPoint;
begin
  Pt1.Initialize(20, 20);
  Pt2.Initialize(200, 20);
  Graphics := TGPGraphics.Create(Handle);
  Pen := TGPPen.Create($FF0000FF, 2);

  Pen.SetDashPattern([8, 2, 1, 2]);
  Graphics.DrawLine(Pen, Pt1, Pt2);

  Graphics.TranslateTransform(0, Pt1.Y);
  Pen.SetDashPattern(DashPatternArr);
  Graphics.DrawLine(Pen, Pt1, Pt2);

  Text := IntToStr(Ord(Pen.DashStyle)); //此值应该是 5, 也就是自定义样式 DashStyleCustom
end;

虚线偏移测试:

---

uses GdiPlus;

procedure TForm1.FormPaint(Sender: TObject);
var
  Graphics: IGPGraphics;
  Pen: IGPPen;
  Pt1,Pt2: TGPPoint;
begin
  Graphics := TGPGraphics.Create(Handle);
  Pt1.Initialize(20, 30);
  Pt2.Initialize(200, 30);

  Pen := TGPPen.Create($FFC71585, 4);
  Pen.DashStyle := DashStyleDashDotDot;

  Graphics.DrawLine(Pen, Pt1, Pt2);
  Graphics.TranslateTransform(0, Pt1.Y);

  Pen.DashOffset := Pen.DashPattern[0] + Pen.DashPattern[1];
  Graphics.DrawLine(Pen, Pt1, Pt2);
end;