Delphi 的绘图功能[11] TPen 类(上)

//TPen 的主要属性有四: Color、Width、Style、Mode

{Color: 颜色}

{Width: 宽度; 默认是 1; 如果赋予 <= 0 的值, 会使用默认值}

{Style: 样式; Delphi 定义了笔样式枚举 TPenStyle, 包含以下样式:}
psSolid       = 0; {实线}
psDash        = 1; {段线; 要求笔宽<=1}
psDot         = 2; {点线; 要求笔宽<=1}
psDashDot     = 3; {线、点; 要求笔宽<=1}
psDashDotDot  = 4; {线、点、点; 要求笔宽<=1}
psClear       = 5; {不可见}
psInsideFrame = 6; {实线; 但笔宽是向里扩展}
psUserStyle   = 7; {自定义, Delphi.Net 支持}
psAlternate   = 8; {交替, Delphi.Net 支持}


//下面的例子依次展示了各种样式:
var
  i,x,y,n: Integer;
begin
  x := 10;
  y := 15;
  n := ClientWidth - 2*x;
  Canvas.Pen.Color := clRed;
  for i := 0 to 8 do
  begin
    Canvas.Pen.Style := TPenStyle(i);
    Canvas.MoveTo(x, y);
    Canvas.LineTo(x + n, y);
    y := y + 15;
  end;
end;


//效果图:

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{Mode: 画笔与背景的颜色混合模式; Delphi 定义了模式枚举 TPenMode, 包含以下模式:}
pmBlack       {总是黑色}
pmWhite       {总是白色}
pmNop         {画笔无效}
pmNot         {背景色取反}
pmCopy        {画笔设置的颜色}
pmNotCopy     {画笔颜色取反}
pmMergePenNot {画笔颜色与背景颜色的反色的组合}
pmMaskPenNot  {画笔颜色与背景公共色的反色的组合}
pmMergeNotPen {画笔颜色取反后与背景颜色的组合}
pmMaskNotPen  {画笔的反色与背景的公共色的组合}
pmMerge       {画笔颜色与背景颜色的组合}
pmNotMerge    {pmMerge 的反色}
pmMask        {画笔与背景公共颜色的组合}
pmNotMask     {pmMask 的反色}
pmXor         {画笔颜色与背景颜色的 Xor 组合}
pmNotXor      {pmXor 的反色}


//颜色模式测试程序:
var
  i,x,y,w,n: Integer;
begin
  {先画竖的颜色背景}
  x := 0;
  y := 0;
  w := ClientWidth div 18;
  for i := 0 to 18 do
  begin
    Canvas.Brush.Color := PaletteIndex(i);
    Canvas.FillRect(Rect(x, y, x+w, ClientHeight));
    x := x + w;
  end;

  {再按不同模式依次画 16 条红色的横线}
  x := 0;
  y := 20;
  n := ClientWidth;
  Canvas.Pen.Width := 4;
  Canvas.Pen.Color := clRed;
  for i := 0 to 15 do
  begin
    Canvas.Pen.Mode := TPenMode(i);
    Canvas.MoveTo(x, y);
    Canvas.LineTo(x + n, y);
    y := y + 20;
  end;
end;


//效果图:

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