Delphi 的绘图功能- TPen类

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

{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;

//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:

{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

//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;