用Pen画线和图形(官网翻译)

Graphics 类提供很多的drawing方法，如下表

• DrawLine Methods
• DrawRectangle Methods
• DrawEllipse Methods
• DrawArc Methods
• Graphics::DrawPath
• DrawCurve Methods
• DrawBezier Methods

这些方法都需要一个Pen对象做为第一个参数。

• 用Pen画线和矩形                Using a Pen to Draw Lines and Rectangles
• 设置Pen的宽度和对齐方式     Setting Pen Width and Alignment
• 画带头的线                        Drawing a Line with Line Caps
• 多条线的连接                     Joining Lines
• 画虚线                             Drawing a Custom Dashed Line
• 画带纹理的线                     Drawing a Line Filled with a Texture

用Pen画线和矩形

Pen pen(Color(255, 0, 0, 0));
graphics.DrawLine(&pen, 20, 10, 300, 100);

Pen blackPen(Color(255, 0, 0, 0), 5);
stat = graphics.DrawRectangle(&blackPen, 10, 10, 100, 50);

设置Pen的宽度和对齐方式

已经有Pen对象的时候可以通过Pen::SetWidth方法来设置宽度。

Pen blackPen(Color(255, 0, 0, 0), 1);
Pen greenPen(Color(255, 0, 255, 0), 10);
stat = greenPen.SetAlignment(PenAlignmentCenter);

// Draw the line with the wide green pen.
stat = graphics.DrawLine(&greenPen, 10, 100, 100, 50);

// Draw the same line with the thin black pen.
stat = graphics.DrawLine(&blackPen, 10, 100, 100, 50);

下面两个例子比较SetAlignment取不同值的时候的差别

Pen blackPen(Color(255, 0, 0, 0), 1);
Pen greenPen(Color(255, 0, 255, 0), 10);
stat = greenPen.SetAlignment(PenAlignmentCenter);

// Draw the rectangle with the wide green pen.
stat = graphics.DrawRectangle(&greenPen, 10, 100, 50, 50);

// Draw the same rectangle with the thin black pen.
stat = graphics.DrawRectangle(&blackPen, 10, 100, 50, 50);

stat = greenPen.SetAlignment(PenAlignmentInset);

画带头的线

gdi+包含几种线头，如round,square,diamond,arrowhead.

Graphics graphics(hdc);
Status stat;
Pen pen(Color(255, 0, 0, 255), 8);
stat = pen.SetStartCap(LineCapFlat);
stat = pen.SetEndCap(LineCapSquare);
stat = graphics.DrawLine(&pen, 20, 20, 300, 20);

stat = pen.SetStartCap(LineCapRound);
stat = pen.SetEndCap(LineCapTriangle);
stat = graphics.DrawLine(&pen, 20, 40, 300, 40);

stat = pen.SetStartCap(LineCapNoAnchor);
stat = pen.SetEndCap(LineCapSquareAnchor);
stat = graphics.DrawLine(&pen, 20, 60, 300, 60);

stat = pen.SetStartCap(LineCapRoundAnchor);
stat = pen.SetEndCap(LineCapDiamondAnchor);
stat = graphics.DrawLine(&pen, 20, 80, 300, 80);

stat = pen.SetStartCap(LineCapArrowAnchor);
stat = pen.SetEndCap(LineCapCustom);
stat = graphics.DrawLine(&pen, 20, 100, 300, 100);

多条线的连接

 gdi+支持四种线的连接风格：miter,bevel,round,miter dipped.

Graphics graphics(hdc);
    Status stat;
    GraphicsPath path;
    Pen penJoin(Color(255, 0, 0, 255), 8);

    path.StartFigure();
    path.AddLine(Point(10, 10), Point(50, 10));
    path.AddLine(Point(50, 10), Point(50, 50));

    penJoin.SetLineJoin(LineJoinMiter);
    graphics.DrawPath(&penJoin, &path);
    
    GraphicsPath path2;
    path2.StartFigure();
    path2.AddLine(Point(10, 110), Point(50, 110));
    path2.AddLine(Point(50, 110), Point(50, 150));

    penJoin.SetLineJoin(LineJoinBevel);
    graphics.DrawPath(&penJoin, &path2);
    
    GraphicsPath path3;
    path3.StartFigure();
    path3.AddLine(Point(10, 210), Point(50, 210));
    path3.AddLine(Point(50, 210), Point(50, 250));

    penJoin.SetLineJoin(LineJoinRound);
    graphics.DrawPath(&penJoin, &path3);
    
    GraphicsPath path4;
    path4.StartFigure();
    path4.AddLine(Point(10, 310), Point(50, 310));
    path4.AddLine(Point(50, 310), Point(50, 350));

    penJoin.SetLineJoin(LineJoinMiterClipped);
    graphics.DrawPath(&penJoin, &path4);

画虚线

Graphics graphics(hdc);
Status stat;
REAL dashVals[4] = {
5.0f, // dash length 5
2.0f, // space length 2
15.0f, // dash length 15
4.0f}; // space length 4
Pen blackPen(Color(255, 0, 0, 0), 5);
blackPen.SetDashPattern(dashVals, 4);
stat = graphics.DrawLine(&blackPen, Point(5, 5), Point(405, 5));

画带纹理的线

Image         image(L"Texture1.jpg");
TextureBrush  tBrush(&image);
Pen           texturedPen(&tBrush, 30);

graphics.DrawImage(&image, 0, 0, image.GetWidth(), image.GetHeight());
graphics.DrawEllipse(&texturedPen, 100, 20, 200, 100);