Setting Pen Width and Alignment

When you create a Pen object, you can supply the pen width as one of the arguments to the constructor. You can also change the pen width by using the Pen::SetWidth method.

A theoretical line has a width of zero. When you draw a line, the pixels are centered on the theoretical line. The following example draws a specified line twice: once with a black pen of width 1 and once with a green pen of width 10.


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);

The following illustration shows the output of the preceding code. The green pixels and the black pixels are centered on the theoretical line.

Illustration showing a thin, diagonal, black line surrounded by a wide, green line

The following example draws a specified rectangle twice: once with a black pen of width 1 and once with a green pen of width 10. The code passes the value PenAlignmentCenter (an element of the PenAlignment enumeration) to the Pen::SetAlignment method to specify that the pixels drawn with the green pen are centered on the boundary of the rectangle.


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);

The following illustration shows the output of the preceding code. The green pixels are centered on the theoretical rectangle, which is represented by the black pixels.

Illustration showing a thin black line in the shape of a rectangle, surrounded by a wider green line

You can change the green pen's alignment by modifying the third statement in the preceding example as follows:


stat = greenPen.SetAlignment(PenAlignmentInset);

Now the pixels in the wide green line appear on the inside of the rectangle as shown in the following illustration.

Illustration showing a thin black line in the shape of a rectange, enclosing a wide green line of the same shape

 

 

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Build date: 3/6/2012

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