实例说明

在本实例中，我们将介绍使用最基本的绘图方法。在"绘图"菜单中可以选择画各种图形；在"选项"菜单中可以选择粗细、颜色等各种选项。程序运行结果如图63-1所示。

图63-1 运行结果

技术要点

l 矢量图形和位图图形的概念

l 绘制各种基本图形

实现过程

■ 新建项目

打开Visual Studio.NET，选择"新建项目"，在项目类型窗口中选择"Visual Basic项目"，在模板窗口中，选择"Windows应用程序"，在名称域中输入"DrawPic"，然后选择保存路径。单击"确认"。

■ 制作菜单

从工具箱中向窗体上添加一个MainMenu控件，并新建菜单项"文件"、"绘图"、"选项"三个主菜单。在文件菜单下有"打开"，"保存"等子菜单；在"绘图"菜单下面有"直线"，"椭圆"，"矩形"，"圆"，"圆弧"等子菜单。

■ 添加代码

Dim DrawMode As Short

Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)

Dim gf As Graphics = e.Graphics

Dim newpen As New Pen(Color.Black,2)

Select Case DrawMode

Case 1

'画线

newpen.Color = Color.Cornsilk

gf.DrawLine(newpen,50,200,200)

Case 2

'画矩形

newpen.Color = Color.LawnGreen

gf.DrawRectangle(newpen,10,20,170,180)

Case 3

'画椭圆

newpen.Color = Color.Olive

gf.DrawEllipse(newpen,180)

Case 4

'画圆

newpen.Color = Color.PeachPuff

gf.DrawEllipse(newpen,150,150)

Case 5

'画圆弧

newpen.Color = Color.Maroon

gf.DrawArc(newpen,300)

End Select

End Sub

Private Sub mnuDrawLine_Click(ByVal sender As Object,ByVal e As System.EventArgs) Handles mnuDrawLine.Click

DrawMode = 1

End Sub

Private Sub mnuDrawRect_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles mnuDrawRect.Click

DrawMode = 2

End Sub

Private Sub mnuDrawEllip_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles mnuDrawEllip.Click

DrawMode = 3

End Sub

Private Sub mnuDrawCircle_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles mnuDrawCircle.Click

DrawMode = 4

End Sub

Private Sub mnuDrawArc_Click(ByVal sender As System.Object,ByVal e As System.EventArgs) Handles mnuDrawArc.Click

DrawMode = 5

End Sub

■ 运行程序

单击菜单"调试|启动"或单击 图标运行程序。

小结

通过对本实例的学习，读者应该掌握了基本的画图原理和方法。对画点、线、矩形等各种形状的图形应该熟知于心。我们将在以后的实例中使用到这些方法。