VB.NET加载图片问题

'先建立一个bitmap对象，指向图像文件

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Dim pic As Bitmap = New Bitmap("e:\1.jpg")

'定义一个图片框的graphics对象

Dim g As Graphics = PictureBox1.CreateGraphics()

'在图片框上绘图

g.DrawImage(pic, 0, 0, pic.Width, pic.Height)

'释放bitmap对象

pic.Dispose()

'现在即可对文件进行操作

在vbnet中，我在picturebox里面画线，用滚动条拉动picturebox显示最新画出的图

vb点虐 没有自动重画功能，要在Paint事件中写代码对图形重画。

另外一种情况，如果在Image属性设置了一幅图像，图像能够保持完整性的。所以你可以把图形绘在位图上，把位图绑定到Image属性上。

先绑定一幅位图：

Dim bm as New BitMap(800,600)

PictureBox1.Image=bm

作图时不是对图片框，而是在位图上作图。

dim gr As Grapthics=Graphics.FromImage(bm) '建立位图的绘图设备

接下来就可用gr 的绘图方法作图

作完图，PictureBox1.Refresh 刷新一下。

请问如何用vb的图片框画图？要求是鼠标按下来画矩形、圆之类的图（旁边有单选按钮来选择图形）。

Dim x1 As Single, y1 As Single, s As Integer

Const pi = 3.14159265

Private Sub Form_Load()

Command1.Caption = "圆"

Command2.Caption = "矩形"

Command3.Caption = "三角"

Command4.Caption = "五角"

Command5.Caption = "清"

End Sub

Private Sub Command1_Click()

s = 1

End Sub

Private Sub Command2_Click()

s = 2

End Sub

Private Sub Command3_Click()

s = 3

End Sub

Private Sub Command4_Click()

s = 4

End Sub

Private Sub Command5_Click()

Picture1.Cls

End Sub

Private Sub Picture1_MouseDown(Button As Integer, Shift As Integer, x As Single, y As Single)

If Button = 1 Then x1 = x: y1 = y

End Sub

Private Sub Picture1_MouseMove(Button As Integer, Shift As Integer, x As Single, y As Single)

If Button = 1 Then

Picture1.AutoRedraw = False

Picture1.Refresh

Picture1.PSet (x1, y1)

Select Case s

Case 1

Picture1.Circle (x1, y1), Sqr((x - x1) ^ 2 + (y - y1) ^ 2)

Case 2

Picture1.Line (x1, y1)-(x, y), , B

Case 3

duobianxing x1, y1, x, y, 3, 60

Case 4

duobianxing x1, y1, x, y, 5, 36

End Select

End If

End Sub

Private Sub Picture1_MouseUp(Button As Integer, Shift As Integer, x As Single, y As Single)

If Button = 1 Then

Picture1.AutoRedraw = True

Select Case s

Case 1

Picture1.Circle (x1, y1), Sqr((x - x1) ^ 2 + (y - y1) ^ 2)

Case 2

Picture1.Line (x1, y1)-(x, y), , B

Case 3

duobianxing x1, y1, x, y, 3, 60

Case 4

duobianxing x1, y1, x, y, 5, 36

End Select

End If

End Sub

'duobianxing函数参数：

'zhongxinX-多边形中心的横坐标

'zhongxinY-多边形中心的纵坐标

'dingdianX-多边形一个顶点的横坐标

'dingdianY-多边形一个顶点的纵坐标

'bianhuoxing-正多边形的边数或者星形的星角数，例如biaohuoxing=5,dingjiao=72则为正五边形,若dingjiao=36则为五角星(该函数将正多边形按相邻顶角点间的折点成直线的特殊星形绘制)

'dingjiao-多边形的顶角的角度(角度制°)

Function duobianxing(ByVal zhongxinX As Single, ByVal zhongxinY As Single, ByVal dingdianX As Single, ByVal dingdianY As Single, ByVal bianhuoxing As Integer, ByVal dingjiao As Single)

If bianhuoxing = 0 Then Exit Function

l = Sqr((zhongxinX - dingdianX) ^ 2 + (zhongxinY - dingdianY) ^ 2) '星形中心到顶角距离

t1 = Abs(Tan((dingjiao / 2) * pi / 180)) '星形顶角的1/2求正切

t2 = Abs(Tan((360 / (2 * bianhuoxing)) * pi / 180)) '星形每条边所对应的中心角的1/2求正切

r = l * t2 / (t1 + t2) / Cos((dingjiao / 2) * pi / 180) '星形边长

If zhongxinX = dingdianX Then '求星形中心到顶角这条线的角度j

j = IIf(dingdianY zhongxinY, 90, -90)

Else

j = Atn((zhongxinY - dingdianY) / (dingdianX - zhongxinX)) * 180 / pi

If dingdianX zhongxinX Then

If dingdianY zhongxinY Then

j = j - 180

Else

j = j + 180

End If

End If

End If

j1 = j - dingjiao / 2 '边偏离初始角1

j2 = 360 / bianhuoxing + dingjiao + j - dingjiao / 2 '边偏离初始角2(如果是正多边形j1=j2)

px1 = dingdianX: py1 = dingdianY '指定星形的第一个顶点

For i = 1 To bianhuoxing * 2

If i Mod 2 = 0 Then

px2 = px1 + r * Cos(j2 * pi / 180): py2 = py1 - r * Sin(j2 * pi / 180) '指定星形下一个顶点

j2 = j2 + 360 / bianhuoxing '边偏角+2个边长对应的中心角

Else

px2 = px1 - r * Cos(j1 * pi / 180): py2 = py1 + r * Sin(j1 * pi / 180)

j1 = j1 + 360 / bianhuoxing

End If

Picture1.Line (px1, py1)-(px2, py2) '画线

px1 = px2: py1 = py2

Next

End Function

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