在VB编程中，可以使用多种方法来将图片缩小一半。以下是几种常见的方法：
方法一：使用PictureBox控件的Stretch属性
1. 将PictureBox控件的Stretch属性设置为True。
2. 通过调整PictureBox控件的宽度和高度来控制图片的大小。
示例代码：
```vb
Private Sub Form_Load（）
Me.AutoRedraw = True
Picture1.AutoRedraw = True
Picture1.Stretch = True
End Sub
Private Sub Picture1_Click（）
' 缩小图片到原来的1/2
Dim newWidth As Integer = Picture1.Width / 2
Dim newHeight As Integer = Picture1.Height / 2
Picture1.Width = newWidth
Picture1.Height = newHeight
End Sub
```
方法二：使用PaintPicture函数
1. 使用PaintPicture函数将图片绘制到目标区域，并调整源图像的宽度和高度来实现缩放。
示例代码：
```vb
Private Sub Form_Load（）
Me.AutoRedraw = True
Picture1.AutoRedraw = True
End Sub
Private Sub Picture1_Click（）
Dim originalWidth As Integer = Picture1.Picture.Width
Dim originalHeight As Integer = Picture1.Picture.Height
Dim newWidth As Integer = originalWidth / 2
Dim newHeight As Integer = originalHeight / 2
Dim destX As Integer = 0
Dim destY As Integer = 0
Dim scrX As Integer = 0
Dim scrY As Integer = 0
Dim scrWidth As Integer = originalWidth
Dim scrHeight As Integer = originalHeight
PaintPicture（Picture1.Picture, destX, destY, newWidth, newHeight, scrX, scrY, scrWidth, scrHeight）
End Sub
```
方法三：使用Image控件的ScaleWidth和ScaleHeight属性
1. 将Image控件加载图片。
2. 设置Image控件的ScaleWidth和ScaleHeight属性来调整图片的大小。
示例代码：
```vb
Private Sub Form_Load（）
Dim img As Image = LoadPicture（"path_to_your_image.jpg"）
Image1.Image = img
Image1.ScaleWidth = img.Width / 2
Image1.ScaleHeight = img.Height / 2
End Sub
```
方法四：使用Graphics对象
1. 创建一个Graphics对象，并使用DrawImage方法将图片绘制到目标区域，同时调整源图像的宽度和高度来实现缩放。
示例代码：
```vb
Private Sub Form_Load（）
Dim img As Image = Image.FromFile（"path_to_your_image.jpg"）
Dim grfx As Graphics = Me.CreateGraphics
Dim newWidth As Integer = img.Width / 2
Dim newHeight As Integer = img.Height / 2
Dim destX As Integer = 0
Dim destY As Integer = 0
Dim scrX As Integer = 0
Dim scrY As Integer = 0
Dim scrWidth As Integer = img.Width
Dim scrHeight As Integer = img.Height
grfx.DrawImage（img, destX, destY, newWidth, newHeight, scrX, scrY, scrWidth, scrHeight）
End Sub
```
总结
以上方法都可以实现将图片缩小一半的效果。选择哪种方法取决于你的具体需求和编程环境。如果需要更复杂的缩放效果或处理，建议使用Graphics对象和DrawImage方法。如果只是简单的缩放，使用PictureBox的Stretch属性或Image控件的ScaleWidth和ScaleHeight属性会更加方便。