通过滚轮改变图片大小

public PostForm()
{
     InitializeComponent();
     this.MouseWheel += PostForm_MouseWheel;
}

void PostForm_MouseWheel(object sender, MouseEventArgs e)
{
     System.Drawing.Size t = pictureBox1.Size;
     t.Width += e.Delta;
     t.Height += e.Delta;
     pictureBox1.Width = t.Width;
     pictureBox1.Height = t.Height;  
}