vb.net picturebox中的内容保存到文件

场景：

在picturebox中写一串字符或draw一个图像，并保存到文件。

示例代码用于解决vb.net 打印条形码code39、code128A、code128C、code128Auto（picturebox和打印机）封装类_vb.net打印标签_WormJan的博客-CSDN博客这篇文章中打印的条码无法保存为文件的问题。

这里以那篇文章里的 code128Mix_Click  方法为例

Dim x As Int16 = 40
Dim y As Int16 = 88
Const lineWidth = 1
If ComboBox1.Text.Trim = "" Then
    MsgBox("选择条码")
    Exit Sub
End If
'以下三行为添加的代码
Dim bmp = New Bitmap(PictureBox1.Width, PictureBox1.Height)
Dim g = Graphics.FromImage(bmp)
g.Clear(Color.White)
'以上三行为添加的代码
Dim final As String = clsBarcode.get_code_128Auto(ComboBox1.Text)
For i = 0 To final.Length - 1
    If (final.Substring(i, 1) = "b") Then
        '下面这一行代码，有修改。以前是pic.creategraphics.fillrectangle
        g.FillRectangle(New SolidBrush(Color.Black), New Rectangle(x, y, lineWidth, 50))
    End If
    x += 1
Next
x = 40 + 2
Dim space As Int16 = final.Length / ComboBox1.Text.Length
 
 
For i = 0 To ComboBox1.Text.Length - 1
'下面这一行代码，有修改。以前是pic.creategraphics.DrawString
    g.DrawString(ComboBox1.Text.Substring(i, 1), New Font("Arial", 6), New SolidBrush(Color.Black), x + i * space, y + 50)
Next i
'以下4行为新添加的代码。
 
'把我们画在位图上的图像赋值给pic的image
PictureBox1.Image = bmp
'保存文件
Try
    Dim fs = New System.IO.FileStream("d:\mycode.jpg", IO.FileMode.Create)
    PictureBox1.Image.Save(fs, Imaging.ImageFormat.Jpeg)
    fs.Close()
Catch ex As Exception
    Debug.Print(ex.Message)
End Try

如果单纯写句话到picturebox，然后保存呢。代码如下：

Dim bmp = New Bitmap(PictureBox1.Width, PictureBox1.Height)
 
Dim g = Graphics.FromImage(bmp)
g.Clear(Color.White)
'下面这行是要写到pic中的文本
g.DrawString("I am WormJan", New Font("Arial", 14), Brushes.DarkRed, 0, 0)
PictureBox1.Image = bmp '指定图像为我们创建的bitmap
Try
    Dim fs = New System.IO.FileStream("d:\savefrompicbox.jpg", IO.FileMode.Create)
    PictureBox1.Image.Save(fs, Imaging.ImageFormat.Jpeg)
    fs.Close()
Catch ex As Exception
    Debug.Print(ex.Message)
End Try