VB.NET WinForm中保存PictureBox缩放后无滚动条的图像

问题出在设置滚动条不可见后，控件还没来得及重绘就执行了DrawToBitmap，导致滚动条痕迹依然被捕获。另外你的原代码逻辑也存在可优化的地方，给你两种可行的解决办法：

方法一：强制Panel重绘后再捕获 #

在隐藏滚动条后调用Refresh()，让Panel立即完成重绘再执行图像捕获：

Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
    SaveFileDialog1.Filter = "Image Files|*.jpg; *.png; *.bmp"
    ' 隐藏滚动条并强制Panel立即重绘
    Panel3.HorizontalScroll.Visible = False
    Panel3.VerticalScroll.Visible = False
    Panel3.Refresh()
    
    If SaveFileDialog1.ShowDialog = DialogResult.OK Then
        ' 创建与Panel客户区（不含滚动条区域）尺寸一致的Bitmap
        Dim bmp As New Bitmap(Panel3.ClientSize.Width, Panel3.ClientSize.Height, picUser.Image.PixelFormat)
        ' 捕获Panel的客户区内容
        Panel3.DrawToBitmap(bmp, New Rectangle(Point.Empty, Panel3.ClientSize))
        bmp.Save(SaveFileDialog1.FileName)
        
        ' 可选：保存完成后恢复滚动条可见性
        Panel3.HorizontalScroll.Visible = True
        Panel3.VerticalScroll.Visible = True
    End If
End Sub

方法二：直接绘制PictureBox的可见区域（更精准） #

Panel的滚动本质是调整PictureBox的位置，我们可以直接计算PictureBox当前在Panel可视范围内的区域，只绘制这部分图像，完全绕开滚动条问题：

Private Sub Button3_Click(sender As Object, e As EventArgs) Handles Button3.Click
    SaveFileDialog1.Filter = "Image Files|*.jpg; *.png; *.bmp"
    
    If SaveFileDialog1.ShowDialog = DialogResult.OK Then
        ' 计算PictureBox与Panel可视区域的交集
        Dim visibleRect As Rectangle = Rectangle.Intersect(picUser.Bounds, Panel3.ClientRectangle)
        ' 转换为PictureBox自身的坐标偏移
        Dim srcRect As New Rectangle(visibleRect.X - picUser.Left, visibleRect.Y - picUser.Top, visibleRect.Width, visibleRect.Height)
        
        ' 创建对应尺寸的Bitmap
        Dim bmp As New Bitmap(visibleRect.Width, visibleRect.Height, picUser.Image.PixelFormat)
        Using g As Graphics = Graphics.FromImage(bmp)
            ' 绘制PictureBox的可见区域到Bitmap
            g.DrawImage(picUser.Image, New Rectangle(Point.Empty, visibleRect.Size), srcRect, GraphicsUnit.Pixel)
        End Using
        
        bmp.Save(SaveFileDialog1.FileName)
    End If
End Sub

方法二更推荐，它直接操作图像本身，不依赖Panel的绘制状态，完全避免滚动条干扰，还能精准捕获当前显示的图像区域。

内容的提问来源于stack exchange，提问作者Humble J.