Question

我正在使用VB.NET尝试捕获屏幕的一部分，所以我在几个地方找到了这个代码来捕获整个屏幕：

Dim screenSize = SystemInformation.PrimaryMonitorSize
Dim bitmap = New Bitmap(screenSize.Width, screenSize.Height)
Using g As Graphics = Graphics.FromImage(bitmap)

    g.CopyFromScreen(New Point(0, 0), New Point(0, 0), screenSize)

End Using
bitmap.Save("c:\scratch\screenshot.png", System.Drawing.Imaging.ImageFormat.Png)

这没有错误抛出，文件创建成功，但生成的图像完全透明（大小正确） - 我缺少什么？

This question涉及相同的错误，但解决方案是使用Win32 GDI，我想尽可能避免

Answer 1

由于CopyFromScreen方法存在问题，我最终决定使用打印屏幕选项：

'declarations
Private Const VK_SNAPSHOT As Integer = &H2C

<DllImport("user32.dll")>
Public Function keybd_event(ByVal key As Integer, ByVal dummy As Integer, ByVal flags As Integer, ByVal info As IntPtr) As IntPtr
End Function


'Usage
Dim loopCount As Integer = 0

Clipboard.Clear()
keybd_event(VK_SNAPSHOT, 0, 0, IntPtr.Zero)
Application.DoEvents()

Do Until Clipboard.ContainsImage Or (loopCount > 10)
    loopCount += 1
    System.Threading.Thread.Sleep(100)
    Application.DoEvents()
Loop

If Clipboard.ContainsImage Then
    Return Clipboard.GetImage
Else
    Return Nothing
End If

Graphics.CopyFromScreen创建一个空白图像

1 个答案: