截图代码创建模糊截图

Question

我一直在我的程序中使用图像识别，并一直认为这是我应用程序中实际图像识别代码的一个问题。在深入研究之后，我意识到我用来创建屏幕截图的代码，包括全屏和屏幕的部分矩形，都是在创建模糊图像。图像很模糊，出来的时候像素化了。

我通常不会保存图像，我只是使用内存中的位图来检查图像识别。尽管在以多种格式保存这些屏幕截图后，我可以看到问题所在。

下面是我用来生成截图的代码。第一个函数创建一个完整的屏幕截图，第二个函数根据屏幕上的坐标创建一个屏幕截图。

   Public Shared Function GetScreen() As Bitmap
    Dim screenSize As Size = New Size(My.Computer.Screen.Bounds.Width, My.Computer.Screen.Bounds.Height)
    Dim screenGrab As New Bitmap(My.Computer.Screen.Bounds.Width, My.Computer.Screen.Bounds.Height)
    Using g As Graphics = Graphics.FromImage(screenGrab)
        g.CopyFromScreen(New Point(0, 0), New Point(0, 0), screenSize)
        Return screenGrab
    End Using
End Function

  Public Shared Function 
    GetScreenXY(TopLeft As Point, BottomRight As Point) As Bitmap
    Dim w As Integer = BottomRight.X - TopLeft.X
    Dim h As Integer = BottomRight.Y - TopLeft.Y
    Dim screenGrab As New Bitmap(w, h)   'width and height of the rectangle you want to grab
    Using g As Graphics = Graphics.FromImage(screenGrab)
        g.CopyFromScreen(TopLeft, New Point(0, 0), screenGrab.Size)
        Return screenGrab
    End Using
End Function

我也有一个截图工具在我的应用程序中，我最近添加。它有一个可以调整大小的表单，它可以截取屏幕截图并保存。这些结果也是模糊的。它使用第二个函数。

        Visible = False
        Dim screenShot As Bitmap = ImageFinder.GetScreenXY(New Point(Left, Top), New Point(Right, Bottom))
        Dim sfd As New SaveFileDialog
        sfd.Filter = "Jpeg image (*.jpg)|*.jpg|Bitmap image (*.bmp)|*.bmp| PNG image (*.png)|*.png"
        sfd.Title = "Save image"
        If sfd.ShowDialog() = DialogResult.OK Then
            If sfd.FileName <> String.Empty Then
                'Set to Jpeg by default.
                Dim MyImageFormat As System.Drawing.Imaging.ImageFormat = System.Drawing.Imaging.ImageFormat.Jpeg
                If sfd.FileName.ToString.ToUpper.EndsWith("JPG") Then
                    MyImageFormat = System.Drawing.Imaging.ImageFormat.Jpeg
                ElseIf sfd.FileName.ToString.ToUpper.EndsWith("BMP") Then
                    MyImageFormat = System.Drawing.Imaging.ImageFormat.Bmp
                ElseIf sfd.FileName.ToString.ToUpper.EndsWith("PNG") Then
                    MyImageFormat = System.Drawing.Imaging.ImageFormat.Png
                End If
                screenShot.Save(sfd.FileName, MyImageFormat)

Answer 1

这是我的截图方法，拍得很好，我想和大家分享一下。

    'Declare my constants here for screenshots'
Private Declare Sub keybd_event Lib "user32" (ByVal bVk As Byte, ByVal bScan As Byte, ByVal dwFlags As Integer, ByVal dwExtraInfo As Integer)
Private Const VK_SNAPSHOT As Short = &H2CS

'Create my function to take the picture of the screen'
Public Function SaveScreen(ByVal theFile As String) As Boolean
    Try
        Dim data As IDataObject
        data = Clipboard.GetDataObject()
        Dim bmap As Bitmap
        If data.GetDataPresent(GetType(System.Drawing.Bitmap)) Then
            bmap = CType(data.GetData(GetType(System.Drawing.Bitmap)), Bitmap)
            Me.picScreen.Image = bmap
            Me.picScreen.Image.Save(theFile, Imaging.ImageFormat.Jpeg)
        End If
    Catch s As Exception
    End Try
End Function

现在让我们保存这张图片。

    Private Sub btnSavePic_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSavePic.Click
    Try

            Call keybd_event(System.Windows.Forms.Keys.Snapshot, 0, 0, 0)
            System.Threading.Thread.Sleep(200) ' To have time to catch the clipboard
            SaveScreen("YOURFILELOCATION" & Format(Now, "MM-dd-yyyy ") & " " & Format(TimeOfDay, "hhmmss") & ".bmp")

    Catch w As Exception
    End Try
End Sub

试一试，当我不在的时候，我用这个向我报告我的屏幕……