Question

我尝试在Microsoft Word中获取图片形状的文本。为此，我使用了Windows 10 windows.media.ocr中包含的OCR库。由于OCREngine需要SoftwareBitmap我还没有合作过，但我尝试了以下方法来实现SoftwareBitmap：

  oWordDocument.Shapes(1).Select() '*** Get shape and copy to clipboard and then to bitmap
  oWordApp.Selection.CopyAsPicture()
  Dim oBitmap As System.Drawing.Bitmap = New System.Drawing.Bitmap(System.Windows.Forms.Clipboard.GetImage())

  Dim oSoftwareBitmap As Windows.Graphics.Imaging.SoftwareBitmap
  Dim oUWPStream As Windows.Storage.Streams.IRandomAccessStream

  Using oNetStream As New System.IO.MemoryStream '*** Get UWP-Stream via .Net-Stream
        oBitmap.Save(oNetStream, System.Drawing.Imaging.ImageFormat.Png)
        oUWPStream = System.IO.WindowsRuntimeStreamExtensions.AsRandomAccessStream(oNetStream)

        '*** in the following line an invalidcast error occurs "Unable to cast object of type 'System.__ComObject' to type 'Windows.Graphics.Imaging.BitmapDecoder'."
        Dim oBitmapDecoder As Windows.Graphics.Imaging.BitmapDecoder = Windows.Graphics.Imaging.BitmapDecoder.CreateAsync(Windows.Graphics.Imaging.BitmapDecoder.PngDecoderId, oUWPStream)
        oSoftwareBitmap = oBitmapDecoder.GetSoftwareBitmapAsync()
  End Using

所以现在代码运行正常，直到我尝试创建BitmapDecoder。从我所看到的，我提供了一个有效的RandomAccessStream，但创建失败，无效。

有人可以请求帮助，甚至提供或指向我创建BitmapDecoder和SoftwareBitmap的代码示例吗？

很抱歉，如果描述复杂或令人困惑 - 英语不是我的母语

问题解决了：实际上解决方案非常简单。我第一次没理解它。我从一开始就知道我应该使用等待异步方法，但我总是遇到来自可视化编辑器的非常有用的错误消息。这只是因为缺少异步上下文。在我的事件处理程序Private Async Sub SelectFilesButton_Click(sender As Object, e As EventArgs) Handles SelectFilesButton.Click中添加了async关键字后，一切正常，我可以按预期使用await语句。

以下是与上述代码相对应的最终解决方案：

'*** Get Bitmap from Word Bitmap-Shape
oWordDocument.Shapes(1).Select()
oWordApp.Selection.CopyAsPicture()
Dim oBitmap As System.Drawing.Bitmap = New System.Drawing.Bitmap(System.Windows.Forms.Clipboard.GetImage())

'*** Convert Streams, get BitmapDecoder + SoftwareBitmap
Using oNetStream As New System.IO.MemoryStream
    oBitmap.Save(oNetStream, System.Drawing.Imaging.ImageFormat.Png)
    Dim oUWPStream As Windows.Storage.Streams.IRandomAccessStream = System.IO.WindowsRuntimeStreamExtensions.AsRandomAccessStream(oNetStream)
    Dim oBitmapDecoder As Windows.Graphics.Imaging.BitmapDecoder = Await Windows.Graphics.Imaging.BitmapDecoder.CreateAsync(oUWPStream)
    Dim oSoftwareBitmap As Windows.Graphics.Imaging.SoftwareBitmap = Await oBitmapDecoder.GetSoftwareBitmapAsync()
End Using

感谢Jimi指出我正确的方向 - 抱歉让我这么久才明白

PS：非常有帮助理解这是来自微软编程指南的2篇文章，您可以使用以下搜索术语找到它们：＆＃34; 异步程序中的控制流程（Visual Basic）＆＃34;和＆＃34; 使用异步和等待进行异步编程（Visual Basic）＆＃34;

使用vb.Net创建BitmapDecoder和SoftwareBitmap的方法是什么？

0 个答案: