Atalasoft's GlyphReaderEngine and AbbyyEngine provide an automatic rotation that is based on the text’s orientation. Unfortunately this is only available when also running the engine. The OCR process, which happens after all of the preprocessing, can be an time expensive process. To reduce the OCR process’s time to almost nothing, the image can be replaced with one that takes no time to read (e.g. 10x10 and just white). Below is an example of handling the ImageTransformation and ImageSendOff events. The ImageTransformation event gets called twice (Once before ImageSendOff and once after), the second on will have the AutoRotate results. At that point the original image can be replaced.

C#

bool SentOff; //This is used as a flag, initalized to false to detect SendOff (AutoRotate happens after SendOff)
 
void engine_ImageTransformation(object sender, OcrImagePreprocessingEventArgs e)
{
     if (!SentOff)
         e.ImageOut = e.ImageIn;
     else //after SendOff ImageIn is rotated
     {
         imageViewer1.Image = e.ImageIn;
         e.ImageOut = new AtalaImage(10, 10, PixelFormat.Pixel1bppIndexed, Color.White);
     }
}
 
 
void engine_ImageSendOff(object sender, OcrImagePreprocessingEventArgs e)
{
    e.ImageOut = e.ImageIn;
    SentOff = true;
}

VB.NET

Private SentOff As Boolean
'This is used as a flag, initalized to false to detect SendOff (AutoRotate happens after SendOff)
Private Sub engine_ImageTransformation(ByVal sender As Object, ByVal e As OcrImagePreprocessingEventArgs)
    If Not SentOff Then
        e.ImageOut = e.ImageIn
    Else
        'after SendOff ImageIn is rotated
        imageViewer1.Image = e.ImageIn
        e.ImageOut = New AtalaImage(10, 10, PixelFormat.Pixel1bppIndexed, Color.White)
    End If
End Sub
 
 
Private Sub engine_ImageSendOff(ByVal sender As Object, ByVal e As OcrImagePreprocessingEventArgs)
    e.ImageOut = e.ImageIn
    SentOff = True
End Sub

Original Article:
Q10280 - HOWTO: AutoRotate an Image Without Ocr Processor Costs