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Programming / Document Cleanup / Auto-inverting negative documents

Auto-inverting negative documents

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Negative documents are documents, that have a reverse color photometry: text is white and the background is black. Since intelligent document recognition assumes the opposite, you need to invert the images. But what if you have hundreds or thousands of them? You cannot possibly invert them manually one by one.

Here is an example how to invert negative documents.

Copy Code 
'We assume that GdPicture has been correctly installed and unlocked.
Dim oGdPictureImaging As New GdPictureImaging()
'Loading the image from a file.
Dim imageId As Integer = oGdPictureImaging.CreateGdPictureImageFromFile("Image.tif")
'Checking if the image resource has been loaded correctly.
If oGdPictureImaging.GetStat() <> GdPictureStatus.OK Then
    MessageBox.Show("The image can't be loaded. Error: " + oGdPictureImaging.GetStat().ToString(), "Auto-invertion Example", MessageBoxButtons.OK, MessageBoxIcon.Error)
Else
    'Checking if the image is inverted.
    Dim isNegative As Boolean = oGdPictureImaging.IsNegative(imageId)
    'If the image is inverted, invert it back.
    If isNegative Then
        Dim status As GdPictureStatus = oGdPictureImaging.FxNegative(imageId)
        If status = GdPictureStatus.OK Then
            'Here you can process your image...
            MessageBox.Show("Done!", "Auto-invertion Example", MessageBoxButtons.OK, MessageBoxIcon.Information)
        Else
            MessageBox.Show("Error: " + status.ToString(), "Auto-invertion Example", MessageBoxButtons.OK, MessageBoxIcon.Error)
        End If
    End If
    'Releasing the image resource.
    oGdPictureImaging.ReleaseGdPictureImage(imageId)
End If
oGdPictureImaging.Dispose()
Copy Code 
//We assume that GdPicture has been correctly installed and unlocked.
GdPictureImaging oGdPictureImaging = new GdPictureImaging();
//Loading the image from a file.
int imageId = oGdPictureImaging.CreateGdPictureImageFromFile("Image.tif");
//Checking if the image resource has been loaded correctly.
if (oGdPictureImaging.GetStat() != GdPictureStatus.OK)
{
    MessageBox.Show("The image can't be loaded. Error: " + oGdPictureImaging.GetStat().ToString(), "Auto-invertion Example", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
else
{
    //Checking if the image is inverted.
    bool isNegative = oGdPictureImaging.IsNegative(imageId);
    //If the image is inverted, invert it back.
    if (isNegative)
    {
        GdPictureStatus status = oGdPictureImaging.FxNegative(imageId);
        if (status == GdPictureStatus.OK)
            //Here you can process your image...
            MessageBox.Show("Done!", "Auto-invertion Example", MessageBoxButtons.OK, MessageBoxIcon.Information);
        else
            MessageBox.Show("Error: " + status.ToString(), "Auto-invertion Example", MessageBoxButtons.OK, MessageBoxIcon.Error);
    }
    //Releasing the image resource.
    oGdPictureImaging.ReleaseGdPictureImage(imageId);
}
oGdPictureImaging.Dispose();